bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative measurement of adhesion between polypropylene blends and paints by tensile mechanical testing
Authors: Tang Houxiang , Foran Brendan , Martin David C. 
Published: April 2004

AbstractA tensile mechanical test suiable to measure the adhesion between brittle coatings and ductile substrates was applied to measure the adhesion of painted layers on polypropylene blends. The test involves the tensile deformation of the painted assembly, resulting in the periodic cracking of the brittle coating on the ductile substrate. The interfacial shear strength was determined by measuring the strength of the coating, the thickness of the coating, and the average width of paint fragment after the crack density reaches saturation. Apparent interfacial shear strength was obtained for different paints on the same kind of blend, which gave consistent results over the experimental strain rate range from 10−4 to 10−3 sec−1. Interfacial delamination was studied by optical microscopy (OM) and transmission electron microscopy (TEM). The delamination was observed to mainly occur near the adhesion promoter and substrate interface.
Crystallization of poly(ethylene terephthalate) and poly (butylene terephthalate) modified by diamides
Authors: Bouma Krista , Gaymans Reinoud J. 
Published: April 2004

AbstractPoly(ethylene terephthalate) (PET) and poly (butylene terephthalate) have been modified by diamide units (0.1–1 mol%) in an extrusion process and the crystallization behavior studied. The diamides used were: for PET, T2T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) and for PBT, T4T‐dimethyl (N, N′‐bis(p‐carbomethoxybenzoyl)butanediamine). The above materials were compared to talc (0.5 wt%), this being a standard heterogeneous nucleator, and to diamide modified copolymers obtained by a reactor process. Two PET materials were used: a slowly crystallizing recycled grade obtained from soft drink bottles and a rapidly crystallizing injection molding grade. The crystallization was studied by differential scanning calometry (DSC) and under injection molding conditions using wedge shaped specimens; the thermal properties were studied by dynamic mechanical analysis. T2T‐dimethyl is effective in increasing the crystallization of PET in both of the extrusion compounds as well as in the reactor materials. It was also found that the crystallization temperature of poly(butylene terephthalate) could be slightly increased by the addition of nucleators.
Transport modeling and thermophysical properties of cellular poly(urethane‐isocyanurate)
Authors: Peng Shuo , Fuchs Alan 
Published: April 2004

AbstractTransport behavior, thermophysical properties and kinetics of cellular poly(urethane‐isocynurate) were investigated. The heat and momentum transport of the flowing and reacting polymers systems was modeled using a computational fluid dynamics (CFD) approach. Two models were developed and compared with the experimental results in order to provide insight into the optimum processing. The models allowed prediction of the temperature profiles under a variety of operating conditions. The model prediction of momentum and heat transport agreed with the experimental results well. the thermophysical properties of the polymer system were obtained from experimental data and were used in the transport model. These properties included heat capacity and thermal conductivity. Reaction kinetics were investigated using differential scanning calorimetry (DSC). The rate constant, activation energy and heat of reaction and the rate constant were obtained from the experimental data.
Stress‐initiated void formation during cure of a three‐dimensionally constrained thermoset resin
Authors: Eom Yongsung , Boogh Louis , Michaud Véronique , Sunderland Paul , Månson Jan‐Anders 
Published: April 2004

AbstractDuring cure of epoxy resins, polymerization induces an increase in mechanical properties, which is accompanied by a volumetric shrinkage. When the resin is cured in a constrained mold to which it adheres, tensile stresses will hence develop, which may exceed the stremgth of the resin at a given curing stage. Voids will then form. The origin and governing parameters of void formation are studied using an epoxy resin cured in a three‐dimensionally constrained glass mold following isothermal cure cycles. Two types of voids are shown to appear during cure, one early in the process and a second around the gelation point. A viscoelastic analysis of the material stress state over the whole range of cure is performed. Both the viscoelastic modulus obtained from a time‐cure‐temperature superposition and the volumetric shrinkage, which was continuously measured by density change, are taken into account. A value for the critical internal stress at void initiation is thus proposed. This criterion can be used to provide guidelines for tailoring the material properties toward an increase of the critical stress for void initiation. Also, since during theprocessing of composite materials, cases may arise where the resin cures within the interstices left between consolidated fibres that do not move, this critical stress failure criterion can be of use in the eastablishment of a process window providing guidelines for the production of void free composites.
Elastomer biaxial characterization using bubble inflation technique. I: Experimental investigations
Authors: Reuge N. , Schmidt F. M. , Le Maoult Y. , Rachik M. , Abbé F. 
Published: April 2004

