bluuebunny/crossref_metadata_2025 huggingface dataset:
Creep, stress rupture, and isothermal aging of reinforced polyphthalamide
Authors: Lyons Jed S. , Tinio Edgardo G. , Berry Scott F.
Published: April 2003

The effects of time, temperature, and particulate filler on the tensile behavior of short fiber‐reinforced polyphthalamide (PPA) were investigated experimentally. Creep and stress‐rupture characteristics and tensile properties before and after isothermal aging were determined. Temperatures ranged from 23 to 150°C and tests lasted up to about 4000 h. Stress‐rupture master curves were created, using a WLF‐type analysis, which can be used for interpolation with reasonable accuracy. Creep rates were low but were affected by increased moisture absorption in the lowest temperature environment. All properties were affected by chemical degradation of the PPA matrix at the highest temperature. Under most conditions investigated, the mineral filler improved the creep resistance and stiffness of the PPA resin at the expense of strength and ductility. Scanning electron microscopy examinations of fractured specimens indicated that the mineral filler embrittled the matrix and may have damaged the fibers during processing. © 1995 John Wiley & Sons, Inc.
Influence of polarity of polymer on inorganic particle dispersion in dielectric particle/polymer composite systems
Authors: Nagata Kazuya , Kodama Souji , Kawasaki Hitoshi , Deki Shigehito , Mizuhata Minoru
Published: April 2003

The influence of the polarity of polymers on the degree of dispersion of BaTiO3 particles in BaTiO3/polymer composite systems was investigated. The BaTiO3 polymer composite systems were prepared from BaTiO3 particles and low‐density polyethylene (LDPE) or ethylene vinyl acetate copolymer (EVA) with 7 and 15 wt % vinyl acetate. Scanning electron microscopy observation showed that BaTiO3 particles aggregated in the polymer matrices and dispersed more readily into the EVA matrix than into LDPE. The shift of the β‐peak temperature by ca. +5°C in the temperature dispersion of the loss modulus was observed for EVA–BaTiO3 composite systems in dynamic mechanical property measurement. On the other hand, the β‐peak temperature of the polymers filled with graphite particles, which have hydrophobic surfaces, was almost constant in a volume fraction region of 0–0.3. The ellipsoidal axes' ratios given by comparison of experimental dielectric constant values and theoretical ones using the Maxwell equation were 4.2, 3.6, and 3.1 for LDPE/BaTiO3, EVA(7%)/BaTiO3, and EVA(15%)/BaTiO3 composite systems, respectively. The axes' ratio decreased by the introduction of polar vinyl acetate groups into nonpolar LDPE. The results confirmed that the polarity of the polymers was one of the key factors governing the dispersibility of BaTiO3 particles in the polymer matrix. © 1995 John Wiley & Sons, Inc.
The compatibility of the blends of PUs with PVC and the adhesion behavior of PU to PVC
Authors: Zhu Y. Q. , Huang Y. J. , Chi Z. G.
Published: April 2003

Three series of polyurethane adhesives—polyethyleneadipateurethane (PEAU), polybuthyleneadipateurethane (PBAU), and polyhexyleneadipateurethane (PHAU)—with the same MW and hard/soft segment ratio, based on the three polyesters polyethyleneadipate (PEA), polybuthyleneadipate (PBA), polyhexyleneadipate (PHA), with 4,4′‐diphnylmethane diisocyanate (MDI), and butendiol were synthesized by solution polymerization. The crystallinity of these polyesters and polyurethanes (PUs) and the compatibility of blends of PUs with PVC were studied by means of wide‐angle x‐ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic thermomechanical analysis (DMA), testing of solubility, and phase contrast microscopy. The results indicated that PBAU/PVC and PHAU/PVC were compatible systems, but PEAU/PVC was incompatible. The adhesive strengths of the three adhesives were quite different from one another, in the order of PBAU ≥ PHAU ≫ PEAU. The influences of crystallinity and compatibility on adhesion were discussed, and the Diffusion Theory for PU‐PVC systems was recommended. © 1995 John Wiley & Sons, Inc.
New method of lifetime prediction for brittle fracture of polyethylene
Authors: Chudnovsky A. , Shulkin Y. , Baron D. , Lin K. P.
Published: April 2003

A new method for predicting the time to brittle failure of polyethylenes is proposed. The method includes modeling slow crack growth in polyethylenes and the experimental determination of material parameters for the model. The model is based on the concept of the crack layer, i.e., a system consisting of the strongly interacting crack and process zone and the kinetic equations which govern the crack layer growth. The process zone in polyethylenes usually appears to be a thin strip of drawn material extending along the crack line. This permits a characterization of the crack layer by two parameters: the crack and process zone lengths. The two‐parameter crack layer kinetic model allows description of slow crack growth as the discontinuous (stepwise) process which is commonly observed in the brittle fracture of polyethylenes. The model also predicts a relationship between time to failure and applied stress, identical to that established experimentally. The material parameters of the kinetic model can be determined by experiments on smooth specimens, i.e., are independent of slow crack growth and require relatively short‐term observations. Thus, the combination of the material testing and the mathematical modeling of the crack layer evolution is proposed as a method for lifetime prediction in the brittle fracture of polyethylenes. © 1995 John Wiley & Sons, Inc.
Copolymerization of the silane‐modified polyvinylimidazole(1) as a metal corrosion inhibitor
Authors: Jang Jyongsik , Kim Hyuncheol
Published: April 2003

