bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prepreg aging in relation to tack
Authors: Ahn K. J. , Peterson L. , Seferis J. C. , Nowacki D. , Zachmann H. G. 
Published: April 2003

AbstractThermoanalytical measurements and tack tests were both performed using a commercially available carbon fiber/epoxy prepreg system (Hercules 3501–6) to examine changes caused by aging as they affect handling and processability of thermosetting matrix‐based composites. Combining these techniques, a relationship between prepreg bulk and surface characteristics in relation to aging was investigated. Isothermal kinetic studies at low temperatures showed maximum conversions (αm) that increased with increasing cure temperatures. In addition, a linear relationship between glass transition temperatures (Tg) and conversions (α) was observed regardless of aging (or cure) temperatures. Energy of separation of prepreg stacks, which may be viewed as a measure of prepreg tack, showed a maximum value at a specific temperature. The maximum energy of separation was observed in the temperature range of 20–25°C above the glass transition temperature for a given sample. However, the maximum energy of separation values decreased with increasing aging times (or conversions), implying that prepreg tack was a viscoelastic property rather than a viscous property of the resin matrix in the prepreg.
A molecular model for solid‐state polymerization of nylon 6
Authors: Kaushik A. , Gupta S. K. 
Published: April 2003

AbstractA theoretical model is developed for the effect of segmental diffusion on reversible step growth polymerization. This model is an adaptation of the molecular model of Chiu et al. for characterizing the Trommsdorff effect in free‐radical polymerization. The model is applied to the specific case of solid‐state polymerization of spherical pellets of nylon 6. The results of the simulation are found to show qualitative trends as found by Gaymans et al. experimentally. The parameters of the model are curve fitted to their data using an optimal parameter estimation computer code. It is found that the optimal values of the parameters, which can be independently measured, are quite close to the values reported in the literature. The effect of varying the individual parameters on the progress of polymerization is also studied.
Porous structure and rheological properties of hydrogels of highly water‐absorptive cellulose graft copolymers
Authors: Yoshinobu Masahiro , Morita Mitsuhiro , Sakata Isao 
Published: April 2003

AbstractThe porous structures of the highly swollen hydrogels of cellulose—acrylamide graft copolymers were studied by the solute exclusion technique. For these hydrogels, the cumulative volume of pores up to 560 Å in pore width was between 450 and 850 mL/g, and was between 20 and 30% of the total pore volume. With an increasing in the amount of crosslinker added in the grafting procedure, the cumulative pore volume up to 560 Å decreased. Furthermore, larger pores shrunk preferentially. In the range of concentration from 0.003 to 0.3%, the viscosity of the hydrogels increased remarkably with an increase in concentration. The concentration dependence of the viscosity showed a transition at about 0.03%, which corresponded to the reciprocal of the water retention values for each copolymer. At concentrations over 3%, fluidity of the hydrogels was lost and the water swollen copolymers became viscoelastic. This dynamic viscoelasticity remained essentially unchanged in the temperature range of 20 to 80°C. The dynamic viscoelasticity was dependent on the concentration, but the concentration dependence was smaller than that of the viscosity. The larger the amount of the crosslinker added, the larger the value of dynamic modulus became.
Enhancing the reactivity and strength of cotton fibers
Authors: Buschle‐Diller G. , Zeronian S. H. 
Published: April 2003

AbstractBoth sodium hydroxide solution of mercerizing strength and anhydrous methylamine are suitable pretreatments for enhancing the reactivity of cotton cellulose. Favorable results are achieved by maintaining the fiber material in the never‐dried state after the swelling treatment. Extraction by organic solvents is to be preferred over water‐washing in order to remove the swelling agent. When cotton is swollen with either aqueous sodium hydroxide or anhydrous methylamine and then washed and dried, its crystallinity, as determined by X‐ray diffraction is not lowered as much as it is if it is acetylated to an acetyl content of about 9% before drying. The greatest modifications of the crystal structure of cotton were found on methylamine treatment followed by chloroform and pyridine washing and acetylation in the never‐dried state (MeCP product), as well as by alcoholic mercerization followed by ethanol and pyridine washing and acetylation in the never‐dried state (AMEP). As determined by moisture regains, no significant differences are apparent between the accessibility of samples of low acetyl content (ca. 9%) prepared by either the AMEP or by the MeCP treatment. The DTA curves of methylamine‐treated cotton with an acetyl content close to that of commercial diacetate and the commercial product are dissimilar. It can be concluded from the DTA curve of the deacetylated product prepared from this MeCP sample that it has a highly disordered structure. The tensile properties of the acetylated products of low acetyl content are considerably improved if acetylation is preceded by mercerization with subsequent solvent exchange, and less so if it is preceded by methylamine followed by solvent exchange. Incorporation of acetyl groups significantly enhances the breaking strength and extensibility of mercerized solvent‐washed materials.
Cationic ring‐opening polymerization of tetrahydrofuran with boron, aluminum, and gallium tristriflate
Authors: Olah George A. , Farooq Omar , Li Cheng X. , Farnia Morteza A. M. F. , Aklonis J. J. 
Published: April 2003

