bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tear and processing behaviour of short sisal fibre reinforced styrene butadiene rubber composites
Authors: Kumar R. Prasantha , Thomas Sabu 
Published: April 2003

AbstractThe tear failure and processing characteristics of short sisal fibre reinforced styrene butadiene rubber (SBR) composites were investigated. Tear strength was examined with special reference to the effects of fibre length, fibre orientation, fibre concentration and bonding agent. It was observed that the tear strength depends on all the above factors. The tear failure mechanism was analysed from fractographs taken using a scanning electron microscope (SEM). During tear testing, the composites failed by a shearing process. Microscopic examination of cracks propagating in SBR composites revealed that the amorphous SBR matrix developed cracks, leaving ligaments of rubber attached to the broken fibres. The rubber particles were stretched as the crack opened and failure occurred at large critical extensions. It was observed that an increase in the concentration of fibres increased the tear strength in both longitudinal and transverse directions. The tear strength values were almost three to four times higher than those of the unfilled vulcanizates under similar conditions. In order to analyse the processing behaviour, the green strength, mill shrinkage and Mooney viscosity of the compounds were determined. Finally, the polymer–filler interaction was studied using the Lorenz–Park and Kraus equations.
Curing of novolac–lignocellulosic composites
Authors: Simitzis J. , Karagiannis K. , Zoumpoulakis L. 
Published: April 2003

AbstractNovalac resin (N) with hexamethylenetetramine (HTA) was cured with biomass (B) or Kraft lignin (KL) or hydroxymethylated Kraft lignin (KLH) or cellulose (CEL). The agricultural/industrial by‐product of olive stones was used as biomass. Kraft lignin, hydroxymethylated Kraft lignin and cellulose were isolated from the biomass. The cure was followed by DSC and IR spectroscopy. Based on the IR spectra of cured materials and their characteristic bands, the proportion of N/B = 50/50 was chosen for the preparation of novolac mixtures with other components. Only N–KLH exhibited values of ΔH higher than ΔHm, calculated from the law of mixtures, indicating that KLH participates in the cure reaction. The kinetic parameters E and K0 of the total cure reactions, calculated by DSC scans, increased in the order N < N–KLH < N–B < N–KL < N–CEL. The incorporation of KLH in the mass of N–HTA led to a slight increase in E and k0. On the other hand, KL, CEL and B acted as diluents in the mass of novolac. Generally, the cure of all materials was a first order reaction, indicating that the cure mechanism of novolac remains the same.
Radical homopolymerization and copolymerizations of ring‐methoxy substituted α‐cyanostyrenes
Authors: Tanaka H. , Teraoka Y. , Yoshida S. 
Published: April 2003

AbstractRadical homopolymerization and copolymerizations of ring‐methoxy substituted α‐cyanostyrenes were studied using benzoyl peroxide and dimethyl 2,2′‐azobisisobutylate at 60°C. It was found that the cyanostyrenes containing 2‐methoxy cyanostyrene gave homopolymer in moderate yield and they were also copolymerized with vinyl monomers such as styrene and vinyl acetate. The relative reactivity of the cyanostyrenes towards a polystyryl radical (1/r2) in the copolymerization of cyanostyrenes (M1) and styrene (M2) was correlated with the Hammett and Taft substituent constants of the methoxy groups and the 13C NMR chemical shift of the β‐carbon of the cyanostyrenes. The enhancement of the radical polymerization reactivity by introducing a nitrile group in the captodative α‐position of styrene was considered to be due to the suppression of the termination reaction and the activation of the propagation reaction. In addition, thermal properties such as glass transition and degradation temperatures of the cyanostyrene polymers obtained were also examined.
Study on phase behavior–impact strength relationship of unsaturated polyester/polyurethane hybrid polymer network
Authors: Xu Mei Xuan , Liu Wen Guang , Guan Yun Lin , Bi Zuo Peng , Yao Kang De 
Published: April 2003

AbstractThe phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)‐co‐(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene‐bis‐ortho‐chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties.
Analysis of Fizeau fringes crossing fibres with trilobal shaped cross‐section having skin–core structure
Authors: Fouda I. M. , El‐Nicklawy M. M. , Hassan A. F. , Kelany A. M. 
Published: April 2003

