bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on mechanical properties of polyethylene–organic fiber composites. I. Nut shell flour
Authors: Raj R. G. , Kokta B. V. , Nizio J. D.
Published: April 2003

Composites were made from polyethylene and an organic fiber (pecan shell and peanut hull flour) using a compression‐molding technique. Studies of variations in molding temperature (145–180°C), fiber concentration (0–40% by weight), and fiber mesh size (100, 200, and 325) were correlated to the mechanical properties of the composites (tensile strength, elongation, fracture energy, modulus, and impact strength). In untreated nut shell composites, tensile strength decreased steadily as the fiber concentration increased. This was due to poor bonding between the untreated fiber and polymer. Polyisocyanate was used as a coupling agent and its effect on mechanical properties of the composites was studied. Significant improvement in tensile strength was achieved with an isocyanate coupling agent, but it had no effect on modulus of the composites. Both untreated and isocyanate‐treated composites had lower impact strength values; further composite matrix modifications would be necessary to maintain or improve impact strength.
Determination of Mark–Houwink constants for polystyrene and polyacrylonitrile terpolymers
Authors: Dayal Umendra
Published: April 2003

Mark–Houwink constants of polystyrene and polyacrylonitrile terpolymers containing acrylonitrile, methyl acrylate, and styrene sulfonic acid or methallyl sulfonic acid as the third comonomer have been calculated from gel permeation chromatography (GPC) and viscosity data. The data have been used to determine molecular weights of polyacrylonitrile terpolymers.
Studies of physico–mechanical properties of wood and wood plastic composite (WPC)
Authors: Khan Mubarak Ahmad , Ali K. M. Idriss
Published: April 2003

An attempt has been made to improve the quality of low grade wood through radiation induced wood plastic composite (WPC) formation in order to use these low grade woods as substitutes for high grade wood. Six kinds of local woods of Bangladesh (simul, korai, mango, jack fruit, teak, and garjon) were investigated. Both soft and hard wood varieties of these were selected. Ten vinyl monomers were used for the WPC. Improvement in the quality of wood was ascertained by determining change in physico—mechanical properties of wood. These properties were tensile strength, Young's modulus, and dimensional stability. Among all the woods investigated, simuls exhibited the best performance for WPC formation. It was found that the tensile strength and Young's modulus of WPC increased about 1.6 and 1.5 times, respectively, as compared with the strength and modulus those of untreated wood.
Preferential adsorption of bovine fibrinogen dimer onto polymer microspheres having heterogeneous surfaces consisting of hydrophobic and hydrophilic parts
Authors: Okubo Masayoshi , Azuma Ichiro , Hattori Hideshi
Published: April 2003

The adsorption onto polymer microspheres of bovine fibrinogen (BFb) containing both dimeric and monomeric species was examined using various homopolymer, copolymer, and poly(2‐hydroxyethyl methacrylate)/polystyrene composite microspheres which were produced by the emulsifier‐free (seeded) emulsion polymerization technique. The preferential adsorption of the BFb dimer was clearly observed in an optimum region of the surface hydrophilicities of the polymer microspheres. The preferential adsorption of the BFb dimer onto the composite polymer microspheres having heterogeneous surfaces with both hydrophilic and hydrophobic parts was more remarkable than that onto the homopolymer and copolymer microspheres having homogeneous surfaces. The behavior is discussed in comparison with those for bovine serum albumin and human γ‐globulin.
Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions
Authors: Nakamura Shigeo , Amano Masato , Saegusa Yasuo , Sato Toshihiko
Published: April 2003

Aminoalkyl celluloses (AmACs) were prepared from 6‐chlorodeoxycellulose and aliphatic diamines H2N(CH2)mNH2 (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu2+, Mn2+, Co2+, Ni2+ and their mixtures were also investigated in detail.

Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu2+ > Ni2+ > Co2+ > Mn2+. Accordingly, their behavior followed the Irving‐Williams series and Cu2+ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.
Ethylene–methacrylic acid copolymers as stress whitening suppressants in polypropylenes
Authors: Rengarajan R. , Kesavan S. K. , Fullerton K. L. , Lee S.
Published: April 2003

