bluuebunny/crossref_metadata_2025 huggingface dataset:
Bead‐spring polymer melts
Authors: Grisafi S.
Published: April 2003

This analysis of polymer rheology uses conditional probability distributions to describe the phase space dynamics of all macromolecules in a polymer melt. The result is a viscoplastic constitutive equation for the polymer stress. Using conditional probability distributions makes the use of a large number of bead‐spring chains in the modeling system possible, but precludes evaluating the intermolecular contribution to the total stress. Both the kinetic and intramolecular contributions are evaluated for a system composed of an arbitrary number of bead‐spring chains that interact with one another using molecular dispersion forces. The analysis predicts that the kinetic contribution is isotropic and the intramolecular contribution is viscoplastic. The intermolecular contribution is assumed negligible in comparison to the intramolecular contribution because it results from physical bonds among chains, while the intramolecular contribution results from chemical bonds within a chain. © 1993 John Wiley & Sons, Inc.
Hydrogels based on copolymers of N‐(2‐hydroxyethyl) methacrylamide, 2‐hydroxyethyl methacrylate, and 4‐t‐butyi‐2‐hydroxycyclohexyl methacrylate
Authors: Friends G. , Künzler J. , McGee J. , Ozark R.
Published: April 2003

A nonionic, high water content, high‐strength hydrogel based on N‐(2‐hydroxyethyl)methacrylamide (HMA), 2‐hydroxyethyl methacrylate (HEMA), and a strengthening agent, 4‐t‐butyl‐2‐hydroxycyclohexyl methacrylate (TBCM). The HMA was prepared by the reaction of methacryloyl chloride with ethanol amine. The copolymerization of HMA with varying concentrations of HEMA and TBCM resulted in transparent hydrogel films possessing a wide range of mechanical and physical properties. A copolymer composition of 79 parts HMA, 20.7 parts TBCM, and 0.3 parts ethylene glycol dimethacrylate (EGDMA) gave a transparent, flexible film possessing a water content of 72.6%, a Young's modulus of 0.45 MPa, oxygen permeability of 28 barrers, and a tear strength of 28 N/m. In contrast, a copolymer composition of 40 parts HMA, 59.7 parts TBCM, and 0.3 parts EGDMA gave a hard, transparent film possessing a water content of 33% and a modulus of 504 MPa. © 1993 John Wiley & Sons, Inc.
Chemiluminescence and thermo‐oxidation stability of poly(2,6‐dimethyl‐p‐phenylene ether) in blends with polystyrene and polybutadiene
Authors: Matisová‐Rychlá Lyda , Chodák Ivan , Rychlý Jozef , Bussink Jan
Published: April 2003

It has been ascertained that chemiluminescence‐time curves for samples of poly(2,6‐dimethyl‐p‐phenylene ether) blended with high‐impact polystyrene containing polybutadiene yield a very reproducible pattern even at a temperature of 190°C. The chemiluminescence light emission has been associated with consumption of double bonds in polybutadiene, and a corresponding rate constant and activation energies of chemiluminescence decay from both the isothermal and nonisothermal parts of chemiluminescence‐time curves have been determined. As demonstrated by these curves, an attempt, to stabilize the blends toward thermooxidation by the peroxide decomposer and stabilizer led to retardation of the oxidation process only and further investigation searching for an optimum stabilizing system is required. © 1993 John Wiley & Sons, Inc.
A fatigue crack initiation map for polycarbonate
Authors: Chen T.‐J. , Bosnyak C. P. , Kao C.‐I. , Chudnovsky A.
Published: April 2003

The mechanisms of fatigue crack initiation for various stress levels and thicknesses have been determined for single‐edge notched specimens of polycarbonate and used to assemble a map. Three basic fatigue crack initiation mechanisms were identified and named as cooperative ductile (the damage zone formed ahead of crack consisting of yielded material), solo‐crack brittle (very little damage zone development), and cooperative brittle (identified as a cloud of microcracks or crazes that developed at the notch tip). With a given applied stress and within the same failure mechanism, the values of the number of cycles to crack initiation decrease with increase in thickness. The transition from cooperative ductile to solo‐crack brittle initiation mechanisms is sudden with increasing thickness. Transition from cooperative ductile to cooperative brittle with decreasing stress was less well defined. Regions where combinations of mechanisms were observed are also identified in the map. © 1993 John Wiley & Sons, Inc.
A new binary accelerator system for the sulfur vulcanization of natural rubber latex
Authors: Mathew George , Kuriakose A. P.
Published: April 2003

Vulcanization of latex products are usually carried out at lower temperatures compared to dry rubber products. It has been suggested that, in latex vulcanization systems where thiourea is used as a secondary accelerator, it acts as a nucleophilic reagent facilitating the cleavage of the sulfur bonds in the primary accelerator like TMTD or CBS at lower temperature. But no conclusive proof is given to such a postulate. In the present study 1‐phenyl‐2,4‐thiobiuret (DTB II) and 1,5‐diphenyl‐2,4‐dithiobiuret (DTB III), which are more nucleophilic than thiourea and which vary in their nucleophilic reactivity, were studied as secondary accelerators along with tetramethyl thiuram disulphide (TMTD) and N‐cyclohexylbenzothiazyl sulphenamide (CBS) in the vulcanization of natural rubber latex. These binary systems were found to be very effective in reducing the optimum vulcanization time. Also it was noted that 1‐phenyl‐2,4‐dithiobiuret, which is more nucleophilic, is more reactive (as observed from the reduction in optimum cure time) as a secondary accelerator, indicating a nucleophilic reaction mechanism in the vulcanization reactions under review. The optimum dosages of the secondary accelerators required were derived. Physical properties like tensile strength, 300% modulus, and elongation at break of the latex vulcanizates were also studied. There is a definite advantage with respect to many of these properties for dithiobiuret systems compared to the systems containing TMTD alone or TMTD/thiourea. DTB III gives higher values in many of these physical properties than DTB II. Chemical characterization of the vulcanizates was also carried out to correlate the physical properties with the type of chemical crosslinks formed. © 1993 John Wiley & Sons, Inc.
A new class of biodegradable materials: Poly‐3‐hydroxy‐butyrate/steam exploded straw fiber composites. I. Thermal and impact behavior
Authors: Avella Maurizio , Martuscelli Ezio , Pascucci Beniamino , Raimo Maria , Focher Bonaventura , Marzetti Annamaria
Published: April 2003

