bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of the atmospheric plasma treatment parameters on jute fabric: The effect on mechanical properties of jute fabric/polyester composites
Authors: Demir Asli , Seki Yoldas , Bozaci Ebru , Sarikanat Mehmet , Erden Seckin , Sever Kutlay , Ozdogan Esen
Published: February 2011

The effect of atmospheric air plasma treatment of jute fabrics on the mechanical properties of jute fabric reinforced polyester composites was investigated. The jute fabrics were subjected to different plasma powers (60, 90, and 120 W) for the exposure times of 1, 3, and 6 min. The effects of plasma powers and exposure times on interlaminar shear strength, tensile strength, and flexural strength of polyester based composites were evaluated. The greatest ILSS increase was about 171% at plasma power of 120 W and exposure time of 6 min. It is inferred that atmospheric air plasma treatment improves the interfacial adhesion between the jute fiber and polyester. This result was also confirmed by scanning electron microscopy observations of the fractured surfaces of the composites. The greatest tensile strength and flexural strength values were determined at 120 W for 1 min and at 60 W for 3 min, respectively. Moreover, it can be said that atmospheric air plasma treatment of jute fibers at longer exposure times (6 min) made a detrimental effect on tensile and flexural properties of jute‐reinforced polyester composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Addition of 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide to improve the thermal stability of regenerated cellulose
Authors: Mahadeva Suresha K. , Kim Jaehwan
Published: February 2011

This article reports the influence of 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide (BMITFSI) addition on the thermal and mechanical properties of regenerated cellulose. Scanning electron microscopy, Young's modulus values, thermogravimetric analysis, glass‐transition temperature values, and ultraviolet–visible spectroscopy were used to assess the effect of BMITFSI addition on the properties of regenerated cellulose. The addition of a room‐temperature ionic liquid, BMITFSI, during the dissolution of cellulose was found to enhance the thermal stability of regenerated cellulose. Compared to other reported plasticizers for regenerated cellulose, such as glycerol, glycols, water, mineral oil, and α‐monoglycerides, the low vapor pressure of BMITFSI led to a long performance with the least evaporation or leaching. In addition, the immiscible nature of BMITFSI in water and its stability against moisture made BMITFSI an effective plasticizer for regenerated cellulose over a broad range of surrounding humidities and temperature conditions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis and properties of multihydroxy soybean oil from soybean oil and polymeric methylene‐diphenyl‐ 4,4′‐diisocyanate/multihydroxy soybean oil polyurethane adhesive to wood
Authors: Choi Seung Woo , Wan Seo Dong , Don Lim Young , Gi Jeong Young , Islam Mollah M. S. , Park Heon , Whan Hong Tae , Gi Kim Whan
Published: February 2011

The reactive multihydroxy soybean oil (MHSBO) was synthesized from epoxidized soybean oil (ESBO). The ESBO was reacted with ethylene glycol to obtain MHSBO having high functionality. This study investigated a feasibility to prepare wood adhesive through the reaction of polymeric methylene‐diphenyl‐4,4′‐diisocyanate (pMDI) with MHSBO. Different polyurethane adhesives were prepared with a variety of equivalent mole ratios (eq. mole ratios) of MHSBO to pMDI. The chemical reactions of adhesives were analyzed using 1H NMR and Fourier transform infrared (FTIR), and their thermal studies were investigated by DSC and TGA. The MHSBO/pMDI resins (3 : 1 and 2 : 1 eq. mole ratios) showed endothermic peaks, whereas the MHSBO/pMDI resins (1 : 2 and 1 : 3 eq. mole ratios) showed exothermic peaks. The best adhesion strength was found when plywood was bonded with the adhesive of a eq. mole ratio of 2 : 1 (MHSBO : pMDI). These results indicated that the bond strength was not related to the reactivity obtained from the FTIR spectra. But it was explained that the adhesion strength increased as the residual NCO groups in the adhesive reacted with the hydroxy groups of wood during the manufacturing of plywood. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis and characterization of hydrogel‐silver nanoparticle‐curcumin composites for wound dressing and antibacterial application
Authors: Varaprasad K. , Mohan Y. Murali , Vimala K. , Mohana Raju K.
Published: February 2011

Hydrogel silver nanocomposites are found to be excellent materials for antibacterial applications. To enhance their applicability novel hydrogel‐silver nanoparticle‐curcumin composites have been developed. For developing, these composites, the hydrogel matrices are synthesized first by polymerizing acrylamide in the presence of poly(vinyl sulfonic acid sodium salt) and a trifunctional crosslinker (2,4,6‐triallyloxy 1,3,5‐triazine, TA) using redox initiating system (ammonium persulphate/TMEDA). Silver nanoparticles are generated throughout the hydrogel networks using in situ method by incorporating the silver ions and subsequent reduction with sodium borohydride. Curcumin loading into hydrogel‐silver nanoparticles composite is achieved by diffusion mechanism. A series of hydrogel‐silver nanoparticle‐curcumin composites are developed and are characterized by using Fourier transform infrared (FTIR) and UV–visible (UV–vis) spectroscopy, X‐ray diffraction, thermal analyses, as well as scanning and transmission electron microscopic (SEM/TEM) methods. An interesting arrangement of silver nanoparticles i.e., a shining sun shape (ball) (∼ 5 nm) with apparent smaller grown nanoparticles (∼ 1 nm) is observed by TEM. The curcumin loading and release characteristics are performed for various hydrogel composite systems. A comparative antimicrobial study is performed for hydrogel‐silver nanocomposites and hydrogel‐silver nanoparticle‐curcumin composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermal, kinetic, and mechanical properties of glycerol‐plasticized wheat gluten
Authors: Pan Yongkang , Wang Xuehong , Yuan Qiaolong
Published: February 2011