AbstractBoron, aluminum, and gallium tristriflate are new effective catalysts for the polymerization of tetrahydrofuran (THF). High‐molecular‐weight polytetrahydrofuran (PTHF) was obtained in excellent yield in the bulk polymerization of THF at ambient temperature with all three catalysts. The PTHF samples were characterized and some of their thermodynamic and mechanical properties were investigated and discussed.
Solubility characteristics of poly(etheretherketone) and poly(phenylene sulfide)
Authors: Beck H. N. 
Published: April 2003

AbstractThe crystalline high‐performance polymers poly(etheretherketone) (PEEK) and poly(phenylene sulfide) (PPS) are generally considered to be highly resistant to dissolution in most common solvents. This article reveals numerous compounds that dissolve in excess of 25 wt % of each polymer at elevated temperatures. Typical binary‐phase diagrams depicting the minimum solubility temperature vs. concentration are also presented for several representative polymer–solvent mixtures for both PEEK and PPS. The phenomenon of the solvent‐induced crystallization of PEEK is presented. The importance of these polymer–solvent systems for the preparation of permselective membranes is discussed.
Water resistance of metalliferous epoxy chelate polymers
Authors: Kurnoskin A. V. 
Published: April 2003

AbstractEpoxy chelate polymers have been produced by hardening of diglycidyl ether of bisphenol‐A (DGEBA) with chelates of metals and aliphatic amines, such as ethylene diamine (en), diethylene triamine (dien), triethylene tetramine (trien), and cyanoethylated diethylene triamine (cydien). The influence of structure and quantity of the hardeners on water resistance of the metal‐containing polymers has been studied. Water sorption was found to be increased depending on the ligands and independently of temperature in the following series:

The influence of anions is determined by ionization constants of corresponding organic acids and depends on temperature. The influence of metal cations on water resistance also depends on temperature. Maximal water resistance can be achieved by hardening of DGEBA with 0.11 mol of chelate per 1 mol of the oligomer. Strengths of the water‐resistant epoxy chelate polymers have been determined. The conclusion has been drawn with respect to copper complexes application in high‐strength water‐resistant polymer production.
Chemical modification of silk with itaconic anhydride
Authors: Tsukada Masuhiro , Goto Yohko , Freddi Giuliano , Shiozaki Hideki , Ishikawa Hiroshi 
Published: April 2003

AbstractBombyx mori silk fibers were chemically modified by acylation with itaconic anhydride. The reactivity of the modifying agent toward silk fibroin was investigated on the basis of the amino acid analysis. We examined the physical properties, the structural characteristics, and the thermal behavior of modified silk fibers as a function of the weight gain. Silk fibers with a weight gain of 9%, corresponding to an acyl content of 68.9 mol/105g, were obtained at the optimum reaction conditions for silk acylation (75°C for 3 h). The amount of basic amino acid residues (Lys, His, and Arg) decreased linearly as the weight gain increased. The alkali solubility increased proportionally with the weight gain, probably due to the dissolution of the modifying agent reacted with silk fibroin, and not to the degradation of the fibers induced by the chemical modification. The birefringence value, related to the molecular orientation, slightly decreased when the weight gain increased. The isotropic refractive index, associated with the crystallinity, increased when the weight gain ranged from about 5 to 7% and then remained unchanged. The moisture regain did not change regardless of the chemical modification, and the crease recovery behavior of modified silk fabrics did not show significant improvement. The thermal behavior of silk fibers was affected by the modification with itaconic anhydride. The decomposition temperature shifted up to 322°C, 10°C higher than the control silk fibers, suggesting a higher thermal stability induced by chemical modification.
Dissolving states of cellulose and chitosan in trifluoroacetic acid
Authors: Hasegawa Makoto , Isogai Akira , Onabe Fumihiko , Usuda Makoto 
Published: April 2003