AbstractA mathematical formula is derived for the shape of multiple‐beam Fizeau fringes crossing a trilobal fibre having a core surrounded by multiple skins. Fizeau fringes in transmission crossing the fibre were obtained experimentally to calculate their optical parameters. Microinterferograms are given for illustration.
Determination of the width of the transition layer between the crystalline and amorphous zones in nylon 1010 by SAXS
Authors: Meng Chaofu , Lin J. S. 
Published: April 2003

AbstractThe width of the transition layer between the crystalline and amorphous zones in nylon 1010 was determined by SAXS with point collimation and long‐slit collimation, respectively. The width of the transition layer, E, was found to be 1.7 nm. The results show that the width of the transition layer is independent of crystallinity.
Monomer sequence length distributions of hard segments of linear segmented poly(urethane–urea)s 1: chromatographic study
Authors: Hanahata Hiroyuki , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to determine, by the chromatographic method, monomer sequence length distributions of the hard segments in segmented poly(urethane–urea)s (PURs) synthesised in a two‐step process: (1) a prepolymer formation reaction of an excess of methylenebis(4‐phenylisocyanate) (MDI) with poly(tetramethyleneoxide) (PTMO) and (2) a polymerisation reaction of the prepolymer containing unreacted MDI with ethylenediamine, giving PUR. The monomer sequence length of the hard segment was found to become longer and its distribution to broaden as the initial concentration ratio of MDI to PTMO increased. This result is attributable to an increase of the concentration ratio of the unreacted MDI to the prepolymer, leading to gelation of the polymer solution. By comparing the chromatographic results with the theoretical data calculated in the simple case of the equal reactivity of the reactants in the prepolymerisation and polymerisation reactions, respectively, the existence of unequal reactivities of the reactants in both reactions, is predicted.
Controlled release of diltiazem hydrochloride
Authors: Xu Ping , Mark James E. , Wang Song‐Bo , Nathan Paul , Korol Bernard 
Published: April 2003

AbstractA new type of complex reservoir–matrix system for the controlled delivery of diltiazen hydrochloride was developed. This capsule‐type device was designed for oral administration to humans and/or animals. It contained (i) an appropriate amount of the drug in a compartment; (ii) a swelling‐controlled membrane which was prepared by mixing polymeric materials with another appropriate amount of the drug; and (iii) a water‐soluble gelatin capsule as container. The swelling‐controlled membranes were prepared from poly(2‐hydroxyethyl methacrylate) hydrogels. The effect of pH on the swelling of the hydrogels was studied. In‐vitro dissolution testing was carried out to evaluate the release of the drug using a continuous‐flow method. Zero‐order release kinetics was obtained over a period of 12 h.
Using a water‐insoluble amphoteric starch to simultaneously adsorb heavy metal ions/phenol from solutions
Authors: Chan Wu‐Chung 
Published: April 2003

AbstractAn investigation was undertaken regarding the adsorption of heavy metal ions (CrO2−4 or Pb2+) and phenol from solution with a highly crosslinked amphoteric starch containing the phosphate anionic group and the tertiary amine cationic group. The adsorption process was found to be dependent on initial pH and concentration for both metal ions, and to be concentration‐independent for the phenol organic substance. The adsorption follows the Langmuir adsorption isotherm for CrO2−4, and the Freundlich adsorption isotherm for Pb2+. The adsorption mechanism confirms that the Na+ of the sodium phosphate group and the Cl− of the tertiary amine group are used to exchange Pb2+ and CrO2−4 ions, respectively, and the tertiary amine group is used to adsorb phenol.
Toughening of aromatic diamine‐cured epoxy resins by modification with hybrid modifiers composed of N‐phenylmaleimide–styrene copolymers and N‐phenylmaleimide–styrene–p‐hydroxystyrene terpolymers
Authors: Iijima Takao , Suzuki Norio , Fukuda Wakichi , Tomoi Masao 
Published: April 2003