AbstractThe biaxial rheological behavior of materials such as elastomers or polymers can be obtained using a bubble‐inflation‐technique. A circular membrane is clamped at the rim and expanded under gas pressure. The inflation of the circular membrane is recorded using a CCD video camera and the blowing pressure by a pressure sensor. Then, from elongation and curvature radius measurement at the pole of the bubble, one can deduce equibixial stress‐strain data. This study describes the optimization of a bubble‐inflation rheometer. The most sensitive point of the technique is the estimation of the elongation at the bubble pole, deduced from video camera measurements. A direct measurement of the bubble thickness was performed using a magnetic probe in order to validate rheometer results. Such a validation has evidently never been carried out before. Results of quasi‐static equibiaxial characterisation of elastomers are presented and analyzed.
Effect of poly(acrylic acid)‐g‐PCL microstructure on the mechanical properties of starch/PCL blend compatibilized with poly(acrylic acid)‐g‐PCL
Authors: Kim Chang‐Hyeon , Cho Kuk Young , Park Jung‐Ki 
Published: April 2004

AbstractPoly(acrylic acid)‐g‐polycaprolactone (PAA‐g‐PCL) graft copolymer was synthesized and starch/PCL blends compatibilized with PAA‐g‐PCL were prepared. The mechanical properties of the starch/PCL blends compatibilized with various PAA‐g‐PCLs that have different graft degrees and graft lengths were investigated. As the graft degree of the PAA‐g‐PCLs that have the same graft length increased, the modulus and the strength of the blends decreased. However, the elongation at break and the tensile toughness of the blends showed a maximum at a certain graft degree (10.8 mol%) owing to the better compatibilizing effect compared to the low (3.9 mol%) and the high (23.4 mol%) graft degree of PAA‐g‐PCL. It was also found that the modulus and the strength of the blends increased with the increase of graft length of the PAA‐g‐PCLs that have the same graft degree (∼11 mol%). However, the blend compatibilized with the short graft length (M.W. of PCL graft: 530) exhibited the highest value of the elongation at break and the tensile toughness. This result is attributed to the self‐crystallization of PAA‐g‐PCL in the blend that has longer PCL grafts.
Weldline morphology of injection molded modified poly(phenylene‐oxide)/polyamide‐6 blends
Authors: Son Younggon , Ahn Kyung Hyun , Char Kookheon 
Published: April 2004

AbstractThe weldline morphology of modified‐poly(phenylene‐oxide)/polyamide‐6 blends has been investigated. A distinct contacting layer consisting of fine spherical particles was observed from the V‐notch at the surface to the center of the molded part for the low viscosity ratio blend. In contrast, such small particles were not found and a slight deformation was observed near the part's surface for the high viscosity ratio blend. The weldline morphology was found to be dominated by the deformation, the breakup, and the relaxation of the dispersed modified‐poly(phenyleneoxide) phase. The effect of injection conditions on the weldline morphology has also been investigated. The morphology of the meldline was quite complicated. Distorted multi‐layered structures were observed. It was found that those structures arise from the subsequent flow after merging of the two flow fronts. Weldlines and meldlines have been studied separately, and their formation mechanisms were found to be basically similar.
Biaxial stress relaxation of high impact polystyrene (HIPS) above the glass transition temperature
Authors: Hummel Scott R. , Hossain Kishwar , Hayes Gregory T. 
Published: April 2004

