bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational prediction of PVC degradation during injection molding in a rectangular channel
Authors: Garcia Jose L. , Koelling Kurt W. , Summers James W. 
Published: July 2004

AbstractA computational model has been developed to calculate the degradation of PVC during injection molding. The results in this work are for the flow in a rectangular geometry. The effects of the injection speed, melt temperature, and material properties were examined. It was determined that the principal factor influencing PVC degradation is the injection speed. Very good agreement between computational and experimental results was obtained. Furthermore, it was calculated that the materials are more thermally sensitive during processing, with activation energy of 65 kcal/mol. Finally, it was calculated that the degradation becomes significant when the melt temperature is above 250°C, independent of the material studied. The model could be used to design the process to avoid degradation. Polym. Eng. Sci. 44:1295–1312, 2004. © 2004 Society of Plastics Engineers.
An experimental study of solid‐bed break‐up in plasticization of a reciprocating‐screw injection molding
Authors: Jin Zhiming , Gao Furong , Zhu Fuhua 
Published: July 2004

AbstractModeling of plasticization during injection molding has been a complex issue, particularly for the solid conveying zone. This can be further complicated by break‐up of the solid‐bed due to the reciprocation motion experienced in injection molding. The break‐up of the solid‐bed can introduce molding quality problems such as inhomogeneities in parts. A transparent barrel system has been set up for injection molding to observe the solid‐bed break‐up mechanism and the conditions that influence this process. This paper summarizes some solid‐bed break‐up results relevant to injection molding. These results may be useful to the modeling community for experimental verification of their simulations, and to the molding community for setting up molding conditions to prevent the occurrence of solid‐bed break‐up. Polym. Eng. Sci. 44:1313–1318, 2004. © 2004 Society of Plastics Engineers.
Environmental stress cracking of a chemical nature in a PBT/PBA co‐poly(ester ester)
Authors: Kuipers N. B. , Riemslag A. C. , Lange R. F. M. , Janssen M. , Bakker A. , Marissen R. 
Published: July 2004

AbstractThe Environmental Stress Cracking (ESC) of a poly(butylene terephthalate)/poly(butylene adipate) (PBT/PBA) copoly(ester ester) was studied by constant‐load time‐to‐failure (TTF) tests performed on sharply notched tensile specimens in water and phosphoric acid solution at 353 K. For comparison, tests were also performed in air at the same temperature. It was found that the time to failure is significantly reduced both in water and in an acid solution as compared with air. ESC implies a mutual intensification of the destructive effect of loading and environment. Owing to the intrinsic hydrolytic instability of polyesters, a failure mechanism due to hydrolysis has to be excluded here to prove the ESC. Therefore the ESC test results are compared with measurements of the exclusive influence of hydrolysis on the degradation of mechanical properties. It was found that the PBT/PBA copoly(ester ester) tested is susceptible to environmental stress cracking in water and even more in a phosphoric acid solution, both at 353 K. From the comparison of the influence of water and a phosphoric acid solution on the time to failure, it was concluded that the ESC of PBT/PBA copoly(ester ester) in a phosphoric acid solution is mainly of a chemical nature. Polym. Eng. Sci. 44:1319–1327, 2004. © 2004 Society of Plastics Engineers.
On the effect of pressure on the shear and elongational viscosities of polymer melts
Authors: Sedlacek Tomas , Zatloukal Martin , Filip Petr , Boldizar Antal , Saha Petr 
Published: July 2004

AbstractThe effect of pressure and temperature on the shear and elongational deformation rate–dependent viscosities has been experimentally investigated for several polymers (HDPE, LDPE, LLDPE, PP, PC, PMMA, and PS) on a capillary rheometer with a back‐pressure device. Pressure, β, and temperature, α, coefficients have been determined through simultaneous fitting of the shear and extensional viscosity data by the modified White‐Metzner model. The dependence of β and α on temperature and pressure, respectively, was investigated and it has been found that simple relationships exist between pressure and temperature sensitivity coefficients for individual polymers. Polym. Eng. Sci. 44:1328–1337, 2004. © 2004 Society of Plastics Engineers.
Rubber plasticizers from degraded/devulcanized scrap rubber: A method of recycling waste rubber
Authors: Tripathy Amiya R. , Williams Drew E. , Farris Richard J. 
Published: July 2004

