bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereocomplex formation between enantiomeric poly(lactic acid)s. X. Binary blends from poly(D‐lactide‐CO‐glycolide) and poly(L‐lactide‐CO‐glycolide)
Authors: Tsuji Hideto , Ikada Yoshito
Published: April 2003

Binary blend films from lactide‐rich poly(D‐lactide‐co‐glycolide) (PDLG) and poly(L‐lactide‐co‐glycolide) (PLLG) were obtained by casting methylene chloride solutions of the two mixed copolymers with different D‐ and L‐lactide contents (XDI and XLI), and their crystallization was studied by differential scanning calorimetry (DSC). Four combinations were selected from the binary (A‐B) blends: mixing of the same polymer [XDI(A) = XDI(B) or XLI(A) = XLI(B)], blending under XDI(B) = XLI(A), blending of a D‐lactide homopolymer [XDI(B) = 1] with other PDLGs, and blending of a D‐lactide homopolymer [XDI(B) = 1] with other PLLGs. Racemic crystallites were exclusively formed between PDLG and PLLG when they had high lactide unit contents. The melting point and enthalpy of fusion of the racemic crystallites decreased with a decrease in XDI of PDLG or XLI of PLLG, suggesting that glycolide units in the polymer disturbed the growth of the racemic crystallites. A similar behavior was also observed for the homocrystallization in nonblended copolymer films. Homocrystallites composed entirely either of D‐lactide unit or L‐lactide unit sequences were formed when one component was crystallizable and the other component had the same sign of optical rotation or very different lactide content. An interesting finding was that even nonhomocrystallizable lactide‐poor PDLG and PLLG could form racemic crystallites when both were blended. © 1994 John Wiley & Sons, Inc.
Studies on interpenetrating polymer networks based on nitrile rubber‐poly(vinyl chloride) blends and poly(alkyl methacrylates)
Authors: Mathew Annakutty , Chakraborty B. C. , Deb P. C.
Published: April 2003

Several interpenetrating polymer networks (IPNs) based on nitrile rubber‐poly(vinyl chloride) blends and various alkyl methacrylates have been synthesized. The rubber blends were swollen in methacrylate monomers containing required amounts of initiator and crosslinker for specific time periods and then polymerized at higher temperature. The composition of the IPNs could be varied by changing the swelling time. The IPNs were characterized for their glass‐transition temperature, dynamic mechanical properties, and tensile properties. The effect of structure and composition on the vibration damping characteristics of these IPNs are discussed. © 1994 John Wiley & Sons, Inc.
Macromolecular entanglement. IV. Modulus of swelling acrylic fibers as a means of studying macromolecular entanglements
Authors: Qian B. , Zhu J. , He J. , Hu P. , Wu C.
Published: April 2003

In a swelling state at a temperature of incipient dissolution, an acrylic fiber is highly elastic just like a rubber. A system of entangled macromolecular chains is considered analogous to a cross‐linked rubber network and from the theory of rubber elasticity, the measured extension modulus of an acrylic fiber at the terminal swelling state may be used to calculate the number of entanglements. By means of a capillary rheometer, a series of model acrylic fibers with varied degrees of entanglements were prepared. The entanglements present in these model fibers were then measured by the other two thermal methods (SDSC and SSS/SS methods) already established in our laboratory. The die swell ratios were also measured microscopically at the exit of the capillary rheometer. The experimental results of entanglements measured by the various methods were well correlated, at least qualitatively. © 1994 John Wiley & Sons, Inc.
Acetylacetonates of nickel(II) and copper(II) as accelerators for the epoxy resin system
Authors: Reddy P. V. , Gowda N. M. Nanje
Published: April 2003

The acetylacetonates of nickel(II) and copper(II) serve as accelerators for the anhydridecurable epoxy resin system. An appreciable lowering in the cure gel time and a substantial increase in the rate of curing is observed with enhanced concentrations of the metal chelates. Cure kinetic studies and cure schedules have been followed using a differential scanning calorimeter. The thermal and electrical insulation characteristics of the cured epoxy system are little affected by the variation of temperature, voltage, and aging under UV radiation. © 1994 John Wiley & Sons, Inc.
Chemiluminescence from amine cured epoxy resins modified with halogenated phenylglycidyl ethers
Authors: Matisová‐Rychĺ L. , Rychlý J. , Verdu J. , Audouin L. , Tcharkhtchi A. , Janigova I.
Published: April 2003

Chemiluminescence from thermooxidized epoxide alone and that modified with phenyl glycidyl ethers has been investigated in isothermal and nonisothermal regime. Isothermal curves are characterized by a monotonous fall of chemiluminescence intensity from some initial value to very low levels of light emission. Nonisothermal curves show a maximum intensity at temperatures above 473 K. The luminescence intensity is influenced by both Tg and thermal stability of epoxide. The higher Tg or higher thermal stability brings about the higher intensity of light emission and vice versa. © 1994 John Wiley & Sons, Inc.
Copolymerization of ethylene and styrene with supported TiCl4/NdCl3 catalyst
Authors: Lu Zejian , Liao Kairong , Lin Shangan
Published: April 2003

The copolymerization of ethylene and styrene was carried out in the presence of TiCl4/NdCl3/MgCl2/AlEt3 catalyst. The influences of comonomer ratio, concentrations of catalyst and AlEt3, solvents, and temperature on the copolymerization were investigated. Copolymerization products containing styrene of 4–85 mol % were obtained with good yield. The results of 13C‐NMR, IR, X‐ray diffraction, and solvent extraction show that the products are mainly copolymers with various comonomer sequences and exhibit special mechanical properties. © 1994 John Wiley & Sons, Inc.
Carbon dioxide foaming of glassy polymers
Authors: Wessling M. , Borneman Z. , Van Den Boomgaard Th. , Smolders C. A.
Published: April 2003

