bluuebunny/crossref_metadata_2025_split huggingface dataset:
An experimental examination of fracture criteria using brittle polystyrene
Authors: Gupta Surendra Kumar , Quesnel David J. , Lambropoulos John 
Published: April 2003

AbstractA four‐point bend test was performed on injection‐molded bar‐shaped polystyrene specimens with notches of varying depths. The material investigated was found to be linear elastic and brittle. From the load–displacement curves, various fracture toughness parameters based on energy release rate theories and stress–intensity factors were calculated. The stress concentrations arising from the presence of finite size notches with finite root radii were also calculated. The local stress at crack initiation was found to be nearly constant for all specimens investigated while the fracture toughness parameters based on energy release rates were not constant. A distinct change in the crack propagation behavior was observed when the curvature of the stiffness vs. notch depth curve changed sign, clearly defining the onset of unstable crack growth.
Radiationresistance and thermal stability of nylon 6, acrylonitrile copolymer and polyester fabrics
Authors: Lawandy S. N. , Abd‐El‐Zaher N. 
Published: April 2003

AbstractThe thermal stability and radiation resistance of three polymers Nylon 6, acrylonitrile copolymer and polyester were investigated. The polymer samples were irradiated by low rate fission neutrons from a 252Cf source. The polyester showed a higher heat and radiation resistance than the two other polymers. It has to be recommended herein that polyester is the most suitable fiber for the manufacture of products in which heat buildup is produced during application, or products where radiation and heat resistance are required.
Swelling studies of perfluorinated ionomer membranes
Authors: Yeo R. S. , Cheng C.‐H. 
Published: April 2003

AbstractThe swelling behavior of perfluorinated ionomer membranes in various solvents were studied. It was found that the sample pretreatments and the type of the functional group have a strong effect on the swelling properties of these membranes. The swelling of sulfonate membrane is higher than that of the carboxylate membrane. Also, the membrane swelling can be increased by quenching the sample and increasing solvent temperature. Finally, the dissolution properties of this membrane are discussed.
Mechanical relaxations and moduli of isotropic and oriented linear low‐density polyethylene
Authors: Choy C. L. , Leung W. P. , Ng H. C. 
Published: April 2003

AbstractThe mechanical relaxations of isotropic and oriented linear low‐density polyethylene have been studied between −180 and 90°C by the use of a torsion pendulum (1 Hz), a dynamic tensile apparatus (5–90 Hz), and a longitudinal wave attenuation technique (10 MHz). The five independent elastic moduli of the oriented samples have also been measured from −60° to 50°C by an ultrasonic method. Wide‐angle X‐ray diffraction and birefringence measurements reveal that the chains in the crystalline phase are fully aligned at draw ratio λ = 4, but the degree of amorphous orientation increases steadily, indicating that the number of well‐aligned tie molecules continues to increase up to the highest attainable draw ratio (λ = 6.1). The slight depression of the γ and β relaxation peaks upon drawing results from a lowering of molecular mobility in the amorphous and interfacial regions due to the constraining effect of taut tie molecules. At low temperature, the sharp rise in the axial Young's modulus E0 and slight drop in the transverse modulus E90 with increasing λ largely reflects the overall chain orientation. Just above the β relaxation, the stiffening effect of taut tie molecules leads to increases in all moduli including the shear moduli. The two‐phase Reuss (uniform stress) model provides an adequate description of the elastic anisotropy only at λ < 3, mainly because the internal stress distribution in a highly oriented sample is not uniform but corresponds to a situation intermediate between uniform stress and uniform strain field.
Sensitivity and sensitization mechanism of halomethylated polystyrene to near UV region
Authors: Zhang Yu‐Chuan , Morita Hiroshi , Yamaoka Tsuguo 
Published: April 2003

AbstractBromo‐ and chloromethylated polystyrene (BCMS) prepared for an X‐ray resist was sensitized to near UV region by addition of some sensitizers. Among them, 2,4‐diisopentylthioxanthone (DITX) and Michler's ketone were found to be efficient sensitizers for BCMS and related polymers under irradiation with a high pressure mercury lamp. To investigate the sensitization mechanism, IR and UV spectra were measured with the BCMS/DITX system under light irradiation. From the results, together with those of oxygen and radical scavenging effects on sensitivity of the polymer, it was suggested that hydrogen abstraction of the triplet state of DITX from the polymer induces photocrosslinking between the polymer chains.
Mechanisms of antioxidant action: The role of nitroxyl radicals in the stabilization of PVC
Authors: Adeniyi J. B. , Al‐Malaika S. , Scott G. 
Published: April 2003

