bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantitative analysis of branching in poly(ortho ester) networks
Authors: Shih Chung , Waldron Niki , Traugott Cathy 
Published: April 2003

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractPhase 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

AbstractA 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

AbstractThis 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

AbstractThermal 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

AbstractWhile 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

AbstractWe 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

AbstractRaman 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

AbstractThe 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

AbstractOligomers 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

AbstractPoly[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

AbstractMetal‐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

AbstractBlends 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

AbstractThe 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

AbstractThermooxidative 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

AbstractPolystyrene‐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

AbstractThe 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

AbstractIn 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

AbstractMicroporous 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

AbstractPolyurethane (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.