Biodegradable thermoplastic composites reinforced with wheat straw fibers were prepared. The matrix was an expensive polyester, poly‐3‐hydroxy‐butyrate (PHB), produced by bacterial fermentation. Before being mixed with the PHB, the wheat straw fibers were subjected to a steam explosion process that induces morphological and structural changes in lignocellulosics. Such changes enhance the interaction with the thermoplastic matrix. The two components were melt mixed and the composite molded under hot compression. Compared with neat PHB, not only does the composite material show better mechanical properties but, moreover, production costs are dramatically reduced because wheat straw is a very inexpensive product. Finally, FTIR measurements revealed some PHB/straw fiber molecular interactions that interfere with the PHB crystallization. © 1993 John Wiley & Sons, Inc.
High performance semi‐interpenetrating polymeric networks based on acetylene‐terminated sulfone. Part I. Cure and thermal characteristics
Authors: Mai Kancheng , Zeng Hanmin
Published: April 2003

A series of semi‐interpenetrating polymer networks (semi‐IPN) have been prepared from acetylene‐terminated sulfone (ATS‐C) oligomer and high‐performance thermoplastic (TP) blends. The cure characteristics and thermal properties of ATS‐C and semi‐IPNs are presented in this paper. The addition of thermoplastics has no effect on the mechanism of ATS‐C cure reaction and thermal behavior of cured systems. The glass‐transition temperature (Tg) and heat distorsion temperature (HDT) of thermoplastics are remarkably decreased with adding ATS‐C. The higher the Tg and HDT of the thermoplastics, the more obvious the reduction of Tg and HDT. In the case of fully cured semi‐IPNs, the Tg and HDT value of the TP phase are higher than or equal to the Tg and HDT of pure TP. The thermal stabilities of semi‐IPNs decrease as the content of ATS‐C oligomer increases. © 1993 John Wiley & Sons, Inc.
Synthesis and thermal characterization of chemically modified cardanol polymers
Authors: Antony Rosy , Pillai C. K. S.
Published: April 2003

Cardanol was functionalised to incorporate elements such as phosphorus and bromine and polymerised with formaldehyde or hexamethylenetetramine (HMTA) to get flame retardant polymers. Thus, monocardanyl phosphoric acid (MCPA), its bromoderivative (BrMCPA), and their formaldehyde condensates (MCPAF and BrMCPAF) and cross‐linked polymers were prepared and characterized by IR, NMR, and GPC. Flammability and thermal stability of these polymers were evaluated by LOI and TGA, respectively, and compared with those of conventional cardanol‐formaldehyde (CF) resin and its bromoderivative. TGA of MCPAF showed that although it is initially less stable than that of CF, its stability increases above 500°C over that of CF. Char yields of MCPAF and BrMCPAF are 21 and 27, respectively, and corresponding LOI values are 27 and 49. The present data do not support any synergism nor any additive effect between phosphorus and bromine, but a positive interaction between them is indicated with phosphorus mainly contributing in the condensed phase and bromine in the vapour phase mechanism. The activation energies in the range 20–30 kcal/mol for MCPAF suggest an ionic mechanism for its decomposition, whereas mainly a free radical type of decomposition is inferred for BrMCPAF with an activation energy in the range of 35–50 kcal/mol. © 1993 John Wiley & Sons, Inc.
Quantitative analysis of branching in poly(ortho ester) networks
Authors: Shih Chung , Waldron Niki , Traugott Cathy
Published: April 2003

A direct method to quantify the branching attributable to fully reacted hexane‐1,2,6‐triol (HT) in poly(ortho ester) networks is reported. The method was based on the presence of free hydroxyl groups on incompletely reacted HT in the poly(ortho ester) matrix that were “tagged” prior to matrix hydrolysis. HT molecules that were completely reacted, i.e., acting as cross‐linker, within the polymer matrix would have no free hydroxyl groups available for “tagging” and posthydrolysis would be present as free HT. Experimentally, the matrix was swollen in p‐dioxane, then phenyl isocyanate (PhCNO) was added to “tag” the hydroxyl groups in the presence of a stannous octoate catalyst. After removal of excess PhCNO, the matrix was hydrolyzed under mild acidic conditions. Any “untagged” HT was subsequently derivatized into trimethylsilyl ethers and analyzed by gas chromatography (GC). The level of branching determined by this direct chemical method correlated well with conventional swell ratio measurements. Furthermore, the extent of hydrolysis of the polymer backbone covalent bonds were also measured by this method since the resulting hydroxyl groups were “tagged” by PhCNO. All polyols were analyzed simultaneously by GC. Application of this method in characterization of the solid‐state hydrolysis of a poly(ortho ester) network was demonstrated. The degradation profiles of the branch sites and other backbone ortho ester bonds showed that the hydrolysis was initially slow, becoming progressively rapid. © 1993 John Wiley & Sons, Inc.
Swelling of hydrophilic polymers. II
Authors: Ogawa Ikuko , Yamano Hideki , Miyagawa Kinjiro
Published: April 2003