The mechanism of foaming a glassy polymer using sorbed carbon dioxide is studied in detail. A glassy polymer supersaturated with nitrogen forms a microcellular foam, if the polymer is quickly heated above its glass transition temperature. A glassy polymer supersaturated with CO2 forms this foam‐like structure at much lower temperatures which indicates the Tg‐depressing effect of CO2. Having this interpretation in mind, the overall sample morphology, i.e., a porous foam enclosed by dense outer skins, can be completely explained. The dense skins, however, are not homogeneous but show a nodular structure when analyzed by SEM and AFM. Foaming experiments with samples having a different thermal history suggest that the nucleation mechanism underlying the foaming process is heterogeneous in nature. © 1994 John Wiley & Sons, Inc.
High‐temperature SEC coupled with MALLS detector for evaluating the end‐use performance of LDPE
Authors: Dayal Umendra
Published: April 2003

Low‐density polyethylene (LDPE) is the most widely used plastic material in the film‐packaging industry. To improve its tensile strength and elongation, it is blended with linear LDPE. Three commercial samples of LDPE, which were found to give different performances in the sealing strength of films prepared from their blends, have been evaluated for their molecular weight (MW), molecular weight distribution (MWD), and long‐chain branching by high‐temperature size exclusion chromatography (SEC) and SEC coupled with a multiangle laser light‐scattering (MALLS) detector. It has been shown that the differences in MW and MWD that remain unnoticed by conventional SEC are detected by SEC/MALLS. Wide MWD and a low weight‐average MW of the resin has been found to favor film‐sealing strength. © 1994 John Wiley & Sons, Inc.
Microporous polypropylene hollow fibers containing poly(methylsilsesquioxane) fillers
Authors: Nagō Satoshi , Mizutani Yukio
Published: April 2003

Microporous polypropylene hollow fibers were prepared by stretching polypropylene microtubes containing poly(methylsilsesquioxane) fillers with uniform particle sizes. The properties of the resultant hollow fibers are controllable by adjusting the particle size of the filler, the filler content, and the stretching degree. Also, it is elucidated that the hollow fibers have a fine texture of split PP fibrils, in which the filler particles are dispersed. © 1994 John Wiley & Sons, Inc.
Population balance modeling for a continuous gas phase olefin polymerization reactor
Authors: Choi Kyu Yong , Zhao Xia , Tang Shihua
Published: April 2003

Steady‐state population balance models have been developed for a continuous flow gas phase olefin polymerization process with both uniform sized and log‐normally size distributed high activity catalyst feeds. For the calculation of polymer properties such as molecular weight averages and weight fraction of comonomers in the copolymer, a multigrain solid core model was used with an assumption that intraparticle monomer mass transfer resistance is negligibly small. The multigrain solid core model was incorporated into the population balance model and the effects of feed catalyst particle size distribution and catalyst deactivation parameters on the polymer production rate, polymer particle size distribution, and polymer properties were investigated. It is observed for deactivating catalyst that the polymer particle size distribution tends to be narrower with a reduced amount of large polymer particles. For the catalyst with nonuniform site deactivation, polymer particles of different sizes exhibit different molecular weight and copolymer composition. © 1994 John Wiley & Sons, Inc.
Dielectric normal‐mode relaxation of entangled cis‐polyisoprene melts: Effects of polydispersity
Authors: Fodor Jeffrey S. , Hill Davide A.
Published: April 2003

The effects of polydispersity on the dielectric normal‐mode relaxation of entangled, cis‐polyisoprene melts are considered. We use a linear mixing rule and reptation theory in conjunction with a theoretical molecular weight distribution (MWD) of variable breadth to predict loss spectra of model cis‐polyisoprene melts. The half‐widths of the predicted spectra show a nonlinear dependence on polydispersity index, with the greatest sensitivity near the monodisperse limit. The calculations are in agreement with literature data on narrowly dispersed samples. © 1994 John Wiley & Sons, Inc.
Correlation between mechanical properties and degradation processes of poly(methyl methacrylate‐co‐butyl acrylate) films
Authors: Leskovac M. , Kovac̆ević V. , Stanojević D. , Bravar M.
Published: April 2003

Copolymer systems based on various molar ratios of methyl methacrylate (MMA)/butyl acrylate (BA) and different mass content of N‐methylolacrylamide (NMA), as a crosslinking agent, were investigated. The influence of temperature, 150°C, under conditions similar to those used in the textile industry, and effect of ultraviolet (UV) irradiation were examined. The changes of mechanical properties were found to be connected with the cross‐linking and/or degradation mechanisms. The effect of copolymer composition on the mechanical properties was established, especially during UV degradation. © 1994 John Wiley & Sons, Inc.
Mechanical properties of organic–inorganic polyurethane elastomers. I. Al(OH)3–polyurethane composites based on PPG
Authors: Furukawa Mutsuhisa , Yokoyama Tetsuo
Published: April 2003

Aluminum hydroxide was used as a reactive filler to elastomers prepared from poly(oxypropylene)glycol (PPG), 2,4‐tolylene diisocyanate (TDI), and 1,4‐butane diol (BD). Mechanical properties, dynamic mechanical properties, and thermal properties were measured. Morphologies were observed by use of X‐ray diffraction and scanning electron micrographs. The model reaction of isocyanate and aluminum was also studied. It was found that aluminum hydroxide fillers can be used for cost reduction without any detrimental effects on mechanical properties. Scanning electron micrograph studies of freshly cut surfaces of the aluminum filled elastomers showed that aluminum hydroxide is highly compatible with the elastomer. © 1994 John Wiley & Sons, Inc.
Molecular transport of organic esters into tetrafluoroethylene/propylene copolymer membranes
Authors: Aminabhavi Tejraj M. , Phayde Hemant T. S.
Published: April 2003

