bluuebunny/crossref_metadata_2025 huggingface dataset:
A new carbon fiber from lignin
Authors: Sudo K. , Shimizu K.
Published: April 2003

A new carbon fiber was prepared from the lignin (steam‐exploded lignin), which was isolated from steam‐exploded birch wood (Betula platyphylla). The lignin was modified to melt thermally on hydrogenolysis. The chloroform soluble and carbon disulfide insoluble fraction (HL) of the reaction products was heated at 300–350°C for 30 min, giving a molten viscous material (HHL). The HHL had a softening point of 110°C and melted at over 145°C to form viscous liquid. When HHL was subjected to a spinning test, according to a conventional fusion spinning method at a speed over 100 m/min, a fine filament could be continuously formed through a pinhole (diameter: 0.3 mm). After the filaments were heated in air at 1–2°C/min up to 210°C, by which time the filament was converted to have an infusible property, the filaments were carbonized by heating from a room temperature to 1000°C at a heating rate of 5°C/min in a stream of nitrogen. The typical properties of the lignin based carbon fiber were as follows: Fiber diameter = 7.6 ± 2.7μ Elongation = 1.63 ± 0.29% Tensile strength = 660 ± 230 MPa; Modulus of elasticity = 40.7 ± 6.3 GPa. The chemical structure of the precursor was remarkably changed from that of the original lignin, indicating the elimination of aliphatic functional groups implied originally in the starting material.
Papain immobilization onto porous poly(λ‐methyl L‐glutamate) beads
Authors: Hayashi Toshio , Hirayama Chuichi , Iwatsuki Makoto
Published: April 2003

Water‐insoluble papain was prepared by immobilizing papain onto the surface of porous poly(λ‐methyl L‐glutamate) (PMLG) beads with and without spacer. The mode of the immobilization between papain and porous PMLG beads was covalent fixation. The relative activity and the stability of the immobilized papain was investigated. The retained activity of the papain covalently immobilized by the azide method was found to be excellent toward a small ester substrate, N‐benzyl L‐arginine ethyl ester (BAEE), compared with that of the peptide binding method. The values of the Michaelis constant Km and the maximum reaction velocity Vm for free and immobilized papain on the PMLG beads were estimated. The apparent Km was larger for immobilized papain than for the free enzyme, while Vm was smaller for the immobilized papain. The thermal stability of the covalently immobilized papain was higher than that of the free papain. The initial enzymatic activity of the covalently immobilized papain remained approximately unchanged with storage time, when the batch enzyme reaction was performed repeatedly, indicating the excellent durability.
Infrared photoacoustic and dynamic mechanical spectroscopy of sheet‐molded compounds
Authors: Allen G. M. , Wu G. L. , Prentice S. A.
Published: April 2003

Chemical and physical characteristics of sheet‐molded compounds were investigated using infrared and mechanical spectroscopies. Fourier transform infrared spectroscopy with photoacoustic detection facilitated surface analysis for determination of composition, depth profile, and thermal exposure effects. Dynamic mechanical spectroscopy utilized torsion, tension, and flexure modes to evaluate temperature and frequency‐dependent viscoelastic properties.
Adhesion studies of tyre cords with rubber. I. Synthesis and characterization of natural rubber graft copolymers
Authors: Egboh S. H. O. , Mukherjee A. K.
Published: April 2003

Glycidyl methacrylate and N‐vinyl pyrrolidone have been grafted onto natural rubber at 32°C using the simultaneous cobalt‐60 irradiation technique. The natural rubber samples were swollen in the monomers for 24 h and thereafter subjected to gamma irradiation. The homopolymers formed in the graft copolymerization reactions and unreacted monomer were removed by solvent extraction using acetone and methanol for glycidyl methacrylate and N‐vinyl pyrrolidone monomer, respectively. The influence of total dose and monomer concentration on the graft parameters was investigated. The dependence of the rate of grafting on the monomer concentration was found to be 0.93 and 0.80 for glycidyl methacrylate and N‐vinyl pyrrolidone, respectively. DSC and TGA studies of the polymers were undertaken. Grafted copolymers based on glycidyl methacrylate were relatively less thermally stable compared with ungrafted natural rubber.
Application of UV‐curable diazoresin. II. Characteristics of the immobilized glucose oxidase membrane
Authors: Liu Jui‐Hsiang , Chen Ming‐Yi , Chang Yuh‐Chwen
Published: April 2003

