bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surface structure and adhesive properties of biaxially oriented polypropylene film grafted with poly(acrylic amide) using corona discharge
Authors: Lei Jingxin , He Guangjian , Li Qiman , Lin Xiaohong 
Published: April 2004

AbstractCorona discharge was explored as a means of forming chemically active sites on the surface of biaxially oriented polypropylene (BOPP) film. The active species formed in air was used to induce graft copolymerization of acrylic amide (AAM) in aqueous solution. The surface structure, hydrophilicity and adhesion of the grafted BOPP film were characterized by the extent of grafting, electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), peel strength and contact angle measurements. Surface graft‐copolymerization of AAM onto BOPP film by corona discharge in air can be carried out with high efficiency. With increasing copolymerization time, the degree of grafting of AAM onto BOPP increases. The degree of grafting achieved a relatively high value of 2.13 wt% for the conditions of 1 min corona discharge and a copolymerization reaction time of 2.5 hr in 20% AAM aqueous solution at 70°C. After corona discharge grafting, the contact angle of water on the BOPP film decreased and the peel strength increased compared with those for ungrafted BOPP film. The hydrophilicity and adhesion of BOPP were improved by surface graft copolymerization with AAM induced by corona discharge.
Nonisothermal crystallization kinetics of peo in ethylene terephthalate‐ethylene oxide segmented copolymers
Authors: Kong Xiaohua , Yang Xiaoniu , Zhou Enle , Ma Dezhu 
Published: April 2004

AbstractThe nonisothermal crystallization behavior of Ethylene Terephthalate‐Ethylene Oxide (ET‐EO) segmented copolymers has been studied with the use of differential scanning calorimetry (DSC). The kinetics of PEO in ET‐EO segmented copolymer under nonisothermal crystallization conditions has been analyzed with the Ozawa equation. The results show that there is no agreement with Ozawa's theoretical predictions in the whole crystallization process owing to the constraint of ET segments imposed on the EO segments. A distinct two‐crystallization process has been investigated by using the Avrami equation modified by Jeziorny to deal with the nonisothermal crystallization data. The value of the Avrami exponent n is independent of the length of soft segments. However, the crystallization rate is sensitive to the length of soft segments. The longer the soft segments, the faster the crystallization will be.
Cure kinetics modeling of epoxy resins using a non‐parametric numerical procedure
Authors: Skordos A. A. , Partridge I. K. 
Published: April 2004

AbstractThe paper presents the development of a novel non‐parametric procedure for modeling of the chemical cure kinetics of a commercial resin‐transfer‐molding epoxy resin, RTM6. The procedure is entirely numerical and involves interpolation between experimentally determined values of cure reaction rates. The base data are obtained by Differential Scanning Calorimetry (DSC). The newly developed procedure is set against a background overview of other cure kinetics modeling approaches. It is shown that the numerical procedure can achieve a satisfactory level of accuracy in describing the progress of cure in this resin system. The important advantage, compared with other techniques, is that no information on the chemical naturr of the process is required.
Ultrasonic monitoring of the seal quality in flexible food packages
Authors: Ozguler Ayhan , Morris Scott A. , O'brien William D. 
Published: April 2004

AbstractUltrasonic Backscattered Amplitude Integral (BAI) values are used to detect critical and major defects such as nonbonding, wrinkles and bubbles distributed within the seal area of flexible food packages. The BAI‐mode imaging by itself is not capable of detecting such nonbonding, wrinkles and bubbles distributed within the seal area. For this study, model delects in the seal region of all‐plastic and foil‐containing films were created by varying the sealing‐bar temperature. Seal regions were scanned by a 17.3‐MHz ultrasonic transducer, and the waveform for each scan point was processed by the BAI‐mode method. The mean and the coefficient of variation of the BAI values (BAICV) were calculated. It is shown that a combination of mean BAI vaiae and BAICV value can detect defects distributed in seals in flexible food packages. This technique has the potential of providing a real‐time, on‐line control by sensing whether a proper seal has been achieved.
3‐D non‐isothermal flow field analysis and mixing performance evaluation of kneading blocks in a co‐rotating twin srew extruder
Authors: Ishikawa Takeshi , Kihara Shin‐ichi , Funatsu Kazumori 
Published: April 2004