Diffusion, permeation, and equilibrium sorption coefficients have been determined using a sorption gravimetric technique for methyl acetoacetate, ethyl acetoacetate, methyl benzoate, ethyl benzoate, methyl salicylate, isobutyl salicylate, and diethyl malonate into tetrafluoroethylene/propylene copolymer membranes in the temperature range 25–70°C. The sorption kinetics process has been characterized by first‐order rate constants and penetration velocities. From a temperature dependence of the transport coefficients, the activation parameters have been estimated. It is observed that the values of the transport coefficients for the systems of this study depend on the nature of the penetrant molecules rather than on their molecular sizes. On the whole, the mechanism of solvent transport into the copolymer membranes used here follows nearly the Fickian trend. © 1994 John Wiley & Sons, Inc.
In situcure monitoring of epoxy resins using fiber‐optic Raman spectroscopy
Authors: Lyon R. E. , Chike K. E. , Angel S. M.
Published: April 2003

Fiber‐optic Raman spectroscopy was used to monitor the curing of epoxy resinsin situfor eventual application to polymer composite processing. A 200‐μm diameter quartz fiberoptic sensor immersed in liquid resin was used to obtain Raman spectra for a concentration series of diglicidyl ether of bisphenol‐A in its own reaction product with diethylamine using an 820 nm continuous‐wave diode laser excitation. A Raman peak at 1240 cm−1was assigned to a vibrational mode of the oxirane (epoxide) ring and its normalized intensity was found to be linearly related to the concentration of epoxide groups in the resin mixtures. Raman peaks at 1112 and 1186 cm−1associated with phenyl andgem‐dimethyl resin backbone vibrations, respectively, did not change in intensity due to the curing reaction and were used as internal references to correct the Raman spectra for intensity changes due to density fluctuations and instrumental variations during the experiments. Fiber‐optic Raman spectroscopy was used to monitor the extent of reactionin situfor the room‐temperature cure of phenyl glicidyl ether with diethylamine. The extent of reaction of the epoxide groups calculated from the Raman spectra were in excellent agreement with kinetic data from Fourier transform near‐infrared absorbance measurements made under the same conditions. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Aqueous polymerization of methyl methacrylate and characterization of the obtained polymers in the presence of N,N‐dioxalyl P‐amino benzoyl N,N‐dioxalyl urea and its Fe(II) and Fe(III) complexes
Authors: Sabbah I. A. , Elkhalek A. A. Abd , Sayyah S. M. , Mohamed S. A. , Ewais H. A.
Published: April 2003

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was studied using sodium bisulfite as initiator in the absence and presence of a new organic chelating agent, N,N‐dioxalyl p‐amino benzoyl N,N‐dioxalyl urea, and its iron (II) and (III) complexes. The organic ligand with free carboxyl groups has a retarding effect on the polymerization reaction while its iron complexes have a catalytic effect. The mechanisms of the catalytic effect of iron complexes or the inhibition mechanism of the organic ligand are discussed. The effect of pH values on the polymerization processes was also investigated. The apparent energy of activation was found to be 4.99 × 104 J/mol, 6.38 × 104 J/mol, 4.46 × 104 J/mol, and 3.72 × 104 J/mol in the absence and in the presence of 0.5 g of ligand and 0.1 g of its Fe (II) and (III) complexes, respectively. © 1994 John Wiley & Sons, Inc.
Modification of epoxy resins by hydrosilation for electronic encapsulation application
Authors: Ho Tzong‐Hann , Wang Chun‐Shan
Published: April 2003

Hydride terminated polydimethyl siloxanes were used to reduce the stress of cresol–form‐aldehyde novolac epoxy resin cured with phenolic novolac resin for electronic encapsulation application. The effects of the structure and molecular weight of the hydride terminated polydimethyl siloxane in reducing the stress of encapsulant were investigated. The mechanical and dynamic viscoelastic properties and morphologies of rubber modified epoxy networks were also studied. A “sea‐island” structure (“islands” of silicone rubber dispersed in the “sea” of an epoxy resin) was observed via SEM. The dispersed silicone rubbers effectively reduce the stress of cured epoxy resins by reducing flexural modulus and the coefficient of thermal expansion, while the glass‐transition temperature was hardly depressed. Electronic devices encapsulated with the dispersed silicone rubber modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended use life for the devices. © 1994 John Wiley & Sons, Inc.
Water‐soluble polyamides as potential drug carriers. VIII. Poly(alkylene oxide)‐grafted polyaspartamides bearing ethylenediamine side‐group functions
Authors: Neuse Eberhard W. , Perlwitz Axel G. , Barbosa Anna P.
Published: April 2003

In continuation of previous investigations of aspartamide‐type polymers as drug carriers, polyaspartamides featuring hydrosolubilizing poly(alkylene oxide) side chains in addition to ethylenediamine side‐group functions as potential drug‐binding sites are synthesized from poly‐D,L‐succinimide by successive aminolytic ring‐opening steps. Yields are in the range of 45–55%. Depending on selected feed ratios, the target polymers contain both the poly(alkylene oxide) and the ethylenediamine groups in systematically varied proportions. Compositions are determined microanalytically and from relative band intensities of the 1H‐NMR spectra. The polymers dissolve smoothly and completely in aqueous media and thus fulfill the major design requirement of water solubility. © 1994 John Wiley & Sons, Inc.
Development of polyion complex membranes for the separation of water–alcohol mixtures. I. Synthesis and physical properties of the polycations based on 1,3‐di (4‐pyridyl) propane
Authors: Jegal Jonggeon , Kim Jeong‐Hoon , Park You‐In , Lee Kew‐Ho
Published: April 2003

