bluuebunny/crossref_metadata_2025_split huggingface dataset:
Foam formation in gas‐assisted injection molded parts: Theoretical and experimental considerations
Authors: Potente H. , Moritzer E. , Obermann C. H. 
Published: April 2004

AbstractThis article is concerned with a physico‐mathematical model to describe the foaming phenomenon in gas‐assisted injection molded parts. The investigations have been conducted on polycarbonate grades to begin with. When parts are produced by gas injection molding, foam has the effect of weakening the residual wall thickness and also of impairing optical quality. It would thus be an advantage if a parameter constellation could be defined in advance, which would ensure the suppression of foam formation.
Polymer blends with spatially graded structures prepared by phase separation under a temperature gradient
Authors: Tran‐Cong Qui , Okinaka Jin 
Published: April 2004

AbstractPhase separation of poly(2‐chlorostyrene)/poly(vinyl methyl ether) (P2CS/PVME) blends driven by a temperature gradient was investigated by phase‐contrast optical microscopy combined with digital image analysis. The samples were set in a temperature gradient in such a way that the two ends of the gradient cover both sides of the critical point. When the high‐temperature side of the gradient is increased with a constant rate, the interface that divides the miscible and the phase separated regions of the blend moves toward the low temperature side, leaving the phase separating region behind. It was found that in the vicinity of this interface, the phase separation takes place slowly via the spinodal decomposition process, giving interconnecting structures. In the region far from the newly growing interface, the droplet morphology appears as a result of the late stage of the spinodal decomposition. These droplets grow with time according to the power law ξ ∝ tβ, with β increasing from 0.30 to 0.44 along the temperature gradient. The phase separated blends with these graded morphologies show the broadened mechanical tanδ due to the graded structures distributed along the temperature gradient.
Properties of aminosilane grafted moisture curable poly(vinyl chloride) formulations
Authors: Fernández O. S. Rodríguez , Gilbert M. 
Published: April 2004

AbstractThe reaction of plasticized PVC with [N‐(2‐amino ethyl)‐3aminopropyl trimethoxy silane] yielded silane‐grafted PVC that was crosslinked by a hydrolytic mechanism. It was found that crosslinking resulted in improvement of mechanical properties (tensile strength and elongation at break) specially at temperatures higher than 80°C. Properties at 130°C were substantially enhanced, showing a fourfold increase in ultimate tensile strength (UTS), and a twofold increase in elongation at break. There was a unique relationship between UTS at 130°C and gel content irrespective of processing conditions, with UTS starting to increase sharply around 30% gel content, and reaching a plateau at about 60%. Also, the softening temperature was improved. The crosslinked material had a higher softening temperature (up to 165°C, compared with 95°C for the compound without crosslinking agent), indicating that the hydrolytic crosslinking of PVC yielded a material with improved properties.
Carbon black–filled immiscible blends of poly(vinylidene fluoride) and high density polyethylene: The relationship between morphology and positive and negative temperature coefficient effects
Authors: Feng Jiyun , Chan Chi‐Ming 
Published: April 2004

AbstractConductive polymer composites were prepared by melt‐mixing of an immiscible blend of poly(vinylidene fluoride) (PVDF), high density polyethylene (HDPE), and carbon black (CB). Three major factors—the carbon black content, the carbon black type, and the composite morphology—were shown to have remarkable effects on the positive temperature coefficient (PTC) and negative temperature coefficient (NTC) effect of the composites. The relationship between the morphology and the PTC and NTC effects of the composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The OM micrographs indicated that CB was selectively located in the HDPE phase and the SEM micrographs showed that there were some gaps between the two phases. The PTC effect of the composites is caused by the thermal expansion as a result of the melting of the HDPE crystallites. The morphology of the composites greatly affects the PTC and NTC behaviors of the composites. When the CB‐filled HDPE formed a continuous phase and the PVDF formed a dispersed phase, the PTC and NTC behaviors of the composites were similar to those of CB‐filled neat HDPE composite without crosslinking. When the composite exhibited an interlocking structure, a normal PTC effect could also be observed, but the NTC effect was delayed to higher temperatures. A mechanism was proposed to explain this new physical phenomenon, and the mechanism was verified by another CB‐filled polymer blend comprising an alternating copolymer of tetrafluoroethylene‐ethylene and HDPE.
The properties of recycled PVC bottle compounds. 1: Mechanical performance
Authors: Arnold J. C. , Maund B. 
Published: April 2004

