Philosophy

International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 2, February - 2018, Pages: 22-25  22 Rheological Properties of Polyvinylacetate: Part II Mahmoud Abdel-Halim Abdel-Goad Chemical Engineering Dept., Faculty of Engineering, Minia University, Egypt (E-mail:) Abstract- The dynamic viscoelastic properties of Polyvinylacetate with molecular weight 83000g/mol (PVA 83K) were determined by using a Rheometer operated in the dynamic mode and 8 mm parallel plate over a wide range of temperature as a function of frequency. The measurements were performed successively in the parallel plate geometry using 8 mm plate instead of 25 mm. The glass plateau regime is clearly observed because we could measure PVA 83K sample successively under its glass temperature. The rheological properties of polydisperse PVA 83K were completely studied and the experimental data were analyzed using the Winter model. Keywords: Viscoelastic properties of Polyvinyacetate, Relaxation spectrum, Compliance. 1. INTRODUCTION Rheology is concerned with the description of the mechanical properties of the various materials under the various deformation conditions. Polymer rheology is in its various aspects intimately entwined with molecular physics, continuum mechanics, and the processing of polymeric materials. At present, rheological investigations of polymers are processing at an enormously rapid rate, embracing a wide range of materials: biological objects, paste-like substances such as lubricants. The applied aspects of rheology are tied up with the development of new technological processes for the processing of plastics, elastomers and fibers [1]. The understanding of the relationship between the rheological properties of polymers and their molecular structure has considerably improved in the past few years with the interest of physicists in the matter and particularly with the development of molecular dynamics theories [2]. Besides, rheological measurements are used now as an analytical tool of polymer characterization [3-13]. In this work the rheological properties are investigated in details for a commercial PVA 83K. 2. EXPERIMENTAL SECTION Polydisperse PVA 83K sample was prepared for the Rheological measurements. In the disc form with 8 mm diameter and 1 mm thickness by using a press mould without vacuum at 50 C under 10 bar for 20 min. The preparation steps and conditions are summarized as follows: Approximately 0.1 g of the polymer is placed in a Teflon frame of dimensions 8 mm diameter and 1 mm thickness. This Teflon frame is introduced between two Teflon plates and positioned between two metallic plates in the mould. The sample is positioned on the lower plate followed by lowering the upper plate until just contact the upper Teflon plate. The sample is heated with heat rate 10 C/min. and pressed under 8-10 bar by lowering the upper piston for 20 min. The mould is cooled to 30  C , followed by taking the sample out. After preparation the sample for the measurement, the sample is placed on the lower plate of the ARES-Rheometer followed by lowering the stage until the sample just contacts the upper fixture completely. The ARES-Rheometer, consists of a test station, a furnace and liquid nitrogen controller. The test station contains the motor and transducer between which the sample to be tested is placed. The furnace is a forced convection environmental chamber that encloses the sample. The gas temperature is controlled by two resistive heaters and the nitrogen gaseous is used during testing at or above room temperature. If test temperatures are below room temperature, liquid nitrogen is used. The temperature of the oven is maintained by a control loop that is closed around a platinum resistive thermometer. The normal force of the instrument should be kept around zero and the actual gap size is read electronically to be around 1 mm. The measuring program is adjusted to measure the sample over a wide range of temperature from 25  C up to 150  C as a function of frequencies in parallel plate geometry and dry nitrogen atmosphere .The strain was kept inside the linear regime in the whole frequency range. The strain is applied to the sample and the resulting stress is measured by the transducer. The stress signal generated by the sample separated into two components; an elastic part which is in the phase with strain and a viscouse contribution which is 90   out of phase with the strain. International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 2, February - 2018, Pages: 22-25  23 3. RESULTS AND DISCUSSION The PVA83K sample was measured over a temperature range 25-150°C as a function of frequency. Different temperatures curves were shifted into single curve ( Master curve) to a reference temperature T0 (25  C)by means of the time-temperature superposition principle as proposed by Williams, Landel and Ferry (WLF) [8]. Three regimes are found in Figure 1 where the storage, J'(w) and loss, J'' (w) compliance have roughly the appearance of mirror image of those of G' (w) and G'' (w). Since the rubber-like regime is the indication of the entanglements where the chains are entangled each other above a certain molecular weight that called critical molecular weight, Mc. If the viscoelastic (viscous and elastic at same time) behavior of the polymer is represented by a finite mechanical model, the decay of G(t) must at the end become exponential, proportional to e-t/τi where i  is the terminal relaxation time. The results of the extension in the number of elements in the Maxwell model without limit is a continuous spectrum that is called relaxation spectrum, H(T) (Fig. 2). The characteristic zones of the viscoelastic time scale are clearly apparent in H: the glassy zone to the left of the principle maximum, the transition zone where H drops steeply, the terminal zone where it approaches zero. Figure 3 shows the dynamic viscosity as function of the frequency . At low frequency approaches the steady-flow viscosity, 0  . As shown in Figure 3 at very low frequency the viscosity begins to be independent ( 0  ) on the frequency. This value depends on the temperature and molecular weight of the polymer. 4. CONCLUSION The rheological properties of PVA 83K are evaluated using an ARES Rheometer operated in the dynamic mode. The measurements were performed successively in 8 mm a parallel plate instead of 25 mm. From the results obtaine, the viscoelastic properties of PVA could be evaluated with high accuracy. 5. ACKNOWLEDGMENTS Support for this research was provided by International bureau in Germany. The helpful discussions of Dr.S. Khale and Dr.W.Pyckhout (FZ, Juelich, Germany) are grateful acknowledged. REFERENCES 1. Vinogradov, G.V.and Malkin, A.Ya, Rheology of Polymers (Mir Publishers, Moscow, 1980) 2. H. Nakatani, K.-H Nitta, and K. Soga, Polymer 40, 1547, 1999 3. Billmeyer, Jr., F. W., Textbook of Polymer Science 3rd ed. ( Wiley, Singapore, 1984). 4. A.-Goad, A.-Halim, M., PhD thesis, Münster University, 2000. 5. Kuleznev, V.M.and Shershnev, V.A., The Chemistry and Physics of Polymers, (Mir Publishers, Moscow, 1990) 6. Ferry, J.D., Viscoelastic Properties of Polymers, 3rd ed. ( Wiley, New York, 1980). 7. Eisele, U., Introduction to Polymer Physics, (Springer, Berlin, 1990). 8. Utracki, L.A., Polymer Alloys and Blends, Thermodynamics and Rheology (Hanser Publishers, Munich, 1990). 9. A.-Goad A.-Halim, M., Pyckhout,W., Allgiar, J., Fetters, L.J. and Richter, The Egyptian Society of Chemical Engineers, Vol.27, No. 2, P.245, Oct.2001. 10. Dara S.S., A text book of Engineering Chemistry, (S. Chand & Company LTD, Ram Nagar, New Delhi, 1999). 11. Fetters L. J., Lohse D.J., and Milner S.T., Macromolecules 32, No.20, 6847 (1999). 12. Baumgaertel M., Rosa M. E. De, Machado J., Masse M. and Winter H. H., Rheol. Acta. 31, 75 (1992). 13. J.K. Jackson, M.E. De Rosa, and H.H. Winter, Macromolecules 27, No. 9, 2426 (1994). International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 2, February - 2018, Pages: 22-25  24 The Abbreviations and notation: PVA 83K: Polyvinylacetate with molecular weight 83000g/mol.  : the angular frequency J' : the storage compliance J'' : the loss compliance J* : the complex compliance i G : the relaxation strength i  : the relaxation time Figure 1: Master curve of the compliance for PVA 83K at T0 =25C. 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 10-8 10-7 10-6 10-5 10-4 10-3 j' j" j' & J " 1 /P a  rad/sec. International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 2, February - 2018, Pages: 22-25  25 Figure 2: Plot of the relaxation spectrum for PVA 83K at T0 =25C. Figure 3: Plot of dynamic viscosity at T0 =30C. 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 106 107 101 102 103 104 105 106 H (  ) P a1 time, sec. 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 103 104 105 10-2 10-1 100 101 102 103 104 105 106 107 108 109  P a .s  rad/sec


Bitumen blends were prepared for road applications by the introduction of 9wt% waste Polyethylene, PE bags  in the molten state. The relaxation stress, relaxation and retardation spectrum and viscosity of bitumen blends were studied. At different temperatures and compared to those of the original pure bitumen. These properties were tested using an ARES- Rheometer (Rheometric Scientific, Co.) equipment. The measurements were performed in the dynamic mode, plate-plate geometry of 8 mm diameter over the temperature range  from –10 to 60°C and angular frequency,   varied from  10-1 to 102 radian/s. The relaxation stress and viscosity were modified by the addition of waste PE. The results also evidence that the incorporation of the waste PE enhances stability of the bitumen blends As a consequence, the use of waste PE bags can be considered a suitable alternative from both environmental and economical points of view. Bitumens containing several polymer concentrations have been studied.

Philosophy

International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 3, March - 2018, Pages: 7-11  7 Rheological Rheological Characterization of Bitumen/Waste Polyethylene Composites: Part II Mahmoud Abdel-Halim Abdel-Goad Chemical Engineering Dept., Faculty of Engineering, Minia University, Egypt E-mail: Abstract: Bitumen blends were prepared for road applications by the introduction of 9wt% waste Polyethylene, PE bags in the molten state. The relaxation stress, relaxation and retardation spectrum and viscosity of bitumen blends were studied. At different temperatures and compared to those of the original pure bitumen. These properties were tested using an ARESRheometer (Rheometric Scientific, Co.) equipment. The measurements were performed in the dynamic mode, plate-plate geometry of 8 mm diameter over the temperature range from -10 to 60°C and angular frequency,  varied from 10 -1 to 10 2 radian/s. The relaxation stress and viscosity were modified by the addition of waste PE. The results also evidence that the incorporation of the waste PE enhances stability of the bitumen blends As a consequence, the use of waste PE bags can be considered a suitable alternative from both environmental and economical points of view. Bitumens containing several polymer concentrations have been studied. Keywords: bitumen, waste plastics, relaxation stress, relaxation spectrum, viscosity. 1. INTRODUCTION Bitumen, which remains after vacuum distillation of crude oil, is a complex mixture of organic and inorganic compounds. The physical, mechanical, and rheological behavior of bitumen in road and building construction is governed by its chemical composition. For this reason, considerable effort goes toward widening the knowledge of this composition and relating it to performance [1-8].The chemical composition of bitumen is very complex, although its components can be broadly categorized as maltenes and asphaltenes.[914]. Asphaltenes are defined as the blackcoloured fraction of bitumen that is insoluble in n-heptane. Maltenes, composed of saturated compounds, aromatic compounds and resins are soluble in n-heptane . The ratio of asphaltenes to the other constituents, and the maltenic fraction composition have a significant effect on the viscoelastic properties of bitumens, and hence on their performance as road paving binders [15]. The high temperature sensitivity makes bitument difficult or impossible to optimise both highand low-temperature properties. The binders are too brittle at low temperatures and lack cohesion at high temperatures. The temperature sensitivity of straight-run bitumens can be reduced by adding polymer [16]. The polymer addition allows an increase in the resistance of the binder to permanent deformation at high temperature. Besides, the fracture properties including critical stress intensity factor (K1C) at low temperature of polymer modified bitumen were shown to be higher than those of the bitumen base [17]. Therefore, polymerbitumen blends find considerable interest from different authors[ 1821]. The application of polymeric materials in agriculture and horticulture has increased considerably in recent years, not only as replacement for traditional materials but also as a mean of effecting improvement. Thus, the application of plastics has led to a significant improvement in technological processes in the growing and storing of agricultural crops . As a result, a large amount of waste plastic films, containing LDPE, EVA and a minor proportion of stabilizers, are generated every year all over the world [22]. Therefore, the possibility of disposing of troublesome waste plastics within road bitumens is an environmental and economical point of view, The rheological analysis of the bituminous materials is an important test to better understanding its microstructure. Therefore, the rheological study has a considerable interest by different authors [23-27]. It is well established that the linear behavior of bitumens is described by the general linear visco-elastic model.The rheological analysis is a sensitive and versatile thermal analysis technique, which measures the modulus (stiffness) and damping properties (energy dissipation) of materials as the material are deformed under periodic stress [28]. Since the modulus of bitumen can vary by 3-4 orders of magnitude over the in-service temperature range. It was the objective of this work to modify the bitumen at inservice temperatures by adding waste PE. we analyze the rheology of the bitumen modified with waste PE content up to 11% and neat bitumen. 2. EXPERIMENTS PART Materials and preparation Bitumen blends were prepared by adding waste plastics to commercial bitumen. The waste PE bags were sorted from the garbage and shredded into coarse particles. The waste PE bags and the bitumen were weighted and heated individually in an oven until melt. Waste PE in molten state was poured into the molten bitumen up to a level of 11 wt%, mechanically stirred to give a homogenous sample and then stored at room temperature. The bitumen blends and the International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 3, March - 2018, Pages: 7-11  8 original neat bitumen samples were compression-molded at 70°C and 5 bars for 1 hour and shaped for the rheology measurements in a disc form with 8 mm diameter and 1 mm thickness. 3. METHOD The rheological behavior was studied for pure bitumen and bitumen blends by using dynamic an ARES-Rheometer ( Rheometric scientific) equipment in plate-plate geometry of 25 mm diameter. The sample to be measured was placed on the down plate and the upper plate was lowered until just contact the sample. The measurements were performed in the temperature range from -10 to 60°C and angular frequency,  varied from 10 2 to10 -1 radian/s. In the dynamic mode and the strain amplitude was kept (1%) in the linear viscoelastic regime. 6 points per decade in frequency were obtained. The gap was 2 mm and the actual gap size is read electronically and allows absolute moduli to be determined. 4. RESULTS AND DISCUSSIONS The master curve is obtained by shifting the measured data at different temperatures, T into a single curve at a reference temperature T0 as shown in Figure 1. By using of the time-temperature superposition principle which described by Williams-Landel-Ferry [29] as, log aT = -C1 (TT0) /(C2+(T-T0)).Where aT is the horizontal shift factor and constants C1 and C2 are material specific. C1 and C2 are roughly determined as listed in Table1. aT of bitumen blends is plotted as a function of temperature in Figure 2. In this Figure aT decreases with increasing the temperature up to 25°C (aT ~ T -0.14 ) then becomes nearly independent on the temperatures. aT shifts the data obtained at different temperatures in the horizontal direction. In vertical direction the experiments data are shifted by bT (bT = 00/ TT  [30] ). Where  is the material density. The effect of the temperature on bT is shown in Figure 3 for bitumen blends. bT is nearly constant at low temperatures but after 25°C it falls rapidly (bT ~ T -0.17 ) with increasing the temperature as shown in Figure 3. Material C1 C2 Bitumen base 24.9 196 Bitumen/9%PE 1.8 30 The shear relaxation stresses G(t) is plotted against time with logarithmic scales at T0 = 10, 25 and 60°C in Figures 4-5 for neat bitumen and bitumen/PE blend. G(t) is the relaxation stress at constant deformation. At long times of each T0, the master curve of each G(t) shows flow regime which is related to the complete relaxation of the macromolecules and released from the restrictions of the entanglements. The time taken in the relaxation processes is called the longest relaxation time. In this regime the viscous component is higher than the elastic component because of the release of the entanglements which are the responsible for the elasticity. Therefore, G(t) decreases sharply and falls by many order of magnitude in this regime as shown in Figures 4-5. At intermediate time of each master curve is located the rubbery zone that is the signature of the elasticity. As a result, G(t) is independent on the time in this regime since the loss in the energy in every cycle of the deformation is minimum. At short times the third regime of the viscoelastic behaviour is found only in the case of pure bitumen which is called dynamic glass transition because it was no difficulties to measure the neat bitumen samples at very low temperatures (-10°C). The master curves at reference temperature 10°C are shifted toward the long time, those at 25°C appear to be in the intermediate and the master curves at reference temperatures 60°C are shifted toward the short time-wing as shown in Figure 4. This because the time of relaxation of the entanglement chains is inversely proportional to the temperature, since at low temperatures the chains take a long time in the relaxation processes, unlike at high temperatures. G(t) modulus at 60°C is lower than at 25°C and G(t) at 25°C is lower than at 10°C as seen in Figures 4-5. Figures 4-5 evidence that the incorporation of the waste plastics into the bitumen increases the relaxation stress over all the temperatures and times ranges. This increase in G(t) moduli is more noticeable at long times and high temperatures as shown in these Figures. Where the values of G(t) modulus at 5 seconds and 10°C is 2 times higher than this of neat bitumen by by the addition of 9wt%PE as shown in Figure 4. This factor reaches up to 7 at 50 seconds (the same temperature) as shown in Figure 4. The ratio G(t)bit.9%PE/ G(t)bitumen at the end of flow regime in the cases of T0 = 10, 25 and 60°C are 3, 6 and 10. That means the bitumen/PE blend is more stable than neat bitumen at high temperatures for a long times. This due to the formation of the bitumenpolymer network which increases the stiffness and strength of the bitumen blends. That is confirmed too in Figures 6-7. In these Figures the shear equilibrium creep, Je is logarithamically plotted versus time for bitumen and bitumen/PE blend. The addition of PE to bitumen enhances Je in particular at long times and the differences among Je values of bitumen/PE blend is more observable at long times due to the stability of the bitumen-PE network. The relaxation (H(t)) and retardation (L(t)) spectrum of neat bitumen and bitumen/PE blend are plotted as a function of time at 25°C in Figures 8-9. H(t) and L(t) indicate the distribution of relaxation and retardation mechanisms, respectively in different regions of the time scale. they show a broad spectrum of relaxation and retardation times. A broad mechanical relaxation, observed at 25°C, is associated with the collapse of a compact structure, constituted by asphaltene particles surrounded by solid resin. The addition of PE to bitumen modifies this relaxation. The values of H(t) increase by the addition of waste PE to bitumen. The increase in H(t) is significant at long times as shown in Figure 8. That is clear at 40 seconds where H(t) of International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 3, March - 2018, Pages: 7-11  9 bitumen blend is higher than this of pure bitumen by a factor 2 by the addition of 9% PE as shown in Figure 8. This factor becomes 6 at 100 seconds as shown in Figure 8. The same scenario is observed in L(t) (Fig.6). Since at 40 Seconds the addition of 9% PE to bitumen alters the values of L(t) for pure bitumen from 5.010 -5 to 4.310 -1 Pa -1 as shown in Figure 9. But at 1000 seconds the values of L(t) are 5.010 -3 and 5.710 -4 Pa -1 for pure bitumen and 9%PE , respectively as shown in Figure 9. This as explained earlier due to the increase in the stiffness and strength of the bitumen by the incorporation of the PE. The complex viscosity (*) as a function of temperature for neat bitumen and bitumen blends at  = 0.1 radian/s is plotted in Figure 10. As shown in this Figure the incorporation of the waste PE into the bitumen increases the viscosity over all the temperatures range. This because the viscosity of the bitumen matrix is higher than pure bitumen. * of the blends at high temperatures are higher than at low temperatures. Since the values of * at 15°C increase from 5.010 4 (pure bitumen) to 5.710 5 Pa.s by the addition 9wt% PE , respectively. But at 60°C the differences among the values of * are high. These values are 2.710 5 and 5.710 5 Pa.s for pure bitumen and bitumen-9%PE, respectively as shown in Figure 10. This difference because bitumen components change considerably at ~ 40°C, particularly the ratio of the asphaltenes to the maltenes (the main components of bitumen) which has a significant effect on the viscoelastic properties of bitumen. 5. CONCLUSION Bitumen blends were prepared as a road paving binders by the introduction of 9wt% waste PE bags in the melt state followed by mechanical stirring. The relaxation stress, relaxation and retardation spectrum and viscosity of bitumen blends were studied. At different temperatures and compared to those of the original pure bitumen. These properties were tested using an ARES-Rheometer (Rheometric Scientific, Co.) equipment. The measurements were performed in the dynamic mode, plate-plate geometry of 25 mm diameter over the temperature range from -10 to 60°C and angular frequency,  varied from 10 2 to10 -1 radian/s. The relaxation stress and viscosity were developed by the addition of waste plastics and increase with the waste plastics content. The results also evidence that the incorporation of the waste plastics enhances stability of the bitumen blends. The results showed an increase in these properties by the incorporation of the bitumen at high temperatures for a long time. 6. ACKNOWLEDGMENTS The financial support by the International Bureau in Germany, helpful discussions of Dr. W.Pyckhout and Dr.S. Khale at FZJ, Germany are greatly acknowledged. REFERENCES 1. J. L. Anhorn and A. Badakhshan, Fuel, V 73, P. 14991503, 1994. 2. S. Yui, Fuel and Energy Abstracts, V 38, P.78, 1997 3. F. Bonemazzi and C. Giavarini, Journal of Petroleum Science and Engineering, V 22, P.17-24, 1999. 4. M. Garcìa-Pèrez, A. Chaala, J. Yang and C. Roy, Fuel, V 80, P. 1245-1258, 2001. 5. S. Zhao, L. S. Kotlyar, J. R. Woods, B. D. Sparks, K. Hardacre and K. H. Chung, Fuel, V 80, P. 1155-1163, 2001. 6. K. H. Michaelian, S. L. Zhang, R. H. Hall and J. T. Bulmer, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, V 57, P.73-81, 2001. 7. H.A.El Akrami, M.F.Yardim, E. Ekinci, Energy & Fuels, V13, P.1030-1036,1999 8. R.J.Parker, R.A.McFarlane, Energy & Fuels, V14, P.1113,2000. 9. L.Raki, J.-F.Masson, P.Collins, Energy & Fuels, V14, P.160-163,2000. 10. H.W.Yarranton, H.Alboudwarej, R.Jakher, Ind. Eng. Chem. Res., V39, P. 2916-2924, 2000 11. K.Oh, M.D.Deo, Energy & Fuels, V16, P. 694-699, 2002. 12. Y.Zhao, M.R.Gray, K.H.Chung, Energy & Fuels, V15, P.751-755, 2001. 13. L.M.Proctor, E.Toy, L.Lapham, J.Cherrier,J.P. Chanton, Environ. Sci. Technol., V35, P.1420-1424, 2001. 14. S.Japanwala, K.H.Chung, H.D.Dettman, M.R. Gray, Energy & Fuels, V16, P.477-484,2002. 15. M. García-Morales, P. Partal, F. J. Navarro, F. MartínezBoza, C. Gallegos, N. González, O. González and M. E. Muñoz, Fuel, V83, P31-38, 2004.. 16. P. R. Herrington, Y.Wu and M. C. Forbes, Fuel, V78, P.101-110, 1999. 17. L.Champion-Lapalu, A.Wilson, G.Fuchs, C.Scramoncin, D. Martin, J.P.Planche, Energy & Fuels, P.143-147, 2002. 18. A.H. Fawcett and S.-K. Lor, Polymer, V33, P. 20032006, 1992. 19. A. H. Fawcett and T. McNally, Polymer, V 41, P. 53155326, 2000. 20. X. Lu and U. Isacsson, Polymer Testing, V 20, P. 77-86, 2000. 21. G.D.Airey, FUEL ,V82, P.1709-1719, 2003 22. M. García-Morales, P. Partal, F. J. Navarro, F. MartínezBoza, C. Gallegos, N. González, O. González and M. E. Muñoz, Fuel, V83, P31-38, 2004. 23. A. K. Mehrotra, Journal of Petroleum Science and Engineering, V5, P. 261-272, 1991. 24. R. R. Eastick and A. K. Mehrotra, Fuel Processing Technology, V 26, P.25-37, 1990. 25. G. D. Airey, Fuel, V 82, P. 1709-1719, 2003. International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 3, March - 2018, Pages: 7-11  10 26. D. Mastrofini and M. Scarsella, Fuel, V 42, P. 24, 2001. 27. A. Pérez-Lepe, F. J. Martínez-Boza, C. Gallegos, O. González, M. E. Muñoz and A. Santamaría, Fuel, V82, P. 1339-1348, 2003. 28. A.K.Saha, S.Das, D.Bhatta, and B.C.Mitra, J. of Applied Polymer Science, V.71, P.1505-1513, 1999. 29. J.D. Ferry, "Viscoelastic Properties of Polymers", 3rd ed. ( Wiley, New York, 1980). 30. Mahmoud A.-Halim Abdel-Goad, PhD thesis, Muenster University, Germany, 2000 Figure 1: non shifted experiments data of G(t) at different temperatures are shifted into master curves at T0 =25°C by using aT and bT. Figure 2: aT of bitumen/PE blend as a function of temperature at T0 =25°C Figure 3: bT of bitumen/PE blend as a function of temperature at T0 =25°C Figure 4: G(t) of bitumen/PE and neat bitumen at T0 = 25°C Figure 5: G(t) of bitumen/PE and neat bitumen at T0 = 10 and 60°C 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 3 10 4 10 5 10 6 10 7 b T a T n o n -sh i fte d e xp .d a ta M a ste r cu rve a t T 0 =1 0 °C M a ste r cu rve a t T 0 =6 0 °C G t P a t im e , s -20 0 20 40 60 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 a T Te m p ., °C -20 -10 0 10 20 30 40 50 60 70 1 b T Te m p ., °C 1 0 -8 1 0 -7 1 0 -6 1 0 -5 1 0 -4 1 0 -3 1 0 -2 1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 2 1 0 3 1 0 4 1 0 5 1 0 6 1 0 7 ne a t b itum e n b it . -9 % P E G t P a t im e , s 1 0 -12 1 0 -11 1 0 -10 1 0 -9 1 0 -8 1 0 -7 1 0 -6 1 0 -5 1 0 -4 1 0 -3 1 0 -2 1 0 -1 1 0 0 1 0 1 1 0 2 1 0 3 1 0 4 1 0 5 1 0 6 1 0 2 1 0 3 1 0 4 1 0 5 1 0 6 1 0 7 T 0 = 6 0 °C T 0 = 1 0 °C ne a t b i tum e n b i t.-9 % P E G t P a t im e , s International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 3, March - 2018, Pages: 7-11  11 Figure 6: Je of bitumen/PE and neat bitumen at T0 = 25°C Figure 7: Je of bitumen/PE and neat bitumen at T0 = 10 and 60°C Figure 8: H(t) of bitumen/PE and neat bitumen at T0 = 25°C Figure 9: L(t) of bitumen/PE and neat bitumen at T0 = 25°C Figure 10: * of bitumen/PE and neat bitumen as a function of temperature at  = 0.1 rad/s 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 p ure b i tum e n b i t.-9 % P E J e P a -1 t im e , s 10 -11 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 -7 10 -6 10 -5 10 -4 10 -3 T 0 = 6 0 °C T 0 = 1 0 °C neat bitumen bit.-9 % PE J e (t ) P a -1 tim e , s 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 1 10 2 10 3 10 4 10 5 10 6 10 7 neat bitumen bit.-9% PE H (t ) P a tim e , s 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 10 -3 neat bitumen bit.-9E L (t ) P a -1 tim e , s -20 -10 0 10 20 30 40 50 60 70 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 neat bitumen bit.-9% PE  * P a .s T e m p ., °C


Philosophy

International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 4, April - 2019, Pages: 1-1  1 Systematization Of Art Embroidery Patterns In Design Of Modern Dresses Vakhidova Umida Abduhashimovna 1 , Kayumova Dildora Zafar qizi 2 1Lecturer, Department of Fashion Design Texnology and design of light industry, Tashkent institute of textile and light industry, Tashkent, Uzbekistan. 2Student, Texnology and design of light industry, Tashkent institute of textile and light industry, Tashkent, Uzbekistan. E-mail address: d.zafarovna @mail.ru Abstract: This article explores the stages of Uzbek artistic creation. Museum and written sources were considered traditional Uzbek embroidery types from antiquity to XIX century. Uzbek traditional embroidery patterns, symbolic meaning and usage have been systematized. New patterns and their use have been developed on the basis of traditional embroidery elements. The AutoCAD program has developed a new collection of modern costumes. Keywords: embroidery, rhythm, style, pattern, Islamic pattern, composition, symmetry, asymmetry. 1. INTRODUCTION The cultural heritage created by ancient Turon nations is rich and diverse. The main part of this spiritual treasure, which has been formed over the centuries and is rich in content, is a folk craft. Uzbek art of embroidery plays a special place among the types of folk art. Our artistic insight is tradition and eternal dignity for every uzbek woman. This type of craftsmanship was practiced in every household in the last century. 2. LITERATURE REVIEW Well-known scientist O.Sukhareva, who studies Uzbek national costumes, states that "almost all woman until the Revolution were able to sew" [1]. History does not have a home that Uzbeks did not decorate with an embroidery. The palace images created in the early 20th century are shown in Figures 1 and 2. Picture1.Samarqand palak embroidery Picture 2. Nurata palak embroidery The appearance of embroidery is associated with the appearance of the bark and suture in the garment made of the skin. This kind of art is associated with diving and painting during periods. The rope, wool, silk, dice and silver thread were used in the embroidery. The ancient hymns of embroidery in Central Asia have almost not been preserved. Artifacts and embroidery in museums such as palak, sozana, bed sheets, giraffe, shrubs were only dated to the XIX century. Miniatures in XIV-XV centuries were evidence that embroidery has developed in these regions. Artistic craftsmanship developed in the time of Timur and Timurid; elegant fabrics, floral embroidery, ornamental items. Examples of such applied art are decorated with small sketching and drawing patterns. The bright colors are used in embroidery. Written sources were decorated with embroidery on the walls of Amir Temur's palaces. The Spanish ambassador, Rui Gonzales, who lived in the palace of Amir Temur, also wrote that Claudius, in his memoirs, has seen the embroidery in the palace. Kamoliddin Behzod also reflected a festoon tent in the miniature of the Temurian Tiger who worked at the Zafar writing. Uzbek felt artists International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 4, April - 2019, Pages: 1-1  2 have decorated ornaments of other tupes of applied art in ornamental designs. 3. RESEARCH METHODOLOGY The history of Uzbek national embroidery can be divided into development stages. 1. Central Asian antiquity. (BC VI-IV) 2. The Middle Ages in the Middle Ages. (VII-VIII milliseconds) 3. Central Asia in the late Middle Ages. (IX-XVIII BC) 4. Central Asia XIX-XX centuries. From the earliest historical period, embroidery was made on the basis of patterns, and in craftsmanship a combination of style was created. The enlargement and change of the theme of the applied art was caused by the ethnic composition of the people and tribes, the daily and vital changes. Originally, the pattern was created from simple typical rhythms that make up a frame or carcass. The basic principles of drawing patterns by the method of the ancient people of Central Asia are defined; patterns or figures; the scheme will be divided into topics; themes are subdividedi into elements On this basis, there are other complexs and different patterns that are different from the oldest pattern. Ancient ornament culture was created in the process of interethnic communication between tribes and people. In the late Middle Ages. The patterns on the subjects of evolution changed to evolution. Formsold shapes to form new forms. During this period, the paintings of the Ottomans were described as conditionally and stylistically. In many ways, the theme of the men's and women's clothing reflects the external environment and is often manicured. The history of our embroidery, as well as the flower, pomegranate, horn, and bouquets, have been preserved. 4. ANALYSIS AND RESULTS Today, the high demand for changes, as well as the traditions, creates new design elements in our national embroidery. In the fashion world, designers and craftsmen look for patterns that are used in the dresses created, and on this basis new patterns are offered. At the some time, each pattern is developed on the basis of the organization and the styling of the locals in nature. In the process of creation of patterns, first of all, the function and character of the composition are determined. The patterns are based on the principles of summetry and asymmetry. That is, the elements represent the opposite of one another, which is at the same distance as the white or the particle. Large circle patterns refer to the central axial symmetry law. At the same time, the summetry elements are located in the center of the central white circle covered in the same circumference. In the process of making patterns geometric and archetypal patterns combined with the composition. Art embroidery cabn be used to decorate craftsmanship. The new patterns are shown in Table 1: No Shape Explanation Usage 1 The given pepper patter is of asymmetrical shape and it is created in the XIX century on the basis of papper patterns of Shahrisabz embroidery. The illustrated pattern is auxiliary patterns and can be used in women's undewear. 2 The given pattern is of asymmetrical shape, and its pomegranate image is based on symmetry. The pattern can be used to decorate large ornamental patterns. 3 The given pattern has a symmetrical shape. Created on the basis of styling of leaf types used in composition The applied pattern can be used to decorate large flower decorations. International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 4, April - 2019, Pages: 1-1  3 4 The given pattern has a summetrical shape. Created on the basis of styling of leaf types used in composition Created patterns can be used as ornamental pattern in the melody composition. Our artistic creation is one of the types of applied arts that is being shot from the dynasties by younger generation. The cheerfulness of the cheerful creature, its inexhaustible fantasy and delicate taste, was reflected in Doppler dance of Uzbekistan, and decorative arts. People's artistic craftsmanship is endlessly demanded not only in our country, but also abroad. The art masterpieces created by the Uzbek masters are preserved in France, Italy, Japan, Germany, Belgium, America, India and many other countries, as well as exhibitions in the Republic's applied art museums, which have become a permanent exposition of the Uzbek people's traditions. Nowadays, this kind of art has become a permanent exposition. Nowadays, these works of art are striking with the diversity of their grace and elegance. In the current period of development, the artistic embroidery is adapted to fashion, fashion and modern dresses, and fashion designers and fashion designers of Uzbekistan. 5. CONCLUSION In short, the formation of the embroidery and the needle of the thread, the art of embroidery created in the human hands and the art of creation were formed. The most ancient patterns have been seen and systematized. The new designs were created on the basis of the collection of patterns, which are available in the designer's designs. REFERENCES: 1. Kadurov A. Design of decorative applied art in the direction of artistic embroidery. Toshkent, SHARQ, 2007. 6-7 pages. 2. Uzbek national headdresses XIX-XX centuries. 228238 pages. 3. Hakimov А. "Unique suzane in collections of the State Museum of Art of Uzbekistan" Art 2/2014. 14-15 pages. 4. Hasanboyeva.G. History of Tile Design . Toshkent, ECONOMIC FINANCE, 2006 pp. 127-142 5. . com. National embroidery history.


Philosophy

International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 12, December - 2018, Pages: 6-9  6 Studying the Performance of New Wedge Disc Brake Mechanism Hamada M. Abdel-Rahman 1 , Ahmad O. Moaaz 2 , Nouby M. Ghazaly 3 , Ali. M. Abdel Tawwab 4 1,2Mechanical Engineering Department, Beni-Suef University, Beni-Suef, Egypt 3Mechanical Engineering Department, South Valley University, South Valley, Egypt 4Mechanical Engineering Department, Minia University, Minia, Egypt Abstract: The aim of this research is to investigate the ability of manufacturing and testing a new mechanism for wedge disc brake. The new mechanism consists mainly of the wedge itself, which is controlled by a gear set to change its inclination angle. The wedge is sliding on a surface controlling its inclination angle. The control of the inclination angle can change the factor between the applied force from the brake pressure source and the normal force to the brake pads. Changing the normal force to the brake pads can change the brake force on the rotor disc. The brake force from the pads on the rotor disc is the main goal in this research. The goal is to increase this force by increasing the normal force on the brake pads. The new mechanism was manufactured and tested experimentally in the laboratory by the use of a lathe machine carrying the mechanism for investigation. The results showed the ability of the new mechanism to increase the brake force by about seven times than conventional disc brake. The tested inclination angles were 45o, 35o, 25o, 15o, 12o, and 10o with different rotational speeds of 76, 150, 230, 305 rpm at different applied hydraulic pressure of 5, 7.5, 10, 12.5 bar. In all mentioned cases, the inclination angle of 12o was found to be the best angle in increasing the brake force. Keywords- Wedge disc brake; applied force; wedge inclination angle; brake force 1. INTRODUCTION Brakes can be described as a tool to slow or stop the turning motion of the vehicle wheels through transforming kinetic energy to heat [1]. The drum brake and disc brake are the main two types of friction brake. Disc brake have many advantages than drum brake of that: fade resistance, selfadjustment, and freedom of pull. Therefore, drum brake systems for vehicles are being replaced with disc brake systems. It should be noted that the main disadvantage of disc brake system is non-occurrence of the self-energizing phenomenon [2]. Hence, so there were many efforts to modify the disc brake system that could be self-amplified. In wedge disc brake system, a great brake force can be achieved with small-applied force. There were many models of wedge disc brake systems according to applied force direction whether, is normal or tangential. It has different advantages such as improved ABS performance especially on slippery roads, continuous brake power distribution, shorter stopping distance, and environmentally friendly brake system [2]. Therefor new wedge disc brake will be investigated in this study. Coefficient of friction μ, which is between pads and rotor disc that presented by Coulomb's law, is defined as the ratio of brake force to the applied force. Many efforts were done to determine it accurately, for example, Blau [3], and Serverin and Dörsch [4], presented a friction law depending based on many parameters such as normal force, sliding speed, contact temperature and number of brakes. However, it has no exact trend with these working parameters. The ratio of the total brake force to the applied force is called as the characteristic brake factor C* which is considered as the main performance of the vehicle braking system [5]. It depends basically on the value of friction coefficient. Serverin and Dörsch [4] have presented the variation in the characteristic brake factor C* with different friction coefficients. They found that the characteristic brake factor is affected by friction coefficient μ variations with uneven impact, where the degree of influence of the friction coefficient μ on the characteristic brake factor C* is higher with the self-amplified brakes (drum and wedge) than with the conventional disc brakes. Wedge disc brake, which its mechanical model shown in Fig. 1, is an application of mechatronics in a new disc brake system. The concept of Roberts [6] was based upon the application of self-amplification action in the disc brake system by using a wedge mechanism. This mechanism is similar to the patent presented by Dietrich [7]. In this work, the researcher tries to find the optimal operating point. The characteristic brake factor C* is: ( ) Where, α is wedge inclination angle. They even considered using the operating point when the characteristic brake factor C* is infinity, i.e., the term tan(α) - μ becomes zero. Fig. 1. Mechanical model of wedge disc brake [8] International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 12, December - 2018, Pages: 6-9  7 2. DESCRIPTION OF TEST-RIG The test rig was built in order to generate the kinetic energy required for the system and then brake this energy by the brake wedge mechanism and measure the brake force at different speeds, applied forces, and different wedge inclination angles. The test rig consists of driving mechanism, flexible coupling, brake rotor disc, brake wedge mechanism, hydraulic connections for the brake fluid, and a measuring system for the brake force. The test rig is shown in Fig. 2. The driving mechanism is mainly the gear box of the lathe machine to give the system the ability of working with different speeds. The driving mechanism is also having a flywheel to give the required inertia force for the braking system. The lathe itself is driven by an AC electric motor characterized by a constant rotational speed with maximum power of 10 hp (7.46 kW) at 1450 rpm. (1) Rotor disc (5) Inclination angle Control (2) New wedge disc brake (6) Coupling (3), Hydraulic press (a) (7) Measuring system (4) Hydraulic press (b) (8) Computer Fig. 2. Experimental test rig The brake rotor disc is the element for testing the brake force on it and it has a brake pads installed on it and connected with the brake wedge mechanism by the hydraulic connections. The new wedge mechanism is shown in Fig. 3. The wedge mechanism is the most important part in the system, which consists of: two metallic parts have an inclined sliding surface between them has an inclination of 45o, the lower part is connected to a gear driving mechanism to control the inclination of this part, the upper part is the wedge which is connected to the hydraulic connections from the applied force source and to the normal force on the brake pads which installed on the rotor disc. The lower gear controlling the inclination angle of the wedge mechanism is driven by an electric motor with brake to adjust the inclination of the lower part of the mechanism as shown in Fig. 3. The sliding surface between the two parts of the wedge has a ladder bearing to prevent the friction between these two parts. The hydraulic connection is the main part transferring the pressure from the hydraulic pedal to the brake pads. These connections take the pressure from the hydraulic pedal by means of a hydraulic press, this pressure is transferred to the wedge by another hydraulic press numbered 3 in Fig.2. After the wedge there are other hydraulic connections transferring the pressure from the wedge to the brake pads as shown in Fig.3. After conducting the test and applying the brake force on the rotor disc, a measuring system for the disc braking force is installed to measure and record the brake force. The applied force from the hydraulic pedal to the hydraulic press (a) at fig. (2) can be adjusted by using a pressure gauge with a control valve. The applied force acting from the hydraulic press (a) to the wedge moving it to force the hydraulic press (b) which generates the normal force at the hydraulic connection from press (b) to the brake pads. The normal force from the wedge is measured by a hydraulic gauge and recorded during the test Fig. 3. New wedge mechanism MEASUREMENT INSTRUMENTATION The designed test rig with the measurement instrumentation is shown schematically in Fig. 4. Fig. 4. Schematic sketch of brake force, temperature and speed measurement instrumentations The instrumentation includes:  Applied force measurement.  Rotational speed measurement.  Brake force measurement. International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 12, December - 2018, Pages: 6-9  8  Friction temperature measurement. The applied force can be measured by a pressure gauge installed in the hydraulic line after the pedal. The hydraulic pressure of the brake fluid in the line can be multiplied by the area of the press (a) to obtain the applied force. The hydraulic press (a) and (b) pistons have a diameter of 40 mm. The applied force is adjusted to the required value by using a control valve. The rotational speed of the lathe machine is adjusted to the required rpm and was checked also by the use of a digital photo tachometer. The brake force is measured by a load cell (tensioncompression load cell with 400 kg maximum load) which was installed beside the rotor disc and the force transmitted to it by means of a metallic connection was tightened to the rotor disc. The temperature due to the friction was measured by a thermocouple mounted on the rotor disc above the brake pads. The brake force and the temperature of the friction were recorded using a data logger transferring these readings to the computer to record it as shown in figure 4. 3. EXPERIMENTAL WORK The experiments were conducted to check the new wedge mechanism effect and to decide the optimum inclination angle for the wedge. The selected parameters for the experiments were as follows: The rotational speed (N) of 76, 150, 230, and 305 rpm. The applied pressure (Papp) of 5, 7.5, 10, and 12.5 bar these values of pressure equals applied forces (Fapp) of 628.572, 942.857, 1257.143, and 1571.43N respectively. Inclination angle (α) of 45, 35, 25, 15, 12, and 10 degrees. 4. RESULTS AND DISCUSSION Influence of Wedge Inclination Angle The effect of the wedge inclination angle on the brake force is shown in Fig. 5. The decrease of the inclination angle from 45° to 12° increases the value of the brake force from 4788 N to 8400. N at Papp of 12.5 bar nearly 1.8 times. The results explain that increasing of the self-energizing action of the wedge brake with the decreasing of the wedge angle. Increasing the self-energizing action increases the normal force causing increasing the brake force. This is in agreement with Roberts [6] and Hartman [8]. But less than 12° nearly of wedge inclination causes a reduction of brake behavior due to the resistance of hydraulic press links (number 3 and 4 in Fig.2) to motion of the wedge. Fig. 5. Effect of wedge inclination angle on the brake force at various applied pressures and constant rotational speed of 76 rpm Fig.6 shows that, the brake force fluctuates with no identical trend with the braking time. The variations of the brake force trend are a result of the friction coefficient trend fluctuations. Fig. 6. Variation of brake force with time at various rotational speeds and constant applied pressure of 12.5 bar with inclination angle of 12° Influence of Applied Force The effect of applied force on the brake force, Coefficient of friction μ, and characteristic brake factor C* are shown in Fig. 7, 8, and 9 respectively. From the results shown, it can be seen that, the increase of the applied force cause a great increase of the brake force at all rotational speeds. The effect of the applied force obtain from the relation Fb = Normal * μ. When accruing an increase in the applied force, there is a decrease in the friction coefficient and hence the characteristic brake factor C* also decreases, this due to the increasing in friction temperature between brake pads and rotor disc. International Journal of Academic Engineering Research (IJAER) ISSN: 2000-001X Vol. 2 Issue 12, December - 2018, Pages: 6-9  9 Fig. 7. Effect of applied force on the brake force at various rotational speeds and constant wedge inclination angle of 12° Influence of Rotational Speed From the results, it can be seen that the increase of the rotational speed causes a decrease of the brake force. Increasing the braking time leads to decrease the brake force especially at high speed. This is because of the increase of the friction temperature, which decreases the friction coefficient; therefore, the brake force tends to decrease. Fig. 8. Effect of applied force on Coefficient of friction at various rotational speeds and constant wedge inclination angle of 12° Fig. 9. Effect of applied force on characteristic brake factor at various rotational speeds and constant wedge inclination angle of 12° 5. CONCLUSION The conclusions from the present study can be written as following: (1) The increase of the applied force increases the brake force of the new wedge disc brake. The wedge inclination angle has a significant effect on the new wedge disc brake performances. The self-energizing action of wedge disc brake increases with the wedge inclination angle decrease. (2) The higher the applied force the lesser the coefficient of friction and characteristic brake factor for wedge disc brakes. (3) The brake force decreases with the increase of rotational speed due to the increasing of friction temperature. 6. ACKNOWLEDGMENT The authors would like to thank Beni-Suef University, Faculty of Industrial Education for helping and supporting. REFERENCES [1] Giri, N.K.: Automobile Mechanics: Romesh Chandra Khanna for Khanna Publishers, 2007. [2] Halderman, J. D.: Automotive Technology: principles, diagnoses, and service: Pearson Education, Inc., 2009. [3] Blau, P.J. (1995) Friction Science and Technology, Dekker Mechanical Engineering, CRC Press, ISBN 0824795768, 9780824795764. [4] Dietrich, J., Gombert, B. and Grebenstein, M. (2001) Elektromechanische Bremse mit Selbstverstärkung: Patent, DE 198 19 564 C2. [5] Leber, M., Karheinz, B., Dusil, V.: Selbstversträkende Reibungbremse: Patent, DE 195 39 012 A1, 1998. [6] Roberts, R., Schautt, M., Hartmann, H. and Gombert, B. (2003) Modelling and Validation of the Mechatronic Wedge Brake, SAE Technical Paper 2003-01-3331, Doi: 10.4271/2003-01-3331. [7] Serverin, D. and Dörsch, S. (2001) 'Friction mechanism in industrial brakes', Wear, Vol. 249, pp.771-779. [8] Hartmann, H., Schautt, M., Pascucci, A. and Gombert, B. (2001) eBrake® - The Mechatronic Wedge Brake, Society of Automotive Engineers, 2002-01-2582.


Abstract: Background: Vitamin D insufficiency/deficiency prevalent in all age groups across the world is common in obesity and may play an important role in the risk factors of metabolic syndrome (MS).  Objectives: This cross-sectional study is to evaluate the relationship between levels of adiponectin and circulating 25(OH)D, and its effect on metabolic biomarker among overweight/obese female students.  Methods: Three hundred female students; with mean age 20.9 ± 3.2 years were attending the Aljouf University, Sakaka, Saudi Arabia. They were randomly selected from university during the studying year 2015 – 2016. Anthropometric and biochemical indices were determined. Results: The study showed 19% of the female’s student were either overweight or obese (15% and 4%, respectively). The frequency of MS diagnosis among the students was 17%, with 13% and 4% had either three or four risk factors, respectively. Overweight/obese subjects had significantly worse anthropometric and biochemical characteristics, including waist/hip ratio, blood pressure (BP), fasting blood glucose (BG), insulin, insulin resistance (HOMA-IR), triglyceride levels (TG), low-density lipoprotein cholesterol levels (LDL-C), leptin, adiponectin, leptin/adiponectin ratio and high-density lipoprotein cholesterol levels (HDL-C) compared to normal weight. Of the subjects diagnosed with MS, 59% had mild and 8.6% had severe 25(OH)D deficiency. There was negative association between 25(OH)D and both FBG and HOMA-IR among young women obese/overweight. Conclusion: In our study, it suggested that low level of adiponectin was strongly correlated with low 25(OH)D levels. Also, the prevalence of MS tends to increase with high occurrence rate of low circulating 25(OH)D levels that is, known cause poor glycemic control and prediction of cardiovascular outcomes.

Philosophy

International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2000-007X Vol. 2 Issue 11, November - 2018, Pages: 7-12  7 The Role of Vitamin D in the Incidence of Metabolic Syndrome in Undergraduate Female Students in Saudi Arabia a Hala M. Abdelkarem, a Aishah H Alamri, b Fadia Y Abdel Megeid, c Mervat M Al-Sayed and d Omyma K Radwan a Chemistry DepartmentScience CollageImam Abdulrahman Bin Faisal UniversityP.O. Box 76971 DammamSaudi Arabia; b Chemistry DepartmentScience collageb

Special Need Department- Kindergarten collageHelwan UniversityHelwanEgypt and c Nutrition Department- Food Science & Agriculture -King Saud UniversityRiyadhSaudi Arabia and d Physiology Department- National Organization for Drug Control and Research (NODCAR)Giza 12553- (Egypt) Running title: Vitamin D Deficiency and Metabolic syndrome among Saudi Obese young females The Corresponding author: *Prof. Dr Hala Abdelkarem  Research Centre, Nutrition & Food Science Department, Al Buhouth, Dokki, Cairo, Egypt, Postal Code: 12622, Email: , , Mobil No: 00201023430311 Abstract: Background: Vitamin D insufficiency/deficiency prevalent in all age groups across the world is common in obesity and may play an important role in the risk factors of metabolic syndrome (MS). Objectives: This cross-sectional study is to evaluate the relationship between levels of adiponectin and circulating 25(OH)D, and its effect on metabolic biomarker among overweight/obese female students. Methods: Three hundred female students; with mean age 20.9 ± 3.2 years were attending the Aljouf University, Sakaka, Saudi Arabia. They were randomly selected from university during the studying year 2015 - 2016. Anthropometric and biochemical indices were determined. Results: The study showed 19% of the female's student were either overweight or obese (15% and 4%, respectively). The frequency of MS diagnosis among the students was 17%, with 13% and 4% had either three or four risk factors, respectively. Overweight/obese subjects had significantly worse anthropometric and biochemical characteristics, including waist/hip ratio, blood pressure (BP), fasting blood glucose (BG), insulin, insulin resistance (HOMA-IR), triglyceride levels (TG), low-density lipoprotein cholesterol levels (LDL-C), leptin, adiponectin, leptin/adiponectin ratio and high-density lipoprotein cholesterol levels (HDL-C) compared to normal weight. Of the subjects diagnosed with MS, 59% had mild and 8.6% had severe 25(OH)D deficiency. There was negative association between 25(OH)D and both FBG and HOMA-IR among young women obese/overweight. Conclusion: In our study, it suggested that low level of adiponectin was strongly correlated with low 25(OH)D levels. Also, the prevalence of MS tends to increase with high occurrence rate of low circulating 25(OH)D levels that is, known cause poor glycemic control and prediction of cardiovascular outcomes. Keywords: Vitamin D deficiency, adiponectin, leptin, blood glucose, insulin resistance and lipid profile 1. INTRODUCTION Vitamin D insufficiency/deficiency is prevalent in all age groups across the world. Vitamin D deficiency, which is deemed to occur at a low level of 25(OH)D in blood less than 50 mmol/l, is common in obese people[1]. Several studies have found serum 25(OH)D levels greater than 50 nmol/l to be prevalent (in up to 90% of the population) with partial of < 25 nmol/l in South Asia, Middle East and North Africa[1]. Low vitamin D status which indicated by circulating 25(OH)D is linked to metabolic risk factors such as inflammation, adipokines, insulin resistance, abnormalities of lipid profile, and high (BP) in adults[2]. However, many studies have evaluated the relationship between 25(OH)D concentrations and metabolic components in children and adolescents. Some workers suggested that vitamin D is isolated in excess fatty tissue, resulting in lack of biological availability[3]. In a study of Pittas et al., found that individuals who suffered from CVD were more vitamin D deficient than those without CVD[4]. In a different study that followed young adults for more than 20 years, vitamin D level, in combination with vitamin D supplementation, was inversely related to the incidence of MS in the study population [5]. It also, suggested that lifestyle factors and having high levels of body fat mass might contribute to this development. Kayaniyil et al., reported 25(OH)D levels to be negatively correlated with the first and second phases of insulin secretion, and to be positively correlated with insulin sensitivity in type-2 diabetes[6]. Adipokines secretes by adipose tissue, has a vital role on body weight, blood glucose, and lipid metabolism. Adiponectin, a collagen-like protein has anti-inflammatory, antiatherogenic and antidiabetic properties. Increased circulating of adiponectin is linked with reduced risk of impaired glucose tolerance, decreased myocardial infarction risk, and was suggest as indicator of atherosclerosis early [7]. In obesity, Adiponectin was declined and may be involved in type-2 diabetes and cardiovascular disease pathology [7]. Adipose tissues secrete leptin, a cytokine-like molecule that regulates the fatty mass and body weight by inhibiting eating and stimulating energy consumption [8]. Leptin was increases in obesity, type-2 diabetes, MS and International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2000-007X Vol. 2 Issue 11, November - 2018, Pages: 7-12  8 hypertension. Several studies have found that leptin is a biomarker of obesity, IR, MS and cardiovascular disease in adult[8]. Hyperlipidaemia, which considered to be an independent CVD risk factor, forms a potential link between low vitamin D levels and CVD. Dyslipidaemia, known to be a disorder of lipoprotein metabolism, is the result of excess TG, TC, LDL-C, and is due to the suppression of HDL-C. A favourable serum lipid profile is correlated with high levels of 25(OH)D which regulates the appropriate use of apolipoprotein A-1 (ApoA1), since it is a component of HDL Salehpou et al.,[9] conducted a study on obese individuals who received vitamin D supplement (25μg/d); the results of this study suggested that significantly elevated levels of HDL-C and Apo A-1 lowered body fat in obese individuals. The objective of the current study was to evaluate the relationship between levels of adiponectin and circulating 25(OH)D levels, and its effect on metabolic biomarker among overweight/obese female students who attending in Aljouf University, Sakaka, Saudi Arabia. 2. METHODS Subjects This cross-sectional study, which took place between November 2015 and June 2016, was performed on group of 300 overweight/obese female students; with mean age 20.9±3.2 years. Subjects were selected randomly from female students attended in Al Jouf University, Sakaka, Saudi Arabia. They were excluded from the following criteria: liver disease, kidney disease, diabetes mellitus, use of any medication that could affect bone health or vitamin D status within the previous three years, history of pregnancy, lactation convulsions, thyroid-parathyroid diseases, adrenal disease, or gonadal disease. All participates gave their informed consent before inclusion in this study. The study was approved by the Medical Research Ethics Committee of the Faculty of Medicine, King Saud University. Data collection. Each subject completed a self-reporting questionnaire that revealed their socio-economic status, age, smoking habits, meal and snack frequencies, and level of physical activity, as well as the educational and occupational status of each of their parents . Dietary data. For each subject, the following data were recorded: the frequency of meals and snacks, and daily intake of vegetables, fruits, fatty foods, sugars, milk, mushrooms, fish, and crustaceans. Lifestyle practices, such as physical activity (exercise) and history of vitamin D supplements, were also recorded. Nutrient analysis. Daily dietary intake was recorded over three consecutive days to insure energy and nutrient intake. A software program, purchased from ESHA[10], was used to analyse the nutritional content of each subject's diet. The dietary reference intakes (DRI), which are the recommended dietary intakes for a healthy diet, were calculated for each subject, adjusting for local practices, gender, age, weight, height, and physical activity levels[11] Anthropometric measurements. Anthropometric data, including weight and height, were recorded (to the nearest0.1kg and0.5cm, respectively) using a beam balance scale (Adam Equipment Inc.,USA) after removal of outer garments and shoes; body mass index (BMI) was calculated (body weight/kg/(body height/ m)2)[12]. Body weight was categorised according to BMI values using the National Institutes of Health guidelines: (i) normal with BMI range 18.5-24.9, (ii) overweight with BMI range 25.0-29.9, and (iii) obese with BMI > 30[13]. Waist and hip circumferences(cm) were measured and the weight-to-hip ratio(WHR) was calculated[14]. Systolic and diastolic blood pressures were recorded, using the average of two measurements that were taken within 15-minuts interval using standardised mercury sphygmomanometer. Subjects whose BP measurements were ≥130/85mmHg were classified as being hypertensive[15]. Diagnostic criteria. MS was diagnosed when three or more of the following criteria: abdominal obesity (WC≥88 cm), elevated FBG (≥ 100 mg/dl or diagnosed with diabetes, or taking an oral hypoglycaemic or insulin medication), reduced HDL-C level (≤40 mg/dl), elevated TG level (≥150mg/dl) and elevated BP (SBP≥130 mmHg, DBP≥85 mmHg or taking antihypertensive medication)[16]. Biochemical analyses. Blood samples were drawn after fasting for more than 12-hrs and the serum was separated and frozen at -20°C. Glucose concentration was estimated using a commercially available glucose kit (Randox Laboratories Ltd., UK.) based on the glucose oxidase method. Serum TC, LDLC, HDL-C and TG, creatinine, uric acid, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were estimated colorimetrically using the available kits (cited in Randox Laboratories Ltd., UK). Serum 25(OH)D and insulin levels were measured by enzyme-linked immunosorbent assay (ELISA) (IDS, Tyne and Wear, UK). The interand intra-assay variabilities for 25(OH)D were 5.2% and 4.3%, respectively, and the interand intra-assay variabilities for insulin were 5.7%, and 3.1%, respectively. Insulin resistance was calculated using HOMA-IR (insulin[mU/L] ×glucose[mg/dl]/405[17]. Serum adiponectin and leptin were measured by ELISA. the intra-assay and interassay coefficients of variation for adiponectin was 5.4% and 8.5% respectively and intra-assay and inter-assay coefficients of variation for leptin was 7.4% and 9.3% respectively (Ani Biotech Oy, Orgenium Laboratories Division, Vantaa, Finland). The reading was taken using an ELISA microplate reader (VERSA Max, Molecular Devices Corporation, MN, USA). Vitamin D status was classified as follows: (i) deficient (vitamin D levels < 20 ng/ml), (ii) insufficient (vitamin D levels in the range 20 - 29 ng/ml), and (iii) sufficient (vitamin D levels >30 ng/ml)[18]. Statistical Analysis. Data were expressed as mean ± standard deviation(SD) and data were analysed using SPSS version 12.0 software (SPSS, Chicago, III), using the appropriate statistical tests (chi-square International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2000-007X Vol. 2 Issue 11, November - 2018, Pages: 7-12  9 test, Student's t-test, correlation coefficient, odds ratio). The P values were considered significant for P < 0.05. 3. RESULTS Socio-demographic characteristics of the study group are described in Table 1. The mean age of the subjects was 20.9 ± 3.2 years. The parents of the subjects had been educated to at least University standard in 66% (fathers) and 36% (mothers) of the cases. Most fathers (65%) were employed whereas few mothers (29%) were employed. Family history of MS was 64%. The study showed 19% of the subjects were either overweight/obese (15% and 4%, respectively). The frequency of MS diagnosis of the subjects was 17%, with 13% and 4% of the subjects having three or four risk factors, respectively (Table 2). Anthropometric and biochemical characteristics of the subjects are detailed in Table 3. When compared to normal weight subjects, overweight\obese subjects had statistically significant of anthropometric and biochemical parameters. A higher levels of fasting blood glucose, insulin, HOMA-IR, leptin, leptin/adiponectin ratio, TG, LDL-C, W/H ratio, SBP and DBP in overweight/obese female students; but lower adiponectin and HDL-C levels. Also, overweight/obese subjects had significantly lower levels of 25(OH)D (p<0.01) relative to the normal weight. Fifty-nine percent of the students that were diagnosed as having MS had mild 25(OH)D deficiency and 8.56% had severe 25(OH)D deficiency (Table 5). Serum 25(OH)D levels were negatively associated with BMI, FBG, leptin, leptin/adiponectin ratio, LDL-C, TG and BP, and positively associated with adiponectin and HDL-C (P<0.01) (Table 6). In addition, MS had pronounced impact on elevating leptin and inhibition adiponectin levels that was additive to overweight/obesity. Otherwise, leptin/adiponectin ratio, that had postulated as a biomarker, was increased in subjects with MS than without. Table 7 details the association between MS and different risk factors. It can be observed that the primary predisposing risk factor for MS was abdominal obesity (OR 5.92). The second predisposing risk factor for MS was abdominal obesity, as indicated by WC (OR 5.26), followed by leptin (OR 4.84), Leptin/adiponectin ratio (OR 4.73), adiponectin (4.26), hypertension (OR 4.11), low HDL-C (OR 3.42), FBG (OR 3.11) and vitamin 25(OH)D (OR 2.87). The levels of carbohydrates and sugar consumption were significantly higher in subjects with MS compared to those without (Table 8). Consumption of dietary saturated fats were significantly more by subjects with MS than those without, but dietary fibre was consumed significantly less among subjects with MS than those without. In overweight/obese, the daily dietary intake of vitamin D was 198±136.6 IU/day and in normal weight was 190±129.6 IU/day. The intake of vitamin D as a percental of DRI was 101.0±69.2% in overweight/obese subjects and 89.9±49.8% in normal subjects. Among the groups study, no statistically significant in vitamin D intake was showed either based on daily intake or on the percent of DRI. 4. DISCUSSION Vitamin D has a vital role of public health and human wellbeings and its deficiency has been linked to several metabolic disorders including Cancer, autoimmune diseases, obesity, type-2 diabetes, hypertension and cardiovascular disease and there is a relationship between low serum 25(OH)D, HOMA-IR, type-2 diabetes and low adiponectin in adults[19]. In the finding Leptin was increased and adiponectin decreased in overweight/obese female students relative to normal weight. There was a strong correlation between leptin with abdominal obesity and inverse to adiponectin. Furthermore, leptin, leptin-to-adiponectin ratio and adiponectin were strongly correlated with MS. These results had additive effects to overweight/obesity among female students. The most important outcomes are the combination of risk factors with increased leptin or lack of adiponectin that was found in overweight/obesity among female students. A cross-sectional study by lee et al., conducted on adolescents aged 12-19 years showed that abdominal obesity was the predominate risk factor for IR and there is an inverse correlation between adiponectin and obesity and IR which is linked to risk factors of cardiac disease[20]. The results of our study showed that low serum 25(OH)D associated with abdominal obesity, adiponectin, HOMA-IR as well as leptin/adiponectin ratio. Leptin and adiponectin have adverse effects on inflammation and insulin resistance, the high level of leptin increases the expression of proinflammatory and vasoconstrictive factors[21]; while adiponectin stimulates anti-inflammatory cytokines production and enhanced the sensitivity of peripheral insulin[22]. Al-Daghri et al., observed that a positive correlation between BMI and; 25(OH)D and adiponectin in type-2 diabetes. The fact is that these adipokines has a potential role as a link between 25(OH)D and IR[23]. The current study showed 25(OH)D levels to be significantly lower in subjects who had been diagnosed with MS compared to those without MS. The finding also, observed that subjects who had been diagnosed with MS were mildly 25(OH)D deficient more frequently than those without. Additionally, vitamin D deficiency was more prevalent in obese subjects who had been diagnosed with MS(60.9%) compared to obese subjects without (33.3%). Previous studies have elucidated an inverse association between serum 25(OH)D levels and MS[24]. A cross-sectional study of 101 healthy subjects living in urban areas found a risk of MS increases three-fold in subjects with low levels of vitamin D (23.37% vs. 8.3% P<0.001)[24]. Interestingly, after ameliorating lifestyle intervention in children obese /adults, adiponectin is the most predictive indicator for improving metabolic disorder, while changes in leptin were not related to positive metabolic outcomes[25]. However, the clustering of many unfavorable biomarkers International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2000-007X Vol. 2 Issue 11, November - 2018, Pages: 7-12  10 strongly requires early intervention not only in childhood obesity, but also in normal weight of subjects whose feature appear the risk. The underlying mechanisms of the association between 25(OH)D status and dyslipidaemia are poorly understood. Previous studies have demonstrated that being either overweight/ obese was strongly associated with dyslipidaemia (elevated TG and lower HDL-C) in AsianIndian adolescents living in urban area[26]. In the third National Health and Nutrition Examination Survey[26], adults whose 25(OH)D level was in the lowest quartile had the highest risk of elevated serum TG levels (≥150 mg/dl); this demonstrates that the health dangers of low vitamin D levels. Similarly, in obese subjects, 25(OH)D levels below 50 nmol/l were associated with lower HDL-C and high TG levels[27]. In the present study, it was observed that the level of 25(OH)D was positively correlated with HDL‐C (P< 0.01) and negatively correlated with TG levels and LDL-C (P<0.05). The female students in our study who had been diagnosed with MS had significantly elevated levels of TC, LDL‐C, TG and BP, and significantly reduced levels of HDL‐C compared to those without MS. Several epidemiological studies found that serum 25(OH)D levels to be negatively associated with BMI[28,29]; excessive weight is a major component of MS, which may be attributed to lower 25(OH)D levels. However, in a cross-sectional study conducted on children, it was found that there is a negative correlation between 25(OH)D and BMI, FBG, LDL-C and TG, and positive correlation with HDL-C (P<0.01)[29]. Insulin resistance is strongly associated with obesity and type-2 diabetes, hypertension, hyperlipidaemia and CVD[30]. There is evidence from both clinical and nonclinical studies that glucose homeostasis might affect the level of vitamin D[30]. In pervious study that focussed on pancreatic β-cells and the effect of vitamin D receptors, it was found that glucose intolerance, impaired synthesis and secretion of insulin, as well as an increased risk of type-2 diabetes, may be affected by insufficient 25(OH)D levels[31]. Peterson et al., found that vitamin D deficiency is associated with different metabolic disorders, and the authors concluded that low levels of vitamin D is a risk factor for MS[31]. Our findings illustrated that significant increased odds ratio between high levels of TC, TG and LDL-C in subjects that had serum 25(OH)D levels below 20 ng/ml when compared to subjects that had normal serum 25(OH)D levels. The lower levels of 25(OH)D may be attributed to poor dietary intake of vitamin D as well as insufficient exposure to sunlight, despite the strong natural light of Saudi Arabia. Considering the associations between MS and different predisposing factors, the finding found that obesity was the strongest predisposing risk factor for MS (). The second strongest predisposing risk factor for MS was abdominal obesity (). Unsurprisingly, WC, which is typically used as a surrogate measure of abdominal obesity, is the main criteria when determining MS risk. We also, found that the hypertension to be a strong risk factor for MS (); this similar with a study by Co et al who reported that hypertension (SBP & DBP) was the strongest predisposing risk factor with MS [32] . Previous studies of children living in urban areas have demonstrated that obesity is a major risk factor in the development of childhood hypertension[33]. In addition, we found that lifestyle is a risk factor for MS, with OR of 2.87. previous scientists indicated that regular physical activity and eating healthy diet have positive influence on health status, reducing the risk of obesity and thus reducing the risk of cardiac disease[29]. While elevated blood lipid levels increase the risk of hypertension, increasing physical activity lowers that risk; this is because exercise increases energy requirements and decreases fat deposition[34]. Bombak [35] found the prevalence of obesity to be increased by eating calorie dense food and failing to take adequate exercise While MS can be treated, in part, pharmacologically, the most important strategy for reducing the risk of MS and heart disease is to make lifestyle changes that promote physical activity and reduce excess weight. An analyses of macronutrients showed that the consumption of carbohydrates and sugar were significantly higher in subjects with MS compared to those without MS, Whereas subjects with MS consumed less dietary fibre than without MS. Rapid changes in contemporary lifestyle habits can be seen in Saudi Arabia that are contributing to (i) increased consumption of foods that are high in carbohydrates and sugars, and (ii) lack of adequate physical activity; the combined result of these lifestyle changes is an increase the prevalence of MS in the Saudi Arabian population[36]. These results are consistent with studies that found sedentary lifestyle and poor dietary habits to be important predictors for development of MS[36]. 5. CONCLUSION In our study, it suggested that low level of adiponectin was strongly correlated with low 25(OH)D levels. Also, the prevalence of MS tends to increase with the high occurrence rate of low circulating 25(OH)D levels that is, known cause poor glycemic control. This relationship is unclear and may be a sign of future prediction of cardiovascular outcomes. Further studies are needed in the young population who are overweight/obese to assess the relationship between circulating adiponectin levels, low 25(OH)D and IR for adverse cardiovascular and metabolic outcomes. We suggest requiring strategies efforts to prevent the tendency of deficiency and should be improved in early and middle age by increasing outdoor physical activity and by strengthening dietary vitamin D in the diet part of the Saudi diet. 6. DISCLOSURE STATEMENT The authors report that they have no conflicts of interest. International Journal of Academic Health and Medical Research (IJAHMR) ISSN: 2000-007X Vol. 2 Issue 11, November - 2018, Pages: 7-12  11 REFERENCES 1. Bassil D, Rahme M, Hoteit M, Fuleihan GE-H. Hypovitaminosis D in the Middle East and North Africa: Prevalence, risk factors and impact on outcomes. Dermato-endocrin. 2013; 5(2):274-298. 2. Cheng S, Massaro JM, Fox CS, Larson MG, Keyes MJ, McCabe EL, et al. Adiposity, cardiometabolic risk, and vitamin D status: the Framingham Heart Study. Diabetes 2010; 59:242-248. 3. Pramyothin P, Biancuzzo RM, Lu Z, Hess DT, Apovian CM, Holick MF. Vitamin D in adipose tissue and serum 25-Hydroxyvitamin D after roux-en-Y gastric bypass. Obesity 2011; 19:2228-2234. Doi: 10.1038/oby.2011.170. 4. Pittas AG, Chung M, Trikalinos T, Mitri J, Brendel M, Patel K, et al, Systematic review: vitamin D and cardiometabolic outcomes. Ann Int Med. 2010; 152(5):307-314. 5. Fung GJ, Steffen LM, Zhou X, Harnack L, Tang W, Lutsey PL, et al, Vitamin D intake is inversely related to risk of developing metabolic syndrome in African American and white men and women over 20 y: The Coronary Artery Risk Development in Young Adults study. Amer J Clin Nutr. 2012; 96(1):24-29. 6. Kayaniyil S, Vieth R, Retnakaran R, Knigh, JA, Qi Y, Gerstein HC, et al. Association of Vitamin D With Insulin Resistance and β-Cell Dysfunction in Subjects at Risk for Type 2 Diabetes. Diabetes Care. 2010; 33:137981. 7. Wolfson N, Goldberg Y, Shargorodsky M. Adiponectin and vascular properties in obese patients: Is it a novel biomarker of early atherosclerosis? Int J Obesity. 2009; 3: 553-558. 8. Jéquier E. Leptin signaling, adiposity, and energy balance. Lipids and Insulin Resistance: The Role of Fatty Acid Metabolism and Fuel Partitioning," Ann New York Academy Sci. 2002; 967: 379-388. 9. Salehpour A, Shidfar F, Hosseinpanah F, Vafa M, Razaghi M, Hoshiarrad A, et al, Vitamin D3 and the risk of CVD in overweight and obese women: a randomised controlled trial. Br J Nutr. 2012; 108(10):1866-1873 10. Trumbo P, Schlicker S, Yates AA, Poos M. Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein and amino acids. J Amer Diet Assoc. 2002; 102(11):1621-1630. 11. Hambidge KM. Micronutrient bioavailability: Dietary Reference Intakes and a future perspective. Amerj Clin Nutr.2010; 91(5):1430S-1432S. 12. Woo JG. Using body mass index z‐score among severely obese adolescents: a cautionary note. Pediat Obes 2009; 4(4):405-410. 13. Pi-Sunyer, X. Clinical guidelines on the identification, evaluation and treatment of overweight and obesity in adults-the evidence report. Obes Res. 1998; 6:51S-210S. 14. Nagy E, Vicente-Rodriguez G, Manios Y, Béghin L, Iliescu C, Censi L, et al, Harmonization process and reliability assessment of anthropometric measurements in a multicenter study in adolescents. Intl J Obes. 2008; 32(S5): S58. 15. National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents. Pediat. 2004; 4 (2 Suppl), 555576. 16. Zimmet P1, Alberti KG, Kaufman F, Tajima N, Silink M, Arslanian S. et al.. The metabolic syndrome in children and adolescents - an idfconsensus report. Pediat Diab.2007; 8: 299-306. 17. Matthews D, Hosker J, Rudenski A, Naylor B, Treacher D, Turner R. Homeostasis model assessment: insulin resistance and β-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia.1985; 28(7):412-419. 18. Holick MF, Siris ES, Binkley N, Beard MK, Khan A, Katzer JT, et al, Prevalence of vitamin D inadequacy among postmenopausal North American women receiving osteoporosis therapy. J Clinl Endocrin & Metab. 2005; 90(6):3215-3224. 19. Ashraf AP, Alvarez JA, Gower BA, Saenz KH, Mccormick KL. Associations of Serum 25‐ Hydroxyvitamin D and Components of the Metabolic Syndrome in Obese Adolescent Females. Obesity 2011; 19(11):2214-2221 20. Jackson JL, Judd SE, Panwar B, Howard VJ, Wadley VG, Jenny NS, et al. Associations of 25-hydroxyvitamin D with markers of inflammation, insulin resistance and obesity in black and white community-dwelling adults. 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Abstract— Polystyrene/waste tires composites were prepared in this study by incorporating shredded waste tires into polydisperse polystyrene in a melt-mixing method. The dynamic mechanical properties of PS and PS/composite have been evaluated and compared. These properties were studied using ARES-Rheometer under nitrogen atmosphere in parallel plate geometry with diameter 8 mm. The measurements are carried out over a wide range of temperatures ranged from 120°C to 220°C and frequencies from 100 to 0.1 radians per second. The shear creep stress J(t) and loss factor were studied and compared with those of unfilled PS. The dynamic mechanical properties and stability at elevated temperatures were found to increase with the addition of waste tires to PS as confirmed by the results.
          From the results, the value of  J(t) modulus for PS/waste tire is higher than this for the original material of PS. The incorporation of the rubber to the PS changes the value of J(t) at 0.001 second from 5.610-6 to 3.710-6 Pa-1 for PS and PS/waste tire, respectively and this difference increases with time. This confirmed that PS/waste tire composite exhibits  higher stability at 180°C for a long time than the original unfilled PS. At frequency  = 6.7102 radians/s , the value of tan increases about 20% by the incorporation of the rubber filler, due to the increase in the G'' modulus particularly at low frequencies in the flow regime.

Philosophy

International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 4, April - 2018, Pages: 29-32  29 The Shear Creep Stress and Loss Factor of Polystyrene/ Waste Tires Composites Mahmoud Abdel-Halim Abdel-Goad Chemical Engineering Dept., Faculty of Engineering, Minia University, Egypt (E-mail:) Abstract- Polystyrene/waste tires composites were prepared in this study by incorporating shredded waste tires into polydisperse polystyrene in a melt-mixing method. The dynamic mechanical properties of PS and PS/composite have been evaluated and compared. These properties were studied using ARES-Rheometer under nitrogen atmosphere in parallel plate geometry with diameter 8 mm. The measurements are carried out over a wide range of temperatures ranged from 120°C to 220°C and frequencies from 100 to 0.1 radians per second. The shear creep stress J(t) and loss factor were studied and compared with those of unfilled PS. The dynamic mechanical properties and stability at elevated temperatures were found to increase with the addition of waste tires to PS as confirmed by the results. From the results, the value of J(t) modulus for PS/waste tire is higher than this for the original material of PS. The incorporation of the rubber to the PS changes the value of J(t) at 0.001 second from 5.610-6 to 3.710-6 Pa-1 for PS and PS/waste tire, respectively and this difference increases with time. This confirmed that PS/waste tire composite exhibits higher stability at 180°C for a long time than the original unfilled PS. At frequency  = 6.7102 radians/s , the value of tan increases about 20% by the incorporation of the rubber filler, due to the increase in the G'' modulus particularly at low frequencies in the flow regime. Keywords: Polystyrene/waste tires composites, Shear creep stress, Loss factor. 1. INTRODUCTION Disposal of waste rubber material is a global problem, and used tires constitute the largest volume of scrap rubber. Recycling of waste tires is essential due to economic and environmental reasons. Utilization of ground waste rubber has been reviewed recently. Finely ground waste tire rubber has been used as filler in rubbers and in thermoplastics [1]. Physical properties and processability are reported to be adversely affected when large volumes of waste rubber is added to a rubber compound. Dynamic mechanical analysis over a wide range of temperature and frequencies permits the determination of the viscoelastic behavior of molten polymers and, in particular, the study the glass transition of reinforced composites. Therefore, the investigations of the polymer composites using the mechanical and the dynamic mechanical analysis are becoming of great interesting [2-17]. The main objective of this work was to study in details the shear creep stress and loss factor of polystyrene/waste tire composites compared to the original material of unfilled polystyrene. 2. EXPERIMENTAL PART 2.1 Samples preparation and characterization PS/waste tires composite was prepared by introducing waste tires into commercial PS with molecular weight about 2107 g/mol. The waste tires were shredded into small particles sizes of about 2 mm. The mixture of PS and 12 wt % shredded tires are dry mixed by hand-mixing for around half an hour and heated at 300°C for 2 hours. Followed by preparation the samples of filled and unfilled PS for the rheological measurements under compression-mold at 190°C for 3 hours and 15 bars in a disc form with diameter 8 mm and thickness 2.2 mm. 2.2 Measurements The dynamic mechanical measurements were performed for PS and PS composite by using an ARES-Rheometer (Rheometric Scientific). The rheometer was operated in the dynamic mode on the plate-plate geometry of 8mm diameter and about 2 mm gap. The gap size changes with the temperatures and is read electronically and allows absolute moduli to be determined. The measurements were performed in this study for the samples under nitrogen atmosphere, strain amplitude 1%, over temperature ranged from 120 to 220°C and angular frequency ( ) varied from 10 2 to10 -1 radian/s. International Journal of Engineering and Information Systems (IJEAIS) ISSN: 2000-000X Vol. 2 Issue 4, April - 2018, Pages: 29-32  30 3. RESULTS AND DISCUSSION In this study the experiments data which measured over a wide range of the temperature are shifted into a single log -log curve at a reference temperature T0 by using of the time-temperature superposition principle which described by Williams-LandelFerry [19] as, log aT = -C1 (T-T0) /(C2+(T-T0)).Where aT is the horizontal shift factor and constants C1 and C2 are material specific. aT shifts the data obtained at different temperatures along the log frequency,  axis and in vertical direction is given purely by bT (bT = 00/ TT  [20] ). Where  is the material density. The shear creep stress J(t) is plotted as a function of time in Figure 1. As shown in this Figure J(t) increases with time by a slop about 0.4 up to 0.01 second followed by a deviation in the slop to be about 0.6 in the case of filled PS and about 0.9 in the case of unfilled PS. This due to the relaxation of the polymer molecules with time at 180°C. This difference in the slop between filled and unfilled PS at long time means PS composite is more stable at high temperature for a long time than unfilled PS. At long time zone, the value of J(t) modulus for PS/waste tire is higher than this for the original material of PS as shown in Figure 1. In this Figure, the incorporation of the rubber to the PS changes the value of J(t) at 0.001 second from 5.610 -6 to 3.710 -6 Pa -1 for PS and PS/waste tire, respectively and this difference increases with time as shown in Figure 1. This confirmed that PS/waste tire composite exhibits higher stability at 180°C for a long time than the original unfilled PS. The relative degree of viscous to elastic dissipation of the material is indicated by tan  (Fig.2). Tan is plotted in Figure 2 versus frequency for PS and PS/rubber. tan  is related to the loss modulus by , tan  = G''/G' , therefore, tan  is called the loss factor. Figure 8 shows decreases of tan at the intermediate frequencies-branch and reach the minimum value at about  = 8.6102 radians/s, then increases again. This minimum in tan  is against to the entanglements zone in G'' and G' and it is associated to the high elasticity of the material at this regime which leads to a minimum in the loss energy per a cycle of the deformations. Again Figure 8 shows an increase in tan for filled PS compared to unfilled PS at low frequency. At  = 6.7102 radians/s , the value of tan increases about 20% by the incorporation of the rubber filler, due to the increase in the G'' modulus particularly at low frequencies in the flow regime. 4. CONCLUSION In this study the PS/waste tires composite were prepared. The dynamic mechanical properties for PS composite are evaluated and compared to those of the original material of unfilled PS. These properties are determined by ARES Rheometer under nitrogen atmosphere in parallel plate geometry with diameter 8 mm. The measurements are carried out over a wide range of temperatures, ranged from 120°C to 220°C and frequencies from 100 to 0.1 radians per second. From the results, the value of J(t) modulus for PS/waste tire is higher than this for the original material of PS. The incorporation of the rubber to the PS changes the value of J(t) at 0.001 second from 5.610 -6 to 3.710 -6 Pa -1 for PS and PS/waste tire, respectively and this difference increases with time. This confirmed that PS/waste tire composite exhibits higher stability at 180°C for a long time than the original unfilled PS. At frequency  = 6.7102 radians/s , the value of tan increases about 20% by the incorporation of the rubber filler, due to the increase in the G'' modulus particularly at low frequencies in the flow regime. 5. ACKNOWLEDGMENTS The financial support by the International Bureau in Germany, helpful discussions of Dr. W.Pyckhout -Hintzen at research center Juelich, Germany are greatly acknowledged. REFERENCES 1. 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