AbstractChemical structures of cellulose and chitosan dissolved in trifluoroacetic acid (TFA) and those of cellulose and chitosan films cast from their TFA solutions were studied by 13C‐NMR and infrared (IR) spectroscopy. Cellulose is trifluoroacetylated selectively at the C6–hydroxyl groups in the TFA solution, and chitosan is dissolved in TFA by forming amine salts with TFA at the C2–amine groups. IR analyses of cellulose films cast from its TFA–acetic acid solutions showed that partly trifluoroacetylated cellulose in the solution state turns to partly acetylated cellulose in the solid state during evaporation of the solvents in air by the ester interchange. Chitosan films cast from its TFA–acetic acid solutions still have the amine salts with TFA. These acetyl groups in cellulose films and TFA in chitosan films are removable by soaking the films in 1N NaOH at room temperature for 1 day.
Radiation‐induced wood plastic composites under combinations of monomers
Authors: Khan Mubarak A. , Ali K. M. Idriss , Ahmad M. U. 
Published: April 2003

AbstractRadiation‐induced wood plastic composites (WPC) were prepared from five varieties of Bangladeshi timbers, using seven different types of monomers. The mixtures of double and triple monomers were investigated along with the single‐monomer system for the preparation of composites. Among the three systems, single‐monomer process showed the highest polymer loading with butylmethacrylate (BMA). Tensile strength (TS) property, represented as Tf = TSwpc/TSwood was determined. Highest Tf values were achieved with the soft wood. The effects of dose and dose rate, monomer concentration, and swelling agent were also studied. Suitable total dose was found to be 3 Mrad at 0.8 Mrad/h, and methanol exhibited the best swelling ability for the woods at a ratio of 1 : 9 v/v in all the monomer investigated.
Synthesis and properties of acrylonitrile‐CR‐methyl methacrylate graft copolymer
Authors: Ha Chang Sik , Choi Seung Keun , Lim Dong Soo , Cho Won Jei 
Published: April 2003

AbstractGraft copolymerization of acrylonitrile (AN) and methyl methacrylate (MMA) onto polychloroprene (CR) was carried out using benzoyl peroxide as initiator. The effects of mole ratio of AN to MMA, reaction temperature, reaction time, solvent, and initiator concentration on the graft copolymerization were examined. It was found that the thermal stability and weatherability of the AN—CR—MMA graft copolymer (ACM) were considerably better than those of CR.
Immobilization of glucose oxidase on nonwoven fabrics with bombyx mori silk fibroin gel
Authors: Asakura Tetsuo , Kitaguchi Motohiro , Demura Makoto , Sakai Harutoshi , Komatsu Keiichi 
Published: April 2003

AbstractThe enzyme glucose oxidase (GOD) was immobilized on the nonwoven fabrics, which have excellent properties in diffusivity of substrates, mechanical strength, and handling, with Bombyx mori silk fibroin gel. The nonwoven fabrics of silk fibroin, viscose rayon, poly‐ethyleneterephthalate, 6‐nylon, and polypropylene with activated surface by fluoline treatment were used. The stabilities of GOD to heat or pH changes were much improved by the immobilization as well as the case of the GOD immobilized in the silk fibroin membrane. Among nonwoven fabrics, silk fibroin was the most excellent support material for the immobilization of GOD although all nonwoven fabrics used here are able to be used as the support materials. The increase of the sensitivity was observed when the glucose sensor was made with the GOD immobilized on nonwoven silk fabrics as four times compared with the case of the GOD immobilized in the silk fibroin membrane.
Pervaporation separation of pentane–alcohol mixtures using nylon 6–polyacrylic acid (PAA) ionically crosslinked membranes. II. Experimental data and theoretical interpretation
Authors: Huang Robert Y. M. , Balakrishnan Malini , Rhim Ji‐Won 
Published: April 2003