The free radical copolymerization of vinyl imidazole (VI) with γ‐methacryloxypropyltrimethoxy silane (γ‐MPS) by using azobisisobutyronitrile (AIBN) as an initiator was carried out in benzene at 68°C. The copolymer compositions at various monomer feeds were investigated by elemental analysis. The reactivity ratios of two monomers were determined by the Finemann‐Ross method: r1(VI) = 0.22, r2 (γ‐MPS) = 3.18. From these results, it could be concluded that silane‐modified polyvinylimidazoles were random copolymers (0<r1r2<1). Thermal stability of decomposition of the copolymer increased with increasing the mole ratio of VI in the copolymer. Thermal decomposition of the copolymer was caused by the decomposition of the γ‐MPS unit. However, thermal stability above 300°C and maximum thermal decomposition temperature increased with increasing the mole ratio of γ‐MPS due to the crosslinking reaction of hydrolyzed γ‐MPS unit. © 1995 John Wiley & Sons, Inc.
Effects of denaturing agents on the molecular association of dextran. I. Aqueous solutions
Authors: Güner Ali̇
Published: April 2003

Molecular association of aqueous dextran solutions have been investigated by viscosimetric measurements. Intrinsic viscosities of different concentrations of aqueous solutions of dextran with a variety of denaturing agents have been determined. Intrinsic viscosity numbers and Huggins constants of dextran solutions decreased with the addition of denaturing agents. The reducing effect of denaturing agents on the intrinsic viscosities and Huggins constants decreased in the order guanidinium sulfate > guanidinium carbonate > guanidinium chloride > thiourea > urea. The effect of temperature on the intrinsic viscosities of dextran and dextran denaturing agent solutions have also been investigated. A small change in the intrinsic viscosity values was observed for dextran in 1M of guanidinium carbonate and sulfate solutions with the increase of the temperature from 25 to 40 °C. Aqueous dextran solutions, however, showed a significant decrease in the intrinsic viscosities in the same temperature range. © 1995 John Wiley & Sons, Inc.
Effect of blend rheology on the transport property of oriented poly(ethylene terephthalate) blends
Authors: Gopalakrishnan Rajagopalan , Schultz Jerold M. , Gohil Ramesh M.
Published: April 2003

Rheological studies were performed to delineate appropriate stretching windows, and poly(ethylene terephthalate)/poly(ethylene‐co‐vinyl alcohol) blend films were extruded biaxially within such processing windows. The morphology and oxygen permeability properties of these films, with and without a compatibilizer, were characterized. The intent of this study was to achieve a blend oxygen permeability value (OPV) of less than 1. At a fixed draw ratio and draw temperature, appropriate rheological matching could lead to an increase in the aspect ratio of the EVOH phase and, thereby, of oxygen barrier properties. This study concludes that by melt viscosity matching it is not possible to obtain blends with OPV of less than 1. The model of Fricke, used to predict blend permeability, was found to be more accurate at the higher draw temperatures, with the measured values deviating increasingly negatively from the predicted values as the draw temperature is decreased. © 1995 John Wiley & Sons, Inc.
Biodegradation of low‐density polyethylene, polystyrene, polyvinyl chloride, and urea formaldehyde resin buried under soil for over 32 years
Authors: Otake Yoshito , Kobayashi Tomoko , Asabe Hitoshi , Murakami Nobunao , Ono Katsumichi
Published: April 2003

The biodegradation of several polymers that had been buried under soil for over 32 years was examined. No evidence of biodegradation was found for polystyrene, polyvinylchloride, and urea formaldehyde resin. A remarkable degradation was indicated for low density polyethylene thin films which were directly in contact with soil. Severely degraded parts of the film is characterized by whitening. Many small holes were recognized on the surface of the whitened part. The whitened part is specific for the growth of hyphae. FT‐IR spectra of the whitened part showed a characteristic band in the vicinity of 1640 cm−1 which was assigned to the stretching vibration of CC bond. Although the part which was not in contact with soil was clear, it also showed evidence of degradation from the presence of carbonyl band in FT‐IR. It was suggested that the degradation of the clear part is due to the usual thermo‐oxidative process, while the degradation of the whitened part is due to the biotic process. © 1995 John Wiley & Sons, Inc.
Evolution of the molecular weight distribution and linear viscoelastic rheological properties during the reactive extrusion of polypropylene
Authors: Mead D. W.
Published: April 2003

Homogeneous and nonhomogeneous reactive extrusion of polypropylene is modeled using random chain scission statistics coupled with the double reptation mixing rule. In this manner, the evolution of both the molecular weight distribution and the linear viscoelastic material properties is quantitatively predicted for the reactive extrusion–pelletization process. Dispersion in the level of random chain scission has little impact on the MFI for a given average level of chain scission; however, dispersion does generate a marked increase in the recoverable compliance (melt elasticity) relative to the ideal homogeneous random chain scission case. Methods to quantitatively determine the degree of cracking dispersion in processing equipment are identified. Quality control issues such as blending materials of known linear viscoelastic properties to obtain a desired property set is considered in the context of known empirical relations consistent with the double reptation model. Simple mixing rules for the melt flow index and the steady‐state recoverable compliance involving only single component MFI and Je information are derived. © 1995 John Wiley & Sons, Inc.
Optimization of an industrial semibatch nylon 6 reactor
Authors: Sareen R. , Kulkarni M. R. , Gupta S. K.
Published: April 2003