AbstractWe have developed a three‐dimensional non‐Newtonian and non‐isothermal flow analysis of the twin screw extruder (TSE) using the finite element method. This code can simulate the fully filled parts of several kinds of screw elements, such as full flight screws, kneading blocks, rotors and their combinations. A marker particle tracking analysis has also been developed to evaluate the mixing performance of the screw elements.In this paper, simulations for the kneading blocks in a co‐rotating TSE were carried out. The screw configurations are combinations of 2‐lobe kneading blocks with several stagger angles and disk widths. The effects of screw configurations on pressure and temperature distributions are examined. We also evaluate the dispersive and distributive mixing via stress magnitude and area stretch obtained by marker particle tracking analysis. Additionally, we discuss the desirable stagger, disk width and their combinations that promote the mixing performance.
Mixing efficiency in a pin mixing section for single‐screw extruders
Authors: Yao W. G. , Tanifuji S. , Takahashi K. , Koyama K. 
Published: April 2004

AbstractNon‐Newtonian, non‐isothermal, 3D finite‐element simulation of mixing performance in a pin mixing section with different axial gaps in the pins has been carried out according to their realistic configurations. The quantitative evaluation of mixing ability was based on the theory of kinematics of fluid mixing. To learn and to compare the local mixing performance in a standard screw and a pin mixing section, the local mixing efficiency distribution proposed by Ottino was calculated. Also, the RTDs of these mixers were calculated in an attemt to measure mixing. The integration of the two, namely, the integrating local mixing efficiency along a number of particle pathlines from entrance to exit, together with statistical treatment, which was referred as integral mixing efficiency, then gives a quantitative judgment of the total mixing ability of a continuous mixer. The calculated results showed a nonlinear dependence of the mixing ability of a pin mixing section on the axial gap of the pins. Finally, the calculation results were compared with the experimental ones obtained in our previous study.
Crystal‐crystal transformations in isotactic polybutene‐1 oriented filaments and in thick molded rods
Authors: Choi Cheol‐Ho , White James L. 
Published: April 2004

AbstractThis paper reports two related studies of the Form II → Form I crystal‐crystal transformation in isotactic polybutene‐1. First, it was found that in melt spun filaments, the rate of transformation is higher in filaments possessing higher levels of crystalline orientation. Second, we consider the occurrence of this phase transformation in thick quenched cylindrical rods. It was found that the phase transformation occurs more rapidly in the core than at the surface of the part. It is hypothesized that the mechanism of the higher transformation rate in the core is due to the development of residual quench stresses associated with densification at solidification. These stress levels have been calculated and our results compared with earlier studies.
Nonisothermal crystallization behavior of poly(aryl ether ether ketone)
Authors: Seo Yongsok , Kim Sehyun 
Published: April 2004

AbstractA study has been made of the crystallization behavior of poly(aryl ether ether ketone), PEEK, under nonisothermal conditions. A differential scanning calorimeter (DSC) was used to monitor the energetics of the crystallization process from the melt. For nonisothermal studies, the melt was crystallized by cooling at rates from 1°C/min to 10°C/min. A kinetic analysis based on the recently proposed model for nonisothermal crystallization kinetics to remedy the drawback of the Ozawa equation was applied. The Avrami exponent for the nonisothermal crystallization process was strikingly different from that of the isothermal process, which indicates different crystallization behaviors. The results agree with the morphological observation reported in the literature. This study shows that correct interpretation of the Avrami exponent provides valuable information about the crystal structure and its morphology.
Heterogeneization of polymerization catalysts on natural substances
Authors: Eberhardt A. M. , Ferreira M. L. , Damiani D. E. 
Published: April 2004

