bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stability of the chain structure of a styrene–isoprene diblock copolymer during the hydrogenation by diimide
Authors: Podešva J. , Špaček P. , Koňák Č. 
Published: April 2003

AbstractOlefinic double bounds of a model styrene–isoprene diblock copolymer were hydrogenated using diimide (generated by a thermal decomposition of p‐toluenesulfonyl hydrazide). The presence of byproducts and/or main‐chain structural alterations (e.g., degradation or cross‐linking), as a possible side effect of this polymer analogous reaction, was checked by NMR spectroscopy, elemental analysis, static and dynamic light scattering, and GPC. A twofold concentration of Irganox 1010 antioxidant in the reaction mixture (as compared to the original reported procedure) seems to inhibit the formation of byproducts as well as to prevent any alterations on the macromolecular level. No reactions of isoprene monomer units (other than the addition of hydrogen atoms) and no changes in molar‐mass distribution of the substrate were detected by the methods used.
Prediction of the mechanical properties of a crosslinking polymer from a combination of the measured kinetics and a model for network growth
Authors: Claybourn M. , Reading M. 
Published: April 2003

AbstractThe mechanical properties of a crosslinking isocyanate–hydroxy system were predicted by a combination of the measured curing kinetics and a model for polymer network growth. The kinetic parameters were determined from FTIR using the linear rising temperature method (the activation energy = 52 kJ/mol, reaction order = 2.9). This data, combined with the network model, was used to predict the rise in elastic modulus as measured by dynamic mechanical analysis (DMA). The agreement between the predicted and experimental results was excellent over the early part of the curing, but the model failed at higher isocyanate conversions. In addition a novel method for obtaining the activation energy for the reaction directly from DMA results is presented; the value obtained from this method was in excellent agreement with that obtained by FTIR.
Miscibility of some hydroxyl‐containing polymers with poly(acetonyl methacrylate), poly(tetrahydropyranyl‐2‐methacrylate), and poly(cyclohexyl methacrylate)
Authors: Chong Y. F. , Goh S. H. 
Published: April 2003

AbstractPoly(tetrahydropyranyl‐2‐methacrylate) (PTHPMA) was found to be miscible with Poly(vinyl phenol) (PVPH), Poly(hydroxy ether of bisphenol A) (Phenoxy), and Poly(styrene‐co‐allyl alcohol) (PSAA). However, Poly(cyclohexyl methacrylate) (PCHMA) is immiscible with all these three hydroxyl‐containing polymers. Poly(acetonyl methacrylate) (PACMA) was found to be miscible with PVPH but immiscible with Phenoxy and PSAA. Miscible PTHPMA‐Phenoxy blends showed lower critical solution temperature behavior.
XPS study of radiation crosslinked copolymer of tetrafluoroethylene with hexafluoropropylene
Authors: Zhong Xiaoguang , Sun Jiazhen , Wang Fusong , Sun Ying 
Published: April 2003

AbstractIn this work the radiation‐induced structural changes in F‐46 were studied by XPS. In carbon‐1s spectra of a highly crosslinked F‐46 sheet, the slight increase observed in relative area under the peak due to CF3 was explained by the radiation‐induced scission of polymer chains. The peak at 287.6 eV appearing in the spectra caused by ionizing radiation was attributed to carbon structures without primary fluorine substituents, in both branching and unsaturated structures, while that at 289.3 eV was assigned to =CF groups in mid‐chain double bonds.
Syntheses and reactions of urethanes of cellobiose and cellulose‐containing uretdione groups
Authors: Meyer‐Stork L. Sebastian , Höcker Hartwig , Berndt Heinz 
Published: April 2003

AbstractUrethanes of cellobiose and cellulose‐containing uretdione groups are synthesized by the reaction of aliphatic and aromatic diisocyanate uretdiones with the saccharides. The syntheses are performed as a heterogeneous reaction in dimethyl acetamide using dibutyl tin dilaurate as a catalyst, as well as a homogeneous reaction in dimethyl acetamide‐lithium chloride. Thus, Semisynthetic prepolymers are formed that offer the reactivity of (blocked) isocyanate groups. To demonstrate their reactivity, ring opening of the uretdiones is performed by the addition of a secondary amine to yield the corresponding ureas.
New macromolecular carriers for drugs. I. Preparation and characterization of poly(oxyethylene‐b‐isoprene‐b‐oxyethylene) block copolymer aggregates
Authors: Rolland A. , O'Mullane J. , Goddard P. , Brookman L. , Petrak K. 
Published: April 2003