An industrial semibatch nylon 6 reactor has been optimized using a one‐variable (at a time) search technique. The vapor release rate from the reactor and the final monomer conversion have been constrained to lie very close to the values currently present. The degree of polymerization of the product is , similarly, constrained to lie at a value of 152. The optimal pressure histories for two values of the jacket fluid temperature, Tj, have been evaluated using two objective functions, I1 and I3, namely, the total reaction time (I1 = tf) and the concentration of the cyclic dimer (I3 = [C2]f) in the product. It is observed that as Tj is increased from 270 to 280°C, I1 improves while I3 worsens simultaneously. This suggests that these two optimal points lie on the Pareto set for the two‐objective function problem. © 1995 John Wiley & Sons, Inc.
Synthesis and metal binding properties of poly(hydroxamic acid) resins from poly(ethyl acrylate‐co‐divinylbenzene) beads
Authors: Lee Taek Seung , Hong Sung Il
Published: April 2003

Poly(hydroxamic acid) resins from crosslinked poly(ethyl acrylate)s were prepared and their metal binding properties were investigated. The metal binding capacities of this type resin for metal ions were determined at specific pH. In the acidic region, the chelating resin showed high adsorption capacity for copper, iron, vanadium, and uranium. Metal adsorption capacities varied according to polymerization condition, i.e. crosslinking ratio and degree of dilution. Equilibration rates of the chelating resins were investigated to evaluate their use as materials for chromatographic separation. Selectivity for various metals was also observed from the mixed metal solution. © 1995 John Wiley & Sons, Inc.
Computer simulation of phase separation in binary polymer mixtures
Authors: Matsuoka Takaaki , Yamamoto Satoru
Published: April 2003

Phase separation of binary polymer mixtures was numerically simulated by solving the time‐dependent Langevin equation with Flory–Huggins free energy in two dimensions by using a finite difference method. Spinodal decomposition following structure coarsening was calculated. Simulation results were verified by evaluating the evolution of the wave number obtained from the calculated phase structure by Fourier transformation. Then, computer experiments were carried out to investigate effects of volume fraction and polymer characters, the number of segments, and solubility parameter on morphology. The phase separation time, when the phase began to separate, decreased with deviating volume fraction from 0.5 and with decreasing number of segments and difference between solubility parameters. The difference between solubility parameters had the largest influence on the phase separation time among them and had two effects, the acceleration of phase separation and the restriction of structure coarsening. © 1995 John Wiley & Sons, Inc.
High density polyethylene/acrylonitrile butadiene rubber blends: Morphology, mechanical properties, and compatibilization
Authors: George Josephine , Joseph Reethamma , Thomas Sabu , Varughese K. T.
Published: April 2003

Polymer blends based on high‐density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two‐phase structure in which NBR phase was dispersed as domains up to 50% of its concentration in the continuous HDPE matrix. However, 70 : 30 NBR/HDPE showed a cocontinuous morphology. The tensile strength, elongation at break, and hardness of the system were measured as a function of blend compostion. As the polymer pair is incompatible, technological compatibilization was sought by the addition of maleic‐modified polyethylene (MAPE) and phenolic‐modified polyethylene (PhPE). The interfacial activity of MAPE and PhPE was studied as a function of compatibilizer concentration by following the morphology of the blend using scanning electron micrographs. Domain size of the dispersed phase showed a sharp decrease by the addition of small amounts of compatibilizers followed by a leveling off at higher concentrations. Also, more uniformity in the distribution of the dispersed phase was observed in compatibilized systems. The tensile strength of the compatibilized systems showed improvement. The mechanical property improvement, and finer and uniform morphology, of compatibilized systems were correlated with the improved interfacial condition of the compatibilized blends. The experimental results were compared with the current theories of Noolandi and Hong. © 1995 John Wiley & Sons, Inc.
Use of epoxy reactivity for compatibilization of PP/PBT and PP/LCP blends
Authors: Holsti‐Miettinen Riitta M. , Heino Markku T. , Seppälä Jukka V.
Published: April 2003

Binary blends of a reactive ethylene‐based terpolymer with polybutylene terephthalate (PBT) and with a liquid crystalline polyester (LCP) were studied to clarify the possible interactions between the blended polymers. The aim was to determine the suitability of the reactive terpolymer containing epoxy reactivity as a compatibilizer in blends of polypropylene (PP) and these two polyesters. The binary blends exhibited increased viscosity during blending, changes in the crystallization of the PBT phase, and an intimate contact between the blended polymers, which pointed to strong interactions or chemical reactions between the compatibilizer and both PBT and LCP. FTIR analysis confirmed the reaction of the epoxide and formation of new esters. Most probably the carboxyl end groups of the polyesters reacted with the epoxy group of the compatibilizer. In the second part of the work the same terpolymer was shown to act as a compatibilizer in PP/PBT and PP/LCP blends. This behavior was based on good mixing with the PP phase and on the chemical reactivity or strong interactions with the polyesters demonstrated in the investigations on binary blends. Addition of 5 wt% of the compatibilizer improved the impact strength, especially in PP/PBT blends where synergistic behavior was found at compositions of 80/20 and 20/80. In PP/LCP blends, the compatibilizer significantly improved the impact strength of unnotched samples at 20 wt % LCP content. In both blends, the compatibilizer reduced the size of the dispersed domains and caused them to attach better in the matrix. © 1995 John Wiley & Sons, Inc.
Cationic conduction in oligoether salt–comblike polyether complex
Authors: Zheng Yungui , Wan Guoxiang
Published: April 2003