To prepare good polymeric materials for the preparation of the polyion complex membranes useful for water–alcohol separation, polycations were synthesized by the quaternization polymerization of 1,3‐di(4‐pyridyl)propane with dibromoalkanes or with 1,8‐bis (p‐toluenesulfonyl)octane. The polycations were characterized by FTIR spectroscopy, viscometry, DSC, and X‐ray diffractometry. The polycations were in molecular weight ranges good enough to be used as membrane materials. The polycations were very hygroscopic and easily soluble in highly polar solvents such as water and these properties might be good for the membrane materials. The thermal properties and X‐ray diffraction patterns of these polycations suggested that the polycations were semicrystalline and difficult to form crystals by melt crystallization. © 1994 John Wiley & Sons, Inc.
Rubbery and rigid particle toughening of epoxy resins
Authors: Geisler B. , Kelley F. N.
Published: April 2003

Four types of materials were evaluated in this study: neat epoxy resins of differing initial molecular mass, and their rubbery particle‐filled, rigid particle‐filled, and hybrid particle‐filled counterparts. Both rubbery and rigid particle‐filled epoxies exhibited fracture energies,GIc, greater than the neat resins. Cured resins prepared with an optimum loading of both rubbery and rigid particles gaveGIcvalues greater than those from rubbery or rigid particles alone (approximately sixteen‐fold increase over the neat resins). Rigid particle composites were toughened by means of a crack front impedance mechanism. In hybrid particle composites, rigid particles enhanced localized plastic deformation ahead of the crack front. © 1994 John Wiley & Sons, Inc.
Improvements of fiberboard properties through fiber activation and subsequent copolymerization with vinyl monomer
Authors: Rozman H. D. , Banks W. B. , Lawther M. L.
Published: April 2003

High‐temperature refined thermomechanical pulp (MDF fiber) was dried, extracted with neutral organic solvent, and reacted with three types of electrophilic reagents (glycidyl methacrylate, maleic anhydride, and succinic anhydride). The adducts formed were further reacted in a hot press with a vinyl monomer in the presence of a free‐radical initiator (benzoyl peroxide). Well‐conformed boards were produced by the process. Modified boards showed significant improvement in thickness swelling as well as in strength properties compared to control phenol–formaldehyde boards. Glycidyl methacrylate modified/methyl methacrylate boards were the most stable toward the wet‐and dry‐exposure cycles, whereas succinic anhydride/methyl methacrylate boards showed the lowest water absorption. © 1994 John Wiley & Sons, Inc.
Chlorinated polyolefins for asphalt binder modification
Authors: Morrison Geoffrey R. , Lee Jin K. , Hesp Simon A. M.
Published: April 2003

The benefits obtained from the addition of small quantities of chlorinated polyolefins to paving grade asphalt binders were investigated. A chlorinated polyethylene plastomer, Tyrin 2552, and a chlorinated olefinic elastomer, Tyrin CM0730, were added to asphalt binders at 3 and 5 wt % and subsequently reactively processed to facilitate compatibilization. The mixtures were analyzed for rheological performance relating to fatigue and rutting as well as low‐temperature fracture performance. The addition of small quantities of these polymers to the asphalt binders resulted in significant improvements over conventional modifiers at both the high and low temperature extremes. © 1994 John Wiley & Sons, Inc.
Quantification of free ketene acetals and determination of cure kinetics of poly(ortho ester)s by a facile deuterium labeling method
Authors: Shih Chung , Waldron Niki , Deeken Rodney
Published: April 2003

A facile method was developed to quantify unreacted ketene acetals during polymerization of poly(ortho ester)s. The method was based on isotopic (deuterium) labeling of the unreacted ketene acetal groups arising from the diketene acetal monomer, 3,9‐diethylidene‐2,4,8,10‐tetraoxaspiro[5,5]undecane (DETOSU). In deuterium oxide, free ketene acetals are hydrolyzed to an α‐deuterated ester; ortho ester bonds are hydrolyzed to the nondeuterated analog. The relative abundance of the deuterated ester side chain can be quantified by gas chromatography‐mass spectrometry (GC‐MS). In the current method, aliquots of a diketene acetal/polyol(s) reaction mixture were dissolved (crosslinked polymers swollen) in methylene chloride and excess D2O. The diketene acetal/polyol(s) reaction mixture was hydrolyzed under mildly acidic conditions to yield pentaerythritol dipropionate (PDP; hydrolysis product of DETOSU). PDP was extracted into an organic phase, silylated, and analyzed by GC‐MS. Fragments corresponding to the C2H5CO+ ion (57 a.m.u.) and C2H4DCO+ ion (58 a. m. u.) were monitored and the quantity of free ketene acetal groups were calculated from the peak areas of the chromatograms. The precision of the method was ±0.1%. The accuracy, as compared to a parallel 1H‐NMR study, was within 5%. This method permits determination of the cure end‐point of a poly(ortho ester) polymerization reaction to within ±0.25%. The curing kinetics agreed well with DSC branching/crosslinking measurements. © 1994 John Wiley & Sons, Inc.
A study of microwave transmission, reflection, absorption, and shielding effectiveness of conducting polypyrrole films
Authors: Kaynak Akif , Unsworth Joe , Clout Ray , Mohan Ananda S. , Beard Geoffrey E.
Published: April 2003