AbstractHindered amines and their derived oxidation products, the hindered nitroxyls and hydroxylamines are processing stabilizers and photoantioxidants for poly(vinyl chloride). The evidence suggests that oxidation of the amines occurs very rapidly and completely during mechanooxidation and that the resulting redox couple operates by a catalytic mechanism as described previously for hydrocarbon polymers.
Multiphase polymer systems: PVC/styrene copolymer alloys
Authors: Bourland Larry G. , Braunstein David M. 
Published: April 2003

AbstractThe compatibility of blends of poly(vinyl chloride) (PVC) and styrene copolymers containing maleic anhydride have been investigated by thermal and dynamic and mechanical studies. Unlike homopolymer polystyrene, these styrene/maleic anhydride copolymers, when blended with PVC, provide a degree of miscibility. Complete miscibility or single phase morphology is present only at low concentrations. At higher concentrations, the alloy system separates into two altered phases—neither of which is a pure component. At intermediate alloy compositions, the phases are relatively constant in polymer composition, but the ratio of phases can vary. These altered phases are dispersed at extreme concentrations and are cocontinuous at levels approaching approximately 60 wt % PVC. The intermixed, altered phases show various degrees of miscibility and provide significant adhesion between the two phases. Physical property improvements are attributable to the partial miscibility of the phases.
Control of interchange reactions of polycarbonate/polyarylate blends and their influence on physical behavior
Authors: Mondragon I. , Nazabal J. 
Published: April 2003

AbstractBlends of polycarbonate of bisphenol A (PC) and a polyarylate of bisphenol A (PAr) are susceptible to showing interchange reactions in the melt state. The control of these reactions was carried out by means of the observation of the torque required to turn the Brabender and of its increase against the time due to copolymer formation in the processing equipment. Based on this variation and on glass transition temperature (Tg) measurements, the possibility of an exchange reaction in two steps in this blend was suggested. Tg measurements in melt‐ and solvent‐cast blends also showed that this mixture is immiscible at all compositions and that, by copolymer evolution, a single Tg intermediate between those of the individual constituents can be found in all compositions. The influence of immiscibility on the mechanical properties of the blends was shown by the appearance of a minimum in large‐strain properties at about 25% PAr. The behavior of the transesterified blends was very different showing a clear improvement of the tensile properties compared with those of the corresponding blends.
Semi‐1 thermoplastic interpenetrating polymer networks of physically crosslinked poly(n‐butyl acrylate) and polystyrene
Authors: Nishiyama Y. , Sperling L. H. 
Published: April 2003

AbstractPoly(n‐butyl acrylate) (PnBA) chemically crosslinked with tetraethylene glycol dimethacrylate (TEGDM) and physically crosslinked PnBAs produced by neutralization of poly(n‐butyl acrylate‐stat‐acrylic acid) with NaOH or Ca(OH)2 were prepared as a polymer I network. Each polymer I was swollen with styrene and cured in situ into semi‐IPN‐TEGDM, semi‐IPN‐Na, or semi‐IPN‐Ca, respectively. Both physically crosslinked polymers maintained their shapes during the swelling procedure. Dynamic mechanical spectroscopy indicated that good mixing of the two polymers took place in the semi‐IPN‐Ca as well as in semi‐IPN‐TEGDM, but a distinct phase separation occurred in the semi‐IPN‐Na. These results were supported by their transparent or optical opaque appearances, respectively. Annealing at 180°C developed further phase separation in the semi‐IPN‐Na, but very little in the semi‐IPN‐Ca. Analyses by the incompatibility number (based on the modulus–temperature curve) and the calculation of individual phase compositions (from the glass transition temperature shifts) were used in estimating the extent of molecular mixing.
Liquid‐rubber‐modified epoxy adhesives cured with dicyandiamide. I. Preparation and characterization
Authors: Lee Yu‐Der , Wang Shi‐Kwun , Chin Wei‐Kuo 
Published: April 2003