Polymeric solid electrolytes, with excellent cationic conductivity, were prepared from the complexation of lithium methoxyoligo(oxyethylene) sulfate and lithium methoxyoligo(oxyethylene) sulfonate with poly[methoxyoligo(oxyethylene)methacrylate‐co‐acrylamide]. The electrolytes exhibit low glass transition temperature and have almost no crystal. Their ionic conductivities at 25°C are over 10−5 S/cm. The carrier number in the complex decreases while ionic mobility increases considerably with increasing considerably with increasing temperature. The polarization reversing method confirms that the cationic transference numbers are all over 0.9. The electrolytes have single ion conduction characteristics in DC polarization. © 1995 John Wiley & Sons, Inc.
Toughening of epoxy resin by reacting with functional terminated‐polyurethanes
Authors: Wang Huei‐Hsiung , Chen Jung‐Chieh
Published: April 2003

Hydroxyl‐, amine‐, and anhydride‐terminated polyurethane (PU) prepolymer which were synthesized from polyether (PTMG) diol, 4,4′‐diphenylmethane diisocyanate (MDI), and a coupling agent bisphenol‐A, 4,4′‐diaminodiphenyl sulfone (DDS), or benzophenonetetracarboxylic dianhydride (BTDA) were used to modify the toughness of bisphenol‐A diglycidyl ether epoxy resin (DGEBA) cured with 4,4′‐diaminodiphenyl sulfone. From the experimental results, it was shown that the modified resin displayed a significant improvement in fracture energy (GIC) and also in its interfacial shear strength with polyaramid fiber. It was more enhanced with increase of the PU modifier wt % content. The hydroxyl‐terminated PU was found to be the most effective among those three prepolymers. In addition, the toughening mechanism was discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by transmission (TEM) and scanning electron microscopy (SEM) revealed that the modified resin had a two‐phase structure. The existence of an unclean fiber surface after its fiber pullout test suggested that a ductile fracture might have occurred. © 1995 John Wiley & Sons, Inc.
Quantitative measurement of interdiffusion at polymer–polymer interfaces with TEM/EDS and EELS
Authors: Jabbari Esmaiel , Peppas Nikolaos A.
Published: April 2003

Transmission electron microscopy and energy dispersive spectroscopy (TEM/EDS) were used to map the concentration profile at the interface of a poly(vinyl chloride) and poly(methyl methacrylate) bilayer. Thin sections in the order of 800 Å were cut using an ultramicrotome, examined with TEM, and the concentration profile was mapped with EDS. The intensity of fluorescene X‐rays was adjusted for sample thickness variation by measuring the relative thickness across the interface with electron energy‐loss spectroscopy (EELS). The interfacial thickness of the bilayer after 6 h at 120°C was 1.5 μm, whereas the interdiffusion coefficient was determined as 8.0 × 10−14 cm2/s. © 1995 John Wiley & Sons, Inc.
Monomer reactivity ratios in UV‐initiated free‐radical copolymerization reactions
Authors: Ramelow Ulku S. , Qiu Qing Hua
Published: April 2003

The homopolymers of styrene (S) and vinyl acetate (VA) and their copolymers were prepared in bulk by ultraviolet (UV)‐radiation‐initiated free‐radical polymerization with azobisisobutyronitrile (AIBN) as an initiator. The reacitivity ratios for these copolymerizations were determined by analyzing the monomer content in the copolymers by UV spectroscopy. The same method was extended to other copolymers of styrene such as styrene–methyl methacrylate and styrene–ethyl acrylate. A new analysis method was developed to measure reactivity ratios. For this purpose, UV light was used as a photochemical initiator and UV absorption spectroscopy was used for the determination of the instantaneous composition of copolymers. Nuclear magnetic resonance (NMR) was used to calculate percent conversion. © 1995 John Wiley & Sons, Inc.
Melting behavior of polypropylene fibers studied by differential scanning calorimetry
Authors: Andreassen Erik , Grøstad Kristin , Myhre Ole Jan , Braathen Marianne D. , Hinrichsen Einar L. , Syre Anne Marie V. , Løvgren Tor Bertel
Published: April 2003

Polypropylene fibers produced in a compact‐spinning process were studied by differential scanning calorimetry (DSC). With unrestrained fibers, the onset of melting increases with decreasing draw ratio, increasing Mw/Mn, decreasing extrusion temperature, increasing annealing ratio, and increasing draw‐down ratio. These trends are discussed in terms of restraints and reorganization. The onset of melting is shifted to lower temperatures as the heating rate increases for all combinations of material and processing parameters, indicating suppressed reorganization. At low draw ratios, the height and width of the endotherm are affected by the spinline stress, and a secondary peak or shoulder is observed on the high temperature side of the main peak. The magnitude of the secondary peak increases with decreasing Mw/Mn, increasing draw ratio, decreasing draw‐down ratio, and decreasing heating rate, but its position mainly depends on the heating rate. This indicates that the secondary peak may be due to the melting of structures that have been reorganized during the heating scan. As the draw ratio increases, the melting regime broadens, especially towards lower temperatures, and several maxima emerge on the DSC curve. Reorganization and shrinkage during heating may explain these observations. © 1995 John Wiley & Sons, Inc.
Study on ketalization reaction of poly(vinyl alcohol) by ketones. VII. Reaction between poly(vinyl alcohol) and aromatic ketones and behavior of poly(vinyl ketal) in water
Authors: Nakamura Naofumi
Published: April 2003