Impact‐modified polypropylenes were prepared by incorporating copolymers of ethylenemethacrylic acid (E‐MAA) with different cations (zinc or sodium) and varying degrees of neutralization. These blends gave low stress whitening on impact. This phenomenon was due to the unique morphology of the blend. It was found that unneutralized acid copolymer and the zinc ionomer formed chainlike structures in the polypropylene matrix. These uniform chains crisscrossed the polypropylene matrix providing impact strength to the matrix. The matrix deformed on impact by the shear yielding mechanism, thus suppressing stress whitening. The impact modifier in the matrix did not form micro crazes in the matrix but formed several layers of crisscrossing chains. On the other hand, the sodium ionomer did not form chainlike structures. The impact modifier was dispersed evenly in the matrix. This type of morphology resulted in a higher degree of stress whitening. The failure on impact was due to crazing and not by shear yielding. This size of the impact modifier in the polypropylene matrix varied significantly depending on the melt processing equipment used. The dependence of polymer alloy mechanical properties on the composition has been studied to help in ionomer comparison.
Medical‐grade acrylic adhesives for skin contact
Authors: Kenney J. F. , Haddock T. H. , Sun R. L. , Parreira H. C.
Published: April 2003

Pressure‐sensitive acrylic adhesives for application to skin are made from 2‐ethylhexyl acrylate, isooctyl acrylate or n‐butyl acrylate copolymerized with polar functional monomers such as acrylic acid, methacrylic acid, vinyl acetate, methyl acrylate, N‐vinylcaprolactam, or hydroxyethyl methacrylate. Functional comonomers increase cohesive strength, provide surface polarity, and enhance wear performance. Tack, adhesion to skin, adhesive transfer to skin, and wear performance of the adhesive are governed by the molecular weight, glass transition temperature, and the viscoelastic behavior of the adhesive. Viscoelastic properties of the adhesive as measured by the Williams plasticity number (WPN), dynamic storage modulus (G′), dynamic loss modulus (G″), and tan δ are important polymer properties for good wear performance. Sweating skin, a moist environment, and physical activity are the most important factors influencing the failure of an adhesive tape during wear. A medicalgrade adhesive for application to human skin should be hypoallergenic. Medical‐grade adhesives are utilized in making surgical tapes for holding dressings in place, adhesive bandages, adhesive dressings to cover wounds, and surgical operating drapes.
Generation of porous polymer surfaces by solvent–nonsolvent treatment
Authors: Chen Jyh‐Herng , Ruckenstein Eli
Published: April 2003

A method to generate a porous region near the surface of a polymer is suggested. In this method the region near the surface is swollen by immersing the polymer for a short time in a solvent. Subsequently, the polymer is introduced in a nonsolvent (for the polymer) that is, however, miscible with the solvent. The formation of the porous region is a result of (1) the swelling accompanied by the disentanglement of the surface molecular chains, and the dissolution of some of them during the immersion in the solvent, and (2) the rapid extraction of the solvent from the swollen region by the nonsolvent. The porous surface provides a matrix into which a second incompatible monomer can be polymerized so that the two otherwise incompatible polymers can adhere to one another.
Liquid crystalline phase‐formation behavior of cellulose cinnamate
Authors: Arai Kenichiro , Satoh Hidetoshi
Published: April 2003

Cellulose cinnamates with degrees of substitution (DS) of up to 2.3 were prepared by a reaction of cellulose with cinnamoyl chloride in pyridine. The cellulose cinnamate was found to form a cholesteric liquid crystalline phase at the concentrations higher than a critical concentration in some organic solvents. The critical concentration showed tendencies to be higher for the cellulose cinnamate with higher DS and with higher degree of polymerization (DP). Influences of formation of liquid crystalline phase and of irradiation with UV light on the physical strength of the cellulose cinnamate film were investigated and both were found to make the breaking strength and modulus of elastisity of the film higher.
Prepreg aging in relation to tack
Authors: Ahn K. J. , Peterson L. , Seferis J. C. , Nowacki D. , Zachmann H. G.
Published: April 2003

Thermoanalytical 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

A 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

The 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

Both 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

Boron, 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

The 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

Epoxy 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

Bombyx 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

Chemical 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

Radiation‐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

Graft 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

The 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

Novel 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

The 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

Chitin 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

The 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

An 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

A 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

Porous 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

The 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

The 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.
Molecular weight characterization of polyacrylamide‐CO‐sodium acrylate. II. Light scattering
Authors: Hunkeler D. , Wu X. Y. , Hamielec A. E.
Published: April 2003