AbstractThis work describes the formation of discrete micelles (⋍ 0.1 μm) from ABA poly(oxyethylene‐b‐isoprene‐b‐oxyethylene) block copolymers in water. An efficient labeling of the micelles by polymerization of [14C]‐styrene within the hydrophobic core is also described. These micellar nanoparticles are being considered as promising materials for controlled release and/or site‐specific drug delivery systems. In experimental animals the micelles remained in circulation with a half‐life in excess of 50 h. Our results demonstrate the advantages of using block copolymers for the preparation of “perfect” biocompatible surfaces such as are required for well‐tolerated, long‐circulating particulate drug carriers.
Synthesis and polymerization of lignin macromonomers. II. Effects of lignin fragments on methyl methacrylate radical polymerization
Authors: Da Cunha C. , Deffieux A. , Fontanille M. 
Published: April 2003

AbstractIn the course of a study on the synthesis and polymerization of lignin macromonomers, the effect of lignin fragments and acetylated lignin ones on the radical polymerization of methyl methacrylate has been investigated. Kinetics show that lignin moieties act first as inhibitors of the MMA polymerization. The inhibition process has been attributed to the phenolic groups, which primarily react through hydrogen transfer with free radicals issued from benzoyl peroxide dissociation, thus leading to a series of lignin free radicals inactive towards ethylenic groups. The derivatization of lignin hydroxyl groups into ester groups totally suppresses the inhibition process. Besides, it was also shown that both lignin and acetylated lignin units act as chain limiting agents towards MMA polymerization. As indicated both by the chemical composition of the polymers produced and the kinetic data, the latter process might involve the formation of a new type of lignin free radicals, able to initiate MMA polymerization. A reaction scheme is proposed.
Study of cryostructurization of polymer systems. IX. Poly(vinyl alcohol) cryogels filled with particles of crosslinked dextran gel
Authors: Lozinsky V. I. , Zubov A. L. , Kulakova V. K. , Titova E. F. , Rogozhin S. V. 
Published: April 2003

AbstractThe influence of deformable disperse filler on rheological and thermal properties of poly(vinyl alcohol) cryogels (obtained by freezing–thawing of concentrated aqueous solutions of the polymer) was studied. Spherical particles of crosslinked dextran gel—the Sephadex beads of two types: G‐25 and G‐100—were used as filler. It was found that an increase in the filler concentration from 0 to 20 wt% produced and increase in the composite cryogel strength; the greater reinforcement effect was observed with large‐pore Sephadex beads into the cryogel matrix. An increase in the fraction of disperse phase also leads to an increase in fusion temperatures of these composites, such effect being determined mainly by the filler type. The filling of cryogels with G‐100 beads improves the thermostability of composite samples to a higher extent as compared with the use of G‐25 particles. Several possible reasons for the trends observed in rheological and thermal properties of Sephadexfilled PVA cryogels were revealed.
Toughening epoxy resins by liquid crystalline polymers
Authors: Carfagna C. , Nicolais L. , Amendola E. , Carfagna C. , Filippov A. G. 
Published: April 2003

AbstractToughening epoxy resins can be achieved by blending a low percentage of Liquid Crystalline Polymer with the thermoset. The processing technique consists of the spinning of blends of a thermoplastic (Ardel) with the LCP (PET/PHB60). The bundled filaments are subsequently dissolved in the uncured epoxy resin (Epon 825). After curing, the LCP phase separates from the matrix in the form of microfibers with a very high aspect ratio, which act as crack stoppers and improve fracture toughness of the material.
Study on modified phenolic resin. III. Modification with p‐hydroxyphenylmaleimide/acrylic ester copolymer
Authors: Matsumoto A. , Hasegawa K. , Fukuda A. , Otsuki K. 
Published: April 2003

AbstractThe improvement of toughness and heat resistance of phenolic resin was examined by blend of novolac and copolymers prepared from p‐hydroxyphenylmaleimide (HPMI) and acrylic ester. Copolymers of HPMI and acrylic esters, such as methyl acrylate, ethylacrylate, n‐butylacrylate, or 2‐ethylhexyl acrylate, were synthesized. Average molecular weights, glass transition temperatures (Tg) and thermal decomposition temperatures were measured. The miscibility of the copolymers with novolac was evaluated. It was found that these copolymers had higher average molecular weight and higher thermal decomposition temperature than those of novolac; they also had good miscibility with novolac. Molding compounds were prepared by hot roll‐kneading of mixtures, which involved novolac, the copolymer, hexamethylenetetramine (hexamine), and glass fiber. Test pieces of the modified phenolic resins were prepared by transfer molding from the molding compounds. It was found that phenolic resin, modified with HPMI/ethylacrylate copolymer or HPMI/n‐butylacrylate copolymer, which consisted of numerous units of acrylic ester, showed both good toughness and good heat resistance.
Study on organosilicon positive resist. II. Organosilicon positive photoresist (OSPR–1334) and its application to bilayer resist system
Authors: Sugiyama Hisashi , Mizushima Akiko , Inoue Takashi , Nate Kazuo 
Published: April 2003