The swelling of five types of Sephadex that are either nonionic (G) or possess one of four different ionic groups [sodium carboxymethyl (CM), sodium sulfopropyl (SP), diethyl‐aminoethyl chloride (DEAE), diethyl ‐ (2‐hydroxypropyl) aminoethyl chloride (QAE)] in the same skeleton of the molecule has been studied by picture analysis and by calorimetry. Inducing dissociation of the ionic group in the polymer skeleton increased the water swelling. By the addition of sodium chloride, the maximum swelling volume of nonionic Sephadex was only slightly decreased. However, that of ionic polymers was considerably decreased. The variation of the apparent first‐order rate constant of the swelling and that of the maximum swelling volume show the same tendency. The maximum heats of swelling were 93.2 ± 7.1 J g−1 for G, 128.8 ± 9.1 J g−1 for CM, 92.3 ± 8.0 J g−1 for SP, 68.8 ± 10.5 J g−1 for DEAE, and 67.0 ± 7.2 J g−1 for QAE and did not depend on the concentration of sodium chloride. From the results obtained, we conclude that the nonionic Sephadex swells only by hydration but that ionic Sephadexes swell mainly by the osmotic pressure due to the counterions of the ionic groups and that the swelling ratio is not dependent on the kinds of ions but on the ionic concentration. Most of the water in the gels of ionic Sephadexes is free water that does not interact with the Sephadexes. © 1993 John Wiley & Sons, Inc.
The influence of a copolymer as adhesion promoter for polycarbonate and liquid crystalline polymer blends
Authors: Amendola E. , Carfagna C. , Netti P. , Nicolais L. , Saiello S.
Published: April 2003

The modification of the interface between polycarbonate (PC) and Pet Phb60 was studied. The ester interchange reaction between the components of the 50% w/w mixture, responsible for the formation of molecular segments of intermediate affinity toward the parent polymers, has greatly affected the morphology of extrudate samples. The reacted compound was used in the ratio of 5% as compatibilizer in the formulation of the in situ composite between PC and PetPhb60, containing 10% of the reinforcing thermotropic liquid crystal polymer (TLCP). The effects of the adhesion promoter has been evaluated comparing the morphological features of melt‐drawn fibers with the previous result concerning the fibers without the compatibilizer. © 1993 John Wiley & Sons, Inc.
Ternary phase equilibria of tetrahydrofuran‐polystyrene‐polytetrahydrofuran
Authors: Geveke David J. , Bernardin Frederick E. , Danner Ronald P.
Published: April 2003

Phase diagrams including tie lines for three ternary solvent‐polymer‐polymer systems consisting of tetrahydrofuran‐polystyrene‐polytetrahydrofuran at 30°C have been obtained using size exclusion chromatography. The effect of molecular weight on polymer‐polymer compatibility has been investigated. A liquid‐liquid equilibria (LLE) database has been used to compare UNIQUAC and a modified Flory‐Huggins model with respect to their ability to correlate LLE data. Both models contain six adjustable parameters. As previously observed in the literature, the estimation of the UNIQUAC parameters is troublesome due to the model's complexity and the intercorrelation of the parameters. On the basis of better performance and ease of use, the Flory‐Huggins model is recommended. The Flory‐Huggins model is capable of accurately describing LLE of systems which exhibit quite complex tie line behavior. © 1993 John Wiley & Sons, Inc.
Thermal properties of resin copolymers derived from o‐hydroxy acetophenone
Authors: Nayak P. L. , Senapati M. , Choudhury P.
Published: April 2003

A variety of crosslinked resin copolymers have been synthesized by condensing o‐hydroxy acetophenone with formaldehyde and chloro‐substituted benzoic acids and anilines in the presence of acidic and basic catalysts. The physico–chemical properties of the resins are reported. The thermogravimetric analysis method was used to study the thermal behaviour of the resins; the evolution of kinetic parameters and degradation mechanism was also investigated. Resins from chlorobenzoic acids showed clear two‐step degradation neglecting moisture loss, whereas those from chloro anilines gave a somewhat continuous sigmoid. The effect of reaction conditions like monomer, molar ratio, and catalyst is also reported. © 1993 John Wiley & Sons, Inc.
Electrical conductivity and spectral properties of iodine‐doped poly(2‐ethynylpyridine)
Authors: Gal Yeong‐Soon , Choi Sam‐Kwon
Published: April 2003

This article includes the doping and dedoping behaviors, the electrical conductivity, and the spectral properties of poly(2‐ethynylpyridine) and iodine‐doped poly(2‐ethynylpyri‐dine). The doping ability of poly(2‐ethynylpyridine) having a pyridine substituent was greater than that of polyphenylacetylene having a phenyl substituent. The electrical con‐ductivty of iodine‐doped poly(2‐ethynylpyridine) increased with doping time and reached the value of about 5×10−3Ω−1 cm−1 when the mol ratio of iodine to poly(2‐ethynylpyridine) repeating unit was above 0.7. The spectral properties of poly(2‐ethynylpyridine) and iodine‐doped poly(2‐ethynylpyridine) were also studied by infrared and UV‐visible spectroscopies and thermogravimetric analysis. © 1993 John Wiley & Sons, Inc.
Oriented PP–PS composites obtained by polymerization of styrene inside oriented PP matrices. II. Shrinkage behavior and mechanical properties
Authors: Trznadel M. , Pluta M. , Kryszewski M.
Published: April 2003