AbstractNovel ionically cross‐linked blended membranes of nylon 6 and poly(acrylic acid) (PAA) were studied for the pervaporation separation of the binary organic mixture of pentane and methanol. Membranes of composition 25 wt % PAA were used after cross‐linking. The experimental data obtained from the pervaporation runs were compared with the theoretical values of the individual permeabilities for binary mixtures predicted by the modified Fels and Huang model. This new model is based on an extension of the free volume theory and the introduction of Flory–Huggins thermodynamics for the calculations of the binary interaction parameters and the diffusion coefficients. The calculated values of permeabilities obtained from this modified model were reasonably close to the experimental values.
Image enhancement of polyethersulfone ultrafiltration membrane surface structure for atomic force microscopy
Authors: Fritzsche A. K. , Arevalo A. R. , Moore M. D. , Weber C. J. , Elings V. B. , Kjoller K. , Wu C. M. 
Published: April 2003

AbstractThe surface topography and pore structure of ultrafiltration membranes can be investigated with atomic force microscopy. In this study, it was found that the substitution of ethanol for water as the immersion medium improved the resolution of the fine structure of 10K polyethersulfone ultrafiltration membranes. Pores in the membrane surface from 7 to 9 nm in diameter were measured, which coincides with the range expected for 10,000 molecular weight cutoff (MWCO) ultrafiltration membranes. It is believed that this image enhancement results from increased damping and concomitant noise reduction resulting from the higher viscosity of ethanol in contrast to water.
Studies on modified chitosan membranes. I. Preparation and characterization
Authors: Qurashi M. T. , Blair H. S. , Allen S. J. 
Published: April 2003

AbstractChitin was isolated from prawn shells, and chitosan was prepared from it. The degree of N‐deacetylation and the molecular weight were determined using IR spectroscopy and viscometry, respectively. A series of different modified chitosan membranes were prepared by blending with polyvinylpyrrolidone (PVP). These membranes were characterized by various techniques, including differential scanning calorimetry (DSC), wide‐angle X‐ray diffractometry (WAXD), and tensile testing. The physical, thermal, and mechanical properties were evaluated, and the change in these properties upon the addition of PVP into the blends has been discussed in terms of the amorphous and hydrophilic nature of PVP. Hydrophilicity of the blends increases due to the presence of PVP in the chitosan substrate. This helps in breaking the hydrogen bonds in between chitosan molecules and causes the blends to swell in three dimensions.
Studies on modified chitosan membranes. II. Dialysis of low molecular weight metabolites
Authors: Qurashi M. T. , Blair H. S. , Allen S. J. 
Published: April 2003

AbstractThe permeabilities of low molecular weight metabolites were determined through chitosan and a series of chitosan—poly(vinyl pyrrolidone) (PVP) membranes. The dialysis studies were carried out in vitro using a diaphragm‐type test cell. The basic metabolites (urea, creatinine, and glucose) show higher permeation rates than do the acidic metabolites (uric acid and phosphate) through all the modified membranes. The hydrophilicity of the membranes, molecular weight, and chemical nature of the metabolites were important parameters in determining transport properties of the membranes. It was observed that higher permeation rates can be obtained by manipulating the amount of PVP in the blended membranes. The PVP weight loss in the aqueous medium was negligible.
Factors influencing vapor‐phase photografting of styrene/acrylonitrile monomer mixtures on polymer films
Authors: Kubota Hitoshi 
Published: April 2003

AbstractAn accelerating effect due to a styrene (St)/acrylonitrile (AN) monomer mixture was investigated in vapor‐phase photografting on polymer films, on which a photoinitiator was coated. A maximum percent grafting was observed at a certain St concentration of monomer feed irrespective of the nature of photoinitiator, such as benzoyl peroxide, benzophenone, and α,α′‐azobisisobutylonitrile, and the type of polymer flim, such as low‐ and high‐density polyethylene, polypropyrene, and nylon 6. The same effect due to the monomer mixture was recorded for liquid‐phase photografting in a water‐ethanol mixture solvent. With photoinduced copolymerization of the St/AN mixture using benzoyl peroxide, conversion of AN was sharply reduced by the addition of St to the AN system using DMF, DMSO, methanol, and ethyl acetate solvents. In case of saturated hydrocarbon solvents such as n‐hexane, cyclohexane, n‐hexane, cyclohexane, n‐octane, and n‐decane, on the other hand, a maximum conversion was observed at a certain St concentration of monomer feed. The accelerating effect due to the St/AN mixture was discussed in terms of copolymerizability of monomers and a gel effect.
Dielectric relaxations in poly(monocyclohexyl itaconate)
Authors: Díaz‐Calleja Ricardo , Gargallo Ligia , Radić Deodato 
Published: April 2003