AbstractSeeking a solution to the problem of disposing scrap tires, we attempted to depolymerize or degrade vulcanized rubber scrap such that the resulting pseudo‐liquid material could be used as an extender/plasticizer in virgin rubber compounds. As degraded natural rubber (DNR) and degraded styrene‐butadiene rubber (DSBR) are polymeric in nature (confirmed from gel‐permeation chromatography (GPC) and differential scanning calorimetry (DSC) results), they can be unique substitutes for typical rubber plasticizers (oil). DNR‐loaded samples have shown better mechanical property retention after aging and a lower extractable content in acetone than the respective oil‐plasticized samples. Solvent swelling in toluene and 100% modulus values indicate that DNR‐added rubber vulcanizates undergo a phase adhesion between the rubber matrix and the degraded polymer, as well as incurring extra reinforcement due to particulate carbon black present in the degraded rubber. Polym. Eng. Sci. 44:1338–1350, 2004. © 2004 Society of Plastics Engineers.
Free volume changes in mechanically milled PS and PC studied by positron annihilation lifetime spectroscopy (PALS)
Authors: Günther‐Schade K. , Castricum H. L. , Ziegler H. J. , Bakker H. , Faupel F. 
Published: July 2004

AbstractThe effect of mechanical milling on free volume was studied by means of positron annihilation lifetime spectroscopy (PALS) in polystyrene (PS) as a typical brittle polymer and in polycarbonate (PC) as a tough representative. Long‐time milling increases the free volume, while a decrease is observed for short milling times. The changes are mostly irreversible in PS. The irreversible fraction is much smaller for PC. Gel permeation chromatography (GPC) measurements show a decrease of the molecular weight, which is much more pronounced in PS. The milling‐induced irreversible changes in free volume are attributed to chain‐end defects resulting from chain scission. In PC, other deformation‐induced defects that anneal upon heat treatment above the glass transition temperature dominate. Polym. Eng. Sci. 44:1351–1359, 2004. © 2004 Society of Plastics Engineers.
Uniaxial stretching of poly(keto‐ether‐imide) films
Authors: Hinkley J. A. , Dezern J. F. , Feuz L. , Klinedinst D. 
Published: July 2004

AbstractNarrow strips of various fully imidized polyimide films were stretched under constant load either isothermally or during a temperature ramp. The effects of process variables (load and temperature) on modulus, failure strain, and tensile strength of the stretched films were characterized and room temperature moduli of up to 16 GPa were documented. Several materials that undergo strain‐induced crystallization were identified as candidates for further property optimization. Polym. Eng. Sci. 44:1360–1367, 2004. © 2004 Society of Plastics Engineers.
Simulation of PTFE sintering: Thermal stresses and deformation behavior
Authors: Andena Luca , Rink Marta , Polastri Fabio 
Published: July 2004

AbstractA finite element model has been used to study the sintering process of polytetrafluoroethylene (PTFE) cylinders in order to predict residual thermal stresses; both solid (rods) and hollow (billets) blocks were studied. The simulation of the process was performed considering three separate stages: thermal, deformation, and stress analysis. For each stage, relevant material properties were determined experimentally. In particular, the deformation behavior of PTFE was thoroughly investigated by means of thermo‐mechanical analysis (TMA). It is shown that experimental results can be explained considering deformation recovery and orientation effects. Predictions of the model are compared with experimental measurements performed on real PTFE‐sintered cylinders. Temperature and deformation distributions determined with the model agree well with experimental data. Fair agreement between predicted and experimentally measured residual stresses is obtained, and the influence of cylinder size and applied cooling rate on residual stresses is correctly predicted. Polym. Eng. Sci. 44:1368–1378, 2004. © 2004 Society of Plastics Engineers.
A non‐isothermal finite element model for injection stretch‐blow molding of PET bottles with parametric studies
Authors: Yang Z. J. , Harkin‐Jones E. , Menary G. H. , Armstrong C. G. 
Published: July 2004