Glycerol‐plasticized wheat gluten was prepared by mixing in an internal mixer equipped with sigma rotors, and then thermally compression‐molded to form a sheet for crosslinking and tensile tests. Referring to rubber vulcanization process, rotorless curemeter was applied to test the vulcanization characteristic parameters of the molded round samples, which could be used to calculate the activation energy and reaction rate of crosslinking occurring in wheat gluten when heated. Vulcanizing curves obtained show that the optimum temperature for processing glycerol‐plasticized wheat gluten is 150°C, and that activation energy and reaction rate of crosslinking in wheat gluten plasticized with 20 wt % glycerol reach minimum and maximum values, respectively. In addition, glycerol content, plasticizing time, and temperature have significant effects on the mechanical properties of thermomolded wheat gluten plastics. The factors are closely related to the establishment of a covalent network resulting from the formation and rearrangement of disulfide bridges in wheat gluten. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Thermoplastic natural rubber based on polyamide‐12: Influence of blending technique and type of rubber on temperature scanning stress relaxation and other related properties
Authors: Narathichat M. , Kummerlöwe C. , Vennemann N. , Nakason C.
Published: February 2011

Thermoplastic natural rubber based on polyamide‐12 (PA‐12) blend was prepared by melt blending technique. Influence of blending techniques (i.e., simple blend and dynamic vulcanization) and types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends were investigated. It was found that the simple blends with the proportion of rubber ∼ 60 wt % exhibited cocontinuous phase structure while the dynamically cured blends showed dispersed morphology. Furthermore, the blend of ENR exhibited superior mechanical properties, stress relaxation behavior, and fine grain morphology than those of the blend of the unmodified NR. This is attributed to chemical interaction between oxirane groups in ENR molecules and polar functional groups in PA‐12 molecules which caused higher interfacial adhesion. It was also found that the dynamic vulcanization caused enhancement of strength and hardness properties. Temperature scanning stress relaxation measurement revealed improvement of stress relaxation properties and thermal resistance of the dynamically cured ENR/PA‐12 blend. This is attributed to synergistic effects of dynamic vulcanization of ENR and chemical reaction of the ENR and PA‐12 molecules. Furthermore, the dynamically cured ENR/PA‐12 blend exhibited smaller rubber particles dispersed in the PA‐12 matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Migration of novel epoxidized neem oil as plasticizer from PVC: Experimental design approach
Authors: Gamage Padmasiri K. , Farid Ahmed S.
Published: February 2011

Migration behavior of epoxidized neem oil (ENO) from poly(vinyl chloride) (PVC) plasticized with ENO to acrylo nitrile butadiene rubber (NBR) was investigated. Central composite rotatable design (CCRD) for three variables at five levels was chosen as the experimental design. Concentration of Neem oil in PVC matrix, acrylo nitrile (ACN%) content in NBR matrix, and peroxide content used in NBR formulation were selected as three independent variables. Other parameters pertinent to migration phenomena such as partition coefficient, activation energies, rate constants, and diffusion coefficients were evaluated and these properties were fitted to a distinctive response equation generated by CCRD. Proposed response equations for most parameters were considered as having sufficient explanatory power and “good fit” in the statistical sense. Partitioning of ENO as a plasticizer between PVC and NBR follows first order equilibrium kinetics, and the forward reaction is found to be endothermic. The percentage migration of plasticizer at 296 K at equilibrium is well below 25% for the majority of cases irrespective of other pertinent factors. Parameters such as forward, backward, and overall rate constants and their respective activation energies and enthalpy change related to the partitioning phenomenon are influenced to different degrees by plasticizer concentration in PVC, ACN% in NBR and crosslink density of NBR. The influence caused by plasticizer concentration and ACN% was found to be the most significant. Diffusion of plasticizer through PVC matrix is the rate determining step for the overall migration process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Morphology of silver particulate films deposited on softened polymer blends of polystyrene and poly (4‐vinylpyridine)
Authors: Parashar Pratima
Published: February 2011

Results of the morphological studies of silver particulate films deposited at a rate of 0.4 nm/s on polymeric blends of polystyrene (PS) and poly (4‐vinylpyridine) (P4VP) held at a temperature 457 K by evaporation in a vacuum of 8 × 10−6 Torr are reported here. The morphology of silver particulate films was characterized by their size, size distribution, shape and interparticle separation. It has been observed that morphology depends on the composition of polymer matrix and the amount of silver deposited. The red shift in the plasmon resonance was observed with the increasing amount of P4VP in the blends in comparison to the pure PS. This indicates the modification in the silver particulate films deposited on the PS/P4VP blends. Scanning electron microscopy (SEM) was used to study the change in morphology of the silver nanoparticles and was correlated with the optical properties of silver particulate films on PS/P4VP blends. The silver nanoparticles deposited on the thin layers of polymer blends exhibit smaller size with narrower dispersion and wider size distribution due to blending of P4VP with PS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of polypropylene/serpentine composites
Authors: Tan Semra , Tincer Teoman
Published: February 2011

