bluuebunny/crossref_metadata_2025_split huggingface dataset:
Corona‐induced autohesion of polyethylene
Authors: Kim C. Y. , Evans J. , Goring D. A. I. 
Published: April 2003

AbstractIf a low‐density polyethylene sheet is treated in a corona discharge and subsequently pressed to a similarly treated sheet at 45°C, the bond formed is much stronger than that between similarly pressed but untreated sheets. Several series of observations have indicated that this enhanced autohesion is not due to surface oxidation or to surface crosslinking (CASING). Evidence is presented that the effect may be related to some type of electret formation induced in the polymer sheet by the corona discharge.
Mechanical properties of alternating copolymers of acrylonitrile and butadiene
Authors: Furukawa J. , Nishioka A. 
Published: April 2003

AbstractThe alternating copolymer was prepared from butadiene (BD) and acrylonitrile (AN) with ethylaluminum dichloride as a complexing agent and with vanadyl chloride as a catalyst, and was investigated to explain effects of composition and sequence distribution on the physical properties, especially the viscoelastic properties and the ultimate mechanical properties. In the unvulcanized state, the viscoelastic properties of the alternating rubber is not essentially different from the random one, except for a slight difference in the relaxation spectra. However, the vulcanized rubbers show different shift factors. The latter depends upon the glass transition temperature (Tg.) Since the alternating copolymer possesses a Tg lower than the random one, the nature of the alternating copolymer corresponds to that of the random copolymer having an AN content of 40%. The difference in dynamic properties can be expressed with the different shift factors. In the isofree‐volume state or at the temperature Tg + 25°C, the rubbers having various acrylonitrile contents and various degrees of alternation exhibit almost the same dynamic properties. However, the strain at break of the alternating rubber is higher than that of the random one. The temperature of maximum strain increases with increasing degree of alternation. The alternating rubber shows higher stress at break than the random one. The stiffness of the chain of the alternating copolymer is smaller than the random copolymer; in other words, the molecular chain of the former is more flexible than the latter. It can be said that the alternating copolymer is an excellent rubber having high tensile strength and elongation at break.
Electron‐microscopic investigation of cerium–cotton cellulose reactions
Authors: Muller Linda L. , Hebert Jacques J. , Rollins Mary L. 
Published: April 2003

AbstractCotton fibers were treated with an aqueous solution of ceric ammonium nitrate and examined with the electron microscope. The greatest deposition of cerium occurred in the primary wall due largely to the reaction with noncellulosic constituents in this area of the fiber. The use of ceric ions for an electron‐microscopic stain was found ineffective for producing the desired contrast in the cotton fiber.
An improved dilatometer for polymers based on beta‐particle absorption
Authors: Martin‐Löf S. , Söremark Ch. 
Published: April 2003

AbstractThe theoretical background and the operation of a new dilatometric technique based on the absorption of beta particles is described. The thermal expansion of the samples is determined by their change in weight per unit area with change in temperature. The experimental accuracy in a determination of a relative change in weight per unit area is, at a counting time of 103 sec, approximately 4 × 10−5, which is close to the theoretical value. The applicability of the new device is illustrated by six runs on five different samples, among which hygroscopic and porous samples are represented. The temperature range covered is −60° to +70°C.
Dispersion in gel permeation chromatography. A rapid numerical solution to Tung's integral equation
Authors: Smit J. A. M. , Hoogervorst C. J. P. , Staverman A. J. 
Published: April 2003

AbstractA rapid iteration method has been developed to correct the molecular weight averages calculated from raw GPC data for dispersion. Though simple in its performance, it covers the general case that the instrumental spreading characteristics (Tung's resolution factor h) depend on the elution volume. Moreover, it is irrelevant whether the calibration curve, being the logarithmic plot of the molecular weight versus the elution volume, is linear or not. The method has been applied to a number of well‐characterized polystyrene mixtures and yields molecular weight averages which agree with those predicted theoretically. The effect of asymmetry exerted by the dispersion on both molecular weight averages M̄n and M̄w is also discussed.
The flow of very dilute polyox solutions into a region of sudden capillary tube enlargement
Authors: Little R. C. , Wiegard M. 
Published: April 2003

AbstractThe flow of dilute drag reducing polymer solutions through capillary tubes into a region of slightly greater tube diameter is characterized by almost complete recovery of the fluid. It is conjectured that the polymer molecules react to prevent the loss of kinetic energy by minimizing the formation of eddies resulting from the expansion.
Organometallic polymers. II. Crosslinking of ferrocenylene–methylene‐type polymers
Authors: Gal Alon , Cais Michael , Kohn David H. 
Published: April 2003