AbstractThe use of biomass as support for zirconocene catalysts in ethylene polymerization was studied. Cellulose, starch and chitosan were conveniently characterized. Many factors affecting the activity of the catalysts were examined. Parameters such as surface area were found to have no significant influence on the activity of the catalysts. The activity of the catalysts sharply increased with the degree of deacetylation in the chitosan supports. Using this support the highest activity in ethylene polymerization was obtained. The polymers obtained with the zirconocene supported on chitosan or cellulose pretreated with methylaluminoxane exhibited a higher molecular weight than those obtained with a homogeneous system. Polymer particles obtained with these supported metallocene catalysts showed a good replication of the original support particles.
Creep analysis of polymeric pipes under internal pressure
Authors: Guan Z. W. , Boot J. C. 
Published: April 2004

AbstractMedium density polyethylene pipes have been used in the water and gas industries for over a decade. One of the major problems with these pipes is creep under their service pressures. Life prediction is usually based on the secondary creep path until the onset of tertiary creep. Constitutive models such as visco‐hyperelasticity and elasto‐viscoplasticity can be used to make such prediction. Owing to complexity, the latter is usually used in numerical modeling, Medium density polyethylene is an extremely ductile material with a low modulus of elasticity. The corresponding elongation prior to rupture under a tensile creep test can reach a few hundred percent. The appropriate creep law must be established before any life prediction can be made. In this paper, based on a creep law obtained from a series of material creep tests under different stress levels, a visco‐hyperelastic model was developed to simulate Medium density polyethylene pipes under internal creep pressures. Reasonably good correlation has been obtained between the experimental results and the theoretical analysis.
Study on the flow field of the air jet from dual slot die in the melt blowing process
Authors: Chen Ting , Huang Xiubao 
Published: April 2004

AbstractThe possibility of describing the jet from the dual slot die in the melt blowing process with a vortex pair was studied according to the nature of the vortex. A model of the synthesis of two jets was developed. The reliability of the model was confirmed by experimental data cited from literature. The prediction of the fiber diameter using this model coincided with that using the fitted equation with the data advanced by Harpham and Shambaugh. The effects of the equipment parameters, such as the angle between the air flow and the axis of the spinneret, the width of the die head and the width of the slot were also discussed.
Prediction of long‐term service performance of polymeric materials from short‐term tests: Creep and prediction of the stress shift factor of a longitudinal polymer liquid crystal
Authors: Akinay Ali E. , Brostow Witold , Maksimov Robert 
Published: April 2004

AbstractThe material studied is a longitudinal polymer liquid crystal (PLC). The creep behavior of the PLC is examined in the region of nonlinear viscoelasticity. The creep compliance D curves at nine different stress σ levels, from 10 to 50 J.cm−3 at a constant temperature are determined and shifted along the log time axis for σref = 10 J · cm−3 to produce the D versus t/aσ master curve. A fairly general formula for stress shift factor aσ based on free volume vf and the chain relaxation capability (CRC) derived by one of the authors is applied. The formula predicts values that agree with the experimental ones within the limits of the experimental accuracy. Thus, experiments at several stress levels can serve for prediction of long‐term behavior from short‐term tests. The same value of the Doolittle constant B is obtained separately from temperature shift and stress shift experiments for the PLC.
Gas absorption with filled polymer systems
Authors: Chen Lee , Sheth Himanshu , Kim Roland 
Published: April 2004