The ketalization reaction of poly(vinyl alcohol) (PVA) by aromatic ketones, with dimeth‐ylsufoxide (DMSO) as solvent, under the presence of an acidic catalyst in homogeneous system, was carried out. The synthesis of poly(vinyl ketal) (PVKL) for the case of phenylacetone and benzylacetone was thus successfully performed, but for the case of acetophenone was performed only with a ketalization degree of a few molecular percent, and for the case of benzophenone it could not be performed at all. It seems that these different behaviors in synthesis are due to steric hindrance of the bulky side chain of ketones. The equilibrium constant at 40°C was ca. 0.12. in the case of phenylacetone and benzylacetone, and the value is somewhat higher compared with that of aliphatic ketones, but somewhat lower compared with the case of cyclic ketones. Because the heat of reaction is 7.5 kcal/mol in these two aromatic ketones, all ketalization reactions are considered to proceed by the same reaction mechanism. The rate of hydrolysis, contact angle, surface free energy, moisture regain, and water vapor permeability of PVKL films were measured. All results show the PVKL obtained from phenylacetone is nearly equal to PVKL obtained from methyl n‐butyl ketone. However PVKL obtained from benzylacetone shows different behavior compared with other ketones, because the side chain of benzylacetone is flexible and bulky. The hydrophobicity of PVKL seems to depend upon the kind of the original ketones and the flexibility of the side chain. © 1995 John Wiley & Sons, Inc.
Development of a gel‐counting technique for quantifying cleanliness of film‐grade resins
Authors: Huang Yi‐Bin , Wessel Thomas E.
Published: April 2003

A novel gel‐counting technique was developed to precisely quantify the cleanliness of filmgrade resins. The technique involves cross‐polarization on stretched film and counting gels at various magnifications. By combining the gel‐count data and the resolution power of the microscope at these magnifications, one can obtain detailed gel size distribution in the resins. © 1995 John Wiley & Sons, Inc.
Effect of evaporation time on the pervaporation characteristics through homogeneous aromatic polyamide membranes. I. Pure water permeation and membrane characterization by sorption measurements
Authors: Yamasaki Akihiro , Tyagi R. K. , Fouda A. , Matsuura T.
Published: April 2003

The pervaporation of pure water through homogeneous aromatic polyamide membranes was investigated. The structure of the prepared membranes was controlled by varying the solvent evaporation times before the gelation step from 5 min to 240 min. The permeation flux of pure water decreased rapidly when the solvent evaporation time increased from 5 min to 30 min, and the decrease was rather moderate at higher evaporation times. Vapor and liquid sorption measurements were used to characterize the membranes. The amount of vapor sorption at a given relative pressure increased with an increase in the solvent evaporation time. The specific surface area of the membranes, calculated from the vapor sorption isotherm, increased with evaporation time up to 30 min, and remained constant thereafter. Liquid sorption volume, on the other hand, decreased monotonically with an increase in evaporation time. The formation of channels in the membrane is used to explain the morphology change during the solvent evaporation. The increase in the solvent evaporation time gradually increases the number of the channels in the membrane and decreases their average size. Good correlation was observed between the average size of the channels (represented by the ratio of specific volume to the specific surface area) and the parameters associated with pervaporation transport. © 1995 John Wiley & Sons, Inc.
Oxidative aging of thermoplastic polyimide films
Authors: Hinkley Jeffrey A. , Yue Jireh J.
Published: April 2003

Two linear polyimides were subjected to accelerated isothermal aging at temperatures between 300 and 400°C. Losses in toughness correlated well with changes in glass transition temperature (Tg) of the films, but not with weight loss. Both materials have extrapolated lifetimes of 100,000 h near their Tg's. © 1995 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Phenomenological description of strain rate and temperature‐dependent yield stress of PMMA
Authors: Povolo F. , Hermida Élida B.
Published: April 2003

A constitutive equation to describe the yield behavior of poly(methyl methacrylate (PMMA) is useful not only from the technological point of view, but also for the comprehension of the nonlinear mechanisms acting in the material. In both compression and tension, the yield stress is usually represented as a function of the strain rate at different temperatures. In PMMA and other glassy polymers these curves are related by scaling, that is, they can be matched to form a master curve. Particularly in PMMA the temperature and strain rate dependence of the master curve has been characterized by two different models. The first involves two thermally activated rate processes, one acting only at high strain rates. The second model interprets the yield process as a cooperative movement of several independent structural units, all with the same activation energy. In this article it is demonstrated that only the second phenomenological model is correct because it provides a good fit to the master curve of PMMA both in compression and tension, and verifies the properties of a set of curves related by scaling. Moreover, it is pointed out that the first model leads to severe inconsistencies because it does not consider the nonlinear behavior of PMMA. Finally, the physical parameters obtained (internal stress, activation volume, and enthalpy) are compared with those given in the literature. © 1995 John Wiley & Sons, Inc.
Characterization of crosslinked polystyrene beads and their composite in SBR matrix
Authors: Cha Yoon‐Jong , Choe Soonja
Published: April 2003