Microwave transmission, reflection, and absorption behavior and the shielding effectiveness of electrochemically synthesized polypyrrole films with dc conductivities ranging from 0.001 to 50 S/cm are presented. Results show that the electrical conductivity of the doped polypyrrole films has a significant effect on transmission, reflection, and absorption of microwaves. Heavily doped, conducting films were highly reflective, whereas lightly doped, semiconducting films had very high transmission. Intermediate conductivity polypyrrole samples were highly absorptive. The agreement between experimental data and theoretical modeling provided confidence to extend the modeling to include the effect of sample thickness on the transmission, reflection, and absorption properties of films with a wide range of conductivity values, hence, providing valuable information for the design of microwave devices and fundamental understanding of the material properties. A method of measuring the far‐field sheilding effectiveness of polypyrrole films is also presented. Results of shielding experiments indicated the potential for such applications. © 1994 John Wiley & Sons, Inc.
Amidoxime resins based on poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinylbenzene) and their behavior in uptake of uranium from sea water
Authors: Kabay Nalan , Hayashi Terumi , Jyo Akinori , Egawa Hiroaki
Published: April 2003

Amidoxime resins were derived from poly(acrylonitrile‐co‐vinylidene chloride‐co‐divinyl‐benzene) beads, which were prepared by suspension polymerization of the ternary monomeric mixtures in the presence of 4‐methyl‐2‐pentanone (MIBK) or 1,2‐dichloroethane (DCE) as the diluent (porogen), in order to clarify the effect of copolymerized vinylidene chloride on properties of the resulting amidoxime resins. Pore structure analyses of the copolymers as well as of their amidoximated derivatives clarified that MIBK yields larger pores than does DCE and then the latter gives larger specific surface areas than does the former. On the other hand, chemical properties of the amidoximated resins, such as anionexchange capacities and uranyl ion uptake, were not eseentially affected by the diluent species, indicating that both MIBK and DCE as the porogen lead to the amidoxime resins with almost the same ability in recovery of uranium from sea water. The uranium recovery decreased with increase in the vinylidene chloride content, but the decrease in the recovery was minor up to the 10 mol % of vinylidene chloride. It was also clarified that the uranium recovery by the amidoxime resins containing vinylidene chloride is greatly enhanced by the alkali treatment. © 1994 John Wiley & Sons, Inc.
Immobilization of glucose oxidase onto membranes of modified acrylonitrile copolymer
Authors: Godjevargova T. S. , Dimov A. R. , Vasileva N.
Published: April 2003

Acrylonitrile copolymer was modified with sodium hydroxide and 1,6‐hexamethylen diamine (1) and with hydroxylamine (2). The amount of amine and carboxylic groups was studied as a function of the modification conditions. Membranes were prepared from the modified copolymer by the phase‐inversion method. They were used as matrix for covalent immobilization of glucose oxidase by using glutaraldehyde. The amount of bound protein, relative activity, and storage of the activity fo the immobilized enzyme were determined. The results were compared with those obtained with glucose oxidase immobilized onto the surface‐modified membrane of acrylonitrile copolymer with sodium hydroxide and 1,6‐hexamethylendiamine and with hydroxylamine. The results were proved by scanning electron microscopy. © 1994 John Wiley & Sons, Inc.
Studies on oxidative photodegradation of epoxy resins by IR‐ATR spectroscopy
Authors: Zhang G. , Pitt W. G. , Goates S. R. , Owen N. L.
Published: April 2003

This article describes studies on oxidative‐photodegradation of cured Epolite epoxy resin using techniques of IR spectroscopy with attenuated total reflectance optics and scanning electron microscopy. The results show that the oxidative‐photodegradation of this epoxy system is characterized by the formation and subsequent decomposition of carbonyl groups and by epoxy ring opening. The carbonyl bonds are apparently formed in the initial stage of photodegradation and then decomposed upon further aging. Changes in the surface morphology of the samples during degradation suggest that there is significant scissioning of the cross‐linked polymer structure. This phenomenon was reproduced using three different UV lamps that differed in spectral properties. Our studies provide clues to the mechanism of epoxy polymer degradation by solar light. © 1994 John Wiley & Sons, Inc.
Synthesis of liquid crystalline triheptyl cellulose and its blend thin‐film composite membrane for air separation
Authors: Huang Mei‐Rong , Li Xin‐Gui
Published: April 2003

Liquid crystalline triheptyl cellulose (THC) was synthesized directly from cellulose acetate and heptyl bromide with dimethyl sulfoxide as a single‐component solvent. Synthetic conditions were studied with respect to reaction temperature, time, and yield. The molecular structure and liquid crystalline character of the THC obtained as sticky, soft, and birefringent solids at room temperature were investigated by IR, NMR, elemental analysis, and a polarizing microscope. The composite membranes consisting of a THC/ethyl cellulose blend as a dense thin selective layer and polyethersulfone as a porous thick support layer were fabricated and their air‐separation performances were studied by a constant pressure–variable volume method. The data show that the air‐separation performances increase dramatically with operating parameters such as pressure and temperature. No apparent dependence of air‐separation ability on operating time and THC/ethyl cellulose ratio was observed. © 1994 John Wiley & Sons, Inc.
Shear and elongational flow of some branched polyethylenes
Authors: Chohan R. K.
Published: April 2003