Thermal shrinkage and the mechanical properties of oriented polypropylene‐polystyrene (PP‐PS) composites obtained by in situ polymerization of styrene in the oriented PP matrices were examined by the analysis of shrinkage stress curves and dynamic mechanical data. It has been shown that by changing the structure of the oriented matrices it is possible to control the properties of the obtained oriented composites. Some composites reveal an increased stability of the obtained oriented composites. Some composites reveal an increased stability of the molecular network at higher temperatures and the modulus of the material obtained from the matrix drawn at 90°C to the natural draw ratio is significantly increased. It is also shown that the differences between the untreated matrices and the PP component of the respective composites observed in the relaxation of the shrinkage stresses correspond very well with the differences seen in the mechanical loss in the frequency range of about 0.02 Hz. Such behavior suggests that similar molecular motions are involved both in the relaxation of shrinkage stresses and in this part of the mechanical loss. © 1993 John Wiley & Sons, Inc.
Characterization of network structure of rubber vulcanizate by monsanto moving die rheometer (MDR 2000)
Authors: Roychoudhury A. , De S. K.
Published: April 2003

While studying the curing of rubbers in a moving die rheometer, the viscous component (S″) of the measured torque increases with the formation of ionic cross‐linking. But the covalent cross‐linking of elastomers is manifested by a decreases in S″. The mixed cross‐linking system, however, shows an initial rise in S″ value due to ionic cross‐linking, followed by a decrease in S″ due to covalent cross‐linking. As curing progresses, the elastic component (S′) of the measured torque in the case of a mixed cross‐linking system increases in two steps: The first step is due to ionic cross‐link formation, and the second step, to covalent cross‐link formation. The moving die rheometer can be useful in assessing not only the extent of cross‐linking, but also the type of cross‐links formed during the vulcanization of rubbers. © 1993 John Wiley & Sons, Inc.
Curing system involving SiH‐containing organic oligomers
Authors: Iwahara T. , Kusakabe M. , Chiba M. , Yonezawa K.
Published: April 2003

We describe here the preparation and properties of a novel curing system, which has been derived from an SiH‐containing organic oligomer 1 and an allyloxy end‐blocked organic oligomer 2. The composition of these oligomers could be crosslinked via a platinum‐catalyzed hydrosilylation reaction, that is, the addition reaction of the SiH bonds of 1 to the allyl functionality of 2, above 100°C, yields a rubbery material in a short period of time. The compatibility of the SiH‐containing oligomer 1 with the allyloxy end‐blocked oligomer 2 was governed by the oligomer main chain employed. Hence the SiH‐containing oligomer 1 was completely miscible with 2, having the same main chain and, thus, the system yielded a homogeneously cured material. The poly(propylene oxide) curing system 1a/2a was systematically investigated in detail to manifest its curing behavior and crosslink structure. © 1993 John Wiley & Sons, Inc.
Characterization of polyacrylic acid modified zinc phosphate crystal conversion coatings
Authors: Wragg J. L. , Chamberlain J. E. , Chann L. , White H. W. , Sugama T. , Manalis S.
Published: April 2003

Raman spectroscopy and atomic force microscopy have been used to investigate the composition and surface structure of polyacrylic acid modified zinc phosphate crystal conversion coatings on steel. Zinc phosphate coatings are used extensively to provide corrosion protection and to improve adherence of topcoatings to steel. Within the last few years it has been demonstrated that addition of high molecular weight polyacrylic acid (PAA) to the phosphating bath can significantly improve both resistance to corrosion and topcoat adherence. It has been reported that the addition of PAA reduces the size of crystallites, which leads to greater film ductility, and therefore to fewer sites for corrosive attack, and that organic molecular segments from the PAA are incorporated into the surface structure and provide additional adhesive bonding with polymeric topcoats. In this work Raman spectra show the compositions of both unmodified and PAA modified films to be zinc phosphate dihydrate, Zn3(PO4)2·2H2O. Atomic force microscopy (AFM) was used to measure the morphologies of single crystallite surfaces. Morphologies of the unmodified and modified films obtained by AFM are in general quite similar, but subtle differences are apparent. © 1993 John Wiley & Sons, Inc.
Poly(vinyl alcohol) membrane systems for the controlled release of chlorinated isocyanurates
Authors: Lee Ping I.
Published: April 2003

The applicability of membrane‐reservoir devices based on cold water insoluble, fully hydrolyzed poly(vinyl alcohol) (PVA) membranes for the controlled release of chlorinated isocyanurates into aqueous media has been demonstrated. In addition to providing a prolonged constant rate of release, fully hydrolyzed PVA membranes also exhibit, good stability in the presence of saturated solutions of chlorinated isocyanurates. The apparent resistance to degradation by chlorine and the significant retention of wet mechanical strength of these membranes have been attributed to the semicrystalline nature of PVA. © 1993 John Wiley & Sons, Inc.
Vacuum pyrolysis of polystyrene oligomers
Authors: Still Richard H. , Peters Olufemi A.
Published: April 2003

Oligomers of polystyrene (PS) obtained from initial degradation studies of an anionic polymerized styrene have been degraded in vacuo using the molecular still method at temperatures between 150 and 250°C. The volatile decomposition products were separated and characterized by gel permeation chromatography, gas liquid chromatography, infrared spectroscopy, mass spectroscopy, and nuclear magnetic resonance. The products of pyrolysis showed that at 150°C the major component formed was the dimer, whereas at 250°C, the trimer was the major component. © 1993 John Wiley & Sons, Inc.
Poly(N‐phenolicmaleimide) for high‐temperature stable near‐UV resist
Authors: Chiang Wen‐Yen , Lu Jin‐Yuh
Published: April 2003

