bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation behavior of a polyvinyl chloride (PVC) tube by mandrel drawing
Authors: Ulas I. 
Published: April 2004

AbstractBiaxial mechanical properties of products produced by drawing over an expanding mandrel are found to be closely associated with the imposed axial and hoop draw ratio. The paper assists the understanding of the deformation behavior and related mechanical improvements in a processed polyvinyl chloride (PVC) tube and shows that behavior is controlled by the polymer network structure. The effect of post‐mandrel bath cooling on product straightness, spring‐back, and thickness distribution was investigated, and it was shown that bath cooling greatly improves the quality and integrity of the product.
Coarsening in molten quiescent polymer blends: The role of the initial morphology
Authors: Willemse R. C. , Ramaker E. J. J. , Van Dam J. , De Boer A. Posthuma 
Published: April 2004

AbstractCoarsening of the phase dimensions in polymer blends under quiescent conditions is studied in blends of different morphologies; the dependence of the rate and extent of coarsening on the initial morphology is demonstrated. In blends with a droplet/matrix structure, coarsening via coalescence is found only above the percolation threshold for spherical particles (16 vol%). The rate of coalescence in the droplet/matrix structure is shown to obey the theory of Fortelny and Zivny for coalescence of droplets in quiescent media, and no constant level of the phase dimensions is reached. Below a volume fraction of 0.16 limited coarsening is found only for fibrillar and co‐continuous morphologies. This coarsening is in fact the result of a restructuring because retraction and breakup occur, leading to a droplet/matrix morphology in which the droplet diameter is approximately twice the diameter of the original fiber. Breakup and retraction are completed in a short time relative to coalescence. At higher volume fractions in co‐continuous structures (>30 vol%), these structures do not break up, and coarsening is found to take place by retraction only. No constant level of the phase dimensions is reached in the latter case.
Morphology and mechanical performance of pregenerated and “in‐situ” PP/vectra B composites
Authors: Vallejo F. J. , Eguiazábal J. I. , Nazábal J. 
Published: April 2004

AbstractPolypropylene/Vectra B blends were obtained at different LCP contents and barrel temperatures by an extrusion‐injection process. The wide barrel injection temperature range chosen, from 200 to 300°C, gave rise to blends in which the pregenerated extruded morphology was preserved, partially preserved, or lost. The blends processed at 260 and 300°C showed the usual morphology and properties of “in‐situ” composites. The blends injected at 240°C showed the worst properties because of their partially melted and agglomerated morphology. A barrel temperature of 200°C (80°C below the melt temperature of Vectra B) was needed to maintain the pregenerated fibers. These pregenerated composites, without post‐extrusion drawing, showed smaller modulus of elasticity and tensile strength than those of the “in‐situ” composites, but an increased notched impact strength as a consequence of their less perfectly oriented but more homogeneous morphology.
DC conductivity and dielectric response in amorphous polycarbonate of Bisphenol‐A
Authors: Santos S. , Cedeño A. , Gómez C. 
Published: April 2004

AbstractWe report the dielectric response measurements of amorphous polycarbonate of Bisphenol‐A at room temperature in the frequency range from 12 to 105 Hz. The data is analyzed within the graphical representation of Wei and Sridhar. Such an approach has allowed us to estimate the DC conductivity value of the order of 5 × 10−11 S/m in good agreement with the direct DC measurements.
A study of rheological behavior of a polypyrrole modified UHMWPE gel using a parallel plate rheometer
Authors: Chiu Hsien‐Tang , Wang Jyh‐Horng 
Published: April 2004

AbstractPolypyrrole powder was added to a 6% UHMWPE decalin solution as an interfacial modifier. Rheological properties and dynamic viscoelastic properties, including shear viscosity, shear storage modulus (G′), and shear loss modulus (G″), were measured with a parallel plate rheometer using rotation and oscillation modes. The results show that these properties increase with the PPy content. In addition, the gelation temperature decreased with increasing PPy content. This suggests that the presence of PPy enhanced the entanglement network in the solution, which is similar to the role of filler in rubber.
Monodisperse poly(p‐chloromethylstyrene) microbeads by dispersion polymerization
Authors: Bahar T. , Tuncel A. 
Published: April 2004