The elongational properties of some branched polyethylenes are studied. Experimental results of their flow behavior are presented. The Cogswell technique of calculating the elongational viscosity together with another approach based on the work of Huang and Shroff are utilized. The results show close agreement between these two methods. Certain parameters related to material elasticity are employed. Results suggest that the elastic parameters achieve relatively high levels only if the molecular weights are sufficiently high. © 1994 John Wiley & Sons, Inc.
Preparation and structures of ethyl–cyanoethyl cellulose/cross‐linked polystyrene composites
Authors: Jiang S. H. , Huang Y.
Published: April 2003

Ethyl–cyanoethyl cellulose [(E–CE)C]/cross‐linked polystyrene (PS) composites were prepared via polymerization of styrene in (E–CE)C/styrene solution with glycol diacrylate as a cross‐linking reagent. The polymerization of the solution, morphology, and miscibility of (E–CE)C/PS composites were studied with polarizing microscopy, small‐angle light scattering (SALS), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). It was found that the mixing state of the (E–CE)C/PS system and the thermal stability of composites were modified by cross‐linking of PS. In the intensively cross‐linked composite prepared from the anisotropic solution, there existed cylindrical domains in which (E–CE)C spherulites were dispersed in PS. © 1994 John Wiley & Sons, Inc.
Polymer drying. X. A recondsideration of the kinetics of evaporation from polymer–liquid systems during the interval of transition from the rubbery to a glassy state
Authors: Errede L. A. , Henrich P. J. , Tiers George V. D.
Published: April 2003

This kinetic restudy of the physical changes that occur during evaporation‐induced transition from the rubbery to a glassy state of polystyrene–liquid systems shows that such transitions occur via two mechanistic pathways. The first is random nucleation of microdomains of self‐associated polymer segments owing to a time‐dependent logarithmic decrease in the number of adsorbed volatile molecules per phenyl group of residual mobile polymer segments. The second is a therodynamically driven self‐association of adjacent monomer units with concomitant explusion of the adsorbed molecules, which appears to propagate via a “dominolike” chain reaction. Conceptually this is a three‐dimensional “zippering‐up” of suitably close polymer segments to produce the corresponding macrostructural network of self‐associated polymer. The kinetics of the latter is zero‐order, and this dominates the overall kinetics of evaporation during the latter portion of the transition interval, presumably owing to changes in entropy of the system as it progresses from the mobility characteristic of the rubbery state to the rigidity characteristic of a glassy state. © 1994 John Wiley & Sons, Inc.
Structural changes of cellulose, wood, and paper under shear deformation and high pressure
Authors: Teeäär R. , Lippmaa E. , Gravitis J. , Kokorevics A. , Kreituss A. , Zharov A.
Published: April 2003

Structural changes of wood and its components have been studied after shear deformation under high pressure (SDHP) at up to 6 GPa. Cellulose amorphization and chain depolymerization was observed. Approximately 30% of microcrystalline cellulose was soluble in water after a 360‐degree twist of the Bridgman anvils. The water‐insoluble part was re‐crystallized into cellulose II lattice. Repeated treatment applied to the nondissolved part of the sample, the so‐called cascade experiment, permits the dissolving of about 30% of the residual nondissolved material once again. Extraction with water, followed by 10% sodium hydroxide, allows almost complete dissolving of microcrystalline cellulose (98%). Water‐soluble saccharides were studied by HPLC and 13C NMR. It was found that destruction of the wood lignin network needs more severe treatment conditions than cellulose destruction does. Lignin domains in wood act as “grinding stones” during cellulose destruction. Long‐living lignin free radicals have been detected with EPR after SDHP. 13C NMR CP/MAS spin diffusion studies showed that SDHP leads to separation of wood components into different biopolymer domains, which turns the system toward thermo‐dynamic equilibrium. SDHP does not permit achievement of initial compulsary compatibility of components in native wood. SDHP technique appears as a promising method for wood delignification and carbohydrate saccharification in the solid state without using harmful chemical reagents of solvents, which is important for technological safety and ecology. © 1994 John Wiley & Sons, Inc.
Selective crosslinking in polymer blends. II. Its effect on impact strength and other mechanical properties of polypropylene/unsaturated elastomer blends
Authors: Inoue Toshio
Published: April 2003

The effect of selective crosslinking of the unsaturated elastomer particles in polypropylene (PP) matrix was investigated. The crosslink system comprised N,N′‐m‐phenylene‐bismaleimide and 6‐ethoxy‐2,2,4‐trimethyl‐1,2‐dihydroqinoline or polymerized‐(2,2,4‐trimethyl‐1,2‐dihydroquinoline). The system, which produces only carbon radicals, crosslinks the elastomer particles selectively without causing excessive degradation of the PP matrix. The reaction was carried out under a dynamic crosslinking process using a twin extruder on PP/EPDM, PP/SBS, and PP/SIS blends, all of which comprised 80 wt % of PP and 20 wt % of the elastomer. After the crosslinking, the impact strength of the blends increased. Especially remarkable increase is obtained at 23°C where PP is above its Tg. The increase of interfacial adhesion caused by production of PP/elastomer graft copolymer at the interface is considered to be the most important factor in the improvement. It permits the interactions of the stress concentrate zone developed at the elastomer particles and causes shear yielding of the PP matrix. Impact fracture energy absorption can be thus changed by adjusting the degree of the interfacial adhesion even at essentially the same morphology. The crosslinked elastomer particles also play the role of a nucleation agent. The selective cross‐linking of the elastomer particles in PP/elastomer blends is demonstrated to be an excellent technique to produce a high‐impact, high‐modulus PP. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of methyl methacrylate–EPDM–styrene graft terpolymer
Authors: Park Duck‐Jei , Ha Chang‐Sik , Cho Won‐Jei
Published: April 2003