The first large‐scale fractionation method for polyacrylamides is reported. This has been optimized to prepare a series of narrowly distributed polymer standards with molecular weights between 10,000 and 1,000,000. These were subsequently hydrolyzed to between 5 and 35% sodium acrylate content through a saponification reaction. It has been found that the classical light‐scattering theory, derived for nonionic scattering bodies, can be applied to polyelectrolytes provided the specific refractive index increment (∂n/∂c) is evaluated at constant electrochemical potential (μ). This is obtained by dialyzing the polymer solution against the dialysate (0.2MNa2SO4 for polyacrylamide‐co‐sodium acrylate) for a predetermined equilibrium period, specific to the pore size of the membrane used. From such measurements at various copolymer compositions (F), the following empirical relationship is established:

where a was found to be −0.076. The validity of the specific refractive index increment at constant chemical potential is established through light‐scattering measurements of the weight‐average chain length of the hydrolyzed polyacrylamides. These were then compared with the chain lengths of the parent nonionic polymers from which they were derived. Excellent agreement is observed, implying the polyelectrolyte characterization method developed, and specifically the (∂n/∂c)μ's, are accurate and reliable.
Factors affecting the coefficient of friction of paper
Authors: Gurnagul N. , Ouchi M. D. , Dunlop‐Jones N. , Sparkes D. G. , Wearing J. T.
Published: April 2003

Electron spectroscopy for chemical analysis (ESCA) studies on a variety of paper samples show that for samples of similar surface roughness the coefficient of friction is a function of the amount of extractives that are present on the sheet surface. Corona discharge treatment in air is found to produce a marked increase in the coefficient of friction of newsprint due to surface oxidation effects. © 1992 John Wiley & Sons, Inc.
Linear copolymer analysis with dual‐detection size exclusion chromatography: Correction for instrumental broadening
Authors: Bielsa R. O. , Meira G. R.
Published: April 2003

This article deals with data treatment problems associated with the estimation of the combined distribution of molecular weights and chemical composition in linear copolymers by size exclusion chromatography, when correction for instrumental broadening is considered. Standard dual detection is assumed, i.e., the chromatograph is fitted with a “universal” detector (a differential refractometer) and a specific sensor to one comonomer only (a UV spectrophotometer). A real and a “synthetic” example (involving the analysis of a diblock styrene–butadiene rubber) are presented. Also, a propagation of errors study associated with the deconvolution operations is developed. It is concluded that the best calculation procedure is to first compute the combined distributions from the raw chromatograms and then correct such distributions for instrumental broadening. © 1992 John Wiley & Sons, Inc.
Alkaline hydrolysis of homopolymers and copolymers of 2‐hydroxypropyl methacrylate
Authors: Daly Joseph , Lenz Robert W.
Published: April 2003

Homopolymers of 2‐hydroxypropyl methacrylate (HPMA) and copolymers with acrylic acid (AA) were prepared in 1,4‐dioxane. The reactivity ratios were determined to be rAA = 0.27 ± 0.04 and rHPMA = 2.2 ± 0.2. The alkaline hydrolysis by sodium hydroxide of the HPMA monomer and polymers showed that while the HPMA monomer hydrolyzed readily as expected for a low‐molecular‐weight carboxylic ester the HPMA homopolymer and water‐soluble sodium acrylate (NaA) copolymers were extremely resistant to alkaline hydrolysis. The saponification reaction followed a second‐order rate equation, being first order with respect to both HPMA and hydroxide ion concentration. The Arrhenius parameters, activation energy E and frequency factor A, for the alkaline hydrolysis of HPMA monomer in water were found to be E = 10.3 Kcal/mol and A = 1.5 × 108 L/mol min, and those for the NaA–HPMA copolymers in water were found to be E = 24 kcal/mol and A = 4 × 1012 L/mol min. The NaA–HPMA copolymers had a limiting extent of hydrolysis, ranging from 9–90% ester conversion. A sharp rate decrease at low conversion was noted during the HPMA homopolymer hydrolysis in 58/42 dimethyl sulfoxide/water, allowing the calculation of two distinct reaction rates. © 1992 John Wiley & Sons, Inc.
Synthesis and characterization of iminodiacetate cellulosic sorbent and its application in metal ion extraction
Authors: Chan W. H. , Lam‐Leung S. Y. , Fong W. S. , Kwan F. W.
Published: April 2003

Iminodiacetate cellulosic chelating sorbent, derived from cotton fabric, was synthesized in a two‐step reaction sequence. The pH dependence of the metal ion extraction for Cd (II), Co(II), Cu(II), Pb(II), and Ni(II) was studied. Under optimum conditions, the average sorptive capacity of the sorbent was found to be 0.38 mmol metal ion/sorbent. The viability of using this sorbent for recycling, preconcentration of metal ion, and selective metal ion extraction was demonstrated.
Two‐stage drawing of poly(ethylene 2,6‐naphthalate)
Authors: Ito Masayoshi , Honda Katsumi , Kanamoto Tetsuo
Published: April 2003