Composites of serpentine and polypropylene (PP) were prepared by twin‐screw extrusion. Serpentine was collected as rocks from the Ankara–Beynam region and ground into powder with an average particle size of about 3 μm for composite production. Both as‐received (rock) and powdered serpentine were characterized. A silane coupling agent (SCA), γ‐aminopropyl triethoxy silane, was used for the surface treatment of serpentine. Mechanical properties of the composites were measured in terms of impact strength, elastic modulus, stress at yield, stress at break, and percentage strain at break. The addition of serpentine was found to have a profound effect on the reinforcement of the PP matrix. Because of the stronger interactions at the interphase induced by SCA treatment, mechanical properties were improved further in comparison with the untreated composites. Similar thermal and morphological behaviors were recorded for the composites with and without surface treatment. Thermal studies showed an increase in both melting temperature and percentage crystallinity of the composites. Scanning electron microscopy analysis revealed that homogeneous distribution of filler was observed at low filler contents, but a certain extent of agglomeration was also seen at high filler loadings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Capacitance properties of graphite oxide/poly(3,4‐ethylene dioxythiophene) composites
Authors: Han Yongqin , Ding Bing , Tong Hao , Zhang Xiaogang
Published: February 2011

Poly(3,4‐ethylene dioxythiophene) (PEDOT) and graphite oxide (GO)/PEDOT composites (GPTs) doped with poly(sodium styrene sulfate) (PSS) were synthesized by in situ polymerization in aqueous media. The electrochemical capacitance performances of GO, PEDOT–PSS, and GPTs as electrode materials were investigated. The GPTs had a higher specific capacitance of 108 F/g than either composite constituent (11 F/g for GO and 87 F/g for PEDOT–PSS); this was attributable to its high electrical conductivity and the layer‐within/on‐layer composite structure. Such an increase demonstrated that the synergistic combination of GO and PEDOT–PSS had advantages over the sum of the individual components. On the basis of cycle‐life tests, the capacitance retention of about 78% for the GPTs compared with that of 66% for PEDOT–PSS after 1200 cycles suggested a high cycle stability of the GPTs and its potential as an electrode material for supercapacitor applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Mechanical properties, morphology, and crystal structure of polypropylene/chemically modified attapulgite nanocomposites
Authors: Chen Jianjun , Chen Jinyao , Zhu Shipeng , Cao Ya , Li Huilin
Published: February 2011

Atactic polypropylene (aPP) was chemically grafted onto attapulgite (ATP) via the bridge linking of a polymerizable cationic surfactant and poly(octadecyl acrylate) in the presence of ultrasonic oscillation and dicumyl peroxide, and then, the modified ATP was added to a polypropylene (PP) matrix to obtain PP nanocomposites by melt blending. The results of Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy confirmed that aPP and poly(octadecyl acrylate) were chemically grafted onto ATP through a graft polymerization reaction. The results of the mechanical properties testing showed that the addition of modified ATP improved the toughness and strength of PP remarkably. The dynamic mechanical analysis indicated that the modified ATP significantly increased the storage modulus and decreased the glass‐transition temperature of PP. The results of scanning electron microscopy and transmission electron microscopy showed that the modified ATP was uniformly dispersed into the PP matrix as crystal needles; this proved the presence of strong interactions between modified ATP and PP. The crystal structure analysis revealed that the β‐form crystalline of PP was formed within the modified ATP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Adhesion of polyethylene plates photografted with methacrylic acid and acrylic acid with enzymatically modified chitosan solutions and X‐ray photoelectron spectroscopy analysis of failed surfaces
Authors: Yamagami Sho , Kanama Wataru , Yamada Kazunori
Published: February 2011

An investigation was carried out on the application of dilute chitosan solutions modified by a tyrosinase‐catalyzed reaction with 3,4‐dihydroxyphenetylamine (dopamine) to the adhesion of low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE) plates photografted with carboxyl‐group‐containing hydrophilic monomers, such as methacrylic acid (MAA) and acrylic acid (AA). In the case where photografting was carried out at lower monomer concentrations or at lower temperatures, the adhesive strength sharply increased with lower grafted amounts. A sharp increase in the adhesive strength was found to be due to the formation of shorter grafted polymer chains at lower monomer concentrations and/or the restriction of the location of grafting to the outer surface region at lower temperatures. In addition, the adhesive strength also sharply increased at even lower grafted amounts for photografting onto the HDPE plates and/or that of AA because the location of grafting was restricted to the outer surface region. For the AA‐grafted LDPE and HDPE plates, substrate breaking was observed. This was attributed to the coverage of the substrate surfaces with grafted poly(acrylic acid) chains at lower grafted amounts and a high water absorptivity of the grafted layer. X‐ray photoelectron spectroscopy (XPS) analysis of the grafted LDPE plates incubated in a dopamine solution containing tyrosinase suggested that the increase in the adhesive strength was caused by the penetration of enzymatically modified chitosan solutions in the grafted layers and the subsequent reaction of quinone derivatives enzymatically generated with grafted polymer chains. In addition, the surface analysis of the failed surfaces by XPS showed that as the adhesive strength increased, the location of failure was shifted from the interface between the layers mixed with enzymatically modified chitosan materials and grafted polymer chains to the inside the grafted layer containing enzymatically modified chitosan materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Nanoindentation of isotactic polypropylene: Correlations between hardness, yield stress, and modulus on the local and global scales
Authors: Lesan‐Khosh R. , Bagheri R. , Asgari S.
Published: February 2011