The characteristics of the enzyme electrode, developed using the immobilized glucose oxidase membranes, were investigated. The enzyme membranes were prepared from poly(vinyl alcohol)‐diazoresin and poly(vinyl alcohol)‐sensitizer systems, cross‐linked by means of ultraviolet light irradiation. Temperature and pH dependencies of the relative activity, stability in repeating usage, storage stability, and calibration plots were evaluated. The unstable phenomenon, found in the initial usage of the immobilized glucose oxidas membrane, which was prepared from poly(vinyl alcohol)‐sensitizer system, was also investigated.
Studies on enzymatic resistance and molecular structure by 13C‐NMR of cellulosic ethers
Authors: Martinez‐Richa A. , Muñoz‐Alarcon H. , Joseph‐Nathan P.
Published: April 2003

A viscometric method to evaluate the enzymatic resistance of cellulosic ethers is proposed. The method was applied to samples of hydroxyethylcellulose (HEC) with molar substitution between 1.8 and 2.5. The results are discussed in terms of the values of Degree of Substitution and the average unsubstituted primary hydroxyl groups, obtained by high‐resolution 13C‐NMR of the neat polymers.
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

Olefinic 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

The 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

Poly(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

In 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

Urethanes 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

This 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

In 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

The 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

Toughening 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

The 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

A 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

A 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

A 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

To 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

This 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

The 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

Darkening 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

Polyimidothioethers 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

During 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

Experiments 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

The 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

Graft 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

Dielectric 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).
Structural changes in rubber during milling
Authors: Kumar N. R. , Roy S. , Gupta B. R. , Bhowmick A. K.
Published: April 2003

Processing operations such as milling, change the chemical structure of rubber. Infrared (IR) spectroscopy and electron spectroscopy for chemical analysis (ESCA) have been used to detect the formation of functional groups during the milling of natural rubber (NR), epoxidised natural rubber (ENR), styrene butadiene rubber (SBR), neoprene (CR), and acrylic rubber (AR). The concentration of carbonyl () groups as detected by IR spectroscopy increases with the time of milling for all the rubbers. The concentration of hydroxyl groups (OH) in NR and ENR also increases during milling. ESCA spectra of the rubbers before and after milling reveal that the peaks are broader for milled rubber, and that the concentration of oxygen is also greater. In the case of ENR, however, the concentration of epoxide rings decreases and that of furan rings increases with the time of milling.
Studies on the adhesion of polyimide coatings on copper foil
Authors: Chen K.‐M. , Ho S.‐M. , Wang T.‐H. , King J.‐S. , Chang W.‐C. , Cheng R. P. , Hung A.
Published: April 2003

The peel strength and the color of the copper foil peeled at 90 degrees from five different polyimide films were studied. The interfacial surfaces of copper foil and polyimide were examined by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and energy dispersion analysis by X‐ray (EDAX). There is a correlation between peel strength, and the color of the interfacial side copper caused by oxygen diffusion. Study of the imidization process carried out in vacuum indicates that the geometric arrangements of the atoms of polyimide also play a very important role in peel strength.
Copolymer composition control by means of semicontinuous emulsion copolymerization
Authors: van Doremaele G. H. J. , Schoonbrood H. A. S. , Kurja J. , German A. L.
Published: April 2003

The effect of two different monomer addition strategies on the chemical composition distribution of the copolymer formed by the (seeded) semicontinuous emulsion copolymerization of styrene and methyl acrylate has been investigated. 1. The addition of a mixture of the monomers at a constant feed rate results in a homogeneous copolymer, provided that extremely long process times are used (starved conditions). When not starting from a seed latex, aqueous phase polymerization was observed at low feeding rates. When using a seed latex, aqueous phase polymerization appeared to be negligible. 2. In order to achieve an optimal monomer addition pattern, a pragmatic approach is presented. An optimal monomer addition profile was calculated from accurate monomer partitioning data using a short iteration procedure. Gradient high performance liquid chromatography (HPLC) was successfully applied as a rigorous test of the homogeneity of the copolymer formed. The information obtained contains much more detail than in the case of using differential scanning calorimetry of 1H NMR. In contrast to 1H NMR that provides only average cumulative chemical compositions, the complete chemical composition distribution can be obtained by means of HPLC.
Dynamic analysis of flat‐spring supported polymers
Authors: Ding Jianfu , Xue Gi , Cheng Rongshi
Published: April 2003