Monodisperse crosslinked polystyrene (PS) beads were prepared by a reaction of semibatch emulsion polymerization with styrene monomer, divinylbenzene (DVB) crosslinking agent, and potassium persulfate (K2S2O8) initiator in the absence of emulsifier. The glass transition temperature (Tg) and the mean diameter of the beads were increased from 100 to 135°C and from 402 to 532 nm, respectively, for an incorporation of 2–10 mol % DVB. Crosslinking density was also linearly increased with DVB content. Scanning electron microscopy (SEM) photographs of styrene–butadiene rubber (SBR) composite filled with various contents of PS beads revealed that PS beads are relatively well dispersed without changing the spherical shape of the beads in all ranges of compositions. In stress–strain analysis, elongation at break and tensile strength of SBR composite were increased with the bead content. Applicability of the PS beads as a filler in SBR matrix is tested by plotting Mooney–Rivlin or Guth–Smallwood equations. However, mechanical properties of the composite with the beads were not so excellent as those of the composite with carbon black. Crosslinked PS beads are still tentative as a white color reinforcing filler on the SBR matrix. © 1995 John Wiley & Sons, Inc.
Study of cryostructuration of polymer systems. XI. The formation of PVA cryogels by freezing–thawing the polymer aqueous solutions containing additives of some polyols
Authors: Lozinsky V. I. , Solodova E. V. , Zubov A. L. , Simenel I. A.
Published: April 2003

The influence of the presence of some polyols in initial poly(vinyl alcohol) aqueous solutions on rheological and thermal properties of the cryogels, which were produced by the freezing–thawing method, was investigated. The polyol additives (cosolvents) were as follows: glycerol, propylene glycol, mono‐, di‐, and triethylene glycols, and oligoethylene glycols (PEG‐400 and PEG‐1000). It was shown that the introduction of glycerol, propylene, or ethylene glycols into the polymer solution resulted in a decrease of cryogel's shear modulus and fusion temperature, whereas the use of triethylene and higher ethylene glycol oligomers as cosolvents gave rise to an increase in the gel's strength and thermostability, and diethylene glycol exhibited a transitional influence. The possible mechanism of the action of reinforcing cosolvents is discussed. © 1995 John Wiley & Sons, Inc.
1H‐NMR studies of nonionic surfactant adsorption onto colloidal particles
Authors: Haggerty John F. , Roberts James E.
Published: April 2003

Proton Nuclear Magnetic Resonance (NMR) spectroscopy was used to study the adsorption of a hexadecyl‐terminated poly(oxyethylene) surfactant (nominal molecular weight of 1120 g/mol) onto hydrophobic polystyrene latex particles. The adsorption process affects the NMR response of the surfactant; various surfactant populations are represented by different features in the NMR spectra. An analytical method that utilizes surfactant systems with and without polystyrene latex particles was employed to determine the capability of NMR to observe adsorbed surfactant close to the particle surface. At the initial stages of surfactant adsorption, the oxyethylene chain interacts with the particle surface in a pancake‐like conformation. At higher surfactant concentrations, surfactant molecules are bound to the particle surface and also exist as micelles or are free in solution; approximately one‐third of the bound, 20‐unit oxyethylene chains are near the surface and are not detected by NMR. Using a theoretical monomer density profile, laser light‐scattering measurements, and the NMR results, an effective NMR detection limit of 1 nm from the particle surface has been calculated. © 1995 John Wiley & Sons, Inc.
Synthesis and characterization of core/shell ionomeric latexes. II. Surface analysis by X‐ray photoelectron spectroscopy
Authors: Arora A. , Daniels E. S. , El‐Aasser M. S. , Simmons G. W. , Miller A.
Published: April 2003

It is generally accepted that conductometric titration is a time‐dependent technique in the case of highly carboxylated latexes because of the changes in the structure of the particle surface resulting from the neutralization and the alkali swellability imparted by the carboxyl groups when titrated with an alkali. At high levels of neutralization, the diffusion of the hydroxyl groups into the shell will be much faster than at the lower levels of neutralization. Due to this changing rate of the diffusion of the hydroxyl groups into the highly alkaliswellable copolymer shell, the assignment of the carboxyl groups to the different sublevels inside the particle shell can, at best, be arbitrary. To overcome this handicap, x‐ray photoelectron spectroscopy (XPS or ESCA) was used to obtain the depth profile of methacrylic acid near the surface of the particles. It is expected that by accurately characterizing the surface loading of the carboxyl groups, it will be possible to control the microphase separation process of the system. Considering the high concentration of the carboxyl groups on the surface of the core/shell latexes prepared in this study, XPS experiments were conducted to obtain the depth profile of the carboxyl groups. Angle‐dependent XPS studies were performed on films derived from the core/shell latexes with different amounts of methacrylic acid in the shell layer in order to determine the compositional heterogeneities between the surface and subsurface layers. In addition, x‐ray photoelectron spectroscopy was used to study the changes in the surface composition of solvent‐cast core/shell latex films prepared in this study upon treatment with alkali solution. It was discovered that a large‐scale migration of the carboxyl groups could occur as a result of coulombic interactions. © 1995 John Wiley & Sons, Inc.
Characterization of the interphase in poly(divinylbenzene)/poly(N‐butyl acrylate) core/shell latexes by high‐resolution solid‐state NMR relaxation studies
Authors: Nelliappan V. , El‐Aasser M. S. , Klein A. , Daniels E. S. , Roberts J. E.
Published: April 2003

