bluuebunny/crossref_metadata_2025 huggingface dataset:
Hybrid organic inorganic nylon‐6/SiO2nanocomposites: Transport properties
Authors: García Monserrat , Barsema Jonathan , Galindo Ramon E. , Cangialosi Daniele , Garcia‐Turiel Javier , van Zyl Werner E. , Verweij Henk , Blank Dave H. A.
Published: July 2004

Organic‐inorganic hybrid membranes of nanosized SiO2‐filled polyamide composites were prepared via film casting and their transport properties were studied. Gas permeation measurements were performed at room temperature, and the membrane exhibited an increase in membrane permeability performance. In contrast to the performance of traditional dense filled polymer systems, the permeability increased with an increased number of nanosilica particles. The nanocomposites were studied using positron annihilation lifetime spectroscopy (PALS). From the ortho‐positronium (o–Ps) lifetime (τ3), the size of the local free volume (holes) was estimated. The increase in permeability is ascribed to the additional free volume obtained. This is created by the presence of nanoparticles that alter the PA chain packing. Furthermore, wide angle X‐ray diffraction (WAXD) patterns revealed that the incorporation of silica induced the structural modification of polymer chains by modifying the degree of crystallinity in comparison with the neat polymer. Polym. Eng. Sci. 44:1240–1246, 2004. © 2004 Society of Plastics Engineers.
Dispersion, temperature and torque models for an internal mixer
Authors: Campanelli J. R. , Gurer C. , Rose T. L. , Varner J. E.
Published: July 2004

Models based on kinetic, thermodynamic and rheological equations have been developed to compute dispersion extent, batch temperature and relative batch viscosity at discrete intervals during a mix cycle in an internal mixer. The calculated relative bulk viscosity can be linked empirically to a measured variable such as rotor torque or power consumption. Solution of the models over successive time intervals allows the computation of complete dispersion, temperature, and torque/power profiles for a mix cycle. The mix models exhibit good fits to experimental torque and temperature curves for mixing natural rubber with carbon black over a wide range of carbon black loadings (0 to 50 phr) for rotor speeds ranging from 40 to 70 RPM in two lab‐scale internal mixers. The models are shown to be suitable for moderately reinforcing (ASTM N660) as well as highly reinforcing (ASTM N121) grades of carbon black. Rate constants for filler dispersion, incorporation and erosion can be extracted from the models and can be interpolated to generate dispersion, temperature and torque curves at new conditions of carbon black loading and rotor speed. The mix models could thus be used for process‐control purposes and for specifying drop targets based on batch properties in addition to the time‐temperature‐energy criteria typically used today. Polym. Eng. Sci. 44:1247–1257, 2004. © 2004 Society of Plastics Engineers.
Modeling of polymer melting, drop deformation, and breakup under shear flow
Authors: Chen Hongbing , Sundararaj Uttandaraman , Nandakumar K.
Published: July 2004

Polyethylene (PE) or polycarbonate (PC) drop deformation and the breakup mechanism in a PE melt under shear flow were investigated using numerical simulations. The volume of fluid (VOF) method in FIDAP was used to track the dynamic interface. Two models were built for the investigation of a PE/PE system and a PE/PC system. Experimental data of polymer properties, such as specific heat capacity, viscosity, and heat conductivity, were incorporated in the simulations. For the PE/PE system, a temperature‐dependent viscosity model was used for the matrix PE and the dispersed PE. For the PE/PC system, generalized viscosity models were used for PE and PC with time‐dependent moving boundaries. An erosion mechanism similar to that observed in previous experiments was found for deformation and breakup of both PE and PC in the PE melt under simple shear flow. Local flow information, such as temperature, shear rate, viscosity, and shear stress, was obtained from the simulation results. The shear stress at the interface was much higher than the shear stress either in the dispersed phase or in the matrix phase, which could explain the erosion breakup mechanism. Polym. Eng. Sci. 44:1258–1266, 2004. © 2004 Society of Plastics Engineers.
Comparison of the dynamic thin shell and quasi‐cylindrical models for blown film extrusion
Authors: Pirkle J. Carl , Braatz Richard D.
Published: July 2004