A flat‐spring supported sample technique has been developed for studying the dynamic mechanical properties of a polymer in all its mechanical states, especially for materials with insufficient tensile strength for tensile mode test. The results obtained by this new technique show good agreement with the data from tensile mode tests for poly(ethylene terephthalate) and polystyrene. A high crystallization rate in temperature region 110–160°C for a quenched poly(ethylene terephthalate) and a secondary relaxation at the temperature of 100°C above Tg for a monodispersed polystyrene with a molecular weight of 3 × 105 could be measured quantitatively by the flat‐spring supported polymer technique. This is an important improvement over the existing supported sample techniques.
Preparation and electrodeposition properties of trimethylolpropane–toluene diisocyanate–dimethylaminoethanol/2‐ethylhexanol resins
Authors: Yang Chin‐Ping , Chen Yahn‐Haur
Published: April 2003

2,4‐Toluene diisocyanate (TDI) was partially blocked with equimolar mixtures of dimethylaminoethanol (DMAE) and 2‐ethylhexanol (2EH) of different ratios to form the DMAE/2EH half‐blocked TDIs, which were subsequently reacted with 1/3 mol trimethylolpropane (TMP) to yield the trimethylolpropane–toluene diisocyanate–dimethylaminoethanol/2‐ethylhexanol (TMP–TDI–DMAE/2EH) resins having various content of tertiary amine groups. These resins were neutralized with acetic acid and then dispersed in deionized water, resulting in the milky emulsions used for cationic electrodeposition. Some electrodeposition properties, such as deposition yield, conductivity, rupture voltage, and throwing power, of the resins were investigated. In addition, one of the obtained resins (added as a crosslinker) and an amine–epoxy adduct were codispersed in deionized water, and the nature of electrodeposition of the two‐component emulsion is discussed.
Effect of coupling agent and absorbed moisture on the tensile properties of a thermoplastic RRIM composite
Authors: Otaigbe J. U.
Published: April 2003

The effect of introduction of a silane coupling agent and absorbed moisture (i.e., equilibrium hygroscopic state) on the tensile properties of a thermoplastic reinforced reaction injection molding (RRIM) composite, having a fiber volume fraction of 0.33, was evaluated. The composite was produced by anionically polymerizing caprolactam monomer within a continuous strand (swirl) glass fiber mat using a RRIM method. In addition to the expected strong dependence of the composite tensile stiffness and strength on introduction of 1.5 wt % (based on the total weight of glass fibers) of γ‐amino propyl triethoxy silane coupling agent, the effect of the mode of application of the coupling agent on the resultant composite properties, under tensile loading, was observed to be insignificant in the dry state but quite important in the wet state. Microscopic examination of the fracture surfaces revealed a three‐stage tensile failure mechanism that is associated with debonding at low strains of the fibers, fiber failure (at the weakest point), and pull‐out of the fibers resulting in catastrophic failure, at the ultimate tensile strain, of the composite.
Gas solubility and diffusion in a polystyrene–polybutadiene block copolymer
Authors: Rein D. H. , Baddour R. F. , Cohen R. E.
Published: April 2003

Over the temperature range of 20 to 90°C, the equilibrium solubility of methane or argon in a star‐branched polystyrene–polybutadiene (SB) block copolymer can be reliably estimated from a volume‐fraction‐weighted average of the homopolymer solubilities; the value of heat of solution for SB block copolymer lies between the two values associated with the constituent homopolymers. Diffusion coefficients for gases in the block copolymer are bracketed by the homopolymer values over the range of temperature employed, but the activation energies for diffusion in SB are higher than either of the homopolymer values. The anomalous temperature dependence and the inability of a computer simulation to reproduce experimental diffusion coefficients supported the concept of a temperature‐dependent restriction on chain mobility in the polybutadiene regions of the block copolymer. This β factor embodies the relative reduction in the rate of gas diffusion through the B regions of the copolymer compared to B homopolymer; β has a value of about 2–3 at room temperature but decreases to unity when the polystyrene chains become mobile at the polystyrene Tg.
Effect of melt annealing on the morphology and properties of polycarbonate blends
Authors: Cheng T. W. , Keskkula H. , Paul D. R.
Published: April 2003