Poly[N‐(4‐hydroxyphenyl)maleimide] (PHPMI) was prepared by the radical polymerization of N‐(4‐acetoxyphenyl) maleimide, followed by transesterification of the acetoxy group. The cyclic maleimide group was responsible for high‐temperature stabilities. Thus, a high glass transition temperature of 227°C and a thermal decomposition temperature of 417°C were found. PHPMI sensitized by a diazonaphthoquinone or an aromatic bisazide was prepared and evaluated as a positive or a negative near‐UV resist. Microlithographic positive/negative images were obtained that were stable to temperatures higher than 200°C. The developed images showed no pattern deformation induced by swelling during development. © 1993 John Wiley & Sons, Inc.
Catalytic hydrogenation and gas permeation properties of metal‐containing poly(phenylene oxide) and polysulfone
Authors: Gao Hanrong , Xu Yun , Liao Shijian , Liu Ren , Yu Daorong
Published: April 2003

Metal‐containing polymers, PPO–DPP–Pd, PPO–CPA–Pd, PSF–DPP–Pd, PSF–CPA–Pd (DPP = diphenylphosphinyl, CPA = o‐carboxy phenyl amino), PPO–M (M = Pd, Cu, Co, Ni), and PSF‐Pd, were prepared by incorporating metal chloride with either modified or unmodified poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) and polysulfone (PSF). The Pd‐containing polymers exhibit catalytic activity in the hydrogenation of cyclopentadiene under mild conditions (40°C, 0.1 MPa) both in alcohol solution and in the gas phase. The selectivity in the hydrogenation of diene to monoene in the gas phase can be controlled by adjusting the hydrogen partial pressure. The metal‐containing polymers, PPO–M and PSF–Pd, can be cast easily into the membranes. The H2/N2 permselectivity for PPO–M is higher than that for unmodified PPO, whereas the permeability of H2 changes slightly. The H2 permeability and H2/N2 permselectivity for the PPO–Pd membrane are up to 67.5 barrers and 135, respectively. © 1993 John Wiley & Sons, Inc.
Gas‐separation applications of miscible blends of isomeric polyimides
Authors: Coleman M. R. , Kohn R. , Koros W. J.
Published: April 2003

Blends of polyimide isomers containing hexafluoroisopropylidene in the central moiety of the diamine residue have been studied. The isomers differed by having either a meta or a para linkage between the diamine and dianhydride residues. The miscibility of these materials was investigated by studying the glass transition temperature behavior using differential scanning calorimetry. Mixtures of isomer pairs, such as 6FDA–6FmDA and 6FDA–6FpDA, exhibited one glass transition temperature. Tg, and were therefore miscible. Mixtures of nonisomer pairs exhibited two Tg's and were immiscible. The gas sorption and transport properties of the blends of the 6FDA–6FmDA and 6FDA–6FpDA isomers were characterized for a variety of gases at 35°C for pressures up to 60 atm. The permeabilities and permselectivities in the miscible blends fell between those of the pure components and were approximately logarithmic averages of the pure component properties. The miscibility of the polyimide isomers enables one to tailor the composition of the material to optimize the gas separation and mechanical properties. © 1993 John Wiley & Sons, Inc.
Investigation of optical effect of lignin solution and determination of M̄w of kraft lignin by LALLS
Authors: Dong Daojie , Fricke Arthur L.
Published: April 2003

The optical effects (fluorescence, anisotropy, and absorption) of kraft lignin solutions in three different kinds of solvents (0.1N NaOH, DMF, and pyridine) on the measurement of the weight‐averaged molecular weight of lignin were investigated, and a correction procedure for these optical effects in the determination of the weight‐averaged molecular weight of kraft lignin was developed. It was found that the fluorescence effect is the main source of error in the determination of the molecular weight of lignin, and the anisotropy and absorption strongly affect the second virial coefficient. It was also found that the anisotropic effect of kraft lignin dissolved in DMF and pyridine is contributed mainly by the anisotropic solvents rather than by the lignin particles and that the lignin solution in 0.1N NaOH is essentially optically isotropic. By using the correction procedure provided, the corrected molecular weight of lignin determined in three kinds of solvents varies only about ±10%, whereas the apparent weight‐averaged molecular weight of the same lignin differs by ±57%. © 1993 John Wiley & Sons, Inc.
Surface modification and stabilization of rubber materials: Plasma polymerization and photografting
Authors: Mattson Bengt , Stenberg Bengt
Published: April 2003

Thermooxidative degradation of thick‐walled rubber materials is dependent on oxygen diffusion. The oxidative degradation ceases due to a lower permeability of oxygen through the oxidized material formed at the rubber surface. This phenomenon indicates a paradoxical effect of antioxidant loading. Since antioxidants prevent oxidation, antioxidants also prevent the formation of the protective oxidized layer. This paper suggests and explores an attempt to stabilize polymer materials using surface‐modification techniques in order to form an oxygen permeation barrier at the surface. Two techniques, plasma polymerization and photografting, suitable for such surface modifications are described. © 1993 John Wiley & Sons, Inc.
Thermal characteristics of iron(III), cobalt(II), and copper(II) complexes of dipyridylamine anchored on polystyrene‐divinylbenzene copolymer
Authors: Mukherjee Amit , Biswas Mukul
Published: April 2003