Poly(divinylbenzene)/poly(n‐butyl acrylate) core/shell latexes were investigated using solid‐state 13C‐NMR. The (H)T1ρ relaxation time was found to be substantially affected by many of the seeded emulsion polymerization parameters, such as the core/shell ratio, the mode of addition of the second‐stage monomer, the addition rate of the second‐stage monomer, and the level of conversion of the seed latex at the time of addition of the second‐stage monomer. The existence of an interphase region between the core and shell polymers was detected. Maximum interphase region thickness was achieved when the butyl acrylate was added under starved conditions. The thickness of this interphase layer was calculated to be 5–7 nm based on a model proposed by McBriety.1 Solid‐state NMR was found to be an excellent spectroscopic technique to probe the interphase region in core/shell latexes. © 1995 John Wiley & Sons, Inc.
Simultaneous interpenetrating networks of a polyurethane and poly(methyl methacrylate). I. Metastable phase diagrams
Authors: Mishra V. , Du Prez F. E. , Gosen E. , Goethals E. J. , Sperling L. H.
Published: April 2003

Any simultaneous interpenetrating network (SIN) synthesis contains three key events. These are gelation of polymer I, gelation of polymer II, and phase separation of polymer I from polymer II. Metastable phase diagrams of SINs are developed, in which the time occurrence of these three events is represented. A polyurethane/poly(methyl methacrylate) (PU/PMMA) system was chosen as a model. Polymerization kinetics were followed in situ for both PU and PMMA using Fourier Transform Infrared Spectroscopy (FTIR) with the aid of a heated demountable cell. Glass transitions of fully cured samples were determined by dynamic mechanical spectroscopy (DMS) and differential scanning calorimetry (DSC). Phase separation was determined by the onset of turbidity, and gelation of the first gelling polymer was determined by the sudden resistance of the system to flow. As a result, a metastable phase diagram was constructed for the four‐component SIN system (the two monomers and their respective polymers) as a tetrahedron in three dimensions with the two monomers and two polymers at the four apexes. Phase separation and gelations of the two polymers are indicated by various surfaces. These surfaces intersect at lines and curves, representing unique conditions of an SIN synthesis, e.g., simultaneous gelation of both polymers, or simultaneous phase separation and gelation of polymer I, etc. These conditions are critical in terms of the development of the SIN morphology, dividing the reaction space into specific regions. Finally, it is shown how the tetrahedron diagram helps visualize the course of the three key events during SIN synthesis, and provides direction for controlling them. © 1995 John Wiley & Sons, Inc.
Thermal characteristics of energetic polymers based on tetrahydrofuran and oxetane derivatives
Authors: Liu Ying‐ling , Hsiue Ging‐ho , Chiu Yie‐shun
Published: April 2003

Thermal characteristics and decomposition behaviors of energetic polymers based on oxetane derivatives, 3,3'‐bis(azidomethyl)oxetane (BAMO), 3‐azidomethyl‐3'‐methyloxetane (AMMO), 3‐nitratomethyl‐3'‐methyloxetane (NMMO), and 3,3'‐bis(ethoxymethyl)oxetane (BEMO), were studied by means of differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). These polymers were found to exhibit low glass transition and large decomposition onthalpies which were brought about by the attached azide (N3) and nitrato (ONO2) groups. The decomposition enthalpies depended on the types and contents of the energetic substituents. The NMMO‐based polymers exhibited relatively higher decomposition enthalpies and less thermal stability than the others. Furthermore, the thermal stability of the polymers was further improved by partial curing treatment. These results reveal that these polymers are potentially useful for application in energetic propellant binders. © 1995 John Wiley & Sons, Inc.
Study of reverse osmosis separation and permeation rate for sulfonated poly(2,6‐dimethyl‐1,4‐phenylene oxide) membranes of different ion exchange capacities
Authors: Hamza Ali , Chowdhury Geeta , Matsuura T. , Sourirajan S.
Published: April 2003

The reverse osmosis performance of thin‐film composite membranes prepared from sulfonated polyphenylene oxide polymer with different ion‐exchange capacities was studied using various electrolyte solutes. The effect of the solvent used for the preparation of the polymer solution for surface coating was also studied. It was found that the preparation of thin‐film composite membranes with high selectivities and high fluxes was possible by adjusting properly the ion‐exchange capacity and the solvent. It was also found that the membrane performance was governed primarily by the ion‐exchange reaction between the solute cation and the proton in SO3H and the Donnan equilibrium. © 1995 John Wiley & Sons, Inc.
Thermolysis of polystyrene
Authors: Simard Y. D. M. , Kamal M. R. , Cooper D. G.
Published: April 2003

Styrene was recovered from polystyrene (molecular weight of 138,000) by thermolysis in a nitrogen atmosphere at temperatures between 368 and 407°C. The results were independent of the initial weight of polystyrene, which was varied between 30 and 480 g. Up to 90% of the polystyrene was converted to liquid products. The liquid products had a styrene concentration as high as 90% and the styrene yield increased with temperature. Above 390°C, the residue left in the reactor (less than 30% of initial polystyrene charge) consisted mainly of styrene monomer, dimer, and trimer (MW of 190). The kinetics support a first‐order reaction with regard to the rate of production of volatiles. The activation energy was estimated to be 166.5 kJ/mol. © 1995 John Wiley & Sons, Inc.
Gas transport in poly(vinyl‐p‐isopropylbenzoate): Comparison and correlation with some other poly(vinyl esters)
Authors: Hirose Takuji , Mizoguchi Keishin , Terada Katsuhiko
Published: April 2003