AbstractA procedure was developed and experiments were performed to measure the biaxial stress relaxation of High Impact Polystyrene (HIPS) sheets above the glass transition temperature. Tests were performed at various temperatures and strain magnitudes. The data were normalized to unity at time zero to isolate the time dependence of the stress from the strain dependence. The results show that the time dependent biaxial stress relaxation properties were independent of the magnitude of the stress or strain for small strains. The stress relaxation curves were fitted to a Prony series and i1 was found that time‐temperature superposition could be applied to interpolate the normalized relaxation. Uniaxial stress relaxation tests were also performed and the results were compared to that of the biaxial testing program.
Izod impact strength of a product molded of poly(vinyl chloride)/impact modifier containing voids (void MOD)
Authors: Takaki Akira , Narisawa Ikuo , Kuriyama Takashi 
Published: April 2004

AbstractThe Izod impact strength of a PVC (polyvinylchloride)/MOD (impact modifier) molded product was investigated by suitably reducing the amount of crosslinking agent in the rubber of MOD or by making rubber particles void when they were in the form of a latex. As a result, (1) when the amount of crosslinking agent in rubber was suitably reduced, the Izod impact strength of the PVC/MOD molded product was improved in both ordinary MOD and void MOD. However, with the extremely small amount of crosslinking agent, low Izod impact strength was exhibited. With the same amount of crosslinking agent, the void MOD showed higher Izod impact strength than the ordinary MOD. (2) SEM (scanning electron microscope) and TEM (transmission electron microscope) observations on the broken surface revealed that shear yield and crazing occurred in a whitened portion, and crazing was observed only near the surface of the broken section in a non‐whitened portion. It was also found that when the crosslinking degree of rubber was reduce, cavitations were liable to be formed in rubber under stress and expanded under rubber stress in the void MOD mor‐; than in the ordinary MOD. (3) As a result of a tensile test on the molded product, it was found that the void MOD caused lower yield stress than the ordinary MOD, thereby increasing in stress concentration. (4) P'rom these results, an estimation was earned out of the mechanism of improvement in the Izod impact strength of the MOD or void MOD using rubber with an appropriately lowered crosslinking degree.
Rheokinetics and the influence of shear rate on the Trommsdorff (gel) effect during free radical polymerization
Authors: Cioffi M. , Hoffmann A. C. , Janssen L. P. B. M 
Published: April 2004

AbstractSome rheokinetic studies of free radical polymerization have been published In the past. They generally make modeling of the time dependent increase of viscosity possible at low degrees of conversion, where Newtonian behavior holds and the rheokinetic equations can be linearized. In this paper we try to extend the rheokinetic approach to the region of high degrees of conversion, where the reacting solution is non‐Newtonian and the shear rate at which the polymerization is performed becomes a fundamental parameter. Moreover, nonlinear phenomena such as the Trommsdorff effect and phase separations are likely to occur‐ The principal result of this study is that the Trommsdorff effect is reduced and sometimes eliminated when the polymerization is performed at high shear rate. Instabilities of the time dependent increase of viscosity occurred when the conversion was higher than 85%. They were attributed to phase separation of the macromolecules under shear flow.
Mentallocane plastomer modification of polypropylenes
Authors: C. Yu Thomas 
Published: April 2004

AbstractPlastomers are ethylene alpha‐olefin coplymers made from the single site metallocdene catalyst using a variety of polymerization processes. The key features are uniform intermolecular and intermolecular comonomer distribution, low extractables, comonomer dependent. meleting point, and low ashcontent. The uniform comonomer behavior. The dual characterplastomer evolved into a new class of impact modifiers for polypropylenes replacing the conventional ethylene‐propylene cooplymer (EPR)to produce both thermoplastic olefins (TPOs) and thermoplastic elastomers(TPEs). Ahybrid TPE based on grafting of a functional butyl rubber to plastomer was explored. Low temperature impact and clarity can be achieved by matching the reflective index of a plastomer with a random polypropylene copolymer (RCP).
Disprsion in high viscosity ratio polyolefin blends
Authors: Huneault Michel A. , Mighri Frej , Ko Glen H. , Watanabe Fuminao 
Published: April 2004