Most models of blown film extrusion are based on thin shell theory, which was first applied to these processes by Pearson and Petrie. There has been some contention in the literature as to the suitability of the thin shell model. More recently, Liu and co‐workers presented an alternative quasi‐cylindrical model that neglects longitudinal curvature but was reported to agree more closely with experiments. In later studies, other researchers used the quasi‐cylindrical model to investigate flow‐induced crystallization. The current paper presents finite difference solutions of the quasi‐cylindrical model and quantifies the differences in the steady‐state behavior, dynamics, and stability between the quasi‐cylindrical and the thin shell models. The differences in the steady‐state and dynamic behavior between the thin shell and quasi‐cylindrical models are found to be significant, both qualitatively and quantitatively. This study should aid future researchers in developing dynamic simulation models that include more sophisticated descriptions of the underlying polymer physics. Polym. Eng. Sci. 44:1267–1276, 2004. © 2004 Society of Plastics Engineers.
Photo polymerization of acrylamide onto calcium carbonate particle surfaces and filled nylon‐6
Authors: Gao Jun , He Guangjian , Lei Jingxin , Li Qiman
Published: July 2004

The polymerization of acrylamide (AAM) onto calcium carbonate (CaCO3) particle surfaces induced by ultraviolet light and the properties of polyamide‐6 (PA6) filled with the surface‐treated CaCO3 were studied. Electron spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM), particle size distribution, impact strength and degree of polymerization measurements were determined. After AAM polymerization, a PAAM layer was formed on the CaCO3 surface. This layer tightly banded the CaCO3 particle and could not be washed away by acetone. A N1s peak was observed in the ESCA spectra of the treated CaCO3 particles. The average particle size of the treated CaCO3 increased compared to that of the original CaCO3. The interfacial interaction and impact strength of the treated CaCO3–filled PA6 were enhanced compared to those of the untreated CaCO3–filled PA6. Polym. Eng. Sci. 44:1277–1282, 2004. © 2004 Society of Plastics Engineers.
Shear field induced diffusion and molecular weight fractionation during polymer processing
Authors: Shelby M. David , Caflisch George B.
Published: July 2004

It has been hypothesized that a high shear gradient induced during polymer processing could cause an increased migration of oligomer to the surface, thereby leading to “plateout” on mold and roll tooling. To test this hypothesis, poly(ethylene terephthalate) (PET) and poly(ethylene‐co‐cyclohexylenedimethylene terephthalate) (PETG) were extruded into film, and the molecular weight probed as a function of the depth from the surface by incremental milling. GPC analysis showed an 18% and 14% higher concentration of cyclic oligomer on the surface of these films as compared with the center for PET and PETG respectively. These results compare favorably with predictions from a theoretical shear field model based on a Convected Maxwell fluid. Results from this study should lead to a better understanding of how oligomer buildup at the die wall may relate to roll plateout, die drooling, die lubrication, and possibly even melt fracture. Polym. Eng. Sci. 44:1283–1294, 2004. © 2004 Society of Plastics Engineers.
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

A 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

Modeling 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

The 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

The 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

Seeking 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

The 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

Narrow 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

A 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

A 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

A 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

In 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

The 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

The 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

Ultrafine 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

A 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

The 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

This 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

A 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
Miscible blends of poly(4‐vinyl phenol)/poly (trimethylene terephthalate)
Authors: Lee Li‐Ting , Woo E‐M
Published: July 2004

A new miscible blend of all compositions comprising poly(4‐vinyl phenol) (PVPh) and poly(trimethylene terephthalate) (PTT) was discovered and reported. The blends exhibit a single composition‐dependent glass transition and homogeneous phase morphology, with no lower critical solution temperature (LCST) behavior upon heating to high temperatures. Interactions and spherulite growth kinetics in the blends were also investigated. The Flory–Huggins interaction parameter (χ12) and interaction energy density (B) obtained from analysis of melting point depression are negative (χ12 = −0.74 and B = −32.49 J cm−3), proving that the PVPh/PTT blends are miscible over a wide temperature range from ambient up to high temperatures in the melt state. FTIR studies showed evidence of hydrogen‐bonding interactions between the two polymers. The miscibility of PVPh with PTT also resulted in a reduction in spherulite growth rate of PTT in the miscible blend. The Lauritzen–Hoffman model was used to analyze the spherulite growth kinetics, which showed a lower fold‐surface free energy (σe) of the blends than that of the neat PTT. The decrease in the fold‐surface free energy has been attributed to disruption of the PTT lamellae exerted by PVPh in an intimately interacted miscible state. Copyright © 2004 Society of Chemical Industry
Synthesis and characterisation of hydrophobic modified polyacrylamide
Authors: Wu Shuhui , Shanks RA
Published: July 2004