AbstractPoly(ferrocenylene‐methylmethylene) (PFMM) was prepared and subsequently crosslinked by the aid of either 1,1'‐bis(α‐hydroxyethyl)ferrocene or polyfunctional ferrocene polymers, containing reactive‐CH2OH or‐CH(CH3)OH groups. The thermal behavior of both the primary polymer and the thermoset was investigated. The solubility parameter of PFMM was determined and the degree of crosslinking was studied by solvent swelling and sol fraction measurements. Various thermosetting structural composites were prepared and subjected to mechanical testing.
Failure criteria for polymeric solids
Authors: Nicolais L. , Dibenedetto A. T. 
Published: April 2003

AbstractA theory for predicting the stress–strain characteristics of polymeric solids is developed in terms of a description of microdefect formation. The process of irreversible change in these solids is assumed to be a combination of nucleation of submicroscopic defects at stress inhomogeneities and their subsequent growth to macroscopic dimensions. Straining results in the generation of crazes and cracks which can lead to catastrophic failure through either a general yielding of the material or by brittle fracture. It is assumed that nucleation of submicroscopic defects is an activated process and that defect growth is one‐dimensional and linear. The total strain is expressed as the sum of an elastic recoverable strain and a nonlinear, nonrecoverable strain, and expressions are obtained for the stress as a function of time, temperature, and loading history. The criterion for yielding is defined in terms of a gross volume change associated with cavitation within crazes. The sum of the normal Poisson expansion plus this additional volume change leads to a deflection of the stress–strain curve. The criterion for brittle failure is defined in terms of a critical defect size. If the defects grow to their critical size before the stress–strain curve reaches a maximum, brittle failure occurs. The parameters of the resulting model are calculated for polyphenylene oxide polymer based on constant rate of loading experiments, and then the general creep behavior, including the time required under constant load for cold flow, is predicted. Experimental data are shown to agree with these predictions.
On the single‐point determination of intrinsic viscosity
Authors: Varma T. D. , Sengupta M. 
Published: April 2003

AbstractIn the present paper we have analytically derived a single‐point equation for determining the intrinsic viscosity of a polymer. It is observed that the proposed equation gives a much better agreement with the extrapolated value of [η] over a wide range of concentration for good as well as poor polymer–solvent systems.
Solution of Tung's axial dispersion equation by numerical techniques
Authors: Ishige T. , Lee S.‐I. , Hamielec A. E. 
Published: April 2003

AbstractNumerical methods for the solution of Tung's axial dispersion equation have been developed and comprehensively evaluated. These methods are general and can be applied where the instrumental spreading function is unsymmetrical and nonuniform. Computation times required are comparable to those of the method of Chang and Huang being about 10 sec per case on the CDC6400 computer. Memory requirements are minimal and this should permit their use with minicomputers for data acquisition and processing.
The instrument spreading correction in GPC. III. The general shape function using singular value decomposition with a nonlinear calibration curve
Authors: Rosen Edward M. , Provder Theodore 
Published: April 2003

AbstractThe Gram‐Charlier series was suggested as an empirical instrument spreading function in the first paper (part I) of this series. In the second paper (part II) of this series, the Fourier transform method was used together with the suggested series to solve Tung's integral equation. In this paper, an alternate method for solving Tung's equation is proposed which eliminates some of the limitations of the Fourier transform method. In the approach used in this study, Tung's integral equation is approximated by a set of linear equations. Since no unique least‐squares solution can be computed, a closely related problem whose solution closely approximates the original problem is formulated and solved using singular value decomposition. By avoiding the use of the smallest singular values and forcing the equality of the areas of the corrected and the uncorrected chromatograms, an approximate solution to the original problem is obtained in which the oscillations inherently present due to the ill‐posed nature of the problem are filtered out. The performance of the method with the experimental data given in Part II is indicated.
A moderately high shear viscometer for measuring low specific viscosities
Authors: Chan F. S. 
Published: April 2003

AbstractA simple, moderately high shear capillary viscometer which can be used up to a shear rate of 150,0000 sec−1 is described. The use of a twin viscometer arrangement has eliminated the need of elaborate pressure control and adjustment units. Experimental results obtained by use of the viscometer to measure the specific viscosities of a charged colloid at two different shear rates are presented.
Tensile response of polyacrylonitrile fibers during air heating
Authors: Layden George K. 
Published: April 2003

AbstractAxial stresses generated by polyacrylonitrile filaments heated in air at constant length and length changes of filaments heated at constant load were measured. Fibers subjected to loads less than about 0.1 gpd shrank in the temperature range from about 40°C to 160°C. At about 160°C they began to stretch. Fibers that stretched out again to about their original lengths stiffened temporarily before undergoing a further elongation. At a temperature where the oxidation reaction begins to proceed with appreciable rate, elongation was retarded and finally reversed. Shrinkage was recorded during isothermal heating at 270°C, and a final length was approached when the oxygen content approached about 10 wt‐%. The tension generated when the fibers were restrained from shrinking increased as temperature increased to 160°C but dropped in the temperature range of 160° to 250°C. Tension again built up during isothermal oxidation at 270°C. In the case of one of the samples, the tension generated below 160°C exceeded the ultimate tensile strength of the fibers above 200°C. This condition leads to tensile failures when the filaments are heated in a steep thermal gradient. The tensile behavior of the filaments is discussed in terms of the helical molecular model.
Copolymerization of ethylene with vinyl acetate. I. Effect of polymerization temperature on degree of branching
Authors: Wisotsky M. J. , Kober A. E. , Zlochower I. A. 
Published: April 2003