AbstractThe dispersion of polyethylene and polyropylene in a polypropylene matrix using a co‐rotating twin screw extruder has been investigated. Poymer pairs were selected to study the effect of viscosity ratio, defined as the viscosity of the minor component over that of the matrix, in the range 0.1 to 900. The dispersion quality was defined by determining the number of “gels,”i.e., large undispersed particles, present in thin films and by conventional microscopy techniques. The gel numbers were found to increase steadily with the viscoty ratio. It was also observed that particle size distributions in the high viscosity ratio blends was very broad, with particles as large as a hundred microns coexisting with much finer ones in the sub‐micron range. For a given polymer blend, the re‐processing was found to have and important effect on gel reduction. The effect of rotation speed, flow rate minor phase feeding position was aso investigated and is discussed in the paper.
Shrinkage behavior and optimization of injection molded parts studied by the taguchi method
Authors: Chang Tao C. , Faison Ernest 
Published: April 2004

AbstractShrinkage behavior of a plastic plays a critical role in determining the final dimensions of an injection‐molded part. It is well known that process conditions affect many properties of plastic parts, including shrinkage. This study applies the Taguchi method to systematically investigate the effects of process conditions on the shrinkage (along‐ and across‐the‐flow directions) of three plastics: high‐density polyethylene (HDPE), general‐purpose polystyrene (GPS), and acrylonitrile‐butadiene‐styrene (ABS). The results show that HDPE, a semicrystalline plastic, shrinks more than GPS and ABS, two amorphous materials. The extent of anisotropic shrinkage in the along‐the‐flow and across‐the‐flow directions for HDPE is different from GPS and ABS. More shrinkage occurs in the across‐the‐flow direction of HDPE than in its along‐the‐flow direction. The reverse is true for GPS and ABS. Mold and melt temperatures, along with holding pressure and holding time, are the most significant influences on the shrinkage behaviors of three materials, although the importance of each is different for each plastic. The optimal conditions for reducing shrinkage identified by the Taguchi method are experimentally verified and validated by t‐statistic tests. The prediction matches very well with the experimental value for the along‐the‐flow shrinkage of GPS.
Industrial high pressure ethylene polymerization initiated by peroxide mixtures: A reduced mathematical model for parameter adjustment
Authors: Asteasuain M. , Pereda S. , Lacunza M. H. , Ugrin P. E. , Brandolin A. 
Published: April 2004

AbstractWe present a method for the adjustment of parameters in the mathematical modeling of industrial tubular reactors for high pressure polymerization of ethylene. We propose a reduced mathematical model for these reactors that aids in the task of model parameter update commonly done periodically in industrial plants. This reduced model was built from a detailed model for multiple peroxide and oxygen initiator systems we had developed before. Some of the assumptions in that rigorous model were reviewed in order to minimize computational effort. Good and faster predictions were obtained by assuming different constant jacket temperatures and pressures at each zone. Pressure pulse equations had to be included in the model. A simplification of the adjustment procedure is also proposed here. It consists in using only the reactions considered crucial for the description of this polymerization. The peroxide initiator and solvent mixtures were treated as fictitious unique initiator and solvent respectively. A procedure was established for the quick estimation of the kinetic parameters that represent initiator and solvent mixtures of different compositions. This resulted in a model that can be adjusted rapidly to predict the behavior of a specific industrial reactor. The reduced model was validated using experimental runs initiated by oxygen either alone or together with peroxide mixtures.
Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systems
Authors: Avérous Luc , Fringant Christophe 
Published: April 2004

AbstractDifferent formulations of wheat thermoplastic starch (TPS) have been processed with various plasticizer/starch ratios and moisture contents. The biodegradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA), polybutylene succinate adipate (PBSA) and polybutylene adipate co terephtalate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various properties are evaluated such as the mechanical properties (tensile and impact tests), and the hydrophilic character with contact angle measurements. Additionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post‐injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give some indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measurement show that we have a drastic increase of the hydrophobic character from 10% of polyester in the blend. The different combinations of TPS and polyesters give a wide range of mechanical behavior for compostable materials, to be developed in specific applications.
Foaming of low‐density polyethylene in a dynamic decompression and cooling process
Authors: Song Kwangjin , Apfel Robert E. 
Published: April 2004