Polyacrylamide has been modified hydrophobically with low amounts of N‐alkyl groups by a transamidation method, using alkylamines. The amide group in the polymer backbone has been N‐substituted in water solutions, where the substituting amine is water‐soluble. The alkyl groups include N‐alkyl (up to octyl), N,N‐diethyl, N,N‐dipropyl, N‐isopropyl, N,N‐diisopropyl and N‐cyclohexyl groups. This transamidation method is more convenient compared with the traditional micellar copolymerisation methods and the direct method using alkyl halide substitution. However, a limitation of the method is due to the failure to achieve substitution of highly hydrophobic groups such as dodecyl. The mutual insolubility of dodecylamine and the potential substituted product, with N‐dodecyl substitution of polyacrylamide, makes it impractical to carry out the reaction in water. Other mixed solvents were used for the amine substitution, including water with dimethylsulfoxide and ethylene glycol, without transamidation occurring, since these solvents decreased the solubility of polyacrylamide. The NMR and IR spectra of modified polyacrylamides are reported. The mechanism of the reaction under acid‐ and base‐catalysed situations is discussed. Copyright © 2004 Society of Chemical Industry
Photochromic polyacylsemicarbazides based on azobenzene containing dihydrazide
Authors: Palanisamy Aruna , Radhakrishnan Ganga
Published: July 2004

Polyacylsemicarbazides exhibiting photochromic behaviour were synthesised by solution polymerisation of azobenzene chromophore containing dihydrazide and various diisocyanates (aliphatic, cycloaliphatic and aromatic). A model compound was also prepared from o‐tolylene isocyanate and dihydrazide. The structures were confirmed by 1H NMR and FTIR techniques. The polymers were found to exhibit λmax values around 330 nm corresponding to the trans isomer which reduced with irradiation of the solutions of polymers in DMAc due to trans→cis isomerisation as observed by UV‐VIS spectrometry. The reverse reaction (cis→trans isomerisation) was found to take place photochemically when irradiated with visible light or when kept in the dark. The rates of isomerisation reactions were found to be independent of the chromophore concentration and the nature of the polymer backbone. The inherent viscosity of the solutions of polymers in DMAc reduced upon irradiation with UV light and was regained in the dark. Thermal studies showed that the polymer degradation started with the simultaneous cleavage of imino (NN) and aromatic azo (NN) bond and that recrystallisation occurred on heating the samples. Copyright © 2004 Society of Chemical Industry
Synthesis and electro‐optical properties of novel Y‐type polyurethanes containing dioxynitrostilbene
Authors: Lee Ju‐Yeon , Bang Han‐Bae , Park Eun‐Ju , Lee Won‐Jung , Rhee Bum Ku , Lee Seung Mook
Published: July 2004

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene (2) was prepared by the reaction of 2‐iodoethanol with 3,4‐dihydroxy‐4′‐nitrostilbene. Diol 2 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate and 1,6‐hexamethylenediisocyanate to yield novel Y‐type polyurethanes 3–5 containing dioxynitrostilbene as a non‐linear optical (NLO)‐chromophore. Polymers 3–5 were soluble in common organic solvents, such as acetone and DMF. These polymers showed thermal stability up to 280 °C in TGA thermograms with Tg values in the range of 100–143 °C in DSC thermograms. The approximate lengths of aligned NLO‐chromophores of the polymers estimated from AFM images were around 2 nm. The SHG coefficients (d33) of poled polymer films were around 4.5 × 10−8 esu. Poled polymer films had improved temporal and long‐term thermal stability owing to the hydrogen bonding of urethane linkage and the main‐chain character of the polymer structure, which are acceptable for NLO device applications. Copyright © 2004 Society of Chemical Industry
Synthesis and ring‐opening polymerization of macrocyclic aromatic sulfide oligomers
Authors: Liang Zhi‐An , Chen Ke , Meng Yue‐Zhong , Hay Allan S
Published: July 2004

A series of macrocyclic(arylene sulfide) oligomers were synthesized by reaction of 4,4′‐oxybis(benzenethiol) with a number of difluoro compounds in dimethylformamide (DMF) in the presence of anhydrous K2CO3 under high dilution conditions. The difluoro compound can be 4,4′‐difluorobenzophenone, bis(4‐fluorophenyl)sulfone or 1,3‐bis(4‐fluorobenzoyl)benzene. Detailed structural characterization of these oligomers by matrix‐assisted laser desorption and ionization‐time of flight‐mass spectroscopy (MALDI‐TOF‐MS) demonstrated their cyclic nature. The MALDI‐TOF‐MS technique has proved to be a powerful tool to analyze these cyclics. These cyclic oligomers are amorphous and highly soluble in DMF and N,N′‐dimethyl acetamide. Moreover, these cyclic(arylene sulfide) oligomers readily underwent ring‐opening polymerization in the melt at 285 °C in the presence of 2,2′‐dibenzothiazole disulfide, affording linear, high molecular weigh poly(aromatic sulfide)s. These polymers are insoluble in most common solvents. Copyright © 2004 Society of Chemical Industry
Conformations of polysulfone‐block‐polydimethylsiloxane chains in solution and in the solid state
Authors: Bercea Maria , Airinei Anton , Hamciuc Viorica , Ioanid Aurelia
Published: July 2004