Polystyrene‐divinylbenzene (PS‐DVB) (partially chloromethylated) has been modified by anchoring dipyridylamine (DPA) followed by subsequent complexation with Fe(III), Co(II), and Cu(II). Analytical and spectroscopic evidence has been presented to confirm the attachment of the metal‐dipyridyl complex on the PS‐DVB matrix. All the metal‐loaded polymers exhibit appreciable improvement in thermal stability relative to the base polymer, the initial decomposition temperature and stability order being PS‐DVB‐DPA‐Cu(315°C) > PS‐DVB‐DPA‐Fe(II) (310°C) > PS‐DVB‐DPA‐Co (300°C) > PS‐DVB‐DPA (280°C) = PS‐DVB.DTA studies reveal exothermic peaks between 300 and 380°C, 420 and 440°C, and 500 and 700°C, which are ascribable to the exothermic cleavage of the PS‐DVB‐DPA matrix. The glass transition temperatures of the modified polymers do not reveal any characteristic difference from the corresponding value for the base polymer. © 1993 John Wiley & Sons, Inc.
Studies on the mechanical properties of a glass‐fiber reinforced polypropylene/4‐(hept‐6‐enyl)‐2,6‐di‐tert‐butylphenol copolymer
Authors: Wilén Carl‐Eric , Fälden‐Nylund Marianne , Näsman Jan H.
Published: April 2003

The mechanical properties of a short glass‐fiber reinforced composite based on a commercial polypropylene grade was compared to a composite system where the bulk material had been replaced by a propylene/4‐(hept‐6‐enyl)‐2,6‐di‐tert‐butylphenol copolymer. The mechanical properties of the composites were determined by standard tensile tests. The results indicated that the composite based on the copolymer exhibited a noticeable improvement in tensile properties compared to the composite based on commercial polypropylene. The improved mechanical properties can be attributed to higher wetting of the fibers and to enhanced interfacial adhesion between the fiber and the matrix relative to the composite based on the commercial polypropylene. These assumptions are supported by scanning electron microscopy analysis. © 1993 John Wiley & Sons, Inc.
Surface segregation and tackiness in blends of poly(vinylidene fluoride‐co‐hexafluoro acetone) with poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate)
Authors: Kano Yoshihisa , Akiyama Saburo , Kasemura Tomoyuki
Published: April 2003

In the blends of poly(vinylidene fluoride‐co‐hexafluoro acetone) P(VDF‐HFA) with poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate) P (2EHA‐AA‐VAc), the surface composition was investigated with X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the tackiness was evaluated using the J. Dow ball tack and dynamic mechanical analysis. From surface to a few nm in depth, in the P (VDF‐HFA)/P (2EHA‐AA‐VAc) (50/50) blend, the variation in P (VDF‐HFA) concentration, with increasing distance from the surface, was found by means of XPS with take‐off angle dependence. It was confirmed that surface segregation of P (VDF‐HFA) in the P (VDF‐HFA)/P(2EHA‐AA‐VAc) blends took place. The value of J. Dow ball tack of the surface side in the P (VDF‐HFA)/P(2EHA‐AA‐VAc) blends was smaller than that of bottom side in blends. The delineation of dynamic loss factor Δ vs. the temperature curve of the surface side in a (50/50) blend differed from that of the bottom side. It was suggested that surface segregation affected the difference in tackiness between the surface side and the bottom side. © 1993 John Wiley & Sons, Inc.
Microporous polypropylene sheets containing polymethylsilsesquioxane filler
Authors: Nagō Satoshi , Mizutani Yukio
Published: April 2003

Microporous sheets were prepared by biaxially stretching composite nonporous sheets composed of microspherical polymethylsilsesquioxane particles encased in polypropylene. The structural and physical property studies of the sheets obtained thereby show that the porosity, pore‐size distribution, and the tortuosity vary with the average diameter of the encased particles as expected on the basis of theory. © 1993 John Wiley & Sons, Inc.
Drug‐release behavior of polyurethane microspheres
Authors: Shantha K. L. , Rao K. Panduranga
Published: April 2003

Polyurethane (PU) microspheres were prepared by a novel and simple method using the condensation polymerization technique. Microspheres of different morphological characteristics were prepared using tolylene 2,4‐diisocyanate (TDI) and methylene diphenyl diisocyanate (MDI). These microspheres were fully characterized by thermal analysis, scanning electron microscopy, and spectral techniques. MDI‐containing microspheres were found to be more porous as compared to TDI‐containing microspheres. The infrared spectra indicated the complete utilization of the isocyanate groups in the synthesis of microspheres. Bromothymol Blue (BTB) was used as a model drug for the in vitro release studies from the spheres. The results indicated that BTB released much faster using the MDI spheres as compared to the TDI spheres. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of poly(phenylene sulfide). I. Studies on the synthesis and the property differences of poly(phenylene sulfide) with terminal chloro groups and poly(phenylene sulfide) with terminal thiohydroxy groups
Authors: Yang Suizhou , Zhang Jinhua , Bo Qingchang , Fang Dongpu
Published: April 2003

In this article, two kinds of poly(phenylene sulfide) (PPS) with terminal groups predominated by chloro and thiohydroxy groups have been synthesized using endcapping by adding monomer. Compared with PPS with terminal thiohydroxy groups, PPS with terminal chloro groups possesses a greater crystallinity, larger crystallite dimensions, a larger particle size, higher thermal stability, and a longer gelation time. © 1993 John Wiley & Sons, Inc.
Anomalous behavior of electrical conductivity of solubilized collagen solutions with thermal denaturation
Authors: Matsushita Satoru , Deki Shigehito , Mizuhata Minoru , Sugita Masami , Kanaji Yukio
Published: April 2003