Initially amorphous and semicrystalline films of poly(ethylene 2,6‐naphthalate) with different molecular weights were drawn by two‐stage drawing, that is, coextrusion at low temperatures (25–160°C) followed by tensile drawing at high temperatures (200–245°C). Both films could be drawn up to a draw ratio of 8–10 by this method under controlled conditions. The tensile modulus and strength of drawn samples were greatly affected by the draw temperature for the first stage, predrawn morphology, and molecular weight. The remarkable effects of these variables on the tensile properties are closely related to the difference in the resultant amorphous chain orientation of the samples, reflecting the disentanglements and chain slippage during drawing, and the dissipation of chain orientation after processing.
An equilibrial process zone in polymeric materials
Authors: Stojimirovic A. , Kadota K. , Chudnovsky A.
Published: April 2003

A process zone at the tip of a fatigue crack grown in polymeric materials has been widely reported. A new method that treats the process zone as an allotropically transformed material is employed for the prediction of the process‐zone size. A specific energy of material transformation as well as transformation stress and draw ratio are determined from an independent test on polymer drawing. The prediction of the model with no adjustable parameters appears to be in a good agreement with the experimentally observed process zone for various polyethylenes and polycarbonate.
Analysis of the curing behavior of bismaleimide resins
Authors: Tungare A. V. , Martin G. C.
Published: April 2003

The curing behavior of bismaleimide resins was investigated using formulations containing different stoichiometric ratios of 1,1′‐(methylenedi‐4,1‐phenylene) bismaleimide (BMI) and 4,4′‐methylenedianiline (MDA). The resin cure involved a low temperature primary amine addition to the maleimide double bounds and a high temperature homopolymerization of the maleimide double bonds. The kinetics of the amine addition and the homopolymerization reactions were determined using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry. The nucleophilic addition of the primary amines to the maleimide double bonds occurred by a second‐order reaction, and was at least two orders of magnitude faster than the homopolymerization reaction, which occurred by a multistep mechanism involving thermal initiation of chain growth, followed by chain propagation. A kinetic model for the curing behavior was developed and used to predict the extents of the amine addition and the homopolymerization reactions in networks cured under isothermal or dynamic conditions.
Gas‐permeation properties of asymmetric polycarbonate, polyestercarbonate, and fluorinated polyimide membranes prepared by the generalized dry–wet phase inversion process
Authors: Pinnau Ingo , Koros William J.
Published: April 2003

Essentially defect‐free, ultrathin asymmetric polycarbonate, polyestercarbonate, and 6FDA–IPDA polyimide membranes were prepared by a dry/wet phase inversion process using forced‐convective evaporation. The pure gas permeation properties of these membranes were determined for N2, O2, He, CO2, and CH4. The average apparent skin‐layer thicknesses of the membrane samples varied between 330 and 580 Å, which is substantially thinner than for previous defect‐free membranes formed by the conventional wet phase inversion process. This study indicates that the dry/wet phase inversion process appears to be universally applicable to form ultrathin, defect‐free asymmetric membranes from hydrophobic, glassy polymers. © 1992 John Wiley & Sons, Inc.
Investigations of the crystallinity of polyamide‐6 fibers by two x‐ray diffraction methods
Authors: Rabiej Stanisław , Włochowicz Andrzej
Published: April 2003

The methods of Hindeleh and Johnson and of Ruland and Vonk were employed for determination of the crystallinity in polamide‐6 fibers. The values given by the methods were found to be relatively close to one another. However, using the method of Hindeleh and Johnson, the manner of the amorphous background approximation must be changed. © 1992 John Wiley & Sons, Inc.
Interaction of polystyryl radical with Cu(DMF)2Br2
Authors: Baruah Shashi D.
Published: April 2003

The kinetics of 2,2′‐azobisisobutyronitrile (AIBN) initiated polymerization of styrene in N,N‐dimethylformamide (DMF) at 60°C were investigated in the presence of dibromo(N,N‐dimethylformamide)copper(II) complex. The complex was prepared in situ by mixing tetrakis (N,N‐dimethylformamide)copper(II) perchlorate with LiBr in the molar ratio of 1 : 2. The equilibrium constant for [Cu(DMF)4]2+ + 2Br− ⇌ Cu(DMF)2Br2 + 2DMF was calculated by the limiting logarithmic method as 1.80 × 103 L2 mol−2. The velocity constant at 60°C for the interaction of polystyryl radical with Cu(DMF)2Br2 is 7.46 × 104 L mol−1 s−1.
Modification of styrene–divinylbenzene copolymer by anchoring ferric–dipyridylamine complex
Authors: Mukherjee Amit , Biswas Mukul
Published: April 2003