Polysulfone block copolymers containing polydimethylsiloxane segments were obtained in solution by the condensation reaction of chloro‐terminated polysulfone oligomers and α,ω‐dihydrogensilyl‐polydimethylsiloxane. The conformations of the copolymer chains were investigated both in solution and in the solid state. Viscometric and UV absorption measurements were carried out in dilute dichloroethane solutions over a wide region of concentrations, in the temperature range 20–75 °C. The results point to a conformational transition phenomenon, located at around 55 °C, which is attributed to the transition from a segregated to a pseudo‐Gaussian conformation through a compressed‐segregated conformation. Copyright © 2004 Society of Chemical Industry
Relaxation kinetics in thiophene/3‐alkylthiophene random copolymers
Authors: Buzarovska Aleksandra , Arsov Ljubomir
Published: July 2004

The relaxation kinetics of several thiophene/3‐alkylthiophene (3‐methylthiophene and 3‐octylthiophene) random copolymers have been investigated using the cyclic voltammetric method. The first voltammograms, obtained after the polymer films were maintained at potentials corresponding to their neutral state for various periods of time, have been analyzed according to the procedure developed by Odin et al. Considerable suppression of the relaxation kinetics was achieved in copolymers containing thiophene rings substituted with longer alkyl groups (octyl). Copyright © 2004 Society of Chemical Industry
Swelling behavior of pH‐ and temperature‐sensitive copolymers containing 2‐hydroxy‐ethyl methacrylate and N‐vinyl‐2‐pyrrolidone crosslinked with new crosslinkers
Authors: Atta Ayman M , Arndt K‐F
Published: July 2004

Copolymers of 2‐hydroxyethyl methacrylate (HEMA) and N‐vinyl‐2‐pyrrolidone (VP) and homopolymers of HEMA and VP were crosslinked in the presence of different mol% of melamine trimethacrylamide (MMAm) and melamine triacrylamide (MAAm) as crosslinkers by bulk radical polymerization. The resultant xerogels were characterized by extracting the soluble fractions and measuring the equilibrium water content. Lower critical solution transition temperatures (LCST) were measured by DSC. The properties of crosslinked HEMA and VP copolymers, VP and HEMA series were evaluated in terms of compositional drift of polymerization, heterogeneous crosslinking, and chemical structure of the relevant components. Soluble fractions of the crosslinked networks were reduced by varying the MAAm and MMAm concentrations. The influence of environmental conditions such as temperature and pH on the swelling behavior of these polymeric gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity. This behavior is explained on the basis that amide groups of VP or crosslinkers could be hydrolyzed to form negatively charged carboxylate ion groups in the produced networks in response to an external pH variation. Copyright © 2004 Society of Chemical Industry
IPNs based on unsaturated polyester/epoxy: IV. Investigation on hydrogen bonding, compatability and interaction behavior
Authors: Shih Yeng‐Fong , Jeng Ru‐Jong
Published: July 2004

A series of interpenetrating polymer networks (IPNs) based on unsaturated polyester/epoxy have been developed. The compatibility and interaction behavior of these IPNs have been investigated by DMA, DSC, SEM, FTIR and solid‐state NMR spectroscopies. The glass transition temperatures of IPNs were decreased and their transitions became broader as the content of unsaturated polyester increased in IPNs, based on our DMA and DSC study. The results of FTIR indicate that hydrogen bonding is present between the unsaturated polyester and epoxy. Insufficient degree of hydrogen bonding brought about immiscibility between IPN components. The analysis of proton spin‐lattice relaxation time in the rotating frame of the IPNs was also utilized to investigate molecular interaction between unsaturated polyester and epoxy. From relaxation curves, phase separation was found for the IPN samples with unsaturated polyester content higher than 30 %. This corroborates the DMA and SEM study. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of electrically conducting poly(o‐/m‐toluidine‐co‐o‐/m‐aminoacetophenone) copolymers
Authors: Savitha P. , Sathyanarayana D. N.
Published: July 2004