AbstractThe properties of recycled PVC bottle material separated from the post‐consumer waste stream were investigated. In the first part of this study, attention was focused on the mechanical properties. In order to examine the effects of recycling, the properties of the recycled material were compared with those of virgin PVC and pure material that had been processed into bottles and then granulated. The effects of pulverization of the recycled material were also studied. The mechanical properties investigated included tensile, fatigue, and environmental stress cracking tests, in conjection with fracture surface examination, molecular weight determination, and impurity analysis. It was found that the recycled material did show significant reduction in strength and ductility, though pulverization improved the situation considerably. The main reason for this was the presence of impurities, especially PET, which although present at levels below 0.5% had a large effect on the properties.
The properties of recycled PVC bottle compounds. 2: Reprocessing stability
Authors: Arnold J. C. , Maund B. 
Published: April 2004

AbstractFollowing a study of the mechanical properties of recycled PVC recovered from post‐consumer bottles, this study focuses on the effects of recycled material on processing. In particular, the effects of multiple recycling were studied to investigate any problems that may arise due to the repeated incorporation of recycled material into the processing stream. Batches of recycled flake and powder as well as pure but processed bottle flake material were subjected to simulated multiple recycling using a Torque Rheometer. Ten minutes at 170°C followed by granulation represented one recycle. Molecular weight and Infrared analyses were performed to assess the degree of degradation occurring during reprocessing. The results indicated a rapid degradation of the two recycled grades when compared with the purer bottle flake PVC. Further multiple recycling was then performed on bottle flake mixed with 0.2% polyethylene, which showed that the PE impurities accelerate the degradation process. Finally, the effects of restabilizing by adding new bottle flake material at each step were investigated. It was shown that surprisingly small levels of new material (30%) prevented degradation, even after 15 recycle steps.
Plasticization of poly(styrene‐b‐isobutylene‐b‐styrene) ionomers by acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate
Authors: Storey Robson F. , Baugh Daniel W. 
Published: April 2004

AbstractPoly(styrene‐b‐isobutylene‐b‐styrene) block copolymer ionomer (overall molecular weight = 71,200 g/mole; 25.5 wt% polystyrene, 4.7% sulfonation of phenyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. Results were compared to the same polymer plasticized by zinc stearate. Plasticizers were added to the polymer at levels of ≈5 wt%. Films were prepared by solution casting from tetrachloroethylene. Thermogravimetric analysis (TGA) showed all ODAB derivatives to have lower decomposition temperatures than zinc stearate. Dynamic mechanical analysis (DMA) of the films showed varying degrees of ionic plasticization as evidenced by a lowering of the temperature at which the onset of flow occurred. With the exception of the stearic acid salt of ODAB, all ODAB derivatives were more efficient ionic plasticizers than zinc stearate. Among the ODAB derivatives, the degree of ionic plasticization varied, with the methane sulfonic and p‐toluene sulfonic acid salts being most effective, leading to the conclusion that processing temperatures could be tailored to specific applications by choice of plasticizer and level of incorporation.
Monitoring the evolution of PET branching through chemorheology
Authors: Dhavalikar R. , Xanthos M. 
Published: April 2004