AbstractA non‐isothermal finite element (FE) model for the injection stretch‐blow molding (ISBM) process of polyethylene terephthalate (PET) bottles is presented in this paper. The constitutive behavior of PET is modeled by the physically based Buckley glass‐rubber model in form of UMAT in ABAQUS. The heat transfer between the stretch rod, the preform, and the mold is modeled. Particular attention is paid to thermal and contact modeling, material model, and selection of proper element types. Extensive FE simulations are carried out to model ISBM of a 20 g‐330 ml bottle made in plant tests. Comparisons of numerical results with the measurements demonstrate that the model can satisfactorily predict the bottle thickness and material distributions. Significant nonlinear differentials are found in strain, temperature, and temperature reduction rate in both bottle thickness and length direction during the process. A volume approach is therefore necessary for accurate predictions of final bottle properties because they are governed by orientation and crystallinity, which are highly temperature and strain dependent. Parametric studies on contact modeling and heat transfer coefficient are also conducted and the results are discussed. Polym. Eng. Sci. 44:1379–1390, 2004. © 2004 Society of Plastics Engineers.
Experiments and flow analysis of a micropelletizing die
Authors: Thompson M. R. , Xi C. , Takacs E. , Tate M. , Vlachopoulos J. 
Published: July 2004

AbstractA study has been performed to examine the process of micropelletization on four different polyethylenes with melt index values between 1 and 5 g/10 min. The experiments were done on a 50‐mm 30:1 L/D extruder with an underwater micropelletizer attached. The average micropellet size that was produced ranged from 0.4 to 0.5 mm in diameter depending on whether a plastomer or high‐density grade was selected. The dimensions of the pellets were influenced strongly by the occurrence of die‐hole freeze‐off. Minor sharkskin was observed on the surface of the micropellets, a result of the high stresses experienced in the pelletizer die. A non‐isothermal, axisymmetric flow model was used to assist in the analysis by comparing the observed results to the predicted shear stresses in the die. The calculations revealed that extremely high shear rates were present in the die holes, resulting in a significant degree of wall slip. The measured rheological properties of the micropellets did not show any change in comparison to their virgin resins, likely because of the presence of wall slippage and the short residence time of the polymer in the die holes. Polym. Eng. Sci. 44:1391–1402, 2004. © 2004 Society of Plastics Engineers.
Transcrystalline morphology of nylon 6 on the surface of aramid fibers
Authors: Shi HF , Zhao Y , Dong X , He CC , Wang DJ , Xu DF 
Published: July 2004

AbstractIn this paper, the isothermal crystallization of nylon 6 in the presence of Kevlar 129 fiber was investigated by polarized optical microscopy (POM). The formation of a transcrystalline domain was found to be mainly controlled by crystallization conditions, such as the temperature of the isothermal crystallization, residual time at melting temperature and the cooling rate of the melt. The nucleation rate of nylon 6 on the fibers was mainly affected by the crystallization temperature. The interfacial transcrystallinity of nylon 6 occurred on the surface of Kevlar 129 fiber in the temperature range 130–190 °C. The reason for the formation of interfacial transcrystalline morphology is discussed from the molecular level, based on the understanding of the packing mode of nylon 6 chains around fibers and the interaction between matrix and fibers. It was found that the lattice matching and hydrogen‐bonding between nylon 6 and poly(p‐phenylene terephthalamide) (PPTA) crystals play an important role in the epitaxial crystallization. Copyright © 2004 Society of Chemical Industry
The effect of crystallinity and water absorption on the dynamic mechanical relaxation behaviour of polycaprolactone
Authors: Harrison Kate L , Jenkins Mike J 
Published: July 2004

AbstractThe effect of the degree of crystallinity on the dynamic mechanical relaxation behaviour (flexural storage modulus and loss tangent) of polycaprolactone has been investigated. The degree of crystallinity was found to determine the temperature of the α‐relaxation process and the relaxation strength of the β‐relaxation. The increase in temperature of the α‐process has been ascribed to constrainment of the amorphous regions of the sample by the crystallites. In accordance with the observed effect of the degree of crystallinity, the origin of the dynamic mechanical β‐relaxation has been ascribed to the amorphous regions of the material. The intensity of the β‐process has also been found to depend on the moisture content, becoming more prominent when moisture is present. In addition, moisture has been shown to penetrate the crystalline regions of the sample over a relatively short timescale, as shown by infrared spectroscopy. Copyright © 2004 Society of Chemical Industry
Kinetics of phase separation of poly(styrene‐co‐methyl methacrylate) and poly(styrene‐co‐acrylonitrile) blends
Authors: Tang P , Arrighi V , Higgins JS , Li GX 
Published: July 2004