AbstractIn this study, an alternative dispersion polymerization method for the para isomer of chloromethylstyrene was proposed. Highly monodisperse poly(p‐chloro‐methylstyrene) (PCMS) particles in the size range of 1.67–3.75 μm were obtained. The monodispersity and the isolation yield of PCMS particles were significantly improved relative to the methods available in the literature. Azobisisobutyronitrile and polyacrylic acid were selected as the initiator and the steric stabilizer, respectively, in the dispersion medium composed of ethanol and methoxyethanol. The results indicated that the particle size increased with increasing initiator concentration. An increase in the stabilizer concentration led to a decrease in the particle size. The methoxyethanol/ethanol ratio was found as one of the most important parameters controlling the average size and the size distribution. Contrary to the tendencies noted in the literature, the particle size decreased with increasing polymerization temperature.
Polymer‐dispersed liquid‐crystal polymers (PDLCPs). Morphology of the LCP droplets
Authors: Magagnini Pierluigi , Paci Massimo , Poli Giovanna , Tonti Maria Silvia , Narducci Piero 
Published: April 2004

Abstract“Synthetic blends” of a flexible polymer forming the matrix and a liquid‐crystalline polymer (LCP) forming the dispersed phase have been prepared by transesterification of PET with a mixture of sebacic acid (S), 4,4′‐diacetoxybiphenyl (B) and 4‐acetoxybenzoic acid (H) in the mole ratio 1:1:2. A change of the synthesis conditions causes marked variations of the chemical composition and the morphology of the phases. The SEM investigation of the inner morphology of the LCP droplets of blends consisting of two phases with fairly different aromatic content has shown that the LCP macromolecules are aligned tangentially at the matrix surface boundary, and that the nematic director configuration is toroidal. When the two phases have closer chemical composition, and are therefore supposed to possess improved mutual compatibility, a perpendicular anchoring of the LCP fibrils to the matrix cavity surface, and an axial configuration of the nematic director, are observed. The expected effect of the nematic configuration of the LCP droplets on their ability to deform into fibrils under appropriate flow conditions is preliminarily discussed.
Control of orientation in liquid crystalline epoxies via magnetic field processing
Authors: Lincoln Derek M. , Douglas Elliot P. 
Published: April 2004

AbstractWe demonstrate control over the orientation of the 4,4′‐bis(2,3‐epoxypropoxy)‐α‐methylstilbene (EPAMS)/sulfanilamide (SAA) epoxy system. A statistical experimental design was generated and analyzed to determine the effects of the time in the magnetic field, field strength, and the amount of B‐staging. A regression model with a coefficient of determination, R2, of 0.8577 was calculated to predict the orientation parameter for the input variables. An optimization study was also conducted to check the prediction of the orientation parameters by the model. The model can predict the experimentally measured orientation in regions where the model predicts physically realistic values for the orientation.
Reactive compatibilization of polypropylene and polymide‐6,6 with carboxylated and maleated polypropylene
Authors: Manning Steven C. , Moore Robert B. 
Published: April 2004

AbstractBlends of polypropylene and polyamide‐6,6 have compatibilized with polypropylene that was carboxylated through a reactive extrusion process with an asymmetric functional peroxide. The compatibilized blends demonstrated a finely dispersed minor phase as shown by SEM. Because of the enhanced dispersion, additions of the carboxylated polypropylene to the blends resulted in a change in the crystallization nucleation mechanism of the PA‐6,6 minor phase from heterogeneous to homogeneous in nature. A linear increase in the impact strength and significant enhancement in the tensile properties of the blends was observed with incorporations of the compatibilizer up to 30% of the matrix phase. In addition, the compatibilizing efficiency of the carboxylated polypropylene was compared to the of maleic anhydride functionalized polypropylene. When compared on an equivalent basis (total concentration of carboxylate or anhydride functionality added to the blend), the carboxylated polypropylene demonstrated a slightly better compatibiliziling efficiency than that of the anhydride functionalized polypropylene. The higher compatibilizing efficiency of the carboxylated polypropylene was attributed to a higher grafting efficiency of the carboxylation procedure as compared to the anhydride functionalization procedure.
Numerical modeling of injection/compression molding for center‐gated disk: Part II. Effect of compression stage
Authors: Kim I. H. , Park S. J. , Chung S. T. , Kwon T. H. 
Published: April 2004