AbstractThere is a high interest in modifying the rheological properties of polyethylene terephthalate (PET) through structural modifications while maintaining its thermoplastic nature. This article reports real‐time spectroscopic and rheological monitoring of the effects of reactive melt modification of PET with a multi‐functional epoxide—triglycidyl isocyanurate (TGIC)—that lead to chain extension/branching and subsequently formation of gel‐like structures. An infrared spectroscopic technique to monitor the simultaneously occurring degradation and chain extension/branching reactions was evaluated. The effects of reaction temperature, shear rate, and residence time were also investigated. Frequency scans at various time intervals on the reacting samples provided information on changes in the degree of branching and melt elasticity. The effect of method of sample preparation for chemorheological testing was also evaluated in this study. A 50% excess of the stoichiometric amount of TGIC for complete reaction with terminal carboxyl groups resulted in a self‐similar polymeric structure of PET near the sol‐gel transition point or a critical gel formation whose linear viscoelastic properties obey scaling law. An estimated fractal dimension from the experimental results was used to quantify the evolution of the branched network structure during the reactive melt modification. Polym. Eng. Sci. 44:474–486, 2004. © 2004 Society of Plastics Engineers.
Electrical conductivity of polymer blends containing liquid crystalline polymer and carbon black
Authors: Tchoudakov R. , Narkis M. , Siegmann A. 
Published: April 2004

AbstractThis paper presents results of a study of melt‐processed immiscible polymer blends of high impact polystyrene (HIPS), liquid crystalline polymer (LCP) and carbon black (CB). Relationships between composition, electrical resistivity and morphology of the blends produced by Brabender mixing followed by compression molding, extrusion through a capillary rheometer, extrusion through a single‐screw extruder and injection molding were investigated. The LCP phase morphology in the blends was found sensitive to the processing conditions. A blend composition of at least 20 wt% LCP and 2 phr CB is necessary to preserve the conductivity of filaments produced over a wide range of shear rates. Enhancement of conductivity of blends containing CB and 30 wt% or more LCP was observed, under processing at 270°C and increasing levels of shear rate. An important role of the skin region in determining the resisitivy of injection molded samples was found. A good agreement between resistivity values of extruded or injection molded blends with resistivity values of filaments produced at similar conditions by a capillary rheometer was shown. Hence, the study of shear rate effect on resistivity of capillary rheometer filaments may serve as a predictor of resistivity behavior in real processing procedures. Polym. Eng. Sci. 44:528–540, 2004. © 2004 Society of Plastics Engineers.
Constitutive equations for the viscoplastic response of isotactic polypropylene in cyclic tests: The effect of strain rate
Authors: Drozdov A. D. , deC. Christiansen J. 
Published: April 2004

AbstractA series of uniaxial tensile loading‐unloading tests are performed on injection‐molded isotactic polypropylene at room temperature. In each test, a specimen is stretched up to the maximal strain ϵmax = 0.12 with a constant strain rate, \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}, and retracted down to the zero stress with the same strain rate. The cross‐head speeds vary from 5 to 200 mm/min, which covers practically the entire range of strain rates used in conventional quasi‐static tests. A constitutive model is developed for the viscoplastic response of a semicrystalline polymer at small strains. The stress‐strain relations are determined by five adjustable parameters that are found by matching the observations. Fair agreement is demonstrated between the experimental data and the results of numerical simulation. Polym. Eng. Sci. 44:548–556, 2004. © 2004 Society of Plastics Engineers.
Experimental characterization of fill length behavior in extruders
Authors: Mudalamane Rajath , Bigio David I. 
Published: April 2004

AbstractChannel Fill Length, defined as the length of fully filled regions in an extrusion screw, is gaining importance as a design parameter because of its implications for residence time distribution, distributive and dispersive mixing, and also process stability. Although models exist for theoretical estimation of fill length, it is difficult to apply these models for complex geometries and fluid rheology. Owing to the non‐linear relationship between fill length, geometry and operating conditions, it is time‐consuming to use empirical methods to characterize fill length behavior in any given extrusion process. In this work, it was found that fill length exhibits a linear relationship with the ratio of percent fill to percent empty fraction. Two different sets of fill length data taken from literature, one set from a co‐rotating, intermeshing geometry and the other from a counter‐rotating, non‐intermeshing geometry, were used to verify this relationship. This property of the extrusion process can be used by the researcher to quickly characterize fill length behavior over the entire operating range. Polym. Eng. Sci. 44:557–563, 2004. © 2004 Society of Plastics Engineers.
Production and analysis of injection molded micro‐optic components
Authors: McFarland Andrew W. , Colton Jonathan S. 
Published: April 2004