AbstractThis paper deals with the gas absorption behavior of polymer systems. The emphasis is on the difference between filled and unfilled polymers to explain heterogeneous nucleation in filled polymers. A Foaming Process Simulator has been built to study the gas absorption. It consists of a test chamber that holds the polymer samples. The chamber can be pressurized with gas up to 5000 psi and heated up to 450°F. The gas pressure is monitored by a high‐accuracy pressure transducer and recorded by a data acquisition system. The amount of gas absorbed by a polymer is determined from the pressure change in the test chamber. A rotor applies shear to the polymer melt to investigate the shear effects. Two polymer systems were tested: HDPE with/without talc, and PVC with/without calcium carbonate. The fillers were well dispersed as verified with scanning electron microscope. The tests were done at the melt temperatures from 120°C to 177°C and a saturation pressure of about 18.9 MPa. It was found that the filled polymers absorb more gas compared to the unfilled ones. It is suggested that there is a certain amount of gas accumulated in the filler‐polymer interface. This accumulated gas helps to create cells during the foaming process.
Structure and properties of poly(vinyl chloride)‐triallyl cyanurate plastisols
Authors: Tai Horng‐Jer 
Published: April 2004

AbstractTriallyl cyanurate (TAC) has been used as a reactive plasticizer to promote the high‐temperature creep resistance of poly(vinyl chloride) (PVC) plastisols. The resultant crosslinked structure is characterized using gel content and swell ratio measurements as well as Fourier transform infrared spectroscopy. The crosslinking reaction was initiated using peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. The gel yield and crosslink density in the gel increase with increasing TAC concentration in the plastisol, while the grafted PVC fraction and the residual unsaturation of TAC behave in the opposite way. Introduction of TAC into the plastisol promotes creep resistance at high temperatures, and the logarithmic creep rate was found to decrease linearly with increasing crosslink density.
Impact specific essential work of fracture of compatibilized polyamide‐6 (PA6)/poly(phenylene ether) (PPE) blends
Authors: Chiou Kuo‐Chan , Chang Feng‐Chih , Mai Yiu‐Wing 
Published: April 2004

AbstractThe essential work of fracture (EWF) method has aroused great interest and has been used to characterize the fracture toughness for a range of ductile metals, polymers and composites. In the plastics industry, for purposes of practical design and ranking of candidate materials, it is important to evaluate the impact essential work of fracture at high‐rate testing of polymers and polymer blends. In this paper, the EWF method has been utilized to determine the high‐rate specific essential fracture work,we, for elastomer‐modified PA6/PPE/SMA (50/50/5) blends by notched Charpy tests. It is found thatweincreases with testing temperature and elastomer content for a given specimen thickness. Morphologically, there are two failure mechanisms: shear yielding and pullout of second phase dispersed particles. Shear yielding is dominant in ductile fracture, whereas particle pullout is predominant in brittle fracture.
The effect of scaleup on the processing behavior of a blend exhibiting phase inversion during compounding
Authors: Ratnagiri Ram , Scott Chris E. , Shih Chi‐Kai 
Published: April 2004

AbstractThe scaleup behavior of blends exhibiting phase inversion during compounding in batch mixers was studied. Similar morphological changes were observed during compounding of polystyrene/polyethylene blends of different batch sizes ranging from 12g to 240g. The time to achieve a continuous phase of the major component, polystyrene, was shown to depend on the scale of the mixing device. Based on visual observation of the morphological changes, a constant nominal‐maximum‐shear‐rate scaleup condition was used. Upon a five‐fold increase in batch size the time to phase inversion increased by a factor of 3. This change is explained using a combination of the reduced specific area and reduced mechanical energy input under the experimental conditions. A novel blade design using modular triangular elements was constructed and results from radial and axial scaleup using the new blades are presented. Similarities between the triangular and roller blades are used to highlight the importance of the high‐shear region in determining the softening rate of the polystyrene pellets. The flexibility of the blade design was exploited to study the effect of blade configuration on the time to phase inversion. A relative stagger parameter is introduced to explain the observed dependence. Increasing the relative stagger decreased the stress transfer to the batch and increased the time to phase inversion. Implications of these results for mixing in the kneading sections of twin‐screw extruders is discussed.
Micro‐ and macrorheological properties of polypropylene‐polyoxymethylene‐copolyamide mixture melts
Authors: Tsebrenko M. V. , Rezanova N. M. , Tsebrenko I. A. 
Published: April 2004