The graft copolymerizations of methyl methacrylate (MMA) and styrene (St) onto ethylene–propylene–diene terpolymer (EPDM) were carried out with benzoyl peroxide (BPO) as an initiator in toluene. The effects of EPDM concentration, mol ratio of St to MMA, reaction time, reaction temperature, and initiator concentration on the graft copolymerizations were examined. The synthesized MMA–EPDM–St graft terpolymers (MES) were identified by IR and 1H‐NMR spectra. The number‐average molecular weight (Mn) was 110,000. The thermal stability, tensile strength, light resistance, and weatherability of MES were considerably better than those of the acrylonitrile–butadiene–St (ABS) copolymer. © 1994 John Wiley & Sons, Inc.
Synthesis of nonionic flocculants by gamma irradiation of mixtures of polyacrylamide and poly(ethylene oxide)
Authors: Deng Yulin , Pelton Robert , Xiao Huining , Hamielec Archie
Published: April 2003

The synthesis of polyacrylamide (PAM) graft poly(ethylene oxide) (PEO) has been investigated and the reaction conditions were varied by gamma irradiation to optimize polystyrene latex flocculation by the copolymers. The effects of the gamma ray dosage, the PEO chain length, the ratio of PEO to PAM, and the crosslinking degree of copolymer were studied. The most effective flocculant was obtained by exposing a mixture of 1.2 wt % PAM (Mw = 5 × 106) and 0.94 wt % PEO (Mw = 5000) to 816 krad of gamma radiation. The resulting copolymer contained 24 wt % PEO. Crosslinking to give insoluble gels was an undesirable side reaction increased with γ‐ray dose and decreased with PEO addition. The most effective flocculants contained more than 15 wt % PEO with little crosslinking. The grafting behavior of triblock copolymer, poly(ethylene oxide)‐b‐poly(propylene oxide)‐b‐poly(ethylene oxide) (EmPnEm, where m and n are oxyethylene and oxypropylene unit, respectively), onto PAM by gamma radiation was also studied; grafting occurred but effective flocculants were not obtained. © 1994 John Wiley & Sons, Inc.
Chemical modification of of polypyrrole. I. Preparation and structural characterization of polypyrrole electrophically substituted with phthalic anhydride and pyromellitic dianhydride
Authors: Biswas Mukul , Roy Anindita
Published: April 2003

Polypyrrole (PPY) prepared in ether and in aqueous medium has been modified by polycondensation with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA) in presence of Friedel–Crafts catalysts such as anhydrous zinc chloride and anhydrous ferric chloride at high temperature. The substitution reaction between PPY and the anhydrides presumably proceeds by intra‐and interchain resulting in the formation of intractable products. The characterstic carbonyl absorption band expected for CO and diketone groups in the proposed structure for the polycondensates has been observed in spectra of the anhydride‐modified poly‐condensates. XRD pattern of the polycondensates is totally amorphous. © 1994 John Wiley & Sons, Inc.
Drawing behavior of polyblend fibers from polypropylene and liquid crystal polymers
Authors: Qin Yimin
Published: April 2003

Polyblend fibers were made from mixtures of polypropylene (PP) and thermotropic liquid crystal polymers (LCPs). The as‐spun fibers were drawn to produce the oriented structure for the PP matrix. The LCPs were found to exist in thin and long fibrils in the as‐spun fibers; after drawing, they were split into short fragments. From a simplified model whereby a single LCP fibril is embedded in a PP matrix fiber, it was calculated out that the length of the LCP fibril in the drawn fiber is directly proportional to the fibril diameter and tenacity, and is reversely proportional to the compressional stress on the fibril and the friction coefficient between the fibril and the surrounding matrix. With regard to the drawing conditions, it was found that a long length of the LCP fibrils can be preserved by increasing the drawing temperature, or by reducing the draw rate. The effect of two‐stage drawing on the LCP phase morphology was also studied in the present work. © 1994 John Wiley & Sons, Inc.
Swelling bahavior of hydroxyethylemethacrylate hydrogels modified by copolymerization with furfuryl acrylate
Authors: Peniche Carlos , Zaldíiver Dionisio , Agallardo Alaberto , Román Julio San
Published: April 2003

Hydrogels of biomedical interest were prepared by the free redical copolymerization of 2‐hydroxyethylmethacrylate, H, with furfuryl acrylate, A, at low and high conversion. The microstructural analysis of the copolymer system was carried out by nuclear magnetic resonance (NMR) spectroscopy, taking into consideration statistical perameters according to the Mayo–Lewis copolymerization model. The hydration process in physsiological conditions was studied gravimetrically at 37°C, following the kinetics of swelling of homogeneous thin films. A diffusion mechanism based on the stress relaxation model of copolymer chains accounts satisfactorily for the expermental data obtained. The diffusion coefficents determined according to the classical to the Fickian uptake kinetics are very sensitive to the copolymer's composition. © 1994 John Wiley & Sons, Inc.
Preparation of fine polymer particles containing metallocene derivatives
Authors: Sakurai Hiroyuki , Tamai Hisashi , Nishiyama Fumitaka , Yasuda Hajime
Published: April 2003

This article deals with preparations of fine particles of metallocene copolymers by emulsifierfree emulsion polymerization of vinylferrocene (VFc), ferrocenylmethyl methacrylate (FMMA), 1‐ferrocenylethyl methacrylate (1‐FEMA), 2‐ferrocenylethyl methacrylate (2‐FEMA), and 1‐ruthenocenylethyl methacrylate (1‐REMA) with acrylonitrile (AN), styrene (St), and methyl methacrylate (MMA) in water/ethanol medium. As a result, spherical copolymer particles containing metallocene derivatives have been successfully synthesized in the particle size of ca. 120 to 600 nm. The contents of ferrocenyl or ruthenocenyl groups in copolymer particles increased with increasing concentration of charged metallocene derivatives, while the amounts of metallocene derivatives incorporated into particles are much lower than the charged ratio. © 1994 John Wiley & Sons, Inc.
Studies on a new binary accelerator system containing TMTD and amidinothiourea in sulfur vulcanization of natural rubber
Authors: Mathew Cyriac , Mini Varghese T. Elizabeth , Kuriakose A. P. , Francis D. Joseph
Published: April 2003

It is well known that the use of binary accelerator systems in rubber vulcanization provide better physical and chemical properties to the vulcanizates. The present work reports the results obtained on the study of amidinothiourea as a secondary accelerator along with tetramethyl thiuram disulfide (TMTD) in the sulfur vulcanization of natural rubber. Vulcanizates containing amidinothiourea have an appreciable increase in mechanical properties and better retention of these properties after aging compared to the reference mixes used. These mixes containing amidinothiourea showed appreciable reduction in optimum cure time as well. This suggests a nucleophilic reaction mechanism in the vulcanization reactions under review. Mixes with varying concentrations of amidinothiourea were tried; and the optimum level of amidinothiourea required has been derived based on the cure characteristics of the mixes and physical properties of the vulcanizates. © 1994 John Wiley & Sons, Inc.
Synthesis and properties of two kinds of amphiphilic graft copolymers with well‐defined structure
Authors: Xie Hong‐Quan , Wu Xiang‐Dong , Guo Jun‐She
Published: April 2003

Polyacrylamide with well‐defined polystyrene grafts (PAM‐g‐PS) and poly(methacrylic acid) with well‐defined poly(methyl methacrylate) grafts (PMAA‐g‐PMMA) were synthesized via macromer techniques. Polymerization conditions and reactivity ratios for the copolymerizations were studied. The graft copolymers were purified by extractions and characterized with IR spectra. Structural parameters of PMAA‐g‐PMMA were determined by measurement of number average molecular weight of both macromers and copolymers. Both kinds of the graft copolymers are amphiphilic, exhibiting good emulsifying properties. When PAM‐g‐PS was mixed with PMAA‐g‐PMMA in a molar ratio of PAM/PMAA = 1, an intermolecular complex membrane was formed. This behaves as a chemical valve; its permeability can be controlled reversibly by changing the pH value. © 1994 John Wiley & Sons, Inc.
Enantiomer enrichment of oxprenolol through cellulose tris(3,5‐dimethylphenylcarbamate) membrane
Authors: Yashima Eiji , Noguchi Junko , Okamoto Yoshio
Published: April 2003

Enantioselective enrichment of racemic oxprenolol dissolved in a hexane‐2‐propanol mixture was achieved with a solid chiral polymer membrane consisting of cellulose tris(3,5‐dimethylphenylcarbamate) coated on a Teflon membrane filter. The oxprenolol obtained through the membrane was rich in (S)‐isomer up to about 50% ee at initial stage and (R) enrichment of a source phase (23% ee) was achieved. © 1994 John Wiley & Sons, Inc.
Dynamic mechanical analysis and interpretation of molecular motions in polyarylates
Authors: Charati S. G. , Jog J. P. , Kulkarni S. S. , Kulkarni M. G.
Published: April 2003

Molecular motions in polyarylates synthesized from substituted bisphenols have been investigated by dynamic mechanical analysis. Substitution at the ring carbon atom results in a more pronounced enhancement in glass transition temperature (Tg) as compared to substitution at the bridge carbon atom. The enhancement in mono and disubstituted polyarylates is more consistent than that in the case of polycarbonates and polysulfones. The β transition has been shown to result from defects in the polymer samples. The molecular motion responsible for the τ transition in polyarylates has been shown to be more iocalized than in the case of polycarbonates. Introduction of the phthalide ring in the isopropylidene unit of bisphenol‐A molecule results in splitting of the τ transition peak into two. The results have been compared with those reported for other bisphenol‐based polymers, viz. polycarbonates and polysulfones, and explained on the basis of the structural attributes of the polymers. © 1994 John Wiley & Sons, Inc.
Blends of cellulosic esters with poly(caprolactone): Characterization by DSC, DMA, and WAXS
Authors: Vázquez‐Torres H. , Cruz‐Ramos C. A.
Published: April 2003

Binary blends of poly(caprolactone) (PCL) with cellulosic esters [cellulose diacetate (CDA), cellulose acetate–butyrate (CAB), and cellulose triacetate (CTA)] were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide‐angle X‐ray scattering (WAXS) techniques, and qualitative comparison was made with the results obtained by polarizing optical microscopy. The PCL–CAB system was proved to be partially miscible, whereas PCL–CDA and PCL–CTA appeared to be immiscible. A double‐melting behavior was showed for PCL–CAB and PCL–CTA blends. As these peaks did not shift by varying the heating rate of DSC runs, this behavior can be due to melting of two populations of crystals of PCL, which may be different in size. On the other hand, blends of PCL containing a low amount of CAB or CDA seem to develop more crystallinity for the PCL than this polymer alone. The solvent seems to have a certain influence on the thermal and morphological behaviors of the as‐cast blends of these three systems, affecting the extent of crystallinity of PCL, as well as itsTmand ΔHf. This finding is discussed in the light of WAXS and polarizing optical microscopy results. © 1994 John Wiley & Sons, Inc.