AbstractA new alkali‐developable organosilicon positive photoresist (OSPR–1334) and a bilayer resist process with OSPR–1334 has been developed. OSPR–1334 is composed of poly(p‐hydroxybenzylsilsesquioxane) and naphthoquinone diazide. The sensitivity and the resolution are almost the same as those of conventional novolac‐based resists when aqueous tetrakis (2‐hydroxyethyl) ammonium hydroxide is used as a developer. Also, OSPR–1334 has excellent resistance to O2RIE. The etching rate is 3.6 nm/min, while that of polyimide resins or hard‐baked novolac‐based resists is 100 nm/min. OSPR–1334 is suitable for use as the top layer of the bilayer resist system. OSPR–1334, after O2RIE, can be eliminated by dissolving an unchanged layer followed by spinning out or filtrating a changed surface layer. Submicron patterns with a high aspect ratio can easily be obtained with this bilayer resist process.
A structure rheological study of cellulose trinitrate in ethyl acetate
Authors: Schurz Josef , Marx‐Figini Marianne , Müller Bozena , Gonzales F. Rex 
Published: April 2003

AbstractA structure rheological analysis was undertaken with cellulose trinitrates dissolved in ethyl acetate. Empirical scaling laws with molecular mass and concentration were found for the zero shear viscosity ηo and the critical shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma _C $\end{document} at the onset of shear thinning. Values for the apparent chain element A' were calculated from the concentration dependent network strand Me and extrapolated to zero concentration. They were compared with dilute solution data. From the concentration dependence of the mass of network strand Me a network with hindered penetration was inferred.
Kinetic model for crosslinking free radical polymerization including diffusion limitations
Authors: Batch Gibson L. , Macosko Christopher W. 
Published: April 2003

AbstractA kinetic model for crosslinking free radical polymerization is derived to predict the effect of temperature, inhibitor concentration, and initiator concentration on the rate of cure. The model is based on evidence from the literature that termination and comonomer reactivity differences can be ignored in many crosslinking free radical systems. Because of the complexity of the crosslinking chemistry, empirical relationships are used for decreasing initiator efficiency and radical mobility during cure. A sequential parameter fitting procedure is devised for isothermal curing data, and predictions are affirmed with both divinyl benzene and vinyl ester resin at several temperatures and concentrations of initiator and inhibitor. The key advantages of this kinetic model over previous models are its accuracy at high conversions and its ability to predict the effect of inhibitor and initiator concentrations on the rate of cure. This model is readily applicable to process modeling in the polymer composites manufacturing industry, which largely uses unsaturated polyester and vinyl ester resin matrices.
Volatile compounds extracted from polypropylene pellets by hot water: Influence of the level of the peroxide agent
Authors: Rebeyrolle P. , Etiévant P. 
Published: April 2003

AbstractTo improve the quality level of plastic packaging materials, we determined the influence of chemical degradation of polypropylene (PP) upon the amount of volatile components extracted by hot water from PP pellets. Two formulations were analyzed and compared: PP CR (degraded) and PP (not degraded). After Likens‐Nickerson's extraction of the pellets and concentration of the extract, an HPLC fractionation was made to collect three fractions of different poiarities: a pentane (A), a dichloromethane (B), and an ether (C) fraction. Fractions (B) and (C) were olfactively evaluated by GC sniffing to be most interesting. Their analysis by GC/MS coupling allowed the identification of different components: aldehydes, ketones, and phenols in fraction B and alcohols and acids in fraction C. A quantitative analysis gave us the amounts of volatiles that were compared to their olfactive thresholds in water; thus, in fraction (B), nonanal and decanal were concluded to have a potential olfactive contribution to the odor of water in contact with PP. A statistical analysis showed that chemical degradation had little influence upon the amounts of volatiles extracted from PP pellets by hot water.
The correlation between X‐ray orientation parameters and strength of fibers in native cotton
Authors: Moharir A. V. , Louwagie Johanna , Van Langenhove Lieva , Kiekens Paul 
Published: April 2003