The temperature dependence of the electrical conductivity, σ, for a collagen solution was measured in the temperature region including the thermal denaturation temperature, td. The σ increased with temperature, t, but decreased at ca. 40°C, and then again increased. In this temperature region, a change of optical rotation, αD, was observed. The change is due to the thermal denaturation. The differential curve of σ vs. t gave clear deflection points and a large peak at ca. 40°C. The td could be estimated from the peak temperature. The td decreased with the increase in the concentration of collagen and with the decrease in the heating rate. These measurements were carried out for the collagen prepared by various methods. Some of them showed one peak; others had two peaks. The td obtained by the measurement of σ correlated with that obtained by the measurement of αD. The activation energy of σ, ΔEa, obtained from the linear relationship between log σ and 1/T, increased with the concentration of collagen, but was unchanged for the heating rate. The ΔEa obtained for various types of collagen showed a constant value. © 1993 John Wiley & Sons, Inc.
A morphological study of HDPE‐blown films using small‐angle X‐ray scattering
Authors: Gupta Anunay , Simpson David M. , Harrison Ian R.
Published: April 2003

Discrete small‐angle X‐ray scattering (SAXS) has been used as an analytical tool to study the development of crystalline morphology in a series of blow‐extruded high‐density polyethylene (HDPE) films. Processing parameters, take‐up ratio (TUR) and blow‐up ratio (BUR), were the primary variables used in this investigation. Results from SAXS have led to the consideration of a new microstructural model for crystallite development in blown films. The model incorporates row‐nucleated lamellae, where crystalline morphology is sensitive to TUR and BUR. Increasing TUR results in an increase in the number of lamellae in a particular stack, a decrease in fluctuations of amorphous and crystalline thickness distributions, a flattening out of undulations of crystal surfaces, and an increase in the lateral dimensions of lamellae. Increasing BUR did not significantly influence any of the SAXS parameters studied; this can be attributed to the low BURs at which the films were made. © 1993 John Wiley & Sons, Inc.
Digestion of crosslinked poly(vinylpyridinium halide) by activated sludge, and application to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group into the main chain
Authors: Kawabata Nariyoshi , Uchihori Daisuke , Fukuda Shinji , Funahashi Hirokatsu
Published: April 2003

Crosslinked poly(N‐benzyl‐4‐vinyipyridinium bromide) has been found to be digested by activated sludge obtained from sewage works. As an extension of this work, the authors attempted to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group. Poly(methyl methacrylate) containing a small amount of N‐benzyl‐4‐vinylpyridinium chloride in the main chain showed remarkable reduction in molecular weight and gravimetric weight when placed in an aeration tank of a sewage works. Molecular weight reduction by activated sludge was more conspicuous when content of the pyridinium group was larger and the original molecular weight before the biological treatment was lower. Since insoluble pyridinium‐type polymer captures microbial cells alive, this biodegradation appears to be facilitated by enhancement of affinity of the synthetic hydrophobic polymer with cells of microogranisms. © 1994 John Wiley & Sons, Inc.
Surface treatment of fluorinated rubber with triazine thiols and their properties
Authors: Mori Kunio , Hirahara Hidetoshi , Oishi Yoshiyuki , Kim Saiso , Tamura Kosaku , Iwabuchi Akira
Published: April 2003

Fluorinated (FKM) vulcanizates were treated by immersing in an aqueous solution of triazine thiols, NaOH, and onium salts for 15–60 min at 50–95°C (W‐Method). Treated FKM vulcanizates further were postcured in an air oven for 20 h at 200°C to complete the reaction. The onium salt of triazine thiols were found to be formed by a reaction among the triazine thiols, NaOH, and onium salts and to act as cross‐linking agents to the surface of FKM vulcanizates. In the acetone solution of onium salts of triazine thiols, FKM vulcanizates were also treated by immersing for a few minutes at 20°C and then by heating in an air oven for 20 min at 200°C (A‐Method). Triazine thiols were introduced as crosslinks onto the FKM backbone. The degree of cross‐linking in the surface increased by these treatments and the depth of cross‐linking reached up to about 40 μm thickness by control of treating conditions. The coefficient of friction in FKM vulcanizates decreased as a result of the surface treatment up to about 0.5 from 2.6. FKM vulcanizates decreased the tensile strength by these surface treatments because of the generation of cracks on the surface at 50% or 100% elongation. The surface treatment of FKM vulcanizates suppressed markedly the fixing between FKM vulcanizates and stainless steel at 150°C. Especially, the A‐Method was very effective treating for retarding the fixing between FKM vulcanizates and metals. © 1994 John Wiley & Sons, Inc.
Stereocomplex formation between enantiomeric poly(lactic acid). VIII. Complex fibers spun from mixed solution of poly(D‐lactic acid) and poly(L‐lactic acid)
Authors: Tsuji Hideto , Ikada Yoshito , Hyon Suong‐Hyu , Kimura Yoshiharu , Kitao Toshio
Published: April 2003

To obtain poly(lactic acid) (PLA) complex fibers, spinning was performed by wet and dry methods from 5–10 g/dL chloroform solutions of poly(D‐lactic acid) (PDLA) and poly(L‐lactic), both with a viscosity‐average molecular weight of 3 × 105. The dope was extruded from a monohole nozzle into coagulation baths from ethanol and chloroform for wet spinning and into a drying column kept at 60°C for dry spinning. Scanning electron microscopic observation of the as‐spun fibers showed that the surface of the wet‐spun fiber had large basins with diameters of 50–100 μm and many pores with diameters from sub μm to 10 μm, whereas the surface of dry‐spun fiber had a microporous structure with the pore diameter of 1–3 μm. The tensile strength of the wet‐spun complex fiber was very low and could not be drawn at high temperatures, in contrast to the dry‐spun fiber. The tensile strength of dry‐spun complex fiber increased upon hot drawing and showed the tensile strength of 94 kg/mm2 by drawing at 160°C to the draw ratio of 13. Differential scanning calorimetry revealed that the complex fibers contained both the stereocomplex crystallites (racemic crystallites) and the crystallites of the single polymers, PDLA and PLLA, regardless of the spinning methods. The ratio of the racemic crystallites to the single‐polymer crystallites increased with the draw ratio of the complex fiber. © 1994 John Wiley & Sons, Inc.
Blends of metal acetates and polyurethanes containing pyridine groups
Authors: Yang Chang Zheng , Zhang Xiaomang , O'Connell Ellen M. , Goddard Richard J. , Cooper S. L.
Published: April 2003