Abstractn‐Butylacrylate/acrylic acid (nBA/AA) copolymers were synthesized and used to modify epoxy resin (DGEBA) cured with dicyandiamide (DICY). The precuring reaction between nBA/AA copolymer and DGEBA, the curing cycle of DGEBA, and the effects of DICY and aluminum powder upon the adhesive strengths of modified DGEBA were studied. It was found that the optimum DICY/DGEBA ratio was 6 g/100 g, and lap shear strength and T‐peel strength increased with increasing amount of aluminum powder. The curing cycle for modified DGEBA was determined to be 1 h at 177°C.
Photo‐induced graft copolymerization: XVI: Graft copolymerization of methyl methacrylate onto nylon‐6 using isoquinoline‐sulfur dioxide and α‐picoline‐sulphur dioxide charge‐transfer complexes as photoinitiators
Authors: Lenka Subasini , Nayak Padma L. , Mohanty Indu B. 
Published: April 2003

AbstractThe photo‐induced graft copolymerization of methyl methacrylate onto nylon‐6 fiber was investigated using isoquinoline‐sulfur dioxide and α‐picoline‐sulfur dioxide charge‐transfer complexes as the photoinitiators. The graft copolymerization was carried out within the temperature range of 35–50°C and from the corresponding Arrhenius plot, the energy of activation has been evaluated. The effect of monomer, initiators, inhibitors, etc. on the graft yield has been investigated. The effect of solvent on the rate of grafting has also been investigated from which the chain‐transfer constant (Cs) of the solvent has been evaluated. The kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism. The suitable mechanism has been suggested and the kinetic rate expression has been derived.
The influence of fiber pretreatment on the mechanical properties of nylon 6,6‐asbestos composites. II. Interfacial coating of asbestos fibers with a thin film of nylon 6,6
Authors: Kampouris E. M. , Papaspyrides C. D. 
Published: April 2003

AbstractNylon–asbestos composites comprise a significant proportion of reinforced nylon thermoplastics. To improve the cooperation between matrix and fibers the coating of the asbestos by interfacial in situ polymerization is proposed. Previous work on the system chrysotile‐nylon 6,6 is extended so that the reactants application order is now inversed, in order to consider any differences in the extraction resistance and the polymerization yield, in conjunction with thermal analysis studies. Experimental results gathered provide severe, but indirect, indications for the development of a strong interface bond between polymer and asbestos fibers.
Drag reduction effectiveness, shear stability and biodegradation resistance of guargum‐based graft copolymers
Authors: Deshmukh Suhas R. , Singh Ram Prakash 
Published: April 2003

AbstractGuargum is a seed galactomannan and is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum are very susceptible to microbial degradation. In the present investigation, seven graft copolymers of guargum and polyacrylamide have been synthesized and their drag reduction effectiveness, shear stability, and biodegradation resistance have been determined. It has been shown that the drag reduction effectiveness and shear stability of the graft copolymer depend upon the length of the graft and number of grafts in the molecule. None of the graft copolymer solutions show any microbial degradation up to 10 days.
Thermal properties of tritylated and tosylated cellulose
Authors: Trask Brenda J. , Drake George L. , Margavio Matthew F. 
Published: April 2003

AbstractTriphenylchloromethane and p‐toluenesulfonyl chloride were reacted with chopped or powdered cellulose, with and without premercerization, to form trityl–cellulose ethers or tosyl–cellulose esters. Powdered and premercerized cellulose samples were more readily derivatized. Differential scanning calorimetric (DSC) and thermogravimetric (TG) analyses were performed in nitrogen on these derivatives. DSC and TG thermograms were affected by the particular derivative and the degree of substitution. The decomposition temperatures for both derivatives were lower than for the unmodified cellulose. Trityl cleavage may have been detected by DSC as a broad endothermic area showing no weight loss that preceded the major endothermic decomposition peak. Decomposition temperatures were lowered, but not sufficiently to prevent decomposition products from being combustible. No increase in residue was effected. Thermal decomposition of tosyl–cellulose was substantially different from that of the trityl derivative. As the degree of tosyl substitution increased, decomposition occurred at lower temperatures as an increasing exotherm. Tosyl derivatives all produced high residues. These changes in thermal characteristics were indicative of increased flame resistance. Oxygen index (OI) values relate to flame resistance and show that tritylation was detrimental to the cellulose and that tosylation imparted some degree of flame resistance.
The differential permeation rate measurement of gases in PVAc
Authors: Toi K. , Izutsu M. , Mizushima A. , Ito T. , Ikemoto I. 
Published: April 2003