A series of poly(o‐/m‐toluidine‐co‐o‐/m‐aminoacetophenone) copolymers combining the features of high conductivity and processibility are synthesized and characterized by a number of techniques including 1H NMR; thermogravimetry; IR, Raman, and UV–visible spectroscopy; scanning electron microscopy; and X‐ray diffraction. The copolymers are synthesized by the emulsion and inverse emulsion methods using conventional ammonium persulfate and a new oxidant, benzoyl peroxide, respectively. The influence of the polymerization conditions such as the monomer feed ratios, solvent, and the nonsolvent is investigated. The composition of the resulting copolymers is determined by 1H NMR analysis. The conductivity of the copolymers varies with the aminoacetophenone content in the feed and the polymerization conditions. It is interesting that the conductivity of the copolymers is higher than that of the corresponding homopolymers. The results are rationalized on the basis of the effect of the COCH3 substituent on the polymer structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4300–4310, 2004
Narrowly dispersed micrometer‐sized composite spheres based on diazonium–polystyrene
Authors: Yang Zhaohui , Cong Hailin , Cao Weixiao
Published: July 2004

Diazonium group–substituted polystyrene (PS–N) micrometer‐sized spheres with narrow distribution were prepared from highly crosslinked polystyrene particles. Then a composite sphere was prepared with the micro‐PS–N sphere as core and submicrometer‐sized poly(styrene‐methyl methacrylate‐acrylic acid) [P(S‐MMA‐AA)] colloids or nanometer‐sized SiO2 particles as shell via columbic interaction. The ionic linkages between the core and shell convert to covalent bonds in the thermal treatment process. As a result, the composite sphere becomes very stable toward polar solvents as well as toward ultrasonic treatment. A hollow SiO2 micrometer‐sized sphere then was achieved by removing the core under sintering conditions (700 °C). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4284–4288, 2004
Amphiphilic membranes crosslinked and reinforced by POSS
Authors: Isayeva Irada S. , Kennedy Joseph P.
Published: July 2004

This article concerns the synthesis and characterization of novel tricomponent amphiphilic membranes consisting of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic polydimethylsiloxane (PDMS) segments cocrosslinked and reinforced by octasilane polyhedral oligomeric silsesquioxane (octasilane‐POSS) cages. Rapid and efficient network synthesis was effected by cocrosslinking diallyl‐telechelic PEG (A‐PEG‐A) and divinyl‐telechelic PDMS (V‐PDMS‐V) with pentamethylpentacyclosiloxane (D5H), using Karstedt's catalyst in conjunction with Et3N cocatalyst and water. Films were prepared by pouring charges in molds and crosslinking by heating at 60 °C for several hours. The films were characterized by sol fractions and equilibrium swelling both in hexane and water, extent of crosslinking, contact angle hysteresis, oxygen permeability, thermogravimetric analysis, and mechanical properties. The crosslinking of octasilane‐POSS achieved by the same catalyst system was studied in separate experiments. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4337–4352, 2004
Enzyme immobilization to ultra‐fine cellulose fibers via amphiphilic polyethylene glycol spacers
Authors: Wang Yuhong , Hsieh You‐Lo
Published: July 2004

Ultra‐high specific surface cellulose fibers with an average diameter of 500 nm were generated from electrospinning and alkaline hydrolysis of cellulose acetate and used as porous supports for enzyme immobilization. The cellulose fiber surfaces were reacted with polyethylene glycol (PEG) diacylchloride to simultaneously add amphiphilic spacers and reactive end groups for coupling with a lipase enzyme. The quantity of reactive carboxylic acid on the fiber surfaces could be readily controlled by COCl/OH molar ratios and PEG lengths. The highest free acid (COOH) content of 1.0 mmol per gram of cellulose was obtained at 10 COCl/OH ratio with the 600‐Da PEG diacylchloride. Enzyme coupling on such PEG‐attached cellulose was optimal in the presence of a water‐soluble carbodiimide [1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide (EDC)] at a very low EDC/COOH molar ratio of 0.2 under acidic condition and at ambient temperature. Whereas the free lipase retained only 25% of its original activity, the fiber‐bound lipase possessed much superior retention of catalytic activity after exposure to cyclohexane (81%) and toluene (62%) and hexane (34%). The fiber‐bound lipase also exhibited significantly higher catalytic activity at elevated temperatures than the free form, that is, 10 times at 70 °C. The ultra‐fine, fibrous, and porous structures were retained throughout alkaline hydrolysis, activation, coupling, and activity assays. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4289–4299, 2004