AbstractThis paper reviews the relationship between tensile strength of native cotton fibers and the various orientation parameters and the true spiral angle. It is concluded that the Hermans crystallite orientation factor and the average angle of crystallite orientation, αm, deduced from it are the best parameters to characterize fiber strength. Moreover, αm represents a closer approximation to the true spiral angle in cotton than do the 50% or 75% X‐ray angles. It is recommended that cotton breeders characterize fiber strength and screen genotypes on the basis of the Hermans factor and αm rather than the 40, 50, or 75% X‐ray angles.
Morphology and properties of HDPE/zinc‐neutralized sulfonated EPDM blends
Authors: Xu Xi , Zeng Xiangsheng , Li Huilin 
Published: April 2003

AbstractThe compatibility of zinc‐neutralized sulfonated EPDM (Zn‐SEPDM) and its effect on crystallizing behavior of high‐density polyethylene (HDPE) as well as the morphology of the blend were studied through wide‐angle X‐ray diffractomer (WAXD), differential scannign calorimetry (DSC), transition electron micrography.(TEM), scanning electron micrography (SEM), a capillary rheometer, and mechanical property test. The results show that addition of Zn‐SEPDM decreases both the melting point and the crystallizing temperature of HDPE. The apparent viscosity of the blend decreases with increasing of shear rate and stress. As Zn‐SEPDM content exceeds 20%, Zn‐SEPDM in the blend becomes continuous and an abrupt change in impact strength occurs. Owing to the incorporation of ionic groups into EPDM, the strong interaction between the chains make the impact strength of HDPE incredibly increased without sacrificing much of its tensile strength.
Excimer laser darkening of ETFE polymer films
Authors: Berman Michael R. 
Published: April 2003

AbstractDarkening of ethylene–tetrafluorethylene (ETFE) films caused by exposure to xenon chloride excimer laser radiation at 308 nm was studied. Darkening was determined to result from a rapid, local heating of the film. The laser‐induced heating caused elimination of hydrogen fluoride from the film, leaving a noncrystalline graphitic backbone. A threshold laser fluence for darkening of (205 ± 25) mJ/cm2 was observed. At laser fluences above this threshold the rate of darkening of the ETFE films increased linearly with laser fluence. The rate of darkening was found to decrease as the extent of crosslinking in the polymer sample increased. Observations suggest that low concentrations of monomers in the film might affect the darkening rate.
Synthesis and characterization of polyimidothioethers
Authors: Koelling A. , Surendran G. , James W. J. 
Published: April 2003

AbstractPolyimidothioethers were synthesized as possible polymers for evaluation as X‐ray resists. These polymers were varied in the ratio of the monomers and in their structures. Aliphatic thiols, bismaleimides, and iodonium monomers were used. The composition was varied using ratios of the bisimide to iodonium of 9: 1, 8 : 2, 7 : 3, 6 : 4, 5 : 5, and 0 : 1. The ratio of the thiols, containing 6 to 10 CH2 groups, to the monomers was 1 : 1. The synthesis and characterization of the intermediate compounds and polymers are described in detail.
A study of curative interactions in cis‐1,4‐polyisoprene. IX. The role of ZnO in thiuram‐based vulcanization systems
Authors: Kruger F. W. H. , McGill W. J. 
Published: April 2003

AbstractDuring the vulcanization of cis‐1,4‐polyisoprene (IR) with thiruam‐related curing systems, dimethyldithiocarbamic acid (DMDCA) is formed as a byproduct, in the formation of either pendent groups or crosslinks. DMDCA is unstable, and decomposes instantly to Me2NH and CS2 in the absence of ZnO. The facile reaction of Me2NH and thiuram‐related molecules such as tetramethylthiuram polysulfides, tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide and pendent groups caused (i) increased induction periods, (ii) lower maximum crosslink densities, and (iii) the excessive formation of tetramethylthiourea (TMTU). A most important function of ZnO was to trap the DMDCA via the formation of zinc dimethyldithiocarbamate and water, thereby preventing the detrimental reactions above. The IR/TMTD/ZnO and IR/sulfur/TMTD/ZnO systems were therefore characterized by (i) shorter induction periods, (ii) higher maximum crosslink densities, and (iii) the absence of TMTU.
Effect of titanium dioxide on direct esterification between terephthalic acid and ethylene glycol
Authors: Yamada T. 
Published: April 2003