AbstractPlastic micro‐optic components (smaller than 1 mm in overall dimension, with lenses on the order of 50 microns in radius) will be very useful in future digital imaging and MEMS technologies. Computational fluid dynamics (CFD) and finite element analysis (FEA) predicted the influence of different processing parameters upon the final shape of micro‐optic parts made from polystyrene, polycarbonate, and polymethylmethacrylate. Small‐scale phenomena such as surface tension and mold‐melt slip velocity were included in the models. The simulations were compared to physical parts, through birefringence and interferometry techniques, which permitted assessment of the computer modeling. The predicted radius of curvature trends match the measured trends, and the maximum difference between the predicted and corresponding measured radius of curvature was roughly 3.4%. The average difference between simulation and experiment for astigmatism and comatic aberration was less than 25%. Symmetry assumptions were tested and validated in more than 85% of the measured cases. Polym. Eng. Sci. 44:564–579, 2004. © 2004 Society of Plastics Engineers.
Polymeric composites for use in electronic and microwave devices
Authors: Moulart Alexandre , Marrett Courtney , Colton Jonathan 
Published: April 2004

AbstractThe dielectric and conductive properties of thermoplastic (ABS) composites filled with ceramic powder (barium titanate), conductive powders (carbon black, copper) and conductive fibers (carbon, steel) were investigated for use in electromagnetic crystals and microwave devices. Barium titanate/ABS composites were produced that had dielectric constants over 8 and loss tangents of 0.01, which are the requirements for electromagnetic crystals. Carbon black/ABS and steel fiber/ABS composites were obtained with conductivities suitable for electromagnetic shielding (over 10−3 S/cm). Fused decomposition modeling was tested as a method for building electromagnetic crystals and showed promising results. Polym. Eng. Sci. 44:588–597, 2004. © 2004 Society of Plastics Engineers.
Micromechanical properties on the surface of PVC/SBR blends spatially resolved by a nanoindentation technique
Authors: Zhu Shui‐Han , Chan Chi‐Ming , Mai Yiu‐Wing 
Published: April 2004

AbstractThe microhardness and micromodulus on the surface of poly(vinyl chloride) (PVC)/styrene‐butadiene rubber (SBR) blends were determined using a nanoindenter. A flat surface was obtained by microtoming the sample at −100°C in liquid nitrogen. Dozens of indents along a line with a spatial interval of 0.5 μm were performed. From the loading and unloading curves of each indentation, the stiffnesses of the unloading curve and the contact area between the sample and the indenter were evaluated, and the local modulus and hardness were calculated. Profiles of the local hardness and modulus were obtained from the lines of indents. Pure PVC and a miscible PVC/acrylonitrile‐butadiene rubber (NBR) (40/10) blend showed constant modulus and hardness values. In the case of an immiscible PVC/SBR (50/50) blend, which has a morphology of elongated PVC droplets in the SBR matrix, the hardness and modulus profiles showed regions of the different phases. At the interface between the SBR and PVC phases, a step change in the modulus and hardness profiles was observed. The force required to deform the material at the same displacement increased systematically across the interface from the SBR to the PVC phase because of the increasing contribution of the PVC phase. Polym. Eng. Sci. 44:609–614, 2004. © 2004 Society of Plastics Engineers.
Synthesis and photoconductive characteristics of biphenylporphyrin‐containing poly(amic acid)s and polyimides
Authors: Zhu Bao Ku , Xu You Yi , Wei Xiu Zhen , Xu Zhi Kang 
Published: April 2004

AbstractThree series of biphenylporphyrin (BPP)‐containing poly(amic acid)s (PAAs) were synthesized and converted into heat‐treated polyimides (HPIs) and chemically treated polyimides (CPIs). Viscosity measurements, UV–vis and IR spectroscopies, as well as thermogravimetric analysis (TGA), were used to characterize the structures of the polymers. UV–vis spectra revealed that the BPP units formed aggregates in PAA and CPI films, rather than in HPI films. Photoinduced discharge was used to characterize the photoconductive properties of these polymer films. It was found that the photosensitivity was greatly enhanced by introducing BPP units into the polymer chains. For these three series of polymers, the photosensitivity increased in the order PAA < HPI < CPI according to the content of BPP in the polymers. The photoconductive characteristics were interpreted by the intrinsic π—π* process of BPP aggregation and the extrinsic process of charge‐transfer complex formation. The best photoconductive performances of the CPIs were attributed to the existence of two charge‐carrier‐generation processes. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of novel polyimides starting from 1,2‐bis(p‐dimethylaminobenzylideneimino)alkane homologues and various dianhydrides
Authors: Koytepe Süleyman , Gök Yetkin , Alici Bulent , Seçkin Turgay , Çetinkaya Engin 
Published: April 2004