The correlations between the hardness, yield stress, and modulus of elasticity of isotactic polypropylene (iPP) were evaluated on the local and global scales. Nanoindentation and traditional macromechanical tests were incorporated for this purpose. Thus, local and global mechanical properties were measured at various temperatures and strain rates. A certain relation was found between the local and global mechanical properties. Moreover, Johnson's model (developed according to the expanding cavity model) was also evaluated at various temperatures and strain rates. The Johnson model was valid only for the yield stresses obtained by nanoindentation and compressive tests and also the elastic modulus obtained via nanoindentation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
New hyperbranched polymers for membranes of high‐temperature polymer electrolyte membrane fuel cells: Determination of the crystal structure and free‐volume size
Authors: Bhadra Sambhu , Ranganathaiah C. , Kim Nam Hoon , Kim Seong‐Il , Lee Joong Hee
Published: February 2011

The key requirements for a membrane in polymer electrolyte membrane fuel cells are a high ion conductivity, mechanical strength, and barrier properties. We reported earlier on two new promising hyperbranched polymers: poly(benzimidazole‐co‐aniline) (PBIANI), with a uniform rectangular net structure, and poly(benzimidazole‐co‐benzene) (PBIB), with a honeycomb structure. Both polymers exhibit a high ion conductivity and mechanical strength and have proven themselves suitable for the membranes of high‐temperature polymer electrolyte membrane fuel cells. In this article, we deal with the determination of crystal structure and free‐volume cell/microvoid size of these two polymers. Both PBIANI and PBIB had the same d‐spacing (3.5 Å). However, the percentage of crystallinity was higher and the crystallite size was larger for PBIB. The kinetic diameters of hydrogen (2.89 Å), oxygen (3.46 Å), water (2.60 Å), and methanol (∼ 4.00 Å) were much larger than the free‐volume cell/microvoid diameters of PBIANI (1.81 Å) and PBIB (1.96 Å) but much smaller than those of Nafion 115 (6.54 Å) and polybenzimidazole (PBI) (∼ 6.00 Å). The very small free‐volume sizes of PBIANI and PBIB ensured good barrier properties against hydrogen, oxygen, water, and methanol, unlike those of Nafion‐ and PBI‐type membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Hemp‐fiber‐reinforced unsaturated polyester composites: Optimization of processing and improvement of interfacial adhesion
Authors: Qiu R. , Ren X. , Fifield L. S. , Simmons K. L. , Li K.
Published: February 2011

The processing variables for making hemp‐fiber‐reinforced unsaturated polyester (UPE) composites were optimized through orthogonal experiments. It was found that the usage of initiator, methyl ethyl ketone peroxide, had the most significant effect on the tensile strength of the composites. The treatment of hemp fibers with a combination of 1,6‐diisocyanatohexane (DIH) and 2‐hydroxyethyl acrylate (HEA) significantly increased tensile strength, flexural modulus of rupture, and flexural modulus of elasticity, and water resistance of the resulting hemp‐UPE composites. FTIR spectra revealed that DIH and HEA were covalently bonded to hemp fibers. Scanning electron microscopy graphs of the fractured hemp‐UPE composites demonstrated that treatment of hemp fibers with a combination of DIH and HEA greatly improved the interfacial adhesion between hemp fibers and UPE. The mechanism of improving the interfacial adhesion is proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Fabrication of poly(lactic acid) films with resveratrol and the diffusion of resveratrol into ethanol
Authors: Soto‐Valdez Herlinda , Auras Rafael , Peralta Elizabeth
Published: February 2011

Poly(94% L‐lactic acid) (PLA) films containing 0, 1, and 3 wt % resveratrol (PR0, PR1, and PR3) were extruded in a pilot‐plant scale blown‐extrusion machine. Yellow‐colored PLA films with reduced crystallinity were obtained, and the films absorbed UV‐visible light at 350–200 nm. The diffusion kinetics of resveratrol into ethanol at 9, 23, 33, and 43°C displayed Fick's behavior, and diffusion coefficients between 10−13 and 10−10 cm2/s were obtained. According to the Arrhenius equation, the energy of activation for the diffusion of resveratrol from PR1 and PR3 films was 175 and 177 kJ/mol, respectively. The temperature of diffusion had a stronger effect on the reduction of the weight average molecular weight of PLA than the processing conditions and the contact time with ethanol. However, diffusion of resveratrol was not affected by the degradation of PLA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation and characterization of crosslinked polymer beads with tunable pore morphology
Authors: Liu Qingquan , Li Yanlu , Shen Shaohua , Xiao Qiuguo , Chen Lijuan , Liao Bo , Ou Baoli , Ding Yue
Published: February 2011