Gas permeability in poly(vinyl‐p‐isopropylbenzoate) (PVp‐i‐PrB) was determined by a timelag method. The transport properties were discussed from comparison with the permeability data of other poly(vinyl esters), which were studied previously. All these polymers are structurally related, and the size of a side group or the position of its substituent was changed systematically. The isopropyl group of PVp‐i‐PrB is attached at the para position of a phenyl ring and is the largest in size. As a result gas diffusivity and therefore permeability were increased. The effect of the substituent on gas diffusivity was explained as it increases the interchain and intrachain distances. The discussion was supported from the comparison of the density data between PVp‐i‐PrB and other poly(vinyl esters). The diffusion coefficients of six glassy poly(vinyl esters) were correlated at their Tg and good correlations were shown to the free volume and its fraction. On the other hand, gas solubility was little affected by the change of an alkyl group on a phenyl ring. The solubility data of PVp‐i‐PrB and poly(vinyl benzoate) were shown to be clearly correlated with the critical properties of the penetrants. © 1995 John Wiley & Sons, Inc.
Structure–property relationship in fibers spun from poly(ethylene terephthalate) and liquid crystalline polymer blends. I. The effect of composition and processing on fiber morphology and properties
Authors: Petrović Zoran S. , Farris Richard
Published: April 2003

Poly(ethylene terephthalate) (PET) matrix was modified by blending with a specially prepared thermotropic liquid crystalline polymer (TLCP), in the hope to make the in situ composite during fiber spinning. It has been found that the TLCP did not fibrillate in the PET matrix at any concentration under given processing conditions, although it did in the polycarbonate matrix. This was explained by the low interaction parameter (low surface tension) and partial degree of mixing of PET and TLCP. The TLCP was an excellent processing aid even at very low concentrations, but it had an adverse effect on the strength of highly drawn fibers. The modulus of both undrawn and highly drawn fibers increases slightly with increasing TLCP concentration. © 1995 John Wiley & Sons, Inc.
Tri‐n‐Butylborane oxide‐initiated homopolymerization of vinyl monomers containing cyano or isocyanato groups
Authors: Chappelow Cecil C. , Pinzino Charles S. , Byerley Thomas J. , Eick J. David
Published: April 2003

Homopolymers of 2‐isocyanatoethyl methacrylate, ethyl α‐cyanoacrylate, and ethyl α‐is‐ocyanatoacrylate were prepared in tetrahydrofuran at 22 to 25°C using tri‐n‐butylborane oxide as a free radical initiator. Additionally, ethyl α‐isocyanatoacrylate was homopolymerized using 2,2′‐azobis(2‐methylbutyronitrile) as the initiator. Homopolymers were characterized by photoacoustic FT‐IR, DSC, and elemental analysis. © 1995 John Wiley & Sons, Inc.
Surface grafting of polymer onto carbon thin film
Authors: Tsubokawa Norio , Ueno Hiroshi
Published: April 2003

The surface grafting of polymers onto carbon thin film deposited on a glass plate was achieved by two methods: the graft polymerization initiated by initiating groups introduced onto the surface; and the trapping of polymer radicals by surface aromatic rings of the thin film. It was found that the radical and cationic graft polymerization of vinyl monomers are initiated by azo and acylium perchlorate groups introduced onto the surface, respectively, and the corresponding polymers are grafted onto the surface: the surface grafting of polymers were confirmed by the contact angle of the surface with water. In addition, the anionic ring‐opening alternating copolymerization of epoxides with cyclic acid anhydrides was found to be initiated by potassium carboxylate groups on the carbon thin film to give the corresponding polyester‐grafted carbon thin film. On the other hand, polymer radicals formed by the decomposition of azo polymer, such as poly(polydimethylsiloxane‐azobiscyanopentanoate) and poly(polyoxyethylene‐azobiscyanopentanoate), were successfully trapped by the surface aromatic rings of carbon thin film and polydimethylsiloxane and polyoxyethylene were grafted onto the surface. © 1995 John Wiley & Sons, Inc.
Investigation on suitability of poly(urethaneimides) as biomaterials
Authors: Masiulanis B. , Całusiński G. , Marjański W. , Kotschy M. , Jurkowski P. , Góralczyk B. , Staniszewska‐Kuś J. , Solski L. , Krzemień‐Dabrowska A.
Published: April 2003

The mechanical properties of poly(urethaneimides) (PUI) were compared with known biomedical polyurethanes. The resistance of PUI to extraction with hexane and water and to sterilization with ethylene oxide or water vapor was stated. Water sorption and the permeability of water vapor, oxygen, and carbon dioxide through PUI foils were investigated. In blood compatibility, the PUI foils were similar to cellulose material Cuprophane, used in dialysis. Preliminary in vivo testing of PUI implanted in rats indicated good biocompatibility of this polymer. © 1995 John Wiley & Sons, Inc.
Cure kinetics of a flexible aromatic dicyanate with schiff base structure
Authors: Wang Ying‐Hung , Hong Yeng‐Long , Hong Jin‐Long
Published: April 2003

Polycyclotrimerization of a flexible aromatic dicyanate with a Schiff base structure was studied by means of differential scanning calorimetry (DSC). The study on dynamic DSC evaluated an apparent activation energy (Ea) of 75.8 kJ/mol and autocatalytic first‐order kinetics with rate expression Af(α) = 1.96 X 105 (1 + 4.39 α) (1 ‐ α) min−1. The kinetic feature can be explained by a proposed mechanism consisting of hydroxyl‐catalyzed and autocatalytic paths. The lower value of Ea compared with other aromatic dicyanates is due to the electron‐withdrawing linkage of the inherent imine (—CHN) structure. The kinetic feature is affected by the content of the residual impurities (e.g., phenols or absorbed water) in the corresponding sample. © 1995 John Wiley & Sons, Inc.