AbstractIn the accompanying paper, Part I, we have presented a physical modeling and the associated numerical analysis of the injection molding process with a compressible viscoelastic fluid model. In Part II, effects of the compression stage in the injection/compression molding process are presented. Numerical results showed that the injection/compression molding process reduced birefringence as compared with the injection molding process. In this respect, the injection/compression molding process seems to be more suitable for manufacturing precise optical products of good optical quality than the injection molding process. Effects of the packing stage on the birefringence distribution in the injection/compression molding process were found to be similar to those in the injection molding process. Our numerical results show that the birefringence becomes smaller as the melt temperature gets higher and the closing velocity of the mold gets smaller with the flow rate and the mold temperature affecting the birefringence insignificantly. As far as the density distribution is concerned, the flow rate, melt temperature, and mold closing velocity have insignificant effects on the density distribution in comparison with the mold temperature.
Influence of compatibilization and viscosity ratio on the barrier and impact properties of blends of a modified polyamide‐6 and polyethylene
Authors: Yeh Jen‐Taut , Jyan Chau‐Fae , Yang Shun‐Syu , Chou Shen 
Published: April 2004

AbstractNylon 6 was grafted with a zinc‐neutralized ethylene/acrylic acid copolymer (CP) to produce four different modified polyamides (MPA) with varying CP content. These were mixed with four polyethylenes with different viscosities and the blends were blow‐molded into bottles. The clearest MPA lamina was developed for blends with an optimum ratio of the viscosities of MPA and PE (VRoptimum), and bottles with the clearest lamina exhibited the best xylene permeation resistance, impact strength and the highest melting temperature (Tm). The value of VRoptimum increased with increasing CP content. A maximum improvement in barrier properties of MPA was found as the CP content reached about 15 wt%. The CP content of the MPA, however, only slightly affected the impact strength and xylene permeation resistance of the bottles.
Synthesis and solution properties of poly(acrylamide‐styrene) block copolymers with high hydrophobic content
Authors: Shaikh Sohel , Ali Sk. Asrof , Hamad Esam Z. , Abu‐Sharkh Basel F. 
Published: April 2004

AbstractHydrophobically associating block copolymers of polyacrylamide/styrene with a high hydrophobe content were synthesized using micellar copolymerization under various conditions of surfactant and initiator concentrations with the objective of determining the conditions that produce optimum solution properties for enhanced oil recovery. Solubilities, aqueous solution viscosities and interfacial properties with air and oil of the copolymers were investigated. The influence of salt on the solution properties was also studied. Nature of hydrophobic sites and onset of hydrophobic association were studied by measuring the fluorescence of pyrene in polymer solutions. Optimum solution properties were obtained for copolymers synthesized under conditions of high surfactant and initiator concentrations. The copolymers displayed substantial thickening properties at low concentrations with enhanced thickening in the presence of salt. The interfacial tensions of the aqueous solutions with n‐decane and air were also reduced. Interfacial properties were slightly sensitive to salt concentration. The copolymer solutions showed shear and temperature thinning behaviors typical of polymer solutions.
Numerical simulation of wire‐coating: The influence of temperature boundary conditions
Authors: Wapperom Peter , Hassager Ole 
Published: April 2004

AbstractA finite element program has been used to analyze the wire‐coating process of an MDPE melt. The melt is modeled by a nonisothermal Carreau model. The emphasis is on predicting an accurate temperature field. Therefore, it is necessary to include the heat conduction in the metal parts. A comparison is made with the results of a simulation that models the heat conduction in the metal head by means of a Biot boundary condition. The influence of the wire velocity, inlet temperature and power‐law index will be examined.
Rheokinetical behavior of melamine‐formaldehyde resins
Authors: Hagstrand P.‐O. , Klason C. , Svensson L. , Lundmark S. 
Published: April 2004