AbstractEffects of the properties of polymers and blowing liquids on the macrostructure and microstructure of foamed products in a dynamic decompression and cooling (DDC) process have been investigated. When the homogeneous solutions, prepared by the heating and mixing of the mixtures of low‐density polyethylenes (LDPE) and chlorinated hydrocarbons under nitrogen (N2), go through a rapid pressure quench above the boiling point of the liquids, bubbles nucleate out through liquid/gas phase separation and grow through diffusion and expansion of the gaseous phases. Foam cell stabilization is improved by polymers exhibiting higher extensional hardening and blowing liquids possessing higher latent heat of evaporation. Resultant LDPE foams have mixed cell structures: in the skin parts, more cells are closed, but more cells are open in the core parts. In the polymer matrix, micromorphologies of granules, fibers, and fiber networks, with oriented lamellae, are observed. The formation of these complex structures is described in terms of phase and deformation behaviors of the solutions.
Geometric mean vs. Arithmetic mean in extrusion residence time studies
Authors: Unlu Emine , Faller James F. 
Published: April 2004

AbstractGeometric mean residence time was compared with the arithmetic mean residence time for a residence time distribution study conducted on a twin‐screw extruder using a salt tracer and electrical conductivity measurements. Electrical conductivity of the cornmeal melt was measured at the die exit. All RTD curves obtained during the study were skewed to the right with very long tails that resulted in inflated arithmetic mean residence times. In order to alleviate the problem of long tails, different approaches were considered. Among these approaches, logarithmic transformation of the time scale to calculate the geometric mean residence time was shown to best represent the residence time distribution in terms of mean residence time and spread of the RTD. The log transformation of the time scale alleviates the problem of inappropriate shifting of the mean residence time due to long tails. The difference between the upper limits and lower limits for the log transformed data was found to be more appropriate to define the spreads of the distributions as the untransformed data resulted in quite variable spreads.
Cure kinetics and physical properties of dicyanate/polyetherimide semi‐IPNs
Authors: Kim Dae‐su , Choi Khee‐hwan 
Published: April 2004

AbstractThe curing behavior and physical properties of dicyanate/polyetherimide (PEI) semi‐interpenetrating polymer network (IPN) systems were investigated. Differential scanning calorimetry (DSC) was used to study the curing behavior of the dicyanate/PEI semi‐IPN systems. The curing rate of the semi‐IPN system decreased as the PEI content increased. An autocatalytic reaction mechanism can describe well the curing kinetics of the semi‐IPN systems. The reaction kinetic parameters were determined by fitting DSC conversion data to the kinetic equation. The glass transition temperature of the semi‐IPNs decreased with increasing PEI content. Two glass transitions due to phase‐separated morphology were observed for the semi‐IPN containing over 15 phr (parts per hundred parts of dicyanate resin) PEI. The thermal stability and dynamic mechanical properties of the semi‐IPNs were measured by thermal analysis.
A two‐zone melting model for polymer blends in a batch mixer
Authors: Li Huxi , Hu Guo‐hua 
Published: April 2004

AbstractThe rate of the morphology development of immiscible polymer blends is closely related to the rates of melting of the polymer constituents. A two‐zone model was developed to describe the rate of melting of the polymer pellets of mixtures of two semicrystalline polymers in an internal batch mixer. The mixing chamber was divided into two zones: high temperature and high shear zone, and low temperature and low shear zone. Melting was assumed to occur mainly in the first zone. Moreover, pellets were assumed to be spherical, and melting proceeded from the outersurface to the core in a gradual manner. For a given pellet, the rate of melting depended, among other things, upon the number of passes through the high shear and high temperature zone and the time it experiences therein. The validity of the model was confirmed experimentally in terms of the number and weight fraction of solid pellets as a function of mixing time.