AbstractThe temperature dependence of the CO2 permeability coefficient in poly(vinyl acetate) (PVAc) was measured continuously by a differential permeation rate method. Tg was changed at upstream pressure in PVAc/CO2 system, and curious behavior of Ar was observed after CO2 conditioning. The differential permeation rate experiment successfully exhibits the effects of continuous temperature change for membranes with different histories.
Turbulent drag reduction by polymer‐fiber mixtures
Authors: Malhotra J. P. , Deshmukh S. R. , Singh R. P. 
Published: April 2003

AbstractThe turbulent drag reduction studies by asbestos fiber mixtures with purified guargum, purified xanthangum, and their graft copolymers have been conducted at low concentration and Re 14000 using turbulent flow rheometer designed by Hoyt. A method for making stock suspension of asbestos fibers is also suggested which gives better drag reduction. It has been found from the present studies that purified guargum–asbestos fiber mixtures give positive synergistic effect even at low concentration and synergism in drag reduction may be caused by a mixture when its constituents are rigid. A simple mixture rule equation having interaction parameter may be used for the prediction of drag reduction by the mixture.
Linear polysulfonates. I. Products of 4,4′‐(1‐cyclothexylidene) diphenol and 4,4′‐(2‐norbolidene) diphenol with some aromatic disulfonyl chlorides
Authors: Podgórski Mieczysław , Podkościelny Wawrzyniec 
Published: April 2003

AbstractAromatic (poly)cycloaliphatic polysulfonates of high molecular weight can be easily obtained by interfacial polycondensation of aromatic (poly)cycloaliphatic diphenols with aromatic disulfonyl chlorides. The polysulfonates were found to have a low degree of crystallinity, softening ranges in the region 180–310°C and molecular weights in the region: M̄n 3190–4420, and M̄w 19900–83370, thermal stability to above 300°C, and reduced viscosities in the range 0.2–1.00 dL/g.
Selective etching of thermotropic liquid crystalline polyesters
Authors: Hedmark Per G. , Jansson Jan‐Fredrik , Hult Anders , Lindberg Henrik , Gedde Ulf W. 
Published: April 2003

AbstractDSC, IR, ESCA, macroscopic etching rate measurements, analysis of etchant solution, and electron microscopy conclusively show that n‐alkylamines (ethylamine, n‐propylamine, n‐butylamine, and n‐pentylamine) and NaOH selectively degrade (etch) the ethylene terephthalate (ET)‐rich phase in glassy liquid crystalline poly(p‐hydroxybenzoic acid‐co‐ethylene terephthalate) [P(HBA–ET)] with molar compositions 0.60:0.40 and 0.80:0.20. ESCA demonstrates the excellent selectivity of the n‐alkylamine etchants in the 0.60:0.40 copolymer. The 50 Å top layer of the etched samples contains 95 mol% HBA. Treatment with H2SO4 and NH3 gives ambiguous results, and these compounds are not suitable as etchants. It is demonstrated by electron microscopy on the 0.60:0.40 copolymer, in accordance with earlier reports by Joseph et al.,5–8 that the ET‐rich phase is discontinuous (1–2 μm spheres) and surrounded by an HBA‐rich matrix. SEM is a useful tool for characterization of this morphology. However, both phases have a substracture which is revealed only by TEM. The morphology of the 0.80:0.20 copolymer is fine‐textured, which means that SEM is a less suitable method for the characterization of etched samples.
A mathematical model for the Ziegler‐Natta polymerization of butadiene
Authors: Honig J. A. J. , Gloor P. E. , MacGregor J. F. , Hamielec A. E. 
Published: April 2003

AbstractA mathematical model which describes conversion and molecular weight development in the homogeneous polymerization of butadiene has been developed. The reaction scheme and derivation of the model equations are included. It was found that a catalyst formation efficiency must be estimated for each polymerization. The correct trends were predicted, although weight‐average molecular weight was often underestimated. The model could not fully account for the effect of water concentration.
Osmocentrifugation in density gradients: Application to polymer latex separation
Authors: Winkler‐Hechenleitner Ana A. , Costa M. Célia P. , Galembeck F. 
Published: April 2003

AbstractPolymer latexes can be fractionated by size and by chemical composition through osmocentrifugation. Density gradients are formed by centrifuging Ficoll and Percoll solutions in dialysis cells; mixed polymer latex zones are layered over these gradients and centrifuged again, leading to separated latex bands from which polymer may be collected and further analyzed. Zone migration rates in the osmocentrifugation experiment are faster than in standard centrifugation tubes.
Cold drawing of polyethylene terephthalate/polyethylene films
Authors: Berger W. , Ludwig U. , Hauffe W. , Karasz F. E. 
Published: April 2003