AbstractThe effects of cure temperature and amount of catalyst on the rheokinetical behavior of a melamine‐formaldehyde (MF) thermosetting system is investigated using a dynamic mechanical technique similar in nature to Torsion Impregnated Cloth Analysis (TICA) and Torsional Braid Analysis (TBA). The proposed name of the used technique is Torsional Substrate Analysis (TSA). Isothermal cures of the resin are carried out from 115°C to 160°C for varying amounts of catalyst. Each TSA measurement exposes several transitions. First, a glass‐to‐liquid transition during the heatup procedure is seen, indicated by sharp peaks of the loss shear modulus, G″, and loss tangent, tanδ. Later, vitrification is seen, indicated by a second G″ maximum. Finally, a completion of shift to a diffusion controlled cure reaction occurs, shown as a storage shear modulus, G′, plateau. The rheokinetical data is used to construct Time‐Temperature‐Transformation (TTT) cure diagrams, for each level of catalyst. High pressure differential scanning calorimetry (HPDSC) measurements are carried out in order to estimate the fractional conversion of samples that have been cured isothermally for times corresponding to a second tanδ maximum, the second G″ maximum, and the G′ plateau. The fractional conversion is determined by the residual entalphy technique. The HPDSC measurements do not give a clear answer whether the second tanδ maximum corresponds to gelation or not. It is therefore likely that TSA, like similar techniques, is not capable to detect gelation. A glass transition temperature of 130°C and 150°C is found to correspond to a fractional conversion of 0.65 and ∼0.80, respectively. Preliminary measurements suggest that the maximum glass transition temperature, Tg ∞, of the investigated MF resin is at least 180°C.
Vacuum forming of thermoplastic foam
Authors: Akkerman Remko , Pronk Ruud 
Published: April 2004

AbstractThe process of thermoforming of foam sheet is analyzed using both finite element modeling and experiments. A simple constitutive model for finite tensile deformations of closed cellular material around its glass transition temperature is proposed, starting from well‐known results from Gibson and Ashby (1988). The model is implemented in a finite element code and applied in isothermal vacuum forming simulations. The distributions of thickness and in plane strains are in adequate accordance to the experimental results.
Supercritical carbon dioxide assisted blending of polystyrene and poly(methyl methyacrylate)
Authors: Elkovitch Mark D. , Tomasko David L. , Lee L. James 
Published: April 2004

AbstractA method for blending polystyrene and poly(methyl methacrylate), (PMMA), with the addition of supercritical carbon dioxide has been investigated. The first series of blends was a PMMA and polystyrene with similar melt viscosities. The second series of blends was a PMMA and polystyrene with a viscosity ratio (ηPMMA/ηpolystyrene) of about 20. The results show that a reduction in the size of the minor or dispersed phase is achieved when supercritical carbon dioxide is added to the blend system. A high‐pressure mixing vessel was used to prepare the blends under pressure with carbon dioxide for batch blending. The solubilities of CO2 in PMMA and polystyrene, measured in the high‐pressure mixing vessel at 200°C and 13.78 MPa (2000 psi) was 5.8 and 3.6 wt%, respectively. A single screw extruder was used to study the effects of carbon dioxide on the viscosity of polymer melts. The melt viscosity of PMMA was reduced by up to 70% with approximately 0.4 wt% CO2. The melt viscosity of polystyrene was reduced by up to 56% with a CO2 content of 0.3 wt%. A twin screw extruder was used to study the effects of injecting carbon dioxide in a continuous compounding operation.
An improved kinetic model for the peroxide initiated modification of polyethylene
Authors: Pedernera Marisa N. , Sarmoria Claudia , Vallés Enrique M. , Brandolin Adriana 
Published: April 2004