AbstractThe phase behavior and kinetics of phase separation for blends of the random copolymer poly(styrene‐co‐methyl methacrylate) (SMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were studied by using small‐angle laser light scattering. The partially miscible SMMA/SAN blends undergo spinodal decomposition (SD) and subsequent domain coarsening when quenched inside the unstable region. For blends of SMMA and SAN, the early stages of the phase separation process could be observed, unlike a number of other blends where the earliest stages are not visible by light scattering. The process was described in terms of the Cahn–Hilliard linear theory. Subsequently, a coarsening process was detected and the time evolution of qm at the beginning of the late stages of phase separation followed the relationship qm∝t−1/3, corresponding to an evaporation–condensation mechanism. Self‐similar growth of the phase‐separated structures at different timescales was observed for the late stage. Copyright © 2004 Society of Chemical Industry
Morphology of ultrafine polysulfone fibers prepared by electrospinning
Authors: Yuan Xiaoyan , Zhang Yuanyuan , Dong Cunhai , Sheng Jing 
Published: July 2004

AbstractUltrafine fibers of bisphenol‐A polysulfone (PSF) were prepared by electrospinning of PSF solutions in mixtures of N,N‐dimethylacetamide (DMAC) and acetone at high voltages. The morphology of the electrospun PSF fibers was investigated by scanning electron microscopy. Results showed that the concentration of polymer solutions and the acetone amount in the mixed solvents influenced the morphology and the diameter of the electrospun fibers. The processing parameters, including the applied voltage, the flow rate, and the distance between capillary and collection screen, were also important for control of the morphology of electrospun PSF fibers. It was suggested that uniform ultrafine PSF fibers with diameter of 300–400 nm could be obtained by electrospinning of a 20 % (wt/v) PSF/DMAC/acetone (DMAC:acetone = 9:1) solution at 10–20 kV voltages when the flow rate was 0.66 ml h−1 and capillary–screen distance was 10 cm. Copyright © 2004 Society of Chemical Industry
Photocrosslinkable copolymers based on 4‐acryloyloxyphenyl‐3′‐chlorostyryl ketone and methyl methacrylate: synthesis, comonomer reactivity ratios and UV photosensitivity
Authors: Balaji R , Grande D , Nanjundan S 
Published: July 2004

AbstractA new photosensitive acrylate monomer having a pendant chlorocinnamoyl moiety (APCSK) was copolymerized with methyl methacrylate (MMA) in different feed compositions in ethyl acetate solution at 70°C using benzoyl peroxide as a free‐radical initiator. The newly synthesized copolymers were characterized by FTIR, 1H and 13C nuclear magnetic resonance (NMR) spectral techniques, as well as by size‐exclusion chromatography. Their thermal behaviour was assessed by thermogravimetric analysis in air and differential scanning calorimetry under nitrogen atmosphere. The copolymers exhibit no phase separation since there is only one glass transition temperature (Tg) value in the region of copolymer composition studied. The reactivity ratios of the comonomers were calculated by adopting linearization methods such as the Fineman–Ross (F‐R), Kelen–Tudos (K‐T) and extended Kelen–Tudos (ExtK‐T) methods, and by a non‐linear error‐in‐variables model method (EVM) using a computer program (RREVM). The results suggest that MMA is more reactive than APCSK and that their copolymerization leads to the formation of random copolymers. The photosensitivity of the copolymer samples was studied in solution as well as in thin films through UV irradiation. The influence of different factors, including solvent nature, concentration, temperature, photosensitizer and copolymer composition, on the rate of photocrosslinking of the photoreactive copolymers was investigated for effective industrial application of these polymers as negative photoresists. Copyright © 2004 Society of Chemical Industry
Effects of hydrothermal ageing on the thermal behaviour of poly(vinyl chloride) filled with wood flour
Authors: Djidjelli Hocine , Kaci Mustapha , Martinez‐Vega Juan‐Jorge , Benachour Djafer 
Published: July 2004