The effect of quiescent annealing for brief periods at melt‐processing temperatures (e.g., 270°C) were designed to simulate certain conditions that can occur during molding or extrusion. It was found that significant changes in the phase morphology of polycarbonate‐based blends can occur in less than 2 min under these conditions. Such morphological rearrangements are detrimental to the mechanical properties of multiphase blends of polycarbonate with rigid polymers, viz., polystyrene, poly(methyl methacrylate), and styrene/acrylonitrile copolymers and core‐shell impact modifiers.
Synthesis and characterization of formal‐group‐containing diisocyanates and polyimides therefrom
Authors: Avadhani C. V. , Wadgaonkar P. P. , Vernekar S. P.
Published: April 2003

Four new formal‐group‐containing diisocyanates, namely, bis(3‐isocyanatophenoxy) methane, bis(4‐isocyanatophenoxy)methane, bis[2‐(3‐isocyanatophenoxy)ethyl] formal, and bis[2‐(4‐isocyanatophenoxy)ethyl] formal, were synthesized by the Curtius rearrangement from the corresponding dicarboxylic acids. The diisocyanates were polycondensed with pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylic dianhydride (BTDA) in dimethylacetamide (DMAc) to obtain formal‐group‐containing polyimides. These polyimides were characterized by viscosity measurements, IR spectroscopy, X‐ray diffraction, and thermogravimetric analysis.
Ultraviolet‐radiation‐induced graft copolymerization of styrene and acrylonitrile onto cotton cellulose
Authors: Shukla S. R. , Gopala Rao G. V. , Athalye A. R.
Published: April 2003

Photoinitiated graft copolymerization of the vinyl monomers, styrene and acrylonitrile, onto cotton cellulose was studied using uranyl nitrate and ceric ammonium nitrate as photoinitiators. Uranyl nitrate photoinitiation showed a higher level of grafting for styrene, whereas in the case of acrylonitrile ceric ammonium nitrate was found to be the better photoinitiator. Optimized conditions of grafting, when employed to cotton swollen with sodium hydroxide and zinc chloride, enhanced the graft levels for both monomers. Grafted samples were subjected to thermal analysis, as well as estimation of moisture regain and tenacity. Thermal stability increased, whereas, the moisture regain and tenacity decreased, with the increase in graft add‐on in the case of both monomers. Acrylonitrile‐grafted cotton showed dyeability with cationic dye that improved with the level of graft add‐on. Possible explanations have been given.
The effects of functional azo initiator on PMMA and polyurethane IPN systems. I. Synthesis, characterization, and thermal effects
Authors: Roha M. , Wang B.
Published: April 2003

The use of functional azo initiators and the thermal history of the materials have been shown to exert significant effects on the properties of interpenetrating polymer networks (IPNs). The IPNs prepared with a reactive azo initiator from MDI and 1,2‐PBD (1,2‐polybutadiene diol) with PMMA have been found to exhibit greater ductility, lower rigidity, and lower moduli than IPNs prepared with AIBN. This probably resulted from the attached PMMA blocks modifying the properties of the PU matrix phases. Increasing thermal treatment of IPNs prepared from either the reactive or the normal azo initiators exhibited increased Tg values in both DSC and DMTA scans. These results have been explained by increased association from chemical reactions between the hard segments of the polyurethane and poly(methyl methacrylate) ester groups.
Methods for preparation of absorbent microspherical tannin resin
Authors: Yamaguchi Haruhiko , Higuchi Mitsuo , Sakata Isao
Published: April 2003

Tannin beads formed by reaction of Mimosa tannin (condensed‐type tannin) with formaldehyde in nonpolar polybutenous medium were microspherical resins. Resins prepared with 37.5% tannin concentration were porous spherical resins with 139.22 m2/g of surface area (adsorption method of iodine in n‐hexane, 2.1 m2/g for the dried beads by the Braunauer‐Emett‐Teller (BET) method) and were strong enough to withstand use on a column. The spherical resin adsorbed 3.7 mmol of Cr6+ ions per one gram dry weight of resin (by batch method), this adsorption being comparable to commercial adsorbent.
Biodegradable natural composites. I. Processing and properties
Authors: Gatenholm P. , Kubát J. , Mathiasson A.
Published: April 2003