AbstractWe propose a generalized kinetic model for the peroxide initiated modification of polyethylene. It takes into account not only combination reactions but also transfer to polymer and scission. The model describes the length of the polymer chain and the concentration of vinyl groups simultaneously. Any number of vinyl groups per molecule is allowed. The resulting infinite system of mass balance equations is solved using a double moment technique. The model calculates number, weight and z‐average molecular weights and the average concentration of vinyl groups as functions of time. The kinetic constants and the initiation efficiency were estimated through a nonlinear regression using experimental data. The relevance of each one of the reactions included in the mechanism was assessed. By means of the model we studied the influence of temperature and initial peroxide concentration on the modified polymer properties. It follows well the observed experimental trends and gives good estimates of both average molecular weights and average vinyl content, within experimental error.
Crystallinity and microstructure in injection moldings of isotactic polypropylenes. Part 1: A new approach to modeling and model parameters
Authors: Guo X. , Isayev A. I. , Guo L. 
Published: April 2004

AbstractThe present study is an attempt to formulate a new approach to the modeling of the injection moldings of semicrystalline polymers. A phenomenological approach is employed to develop the qualitative description of crystallization phenomena under nonisothermal flow occurring in various polymer processing operations. The unified crystallization model, which is suitable to describe the multilayer microstructure arising in the injection moldings of semicrystalline polymers, is proposed. The “competing mechanisms” of crystallization in terms of the induction time indices for introducing various microstructure layers are utilized to quantitatively distinguish between the highly oriented skin layer and spherulitic core in the moldings. The application of the equations of continuity, momentum and energy, along with the rheological model, the equation of state and the unified crystallization model, to the injection molding process leads to the modeling of crystallinity and microstructure development in the moldings. The material parameters to be used in the modeling of the crystallinity and microstructure development in the injection moldings of isotactic polypropylenes (i‐PP's) with various molecular weights are determined. The melt viscosity as a function of shear rate and temperature is measured and fitted to the modified Cross model. Quiescent crystallization kinetics, including the induction time and the heat release due to crystallization, is characterized using differential scanning calorimetry. The spherulite growth rate of i‐PP's under isothermal and nonisothermal quiescent crystallization conditions is measured by optical microscopy. The molecular deformation factor during the induction period of shear‐in‐duced crystallization is obtained from the extrusion‐quenching and extrusion‐relaxation‐quenching experiments with a slit die. The variation of the induction time with shear rate obtained by Lagasse and Maxwell from the shearing‐crystallization experiments is used to determine the shear enhancement coefficient of crystallization.
Crystallinity and microstructure in injection moldings of isotactic polypropylenes. Part II: Simulation and experiment
Authors: Guo X. , Isayev A. I. , Demiray M. 
Published: April 2004

AbstractThe injection moldings of isotactic polypropylenes with various molecular weights were simulated using finite difference method. In the simulations, the unified crystallization model proposed in our previous paper was applied. The prediction of crystallinity and microstructure development in the moldings was based upon the crystallization kinetics and the “competing mechanisms” for introducing various microstructure layers in the moldings. Extensive injection molding experiments were carried out. The pressure traces during the molding experiments were recorded. The crystallinity distribution in the moldings was determined using differential scanning calorimetry. The measurements on the microstructure embedded in the moldings were performed, including the thickness of the highly oriented skin layer and the gapwise distribution of the spherulite sizes. The measured data for the crystallinity and microstructure in the moldings were compared with the simulated results. The effects of molecular weight and processing conditions on the development of crystallinity and microstructure in the moldings were elucidated. Theoretical predictions were found to be in a good agreement with experimental measurements.
Attempts to enhance the properties of EPON 830‐4,4′‐methylene bis cyclohexylamine epoxy resin systems by exposing them to 0.1290 to 0.8810 Tesla magnetic fields while thermally curing them
Authors: Gerzeski Roger 
Published: April 2004

AbstractThis effort determined if enhancements to the properties of fully cured EPON 830‐4,4′‐Methylene Bis Cyclohexylamine epoxy resin systems (ERSs) could be induced by thermally curing them, while also simultaneously exposing them to economically generated magnetic fields (MFs). Stoichiometric mixes were cured for 5 hours at 121°C while being exposed to MFs between 0.1290 and 0.8810 Tesla. Exposed and control specimens were simultaneously cast from the same mix in each run. The resulting specimens were mechanically and thermally tested to find any property differences. This effort determined that under these conditions there were no modifications to the properties of MF exposed, fully thermally cured, ERSs relative to their controls.