AbstractFilms made from a 77/23 weight percent polyethylene terephthalate/polyethylene blend were stretched using an Instron apparatus. The structures of the samples were examined by methods which included ion beam etching and electron microscopy. The drawn samples exhibited a metallically lustrous and highly reflective surface up to a draw temperature,TR, of 70°C and a draw ratio of about 5. Under certain conditions the change in structure caused by the stretching resulted in the formation of a highly uniform fibril‐void structure. The voids are up to 3 μm in width and 160 μm in length and are formed primarily as a result of aggregation and then separation of the microfibrils of the individual polymer components.
Aqueous solution properties of poly[3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate]
Authors: Liaw Der‐Jang , Lee Wen‐Fu , Whung Yann‐Ching , Lin Mei‐Chih 
Published: April 2003

AbstractThe aqueous solution properties of an ampholytic poly[3‐dimethyl (methacryloyloxyethyl) ammonium propane sulfonate] [poly(DMAPS)] are studied by measurements of cloud point determination, intrinsic viscosity, degree of binding, and ionic strength. The minimum salt concentration and intrinsic viscosity of this polyampholyte are related to the type and concentration of added salt. Both the polymeric and monomeric betaines in the presence of NaCl have the lower degree of binding, indicating that the proton ion (H+) is relatively difficult to bind the SO−3at the end of sulfobetaine. An increase in ionic strength causes the pKato decrease at the half‐neutralization point.
Relaxation and recovery measurements by the microhardness indentation technique for transparent polymeric materials
Authors: Howes V. R. , Wall P. 
Published: April 2003

AbstractA simple microhardness testing technique is described that enables the identation process to be continuously observed for transparent materials Photographic recording gave measurements of the indentation area and its changes with time, both during the on‐load period and during the subsequent period following the removal of the load. To illustrate the techniques, the time‐dependent mechanical properties of poly(methyl methacrylate) (Perspex) and diallyl diglycol carbonate (CR39) have been studied. Two parameters are defined that could be useful in identifying time‐dependent deformation properties of polymeric materials. The relaxation hardness, analogous to the relaxation modulus, describes the stress–relaxation that occurs for an identation loaded material. The surfaces resistance to damage, defined as the ratio of the applied indentation load to the remaining deformation area after load removal, is useful as an abrasion or wear indicator, particularly for assessing optical deterioration. The changes in this parameter with time describe the mechanical recovery that occurs at an indentation site in the material.
Cellulose bound chlorophenols II: Preparation and characterization of phenyloxycarbonylpentanoyl celluloses dependence of substitution on chlorophenol structure
Authors: Mair Peter , Bahadir Müfit , Korte Friedhelm 
Published: April 2003

AbstractNew types of polymeric phenols (including the fungicide PCP) are prepared by linking phenol and different chlorophenols to cellulose via ester bonds using adipic acid as bridging molecule. Monophenylesteracid chlorides of adipic acid are prepared as intermediates. The yield of esterification of cellulose with these compounds depends in a complicated manner on size and chlorosubstitution pattern of the phenolic substituents. It is tentatively assumed that hydrogen bonding between chlorophenol and cellulose is an important factor. The polymeric PCP ester showed fungicidal activity in an agar plate test.
Polymerization of melamine and formaldehyde in homogeneous continuous‐flow stirred‐tank reactors using functional group approach: Part B: Molecular weight distribution
Authors: Kumar Anil 
Published: April 2003

AbstractPolymerization of melamine and formaldehyde in homogeneous continuous‐flow stirred‐tank reactors (HCSTRs) is reversible and leads to formation of branched polymer due to the hexafunctional nature of melamine. The reversed reaction of branched molecules depends upon the chain structure, and herein a simple model is presented to account for this. The functional group analysis of part A of this series has been extended and the molecular weight distribution (MWD) relations for HCSTRs have been solved. The MWD of the polymer is extremely sharp and the molecules are more branched compared to those for batch reactors and can be explained as follows. A given reacted bond can react with water as well as free formaldehyde through the reversed reaction, and the rate constant for the latter step is much larger. Consequently, the chain growth is limited as long as there is free formaldehyde in the reaction mass. Lower conversion of melamine and formaldehyde in HCSTRs is used to explain the behavior observed.