AbstractThe hydrothermal ageing of wood‐flour‐filled PVC produced by dry‐blending in a high‐speed mixer in the presence of a plasticizer and other processing additives was carried out to investigate its thermal behaviour, and the results obtained were compared with those for the unfilled material. The dry‐blended compounds were prepared as films by a calendering process. The accelerated hydrothermal ageing was carried out by immersing the samples in boiling water at 100 °C for 110 h. The thermal behaviour of the reference and the aged samples in water was characterized by differential scanning calorimetry (DSC) and determination of the weight changes. The study has shown that during hydrothermal ageing, the samples from the whole formulations absorbed water, for instance, for 30 wt% filled PVC (F30), 16 wt% of water absorption was obtained, while this was only 2.2 wt% for unfilled PVC (F0). It was also noticed that the formulations filled with wood flour up to 10 wt% exhibited similar water absorption kinetics, i.e. the water was mostly absorbed during the first 50 h and the amount absorbed was less than 5 wt%. On the other hand, the 30 wt% filled samples regularly absorbed water up to almost 16 wt% after 100 h of immersion. The DSC data showed that hydrothermal ageing significantly affected the onset temperature of decomposition (Td) of the unfilled samples by decreasing this temperature from 228 to 215 °C. For the 30 wt% filled samples, only additive migration was observed, while the Td remained almost unchanged. Furthermore, from the DSC data, processability of the 30 wt% filled PVC samples at elevated temperatures, i.e. 180 to 200 °C was shown. Copyright © 2004 Society of Chemical Industry
Organoclay–natural rubber nanocomposites synthesized by mechanical and solution mixing methods
Authors: López‐Manchado MA , Herrero B , Arroyo M 
Published: July 2004

AbstractThis investigation describes two methods to obtain rubber composites based on natural rubber (NR) and organophilic layered silicates. In order to improve the exfoliation and compatibilization of the organoclays with the rubber matrix, a new approach which involves swelling of the organoclays with an elastomer solution prior to compounding has been used. The effect of the addition during swelling of a coupling agent, namely bis(trietoxysilylpropyl)tetrasulfan (TESPT), on the behaviour of the composites was also investigated. The results show that a low amount of organoclay (10 phr) significantly improves the properties of natural rubber. This suggests a strong rubber–organoclay interaction which is attributed to a high degree of rubber intercalation into the nanosilicate galleries, as was confirmed from X‐ray diffraction. In addition, an ulterior improvement in the properties of the nanocomposites prepared by solution mixing is clearly observed, due to the better filler–rubber compatibility. An even further increase in the properties is observed by treating the silicate with a silane coupling agent. The silane functional groups modify the clay surface, thus reducing the surface energy, and consequently improving the compatibility with the rubber matrix. Copyright © 2004 Society of Chemical Industry
The effect of the mass ratio of hard and soft segments on some properties of thermoplastic poly(ester‐siloxane)s
Authors: Antic Vesna V , Govedarica Milutin N , Djonlagic Jasna 
Published: July 2004

AbstractA series of thermoplastic elastomers based on soft polydimethylsiloxane (PDMS) and hard poly(butylene terephthalate) (PBT) segments was synthesized using a two‐step transesterification reaction in the melt. The molar mass of the soft PDMS component was constant (M̄nPDMS = 1056 g mol−1) while the starting reaction mixture compositions were varied to obtained copolymers with a mass ratio of hard to soft segments in the range from 70/30 to 40/60. The structure and composition of the copolymers was verified by 1H NMR spectroscopy. It appeared that there was a pronounced molar mass maximum when the PBT content of the copolymers was approximately 60 mass%, whereas all samples were considerably inhomogeneous with respect to the distribution of the lengths of the hard segments. Differential scanning calorimetry (DSC) thermograms showed that the melting and crystallization temperature increased with increasing PBT content, as did the total degree of crystallinity, which was confirmed by wide‐angle X‐ray scattering (WAXS) analysis. Thermogravimetric analysis (TGA) performed in nitrogen gave subtle differences for samples of different composition, including that of the PBT homopolymer, whereas in oxygen these differences were more pronounced in the way the thermo‐oxidative stability of the obtained copolymers decreased with decreasing PBT content. Finally, it was shown that the hardness depended directly on the PBT content, ie the higher the PBT content, the greater the hardness of the corresponding copolymer. Copyright © 2004 Society of Chemical Industry