AbstractA study of the dielectric relaxation spectrum of poly(monocyclohexyl itaconate) (PMCHI) is performed by means of two experimental techniques: first, at variable frequency in the audio zone and, second, by thermally stimulated depolarization currents. Because of the high conductivity of the samples, there is a hidden dielectric relaxation that can be detected by using the macroscopic dynamic polarizability ε* defined in terms of the dielectric complex permittivity α* by means of the equation (ε* = 1)/(ε* + 2). The transformation performed through this equation is discussed in order to obtain the dielectric relaxations in the zone of high temperatures and low frequencies of the spectrum.
Synthesis and formation mechanism of porous 2‐hydroxyethyl methacrylate–ethylene glycol dimethacrylate copolymer beads
Authors: Okay Oguz , Gürün Çigdem 
Published: April 2003

AbstractPorous poly(2‐hydroxyethyl methacrylate) (PHEMA) beads cross‐linked with ethylene glycol dimethacrylate (EGDM) were prepared by the suspension polymerization of the monomers in the presence of cyclohexanol or toluene as the diluents. A 20% aqueous NaCl solution containing MgCl2 · 6H2O, bentonite, and gelatine was used as the water phase. In this way, spherical, highly swellable, and/or porous copolymer beads of sizes 0.1–1.0 mm could be synthesized at EGDM contents higher than 20 mol %. The copolymers formed in cyclohexanol, compared to those prepared in the absence of a diluent, exhibit a larger degree of volume swelling in water, indicating that most of the diluent remains in the gel phase throughout the copolymerization. Contrarily, toluene induces porous structures even at a very low degree of cross‐linking (41% porosity at 2 mol % EGDM). An interesting feature of HEMA–EGDM copolymerization in toluene is that the pore volume of the networks increases with increasing EGDM concentration up to 20 mol %, but it decreases again as the EGDM concentration further increases. The results can be explained with the differences in the solvating conditions of the copolymers depending on their EGDM contents.
Concentration distribution of antioxidant additive BHT in polypropylene after heating
Authors: Hayashi Hiromichi , Matsuzawa Shuji 
Published: April 2003

AbstractThe concentration distribution of an antioxidant 2,6‐di‐tert‐butyl‐p‐cresol (BHT) in the polypropylene (PP) after heating the film containing BHT for a long period of time in succession was studied with use of the rolled film method. The film of 0.003 cm in thickness containing uniformly 710 mg kg−1 of BHT was wound tightly around a glass tube. At the beginning, BHT was distributed uniformly in all layers, and after a given time of the heat treatment at 70–100°C, a remarkable alteration of the concentration distribution of BHT in PP took place. The relations between BHT concentration and the distance from the surface were shown by parabolic curves after heating. The BHT concentration was always kept at almost zero concentration at the surface layer of the rolled film. Assuming that the diffusion obeys Fick's law, the diffusion coefficients at 70, 80, 90, and 100°C were estimated to be 1.05, 4.17, 8.69, and 24.7 × 10−9 cm2 s−1, respectively. The activation energy was calculated as 105 kJ mol−1.
Electric field‐associated deformation of polyelectrolyte gel near a phase transition point
Authors: Shiga Tohru , Hirose Yoshiharu , Okada Akane , Kurauchi Toshio 
Published: April 2003

AbstractThe influence of de electric fields on sodium acrylate—acrylamide copolymer gel near a phase transition point in acetone—water mixtures containing NaOH was studied. In the mixtures free of NaOH, the shrunken‐state gel near a phase transition point was not influenced by dc electric fields, while the swollen‐state gel near it shrank from its part facing to the positive electrode in dc electric fields. In the presence of NaOH, unprecedented swelling of the shrunken‐state gel has been observed. The swollen‐state gel showed swelling or shrinking in the field. The type of deformation was determined by the concentration of NaOH. The drift of mobile ions played a role in the deformation. The shrinking occurred through the conformational change of polymer network caused by the drift. The swelling was observed by the change of the osmotic pressure based upon the ion concentration difference between the inside and the outside of a gel.