AbstractThe influence of polyoxymethylene (POM) additives on micro‐ and macrorheological properties of polypropylene‐copolyamide (PP/CPA) mixture melts with the PP/CPA ratios of 40/60 and 20/80 wt% was investigated. We have shown that the microrheological processes such as deformation of dispersed polymer droplets and formation of liquid polymer streams, coalescence of these streams along the longitudinal direction, migration, and fracture of the liquid streams into droplets can be controlled by addition of a third component that may interact with CPA in a specific manner. The ternary mixture melt viscosity was greater than that of the binary mixture melt viscosity. The degree of viscosity increase depended upon the composition of the binary mixture, the value of shear stress, and POM content. This dependence may be explained by formation of hydrogen bonds between POM and CPA macromolecules. The addition of POM improved the specific PP fiber formation in the matrix of CPA. The latter is valid even for a composition (PP/CPA ratio is 40/60) close to phase inversion. POM migration toward the walls of the forming die occurred in the flow of the ternary polymer mixture melts. For the purpose of realizing the specific fiber formation during the processing of the above mentioned mixtures we recommend an addition of 5% to 10% of POM.
Temporal distributions: The basis for the development of mixing indexes for scale‐up of polymer processing equipment
Authors: Wang Winston , Manas‐Zloczower Ica 
Published: April 2004

AbstractNew and better mixing criteria are needed to assess dispersive and distributive mixing efficiency in polymer processing equipment. Such criteria can serve the purpose of process optimization and machine scale‐up. In this work, the history of flow strength and shear stresses experienced by a number of particles in a twin‐flight, single‐screw extruder serve as the basis to produce temporal distributions of these parameters. In turn, the temporal distributions can be used for developing new mixing indexes for process optimization and scale‐up. Using models for dispersion kinetics and experimental data, calculations of agglomerate size distribution and average agglomerate size can be used as a dispersive mixing criterion.
On‐line ultrasonic measurements of methyl methacrylate polymerization for application to reactive extrusion
Authors: Kiehl Christopher , Chu Lih‐Long , Letz Keith , Min Kyonsuku 
Published: April 2004

AbstractAn ultrasonic measurement system was developed for monitoring the polymerization of methyl methacrylate (MMA) in a model batch reactor and a model twin screw extruder. Conversion of MMA polymerized in a home‐made reaction chamber was compared with results obtained from a differential scanning calorimeter (DSC). The objective is to correlate ultrasonic velocity to extent of reaction based on the model experiments of poly(methyl methacrylate) in solution with MMA. This primary ultrasonic measurement system was applied to the on‐line measurement of the extent of MMA polymerization in a model twin‐screw extruder.
Thermoplastic elastomeric composition based on ground rubber tire
Authors: Naskar Amit K. , Bhowmick Anil K. , De S. K. 
Published: April 2004

AbstractGround rubber tire (GRT) is a particulate vulcanizate consisting mainly of rubber hydrocarbon and fillers. Rubber hydrocarbon of GRT (rGRT) has been used as a partial substitute for EPDM rubber in a dynamically vulcanized EPDM/acrylic‐modified HDPE (A‐HDPE) blend. The blends with higher rubber content show poor processability and physical properties, while the compositions with higher plastic content behave like toughened plastics. However, the 60:40 rubber/plastic blend was found to behave as a thermoplastic elastomer, and it was observed that 50% of EPDM can be replaced by rGRT without deterioration in properties.
Effect of non‐isothermal oriented crystallization on the velocity and elongational viscosity profiles during the melt spinning of high density polyethylene fibers
Authors: Makradi A. , Ahzi S. , Gregory R. V. 
Published: April 2004

AbstractBased on the experimental data of spine line temperature and percent crystallization, a time‐integral constitutive equation has been used together with the degree of phase transformation theory to predict the velocity and elongational viscosity profiles. For the velocity profile, our predicted results are compared to experimental data and good agreement is found. Under a drawing force, the elongational viscosity profile shows a stress softening due to the molecular alignment; then the fiber hardens close to the take‐up point, owing to filament crystallization.