Two series of segmented polyurethanes based on 3/2/1 and 2/1/1 molar ratios of methylene diphenyldiisocyanate (MDI), N,N‐bis (2‐hydroxyethyl) isonicotinamide (BIN), and poly(tetramethylene oxide) (PTMO, MW = 1000) were synthesized and blended with different metal acetates. The thermal behavior and mechanical properties of the pyridinecontaining polyurethane precursors and their blends were characterized by DSC, DMTA, and tensile testing. The results suggest that coordination between pyridine groups in the hard segments and the metal ions in the acetates improves hard‐domain cohesion and phase separation and, subsequently, has an effect on mechanical properties. The varying ability of the pyridine group to coordinate with different cations results in different extents of phase separation. The interaction of pyridine with Ni or Cu (II) is much stronger than with Zn. It is shown that coordination interactions can be a driving force for phase separation and hard‐domain aggregation in multiblock copolymer systems. Two different morphologies are proposed for polyurethanes of differing stoichiometry to explain the differences in the results from DMTA and tensile testing. © 1994 John Wiley & Sons, Inc.
Thermal behavior of methacrylic acid–ethyl acrylate copolymers
Authors: Bajaj P. , Goyal Meenakshi , Chavan R. B.
Published: April 2003

The thermal degradation behavior of copolymers of methacrylic acid (81.5–17.4 mol%) was studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC) and the degradation products were analyzed using mass spectroscopy and DSC–FTIR. From mass spectroscopy, it was observed that in the copolymers the main degradation products obtained below 280°C included water, ethanol, and methanol, whereas at higher temperature (up to 400°C), CO2, CO, and small olefins were liberated. Elimination of water and ethanol is attributed to anhydride formation, which is believed to result from two routes: (a) anhydride formation involving adjacent acid groups and (b) anhydride formation involving adjacent acid and ester groups. An endothermic transition in the DSC and percent weight loss in the TGA in the same temperature range (140–280°C) support the above proposal. An increase in weight loss with increase in EA content of the copolymer confirms the participation of EA in the anhydride formation. © 1994 John Wiley & Sons, Inc.
A comparison of specular reflection and PA‐FTIR techniques in the analysis of annealed injection‐molded polyamide 6,6
Authors: Jawhari T. , Quintanilla L. , Pastor J. M.
Published: April 2003

A comparative study between the specular reflectance and photoacoustic FTIR techniques is presented in this work. The potential and limitations of these two methods are investigated by following and analyzing structural variations that take place at the surface in annealed injection‐molded polyamide 6,6. Both spectroscopic techniques appear to be quite sensitive in detecting small structural changes that occur in polyamide 6,6 when submitted to different annealing temperatures. However, the presence of distorted bands in the specular reflection spectra makes the photoacoustic FTIR method more attractive for the IR vibrational analysis of difficult materials (e.g., composites, black‐filled polymers, paints, etc.) that cannot be easily characterized by conventional transmission FTIR. © 1994 John Wiley & Sons, Inc.
Characterization of diol modified epoxy resins by near‐ and mid‐infrared spectroscopy
Authors: Scherzer T.
Published: April 2003

Near‐ and mid‐infrared spectroscopy has been used for the characterization of epoxy networks based on diglycidyl ether of bisphenol‐A cured with linear aliphatic diols of different chain length in the presence of magnesium perchlorate. Absorption bands due to epoxide, hydroxyl, and ether groups were investigated. The intensity of the hydroxyl absorption and the formation of branched and unbranched ether structures in dependence on the molar ratio and the diol chain length are discussed. A mechanism for the network formation process with respect to diol chain length and concentration is proposed: networks with low density are rapidly formed if long diols are used for modification, whereas the incorporation of short diols into the network takes a longer time but yields networks with a higher density. Glass‐transition temperatures of the networks obtained by dynamic thermomechanical analysis confirm the proposed mechanism. © 1994 John Wiley & Sons, Inc.
Composition and temperature effects on air separation through liquid crystalline alkyl cellulose membranes
Authors: Li Xin‐Gui , Huang Mei‐Rong , Lin Gang , Yang Pu‐Chen
Published: April 2003

The air separation through triheptyl cellulose (THC)/ethyl cellulose (EC) blend membranes containing no more than 20 wt % THC at the temperature range from 298 to 358 K was investigated using a variable volume method. The air‐separation ability for the THC/EC membranes were greater than that for the THC‐free pure EC membrane. P for the THC/EC membranes was between 1.06–8.89 × 10−9 cm3 (STP) cm/cm2 s cmHg and P/P 3.04–3.66. The THC/EC membrane showed a unique trend in its P/P − P relationship, i.e., the magnitude of P/P increased simultaneously with that of P. The THC/EC membrane yielded a maximum oxygen concentration in the oxygen‐enriched air (OEA) of 39.5% at an OEA flux of 6.99 × 10−4 cm3 (STP)/s cm2 for a pressure difference of 0.43 MPa at 358 K. After 300 h of measurement at 0.40 MPa and 313 K, the efficiency of the concentrating oxygen was almost constant. © 1994 John Wiley & Sons, Inc.