AbstractExperiments at various concentrations for A and B kinds of titanium dioxide were made in the pilot plant, and the effect of titanium dioxide on continuous esterification between terephthalic acid and ethylene glycol was obtained. Reaction rate constants of the reaction scheme reported by Yamada et al. (1985) were determined o fit with the experimental data obtained. It was found that titanium dioxide ([TDO]) does not exert an influence on the reaction rate constants of k1,
k2, and k4 but does on the reaction rate constants of k3, k5, k6, and k7 as follows:

kl = 1.5657 × 109 exp(−19,640/RT)
k2 = 1.5515 × 108exp(−18,140/RT)
k3 = (0.10[TDO] + 1) × 3.5165 × 109 exp(−22,310/RT)
k4 = 6.7640 × 107 exp(−18,380/RT)
k5 = (0.08[TDO] + 1) × 7.7069 exp(−2,810/RT)
k6 = (0.04[TDO] + 1 ) × 6.2595 × 106 exp(−14,960/RT)
k7 = (0.60[TDO] + 1) × 2.0583 × 1015 exp(−42,520/RT) for B kind
k7 = (0.085714[TDO] + 1) × 2.0583 × 1015 exp(−42,520/RT) for A kind

Applying these reaction rate constants, simulation of continuous esterification in the first tank reactor was made and the following results were obtained ( 1) The acceleration effect of titanium dioxide on the esterification reaction is minor, and there is hardly any difference in the effect on the esterification due to kinds of titanium dioxide. ( 2 ) The amount of diethylene glycol formation largely varies with kinds of titanium dioxide.
The solubility parameters of aromatic polyamides
Authors: Aharoni Shaul M. 
Published: April 2003

AbstractThe degrees of swelling of rigid aromatic polyamide networks in various solvents, nonsolvents, and solvent mixtures were used to determine their solubility parameters. This was made possible because of the amorphous nature of the rigid networks and the low levels of intersegmental H‐bonding. The solubility parameters are: δ = 23.0 (MPa)1/2, δd = 18.0 (MPa)1/2, δp = 11.9 (MPa)1/2, and δH = 7.9 (MPa)1/2. The determined values are believed to be good approximations of the solubility parameters of stiff linear aromatic polyamides, because of the essential identity of their structure and the stiff segments in the networks.
Investigations on vinylene carbonate. IV. Radiation induced graft copolymerization of vinylene carbonate and N‐vinyl‐N‐methylacetamide onto polyethylene films
Authors: Chen Guohua , Van Der Does Leen , Bantjes Adriaan 
Published: April 2003

AbstractGraft copolymerization of binary mixtures of vinylene carbonate (VCA) and N‐vinyl–N–methylacetamide (VIMA) onto low density polyethylene (LDPE) films was studied by the mutual γ‐irradiation technique. Sufficient amounts of functionally active VCA groups could be grafted onto the surface and the hydrophilicity of the surface was also improved. The grafting of VCA onto polyethylene films in the binary solutions was found to be promoted by the presence of VIMA, thus showing a positive synergism. The VCA content in the graft copolymers was always higher than in the copolymers obtained by homogeneous copolymerization using the same monomer feed composition. The monomer reactivity ratios, as well as a preferential partitioning of the monomers surrounding the polymeric substrate, were considered to explain the grafting reactions in the binary systems.
Determination of glass transition temperature from dielectric analysis for a series of epoxide oligomers
Authors: Koike Tsuneo 
Published: April 2003

AbstractDielectric properties have been investigated for a bisphenol‐A type epoxide oligomer, whose weight average molecular weight (M̄w) was 9454. The dielectric α‐relaxation of the oligomer was found to be governed by the Havriliak–Negami equation as well as the same series of oligomers with smaller M̄ws (388≦M̄w ≦ 3903). The dielectric relaxation times (τ)s for the oligomers with different M̄ws (1396 ≦ M̄w ≦ 9454) can be expressed by the Williams–Landel–Ferry (WLF) equation as a function of the glass transition temperature (Tg) at fixed temperatures from 70 to 100°C. The finding indicates that the Tg of the epoxide oligomer is calculated from the τ through the WLF equation, providing the relation between Tg and τ. The same type of WLF equation was also successfully applied to describe the Tg, dependence of the practical dielectric relaxation time (τp), which was obtained from the peak of the dielectric loss vs. frequency curve. The τp can be calculated more easily than the τ, based on the Havriliak–Negami equation, not only in the measurement of epoxide oligomer, but also in that of the reactive epoxy resin systems during curing. The Tg of an epoxy–aromatic amine system, which was determined from the τp nondestructively detected in the dielectric cure monitoring, was consistent with the Tg experimentally measured by differential scanning calorimetry (DSC).