AbstractThe objective of this research was the preparation of polyimides from 1,2‐bis(p‐dimethylaminophenylimino)alkane homologues and various dianhydrides in N‐methylpyrrolidone by one‐stage polycondensation. The monomers were prepared via condensation of p‐dimethylaminobenzaldehyde and the corresponding diamines, 1,4‐diaminobutane, 1,3‐diaminopropane and 1,2‐diaminoethane. The influence of the incorporation of this moiety into the polymer backbone on the properties of the polyimides has been evaluated. The thermogram of the polyimides indicated that PI‐10 to PI‐32 had Tg values ranging from 181 to 290 °C. The inherent viscosities of the polymers ranged from 0.99 to 2.05 dl g−1, and the highest solubility was obtained without significant loss of the thermal properties. Copyright © 2004 Society of Chemical Industry
Effect of hydrotalcite on the thermal stability, mechanical properties, rheology and flame retardance of poly(vinyl chloride)
Authors: Wang Xiaodong , Zhang Qiang 
Published: April 2004

AbstractCompounds of poly(vinyl chloride) (PVC) and hydrotalcite were prepared via melt blending, and the thermal stability, mechanical properties, rheology and flame retardance were studied. Transmission electron microscopy showed that the hydrotalcite achieved an optimal dispersion in PVC compounds when surface‐treated with titanate coupling agent. The Congo Red test and thermogravimetric analysis demonstrated that the thermal stability of PVC was improved significantly only in the presence of a complex of the hydrotalcite and the organotin stabilizer. Such a significantly positive thermal stabilizing effect was attributable to the stabilizing mechanisms that the electrostatic interaction generated between the electron cloud of chlorine atoms in PVC chain and the positive lay charge of hydrotalcite, which resulted in a decrease in electronic cloud density of chlorine atoms. This weakened the activity of chloride atoms, and restricted the initiation of the dehydrochlorination. A surface treatment for the hydrotalcite with the titanate coupling agent could reduce deterioration of the mechanical and rheological properties of the PVC at low concentration of hydrotalcite. The hydrotalcite also enabled useful application of PVC as a flame retardant as well as a smoke retarder in the light of a LOI value of more than 28.7 and UL 94 V‐0 grade at a PVC/hydrotalcite weight ratio of 70/30. Copyright © 2004 Society of Chemical Industry
A comprehensive characterization of the peptide and protein constituents of human seminal fluid
Authors: Fung Kim Y.C. , Glode L. Michael , Green Spencer , Duncan Mark W. 
Published: April 2004

AbstractBACKGROUNDKnowledge of the peptide and protein components of seminal fluid and their role in prostate diseases including benign prostatic hyperplasia and prostate carcinoma is scant. We have undertaken a proteomic analysis of semen as a forerunner to identifying sensitive and specific diagnostic markers of prostatic diseases; to aid in improved therapeutic intervention; and, to enhance our understanding of prostate health and disease.METHODSPeptide and protein components of pooled human seminal fluid (n = 5) were separated by gel electrophoresis (1D and 2D) and identified by either matrix‐assisted laser desorption ionization‐time‐of‐flight‐mass spectrometry (MALDI‐TOF‐MS) or capillary liquid chromatography tandem mass spectrometry (LC–MS/MS).RESULTSAnalysis by two‐dimensional electrophoresis (2DE) established that there were multiple post‐translational variants of the majority of the proteins. Hormones, growth factors and bioactive peptides were detected and identified.CONCLUSIONSWe have identified over 100 protein and peptide components of normal human seminal fluid. © 2004 Wiley‐Liss, Inc.