Crosslinked polymer beads with tunable pore morphology were prepared by suspension polymerization of styrene (St) and divinylbenzene (DVB) with polypropylene in combination with toluene as co‐porogens. The effect of DVB content on the pore morphology was investigated by changing DVB amount in monomer mixture. The results indicated that the specific surface area, the total pore area, and the total pore volume increased with increasing DVB content of polymer beads. Moreover, high‐DVB concentration was favorable to produce more micropores and mesopores. At a given DVB concentration, the volume ratio of co‐porogen/DVB has significant impact on the pore morphology in crosslinked polymer beads. As the co‐porogen amount was increased, the specific surface area, the total pore area, and the total pore volume were dramatically increased, furthermore, the pore size distribution derived from Hg intrusion shifted toward macropore. Overall, the present article provided a novel route to prepare crosslinked polymer beads with tunable pore morphology. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Structure and properties of PP/POE/HDPE blends
Authors: Chen Yanhua , Ye Lin
Published: February 2011

This work was aimed to counteract the effect of ethylene‐α‐olefin copolymers (POE) by reinforcing the polypropylene (PP)/POE blends with high density polyethylene (HDPE) particles and, thus, achieved a balance between toughness and strength for the PP/POE/HDPE blends. The results showed that addition of HDPE resulted in an increasing wide stress plateau and more ductile fracture behavior. With the increase of HDPE content, the elongation at break of the blends increased rapidly without obvious decrease of yield strength and Young's modulus, and the notched izod impact strength of the blends can reach as high as 63 kJ/m2 at 20 wt % HDPE loading. The storage modulus of PP blends increased and the glass transition temperature of each component of the blends shifted close to each other when HDPE was added. The crystallization of HDPE phase led to an increase of the total crystallinity of the blend. With increasing HDPE content, the dispersed POE particle size was obviously decreased, and the interparticle distance was effectively reduced and the blend rearranged into much more and obvious core‐shell structure. The fracture surface also changed from irregular striation to the regularly distant striations, displaying much obvious character of tough fracture. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Polymorphism in a metallocenic isotactic polypropylene as revealed by means of FTIR spectroscopy: Influence of the processing conditions
Authors: Lorenzo V. , Polo‐Corpa M.J. , Pérez E. , Benavente R. , de la Orden M.U. , Martínez‐Urreaga J.
Published: February 2011

The polymorphic structure in specimens of a metallocenic isotactic polypropylene, processed under different conditions, has been studied by means of wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The proportions of the different polymorphs have been evaluated, and the influence of the processing parameters (nucleating agents, cooling rate, and nature of the surface of the molds) has been analyzed. The combination of WAXS, DSC, and FTIR results confirms the adequacy of this last technique to obtain quantitative information about the competition between the crystalline phases of polypropylene. It has also been proved that the nature of the mold can enhance considerably the activity of beta‐nucleating agents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Methyl silsesquioxane/cyanate ester resin organic–inorganic hybrids with low dielectric constant
Authors: Zhang Zengping , Pei Jianzhong , Liang Guozheng , Yuan Li
Published: February 2011

A kind of nonfunctional oligomeric silsesquioxane (SSQ), methyl silsesquioxane (Me‐SSQ), was used to modify cyanate ester (CE) resin in this article. First, Me‐SSQ was synthesized by the hydrolysis and condensation of methyltriethoxysilane. Then, a series of Me‐SSQ/CE hybrids containing 0, 1, 5, 10, and 20 wt % of Me‐SSQ were prepared. The effect of Me‐SSQ content on the reactivity, mechanical, dielectric, thermal, and hot/wet properties of materials was investigated. Fourier transform infrared spectroscopy was used to study the reactivity of hybrid CE resin systems, indicating that the addition of Me‐SSQ does not show significant effect on the conversion of CE. Mechanical and dielectric properties of the Me‐SSQ/CE hybrid materials were also studied. Impact strength of the Me‐SSQ/CE hybrids reaches its maximum value when Me‐SSQ content is 5 wt %. However, the flexural strength reaches the maximum value when Me‐SSQ content is 1 wt %. The Me‐SSQ/CE hybrid containing 20 wt % of Me‐SSQ shows a dielectric constant of 2.78, that is, much lower than the pure CE resin. At the same time, the dielectric loss of the Me‐SSQ/CE hybrids was slightly increased (tan δ < 0.006). Therefore, Me‐SSQ/CE hybrid is a promising candidate for high‐performance printed circuit board matrix materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Comparison of rheological properties of carbon nanotube/polycarbonate and carbon black/polycarbonate composites
Authors: Via Michael D. , Morrison Faith A. , King Julia A. , Caspary Jeffrey A. , Mills Owen P. , Bogucki Gregg R.
Published: February 2011

Conductive fillers are often added to insulating polymers to increase the composite conductivity. Adding fillers often increases the viscosity, which can make the material more difficult to process. In this study, 2–8 wt % multiwalled carbon nanotubes or 2–8 wt % carbon black were added to polycarbonate. The effects on composites' viscosities were studied with small‐amplitude oscillatory shear and capillary rheometer testing. The addition of carbon nanotubes and carbon black created yield‐stress materials with the yield‐stresses increasing with increased filler loadings. The addition of carbon black increased the steady‐shear viscosity of the composite at all shear rates for all loadings. The addition of the carbon nanotubes reduced the steady‐shear viscosity of the composite at high shear rates for all loadings. This is thought to be due to an internal lubrication of the flow (enhanced disentanglement) due to the presence of the carbon nanotubes. The lubrication effect saturates once 3 wt % carbon nanotubes has been reached. The observed rheological behavior of the carbon nanotube composites is markedly different than usually seen in filled systems. A yield‐stress‐modified Carreau‐Yasuda model was used to interpret the effects of carbon nanotube and carbon black fillers on carbon nanotube/polycarbonate and carbon black/polycarbonate composite viscosity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Dimedone and phenylazo dimedone chelates of europium as emitters in polymers
Authors: Seth Susannah , Aravindakshan K. K.
Published: February 2011