This paper presents an investigation of the properties of composites of bacteria‐produced polyesters reinforced with wood cellulose. Although cellulose fibers improved the strength and stiffness of the polyhydroxybutyrate (PHB), the samples were very brittle. The impact strength and elongation at break of these composites were significantly improved when PHB copolymers with increased amounts of hydroxyvalerate (HV) were used as the matrix. Dynamic mechanical properties of PHB copolymers of varying compositions and of cellulose‐filled composites were investigated. The introduction of cellulose resulted in a decreased loss factor owing to restrictions of the chain mobility in the amorphous phase. An improvement was observed in the dynamic modulus, which was seen to be greatest at elevated temperatures. An excellent dispersibility of cellulose fibers was achieved in the PHB matrix as compared with such synthetic matrices as polystyrene or polypropylene. The degree of dispersibility was strongly affected by processing conditions. The defibrillation observed on extracted fibers suggests a possible hydrolysis of cellulose by crotonic acid formed in situ as a result of the thermal decomposition of the PHB matrix.
Reinforcement of natural rubber with nylon 6 short fibers
Authors: Younan A. F. , Ismail M. N. , Yehia A. A.
Published: April 2003

The properties of natural rubber vulcanizates reinforced with nylon 6 short fibers were studied. It was found that the stress of vulcanizates decreased with initial fiber loading, followed by an increase with increasing the amount of fiber. The effect of reinforcing carbon black HAF on the physicomechanical properties was studied in the presence and absence of hydrated silica.
Thermodynamic interactions of solvents with styrene–butadiene–styrene triblock copolymers
Authors: Romdhane I. Hadj , Plana A. , Hwang S. , Danner R. P.
Published: April 2003

Fundamental thermodynamic interaction data for various solvents with two styrene–butadiene–styrene triblock copolymers (Kraton D‐1101 and Kraton D‐1300X) have been collected by the use of inverse gas chromatography at infinite dilution. Experimental results are presented for nine D‐1101/solvent systems and nine D‐1300X/solvent systems at 308, 328. and 348 K. Weight‐fraction activity coefficients and Flory–Huggins χ interaction parameters have been calculated from the retention volumes. The χ parameter is used as a measure of the strength of interaction and therefore as a guide in the prediction of polymer–solvent compatibility. In addition, partial molar heats of mixing, ΔHm∞, and heats of solution, ΔHs, were determined. The Hildebrand–Scatchard solubility theory was combined with the Flory theory in order to estimate the solubility parameter of the thermoplastic rubbers at the three different temperatures.
Swelling equations for confined homogeneous and heterogeneous polymeric networks: Calculation of M̄c in swellable two‐phase systems
Authors: Harland Ronald S. , Peppas Nikolaos A.
Published: April 2003

Swelling equations were derived for polymeric networks that consist of two swellable but distinct phases. These equations can be used to describe the equilibrium swelling behavior of certain two‐phase network systems. Using physicochemical measurements of the equilibrium polymer volume fraction, it was possible to calculate the number‐average molecular weight between crosslinks, M̄c, using these equations. The influence of several structural parameters on M̄c was investigated. © 1992 John Wiley & Sons, Inc.
Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. I. Kinetics in VDC–BMA emulsion polymerization and surface and colloidal properties of VDC–BMA latexes
Authors: Lee K. C. , El‐Aasser M. S. , Vanderhoff John W.
Published: April 2003

Vinylidene chloride (VDC)—butyl methacrylate (BMA) comonomer mixtures with various composition (83 : 17, 60 : 40, 33 : 67 in mol %) were polymerized at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M1)—BMA (M2) emulsion copolymerization system were r1 = 0.22 and r2 = 2.41. Seven 35% solids (83 : 17 mol %) VDC–BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt %/min (E). The kinetic studies of seeded semicontinuous polymerizations A‐E showed that the rates of polymerizations (Rp) were controlled by the monomer addition rates (Ra). The conversion versus time curves for the polymerizations of 0 : 100–100 : 0 VDC–BMA mixtures by batch polymerization showed that the rate of polymerization (Rp) was a function of the number of particles, and that the rate of polymerization in a latex particle (Rpp) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC–BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number‐and weight‐average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong‐acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong‐acid groups did not depend on the monomer composition of the copolymers.