Polystyrene–divinylbenzene (PS–DVB) copolymer was modified by anchoring dipyridylamine (DPA) on it followed by complexation with Fe(III). Under the experimental conditions followed, 9% incorporation of Fe(III) was achieved. PS–DVB–DPA and PS–DVB–DPA–Fe(III) were characterized by IR spectra. Diffuse reflectance spectra for PS–DVB–DPA–Fe(III) and DPA–Fe(III) revealed λmax at ∼ 360 and ∼ 310, respectively. This difference could be due to a difference in the nature of the coordinating moieties complexing with Fe(III) in these two systems. Scanning electron micrographs of PS–DVB, PS–DVB–DPA–Fe(III), and heat‐treated PS–DVB–DPA–Fe(III) revealed some typical surface features. Thermal stability varied in the order PS–DVB–DPA–Fe(III) > PS–DVB–DPA ≅PS–DVB, and DTA showed characteristic exotherms. © 1992 John Wiley & Sons, Inc.
Epoxy composites based on glass beads. II. Mechanical properties
Authors: Amdouni N. , Sautereau H. , Gerard J. F.
Published: April 2003

A DGEBA/DDA network was used to study the toughening effect due to the introduction of glass beads with different volume fractions. The influence of surface treatment was also studied by comparing untreated, silane‐treated glass beads, and beads coated with different thicknesses of an elastomeric adduct. The effect of the volume fraction of glass and the surface treatment were discussed in terms of elastic and plastic properties. The results were compared with the usual theoretical models. Linear elastic fracture mechanics and impact tests were performed to study the crack propagation process. The various parameters influenced the deformation mechanism, especially for the coated glass bead composites, for which an optimum thickness was displayed. A large improvement in GIc value was obtained with a slight decrease for the stiffness. © 1992 John Wiley & Sons, Inc.
Comparison of two distinct phenolic antioxidants in γ‐sterilized NR compounds used as rubber pistons in syringes for single use
Authors: Martakis Nick , Niaounakis Michael
Published: April 2003

The effects of γ‐irradiation and aging on pharmaceutical NR compounds have been studied mainly by DSC. The extent of aging was measured quantitatively by enthalpy changes and peak temperature shifts of the primary oxidation exotherm. Quantitative thermal evaluations were supplemented by extraction tests and mechanical testing. The NR compound formula has been kept constant and only the type and concentration of antioxidant was varied. Two distinct phenolic antioxidants, BHT and Wingstay‐L at four different concentration levels, have been employed for this purpose. The most effective antioxidant package for a given elastomeric compound, subjected to γ‐irradiation and aging, giving the lowest changes in physical properties, is evaluated. © 1992 John Wiley & Sons, Inc.
Preparation and characterization of two HEMA/PVA copolymers: Poly[HEMA‐co‐(PVA‐AA)] and poly[HEMA‐co‐(PVA‐MA)]
Authors: Liou F. J. , Niu G. C. C. , Wang Y. J.
Published: April 2003

The copolymers of poly[HEMA‐co‐(PVA‐AA)] and poly[HEMA‐co‐(PVA‐MA)] were synthesized and characterized. The presence of PVA‐AA in the copolymer increased the mechanical strength but decreased the water content of the material. The presence of PVA‐MA, on the other hand, caused a decrease of mechanical strength and an increase of water content. The ionization of acidic group in poly[HEMA‐co‐(PVA‐MA)] resulted in the swelling of the copolymer, and the swelling extent was controlled by the change of pH. Both copolymers have great potential in biomedical application. © 1992 John Wiley & Sons, Inc.
Polymer bead preparation from bulk polymers
Authors: Davy K. W. M. , Causton B. E.
Published: April 2003

A method of preparing polymer beads from chloroform solutions of bulk polymer was developed. The technique involved solvent removal while the polymer solution was stirred in an aqueous dispersing medium. Bead size could be varied by adjusting the concentration of the suspending medium and the method was found to be applicable to chloroformsoluble, water‐insoluble polymers. Copolymers, low‐tack rubbers, and polyblends were also converted to bead form and, in the latter case, phase separation occurred. Furthermore, it was possible to encapsulate finely divided inorganic fillers within the polymer beads. © 1992 John Wiley & Sons, Inc.