Transparent polymers when incorporated with strongly fluorescent europium chelates were found to be responding to excitation with UV radiation. In this work, two novel europium chelates have been synthesized using the β‐diketones dimedone and phenylazo dimedone along with 1,10‐phenanthroline. These chelates were characterized by elemental analyses, magnetic susceptibility measurements, UV, IR, and ESI mass spectral techniques. The chelates synthesized with metal : β‐diketone : 1,10‐phenanthroline ratio 1 : 3 : 1 were incorporated into polymer matrices. Four polymers, polyethylene vinyl acetate or acetate (EVA), polystyrene (PS), poly methyl methacryalate (PMMA), and polyethylene glycol (PEG) were used for the studies. All these, except the liquid oligomer PEG were cast into thin films. PEG was used as such for the studies. The photoluminescence spectra of the plain polymers were found to be having peaks very close to the absorption peaks of the polymers doped with europium chelate. This observation can be used in optical devices. Thermal analyses like TG/DTG/DTA of the polymer films were conducted to ascertain the thermal stability of the material. The SEM analyses of the films indicated a smooth surface with uniform distribution of the doped chelate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Mesua ferrea L. seed oil based highly branched polyester/epoxy blends and their nanocomposites
Authors: Konwar Uday , Das Gautam , Karak Niranjan
Published: February 2011

Mesua ferrea L. seed oil based highly branched polyester and epoxy resins blends were prepared by mechanical mixing at different weight ratios. The best performing blend was used as the matrix for the preparation of nanocomposites with different dose levels of organophilic montmorillonite (OMMT) nanoclay. The prepared nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Data resulting from the mechanical and thermal studies of the blends and nanocomposites indicated improvements in the tensile strength and thermal stability to appreciable extents for the nanocomposites with OMMT loading. The nanocomposites were characterized as well‐dispersed, partially exfoliated structures with good interfacial interactions. From the X‐ray diffraction analysis, the absence of d001 reflections of the OMMT clay in the cured nanocomposites indicated the development of an exfoliated clay structure, which was confirmed by transmission electron microscopy. The homogeneous morphologies of the pure polyester/epoxy blend and clay hybrid systems were ascertained with scanning electron microscopy. The tensile strength of the 5 wt % clay‐filled blend nanocomposite system was increased by 2.4 times compared to that of the pure blend resin system. The results suggest that the prepared nanocomposites have the potential to be used as active thin films for different applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Influence of chain microstructure on ethylene–norbornene copolymer film properties
Authors: Liu Shaojie , Yao Zhen , Chen Lin , Dai Bin‐Bin , Cao Kun , Li Bo‐Geng , Zhu Shiping
Published: February 2011

The effects of copolymer composition, copolymer composition distribution, and polar α‐olefin incorporation on transparency, refractive index, and hydrophilicity of resultant ethylene–norbornene copolymer films were investigated. It has been found that the transparency is mainly determined by the copolymer composition distribution. The samples having uniform compositions gave better transparency. However, the copolymer composition distribution had little effect on refractive index. The refractive index increased linearly with increasing norbornene content. Furthermore, the incorporation of polar α‐olefin with long carbon chain improved refractive index and hydrophilicity of the films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Effect of high temperature and the role of sulfate on adsorption behavior and effectiveness of AMPS®‐based cement fluid loss polymers
Authors: Lummer Nils Recalde , Dugonjić‐Bilić Fatima , Plank Johann
Published: February 2011

The fluid loss control performance of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS®)‐based copolymers added to cement slurries was studied at 27 and 100°C, respectively. It was found that effectiveness of these fluid loss additives solely relies on achievement of a high adsorbed amount on the surface of cement. At elevated temperature (100°C), CaAMPS®‐N,N‐dimethyl acrylamide copolymer (CaAMPS®‐co‐NNDMA) exhibits reduced adsorption and hence decreased fluid loss control of the cement slurry. The reason behind this behavior is poor calcium binding capability of the sulfonate anchor groups, which coordinate with calcium atoms present on the mineral surface. Whereas, an increase in the sulfate concentration present in cement pore solution instigates partial coiling of CaAMPS®‐co‐NNDMA and causes only a slight influence on the performance of this copolymer. The elevated sulfate content results from thermal degradation of ettringite, a cement hydrate mineral produced during the early stages of cement hydration. Incorporation of minor amounts (∼ 1.3 mol %) of maleic anhydride into this copolymer produces a terpolymer, which exhibits higher and more stable adsorption, even at high temperature. This effect is owed to the presence of homopolymer blocks of polycarboxylates distributed along the polymer trunk. On mineral surfaces, they present much stronger anchor groups than sulfonate functionalities, as evidenced by their higher calcium binding capability. Consequently, fluid loss performance of CaAMPS®‐co‐NNDMA‐co‐MA is little affected by temperature. Understanding the influence of temperature on the physicochemical interactions occurring between additives and the mineral surface can help to design more effective admixtures suitable for high temperature applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Pervaporation separation of isopropanol–water mixtures using mixed matrix blend membranes of poly(vinyl alcohol)/poly(vinyl pyrrolidone) loaded with phosphomolybdic acid
Authors: Mali Mukund G. , Magalad Veeresh T. , Gokavi Gavisiddappa S. , Aminabhavi Tejraj M. , Raju K. V. S. N.
Published: February 2011

Mixed matrix membranes of poly(vinyl alcohol) and poly(vinyl pyrrilidone) blends were prepared by loading with phosphomolybdic acid (PMA) and their pervaporation (PV) properties were investigated for the PV separation of isopropanol. Membrane performance shown a dependence on the extent of PMA loading. The 4 wt % PMA‐loaded blend membrane had the highest separation factor of 29991, which declined considerably at higher loading. The flux of 4 wt % PMA‐loaded membrane was lower than that of nascent blend membrane. Feed water composition and temperature influenced the PV performance. Solubility selectivity was higher than diffusion selectivity. Degree of swelling was smaller after PMA loading exhibiting better separation ability. The PV results were analyzed using the Flory‐Huggins theory and sorption was dominated by Langmuir's mode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Isothermal crystallization kinetics of poly(butylene terephthalate‐co‐sebacate) copolymer
Authors: Zeng Zuoxiang , Zhang Hailing , Xue Weilan , Zhu Wanyu , Xiao Xiaoling , Sun Yu , Li Zhelong
Published: February 2011

Poly(butylene terephalate) (PBT) and poly(butylene terephthalate‐co‐ sebacate) (PBTS) copolymers containing 5 mol % and 10 mol % sebacate components (Mn = 12,700–14,600) were synthesized by polycondensation. The isothermal crystallization kinetics and melting behaviors after isothermal crystallization of the polymers were investigated by differential scanning calorimetry (DSC). The equilibrium melting temperatures of the polymers were determined by Hoffman‐Weeks equation. Analysis of the crystallization kinetic data using the Avrami equation showed that the introduction of sebacate enhanced the crystallization of PBT in PBTS. And the Avrami exponent n varies in the range of 2.16–3.68, indicating that the isothermal crystallization follows two‐ and three‐dimensional growth mechanism. The isothermal crystallization activation energies of the polymers were also calculated by the Arrhenius equation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Polymorphism of Amino Acid‐Based Dendrons: From Organogels to Microcrystals
Authors: Kuang Gui‐Chao , Teng Ming‐Jun , Jia Xin‐Ru , Chen Er‐Qiang , Wei Yen
Published: February 2011

There is a delicate balance for a low‐weight molecule to behave as a gelator or crystal. The synthesis of two novel amino acid‐based naphthalene‐dendrons, Nap‐G1 and Nap‐G2 is described. Both dendrons display polymorphic properties in organic solvents. Nap‐G1 developed a fibrous network with β‐sheet architecture in cyclohexane but exhibited a spherulitic network in mixed solvents (chloroform/petroleum ether 1:5, v/v). On the other hand, Nap‐G2 acted as an efficient organogelator in chloroform but formed crystalline fibers in relatively high polarity solvents (such as acetone and methanol). Combinations of characterizations have been employed to study the polymorphism.
Stability analysis for a class of switched linear systems
Authors: Guo Rongwei , Wang Yuzhen
Published: February 2011

This paper investigates the stability of a class of switched linear systems, and proposes a number of new results on the stability analysis. A novel analysis method is developed by using the 2‐norm technique, and then several stability results are obtained based on the new analysis method. It is shown that the main results obtained in this paper not only guarantee the stability of the systems under arbitrary switching, but also provide an algorithm to find the minimum dwell time (MDT) with which switches make the switched systems stable. Finally, several illustrative examples with numerical simulations are studied by using the results obtained in this paper. The study of examples shows that our analysis method works very well in analyzing the stability of some classes of switched linear systems and, moreover, it has some advantages over the common quadratic Lyapunov function method in some cases.

Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Progress in understanding of weather systems in West Africa
Authors: Lafore J.‐P. , Flamant C. , Guichard F. , Parker D. J. , Bouniol D. , Fink A. H. , Giraud V. , Gosset M. , Hall N. , Höller H. , Jones S. C. , Protat A. , Roca R. , Roux F. , Saïd F. , Thorncroft C.
Published: February 2011

The major advances achieved during African monsoon multidisciplinary analysis in our physical understanding of the West African monsoon (WAM) system are reviewed. Recent research provides an advanced understanding of key WAM features. The Saharan heat low, the interactions of the monsoon flow with the surface and the reversed flow on top of it, all play a more important role than previously assumed, and interact according to the phase of the diurnal cycle of convection. Recent studies also emphasise the significance of upstream conditions in Central and East Africa, as well as strong interactions between midlatitudes and the WAM. Copyright © 2011 Royal Meteorological Society
New perspectives on land–atmosphere feedbacks from the African Monsoon Multidisciplinary Analysis
Authors: Taylor Christopher M. , Parker Douglas J. , Kalthoff Norbert , Gaertner Miguel Angel , Philippon Nathalie , Bastin Sophie , Harris Phil P. , Boone Aaron , Guichard Françoise , Agusti‐Panareda Anna , Baldi Marina , Cerlini Paolina , Descroix Luc , Douville Hervé , Flamant Cyrille , Grandpeix Jean‐Yves , Polcher Jan
Published: February 2011

Research into land–atmosphere coupling within the African Monsoon Multidisciplinary Analysis has highlighted the atmospheric impact of soil moisture on space scales of 5 km upwards and time scales of several days. Observational and modelling studies have shown how antecedent rainfall patterns affect new storms in the Sahel. The land feedback operates through various mechanisms, including a direct link to afternoon storm initiation from surface‐induced mesoscale circulations, and indirectly via a large‐scale moisture transport in the nocturnal monsoon. The results suggest potential for significant improvements in weather forecasting through assimilation of satellite data. Intriguing questions remain about the importance of vegetation memory on seasonal–interannual scales. Copyright © 2011 Royal Meteorological Society
Zur Schadensverteilung des durch Spannungsriss korrosion geschädigten vergüteten Spannstahls bei Brückenbauwerken
Authors: Bauer Thomas , Müller Michael , Patz Rüdiger , Wilhelm Tobias , Schwarz Johannes , Tue Nguyen Viet
Published: February 2011

Die Aussagekraft der rechnerischen Untersuchung zur Abschätzung des Gefährdungspotentials infolge Spannungsrisskorrosion hängt entscheidend von den Annahmen zu Schädigungsverlauf und —verteilung des Spannstahls ab. Mit systematischer Untersuchung des aus einem Bauwerk entnommenen Spannstahls konnte festgestellt werden, dass die bisher angenommene Schadenskonzentration an einer Stelle, welche zum Ausfall des gesamten Spannglieds führt, sehr wenig wahrscheinlich ist. Viel wahrscheinlicher ist die drahtweise Schädigung mit unbegrenzter Anzahl der Risse über die gesamte Drahtlänge. Weiterhin ist keine Korrelation zwischen chemischer Zusammensetzung des Spannstahls bzw. zwischen Zusammensetzung des Verpressmörtels und der Versprödung des Spannstahls feststellbar. Weitere Untersuchungen zur Bestätigung der gewonnenen Ergebnisse sind wünschenswert.

Damage distribution of hardened and tempered prestressing steel dues to stress corrosion in prestressed concrete bridges. The accuracy of the analysis to estimate the hazard potential due to the stress corrosion depends strongly on the assumption of the damage distribution and the damage progress of the prestressing steel in the constructions. Through a systematic test of the prestressing steel, which is taken from an old bridge, it is shown that the traditional assumption of a damage concentration with the breakdown of the whole tendon is less probable. Instead, the damage of single wires over its total length with unlimited number of cracks is considerably more probable. Furthermore, no correlation between the chemical compositions or mixtures of the grout and the brittleness of the prestressing steel is found. More investigations to check these results obtained in this study are preferable.
Geklebte Verbundbauteile aus Holz und hoch‐ bzw. ultrahochfesten Betonen
Authors: Schäfers Martin , Seim Werner
Published: February 2011

Das primäre Ziel der vorliegenden Untersuchungen besteht darin, wesentliche Grundlagen für die Bemessung biegebeanspruchter Verbundbauteile aus Holz und hochfesten bzw. ultrahochfesten Betonen (UHPC) mit geklebtem Verbund zu ermitteln. Weiterhin wird ein Testverfahren für die experimentelle Untersuchung der Verbundfestigkeit geklebter Holz‐Beton‐Verbunde vorgeschlagen. Es werden zwei mechanische Modelle zur Beschreibung des Verbundverhaltens vorgestellt. Neben der Theorie des Verschieblichen Verbunds, die bereits 1953 von Volkersen hergeleitet wurde, wird in diesem Zusammenhang die linear elastische Bruchmechanik (LEBM) herangezogen. Der Versuchsaufbau und die wesentlichen Ergebnisse der experimentellen Untersuchungen werden vorgestellt. Die Verbundversuche belegen, dass das Verbundversagen in den meisten Fällen im Holz, nahe der Klebfuge auftritt. Auf der Grundlage der Verbundversuche wird ein Vorschlag für die Bemessung biegebeanspruchter Bauteile angegeben. Dieser wird mit Hilfe zweier Vierpunkt‐Biegeversuche im Bauteilformat validiert.

Bonded Timber‐Concrete‐Composite Structures with high‐ resp. ultrahigh performance Concretes. The main ambition of the present investigations is to develop the basic information for the design of adhesive bonded composite members from timber and UHPC. Furthermore, a standard test setup for the experimental determination of the bond strength of timber‐concrete composites will be derived. Two mechanical models for the description of the bond behaviour will be documented. The theory of the compliant bond, which was already introduced by Volkersen in 1953 and the linear elastic fracture mechanics (LEFM) are possible approaches for this purpose. The setup and the main results from experimental investigations on the bond behavior will be presented. It is found that the bonding failure occurs in timber close to the bond‐line in most cases. In general, the ultimate loads can be estimated by Volkersen’s theory. On the basis of the bond investigations, recommendations for the design of bending members are given. These recommendations are validated by two full‐scale bending tests. Additional strain‐ and deformation‐measurements proved, that the assumptions which were taken for the design of bending members are sound.