AbstractHybrid modifiers composed of N‐phenylmaleimide–styrene copolymers (PMS), and N‐phenylmaleimide–styrene–p‐hydroxystyrene terpolymers (PMSH) containing pendent p‐hydroxyphenyl groups as functionalities, were used to improve the toughness of bisphenol‐A diglycidyl ether epoxy resin cured with p,p′‐diaminodiphenyl sulphone. The hybrid modifiers were effective in toughening the epoxy resin. When using the modifier composed of 10 wt% PMS (M̄w 313000) and 2.5 wt% PMSH (2.5 mol% p‐hydroxystyrene units, M̄w 316000), the fracture toughness (KIC) for the modified resins increased 100% with no deterioration in the flexural properties and the glass transition temperature. The improvement in toughness of the epoxy resins was attained because of the co‐continuous phase structure and the improvement in interfacial adhesion. The toughening mechanism is discussed in terms of the morphological characteristics of the modified epoxy resin systems.
Isothermal cure of an epoxy/cycloaliphatic amine system. Vitrification and gelation
Authors: Barral L. , Cano J. , López A. J. , López J. , Nogueira P. , Ramírez C. 
Published: April 2003

AbstractTimes to gelation and times to vitrification during isothermal curing for the epoxy system diglycidyl ether of bisphenol A and 1,3‐bisaminomethyl‐cyclohexane were measured at different curing temperatures between 50 and 100°C. Gelation occurs around 56% conversion. Vitrification was determined from data curves of glass transition temperature, Tg, versus curing time obtained from DSC experiments. The minimum and maximum Tg determined for this epoxy system were Tgo = −37°C and Tg∞ = 150°C. Values of activation energy of the epoxy/amine cure reaction of 58 kJ/mol and 49.5 kJ/mol were obtained from Tg versus time shift factors and gel time measurements respectively. The isothermal time–temperature–transformation diagram has been established.
Polypyrrole–poly(heptamethylene p,p′‐bibenzoate) conducting materials. Synthesis and characterization
Authors: de la Plaza M. A. , González‐Tejera M. J. , de la Blanca E. Sánchez , Jurado J. R. , Hernández‐Fuentes I. 
Published: April 2003

AbstractPolypyrrole–poly(heptamethylene p,p′‐bibenzoate) conducting materials, PPy–P7MB/ClO4, were obtained by anodic coupling of pyrrole into a polybibenzoate inert matrix, using perchlorate anions as dopant agent. P7MB is a main‐chain liquid crystalline polybibenzoate with adequate mechanical properties and elastic modulus of 1.4GPa at room temperature. The method of synthesis, galvanostatic or potentiostatic electrodeposition, is responsible for differences in the PPy–P7MB/ClO4 films electrochemical response. FTIR spectra show the complex structures of P7MB and the composite conducting material.The conductivity of PPy–P7MB/ClO4 films maintains a relatively high value, σ = 13.74Scm−1, in spite of the insulating effect of polybibenzoate. Film micrographs reveal the typical cauliflower morphology exhibited by polypyrrole and the evolution of film growth with time.
An improved osmotic balance
Authors: Enoksson Bertil 
Published: April 2003

AbstractThe construction and operation of the osmotic balance has been described. Because of the damping effect of the cell immersed in the solvent the sensitivity of the balance is diminished. This can be avoided if a suitable weight is placed above the central knife‐edge of the beam of the balance. A way to calculate the dimensions of a cell which gives the lowest possible temperature sensibility has been discussed. The disadvantage of a thick cell wall with respect to reference point adjustments has been pointed out. The measurements made with the balance have shown that osmotic pressures of the magnitude 0.011 ± 0.001 g./cm.2 can be measured. An example of the use of the balance has been given for three samples of nitrocellulose.
Polymerization‐degradation of styrene in solution
Authors: Spodheim Hilda W. , Badgley Wilfrid J. , Mesrobian Robert B. 
Published: April 2003

AbstractThe changes in the viscosity–average size distribution of polystyrene under conditions of simultaneous degradation and polymerization in toluene solutions have been observed. The appearance of the differential distribution curves for the degraded polymers and the polymerized monomer in the steady‐state viscosity region are nearly identical. Osmotic pressure data on fractions of the degraded polymers do not show evidence for the occurrence of chain branching.
Depolarization of light scattered from dilute macromolecular solutions. I. Theoretical discussion
Authors: Doty Paul 
Published: April 2003

AbstractThis paper represents an attempt to review the general interpretation of the phenomenon of depolarization of light scattered from colloidal solutions and to combine this with other recently acquired knowledge in order to predict the qualitative behavior of the depolarization ratios, as well as the individual components which make up these ratios, with respect to concentration, solute–solvent interaction, and the characteristics of the macromolecules. The ratio ρv depends inversely on the turbidity of the solution, the behavior of which is now understood due to the investigations of the light scattering method relative to molecular weight determinations. If allowance is made for turbidity changes and the effects of intramolecular interference ρv reflects the optical anisotropy of the segments of polymer molecules and of rigid molecules as a whole. The values of ρh will generally diminish from a value of unity as the size of the scattering particle increases. Sniall rodlike particles appear to be an exception to this behavior according to the works of Gans and Neugebauer but experimental confirmation is lacking notwithstanding recent claims to the contrary.
Heat of crystallization of cellulose
Authors: Calvet E. , Hermans P. H. 
Published: April 2003

AbstractThe measurement of the heats of dissolution of cellulose of diverse percentages of We crystallization has permitted us to find the heat of crystallization of the cellulose. We have found 4100 cal./mole. This number is about 25% less than the heat of crystallization of the beta‐glucose and it is very near that which had been found by one of the authors by means of the heats of wetting. The knowledge of the heats of crystallization of the cellulose and the determination of the heats of dissolution make possible the determination of the percentage of crystallization of a sample of cellulose when the composition of the sample in reference is known.
Photochemistry of proteins. XVII. Inactivation of enzymes with ultraviolet light and photolysis of the peptide bond
Authors: McLaren A. D. , Gentile Philip , Kirk David C. , Levin Norman A. 
Published: April 2003

AbstractRibonuclease and carboxypeptidase are inactivated by ultraviolet light (2537 A.) with quantum yields of 0.03 and 0.001–0.005 respectively. The quantum yields for low molecular weight proteins are of the order of 0.03 and are higher than those for splitting peptide bonds in typical peptides (0.004–0.0004 or less). It is postulated that the primary process of inactivation involves modification of aromatic residues in proteins. A possible reason for the inverse relationship between quantum yields and molecular weights of enzymes and proteins is discussed.
Oxidation of butadiene popcorn polymer
Authors: Miller Glenn H. 
Published: April 2003

AbstractButadiene popcorn polymer reacted readily with oxygen to produce a yellow to orange colored product. The apparent over‐all activation energy for the reaction averaged 16.7 kcal. Using the reaction with oxygen as a measure of the degree of unsaturation, the glassy type butadiene popcorn polymer was found to be more saturated that the earlier generation popcorn from which it was grown. The induction period which precedes the logarithmic growth of the polymer when placed in the presence of monomer increased as the oxygen content of the seeds increased. No increase in growth activity was ever attained by exposing the seeds to oxygen. Short exposures of the seeds to oxygen up to three hours at room temperature had no effect on the growth activity of the seeds. No correlation could be found between the seed growth activity and the degree of unsaturation as determined by the oxidation reaction.
Rheology of polyisobutylene. I. Theory and experimental procedures
Authors: Leaderman Herbert 
Published: April 2003

AbstractA formulation is given of the response of a body manifesting linear viscoelastic behavior in shear to arbitrary simple shear stress history. A description is given of procedures for the measurement of the retarded elasticity function and of the viscosity by means of experiments under constant shear stress and following removal of stress. The non‐Newtonian flow of polymers is considered. Existing information on the viscosity of polyisobutylene as a function of temperature and molecular weight is reviewed. The applicability of the kinetic theory of rubberlike elasticity to a system of linear molecules is discussed. The use is described of the concentric cylinder rotational viscometer for the measurement of non‐Newtonian flow and of linear viscoelastic behavior.
Ionic chlorination of polystyrene
Authors: Teyssié Ph. , De Wilde M. C. , Smets G. 
Published: April 2003

AbstractThe structure of the ionically chlorinated polystyrenes has been investigated by both chemical and infrared spectrometric analyses. The chlorination reaction, performed in the total darkness and in the presence of iodine as catalyst, proceeds only by a substitution mechanism, both in the aromatic nucleus and in the main polymeric chain. The catalyst concentration exercises a determining effect on the over‐all rate of the reaction. The aliphatic chlorine content has been determined by reaction with aniline; indeed preliminary experiments have shown that the aromatic chlorinated isomer has been determined by infrared quantitative spectrometry, by comparison with reference polymers: polystyrene, poly‐para‐ and poly‐ortho‐chlorostyrenes, poly‐3,4‐, ‐2,4‐, ‐2,5‐, and ‐2,6‐ dichlorostyrenes. The chlorine is preferentially oriented in the para, secondarily in the ortho position. From about 37% total chlorine content, nearly all the phenyl groups have reacted and the amount of para‐ and ortho‐chloro units decreases rapidly in favor of dichlorophenyl units. Some evidence is found of a trichloro substitution in samples of about 41% Cl or more. To elucidate the problem of the dichlorophenyl units, some samples of poly‐para‐ and poly‐ortho‐chlorostyrenes were also chlorinated: the second chlorine atom is directed into the phenyl ring mainly in the 3 position for poly‐para‐chlorostyrene, and in the 5 position for poly‐ortho‐chlorostyrene. However, a certain amount of the 2,4‐isomer is also obtained in both cases. By adding the amount of halogen (calculated from infrared analysis) to the aliphatic chlorine content (obtained from aniline analysis), a value has been found which agrees with the total chlorine content determined by the method of Wurzschmitt. The decrease of the degree of polymerization, due to the chlorination, has been followed by osmotic measurements and found to be favored by both a high degree of substitution and a polar character of the catalyst.
Emulsifier‐free polymerization in aqueous media
Authors: Whitby G. S. , Gross M. D. , Miller J. R. , Costanza A. J. 
Published: April 2003

AbstractThe polymerization in solution of a variety of water‐soluble monomers with a variety of water‐soluble redox initiators is described and a detailed study is reported on the polymerization, in aqueous solution, of methyl vinyl ketone and of methyl methacrylate under the influence of potassium sulfate‐silver nitrate. Keeping the persulfate concentration constant and varying the silver nitrate or, conversely, keeping the silver nitrate constant and varying the persulfate, it is found that, except at very high concentration of catalyst, both the rate of polymerization and the molecular weight of the polymer bear a linear relation to the square root of the catalyst concentration, in harmony with the general theory of catalyzed bulk and emulsion polymerization. The molecular weight of the polymer formed diminishes with increase in the temperature of polymerization. The study of redox polymerization in water, without emulsifier, has been extended to the case of a mixture of a water‐soluble and a water‐insoluble monomer, and it has been found that copolymerization proceeds at a reasonable rate and frequently forms a stable latex. The copolymerization of styrene and 5 or 10 per cent of its weight of methacrylonitrile in water under the influence of a water‐soluble persulfate‐bisulfite redox pair has been examined with some closeness. Polymerization is apparently initiated in the aqueous solution, since, contrary to the state of affairs in emulsion polymerization, water‐soluble retarders are more effective than oil‐soluble ones, when the retarder is added at the outset. If the retarder is added at a later stage of polymerization, oil‐soluble reagents are more effective than water‐soluble ones. The water‐soluble monomer enters into the polymer at a greater rate than the water‐insoluble one, but it appears that, even at the earliest stage at which it is practicable to take samples co‐polymerization occurs. The influence of catalyst concentration on the rate of polymerization, the molecular weight of the polymer, and the latex particle size was examined.
Enzyme models and their relation to inclusion compounds
Authors: Lautsch W. , Broser W. , Biedermann W. , Gnichtel H. 
Published: April 2003

AbstractSyntheses of high polymers with active groups of the hemin and chlorophyll series and their optical properties, the shifts of the band maxima, and the change of the acid dissociation constants of the active groups are discussed. This touches upon the question of the existence of inclusion compounds in solution. The existence of true compounds in solution was proved by applying the law of mass action to several known inclusion systems. The acid dissociation constants of some dyes and their cyclodextrin inclusion compounds were determined by means of prototropy equilibria. The system serum albumin/methyl orange and macromolecular compounds with active groups of the hemin and chlorophyll series show a similarity to true inclusion compounds in solution, which suggests the existence of inclusion regions in the high polymers in question. Furthermore, syntheses of D‐, L‐, and DL‐forms of polyphenylalanines substituted by active groups, their optical and catalytic properties, and first experiments regarding a synthesis of cytochrome c models are discussed.