AbstractThe degree of branching of a series of ethylene–vinyl acetate copolymers was found to be strongly dependent upon polymerization temperature. The copolymers were prepared by free‐radical polymerization and had low molecular weights and molar ratios of ethylene: vinyl acetate greater than 3:1. Nuclear magnetic resonance and infrared studies showed that copolymers prepared at 150°C were highly branched and had little crystallinity. Branches were mainly alkyl groups on the polymethylene backbone segments. There was no evidence of δ‐acetoxyalkyl branches. Long branches originating by intermolecular H abstraction from the acetylmethyl groups were also expected but could not be detected. These results were consistent with an intramolecular “backbiting” mechanism similar to that found in ethylene homopolymerizations. There was little or no participation by the vinyl acetate moiety in the branching scheme. Copolymers prepared at about 90°C had very few long or short branches and were more crystalline. Copolymers prepared between these temperatures had intermediate degrees of branching and crystallinity.
Preparation and purification of bisacid A2 (2,2‐diphenylolpropane 4,4‐dioxyacetic acid). II
Authors: Lenk R. S. 
Published: April 2003

AbstractIn an earlier communication1 the preparation of Bisacid A2 was described. This paper describes the attempts at spotting impurities in the products so obtained by subjecting them to thin‐layer chromatography. No traces of impurities could be detected since no separation whatever was observed. Infrared spectra of pure Bisacid A2 were found to be identical with the spectrum of Nanu and Boboescu.2 It was also seen that the product obtained by the standard preparation in 70–73% yield with a minimum melting point of 173°C could not be demonstrably improved by esterification and rehydrolysis. Second crops from first mother liquors from the aqueous acetic acid recrystallization of the crude precipitated product of the condensation reaction (as well as ether extracts from these mother liquors) showed that both contained material with phenolic OH groups. These are the inpurities in the crude product which must be completely removed during purification if the final material is to be used for the synthesis of unsaturated polyester resins for ultimate use as crosslinked reinforced plastics, as alkyd varnish bases, or as fiber‐forming saturated polyesters and polyamides. The need for adhering to the standard synthetic procedure was confirmed, in particular the need for multistage condensation, giving an effective yield of 70–73% of pure material
Correlation between some solution and mechanical properties of poly(vinyl chloride) and chlorinated poly(vinyl chloride)
Authors: Krozer Shimon , Schneier Bernard 
Published: April 2003

AbstractCorrelations have been found between solubility parameters and some mechanical properties of a series of vinyl polymers containing 56.6–69.9% chlorine when tested below their glass transition temperature. It is shown that stress at yield increases similarly with chlorine content and with the volume occupied by a monomer unit in the polymer. Using the Reiner‐Weissenberg theory of the dynamic strength of materials as a criterion and a rheological model based on a pair of Maxwell bodies in parallel with a Hooke spring, the amount of dissipated and conserved work to yield point was calculated. A parameter, defined as the ratio of work to cohesive energy density, describes the efficiency of the system. The overall efficiency of the system, based on work to break, and proportional efficiency, based on work to yield point, are affected by chlorine content and strain rate. In addition, a potential energy parameter is defined which describes the cohesive energy per volume occupied by monomer unit of the polymer. This parameter is proportional to the total work to break as well as to the ratio of the residual work after yield to total work at all strain rates tested. The major portion of work is conserved up to yield; only a small portion is dissipated. From the yield point to break, after the onset of viscous flow, the major part of this work is dissipated.
Graft polymerization of some vinyl monomers onto acrylic rubber. I. Chain transfer and grafting reaction
Authors: Ide Fumio , Sasaki Isao , Deguchi Seiji 
Published: April 2003

AbstractThe grafting reactions of styrene (St), methyl methacrylate (MMA), and vinyl acetate (VAc) were investigated in the presence of n‐butyl acrylate–acrylonitrile copolymer. Results showed that the nature of monomer and initiator were the major factors influencing the grafting activity. The grafting efficiency was 0.87 for St, 0.26 for MMA, and 0.18 for VAc under the most favorable conditions. Acrylic rubber reduced the rate of polymerization, and the retarding effect increased in the order St, MMA, VAc. The chain transfer constants for acrylic rubber were evaluated to be 4.8 × 10−4 for St, 1.27 × 10−3 for MMA, and 1.45 × 10−3 for VAc. The rate of polymerization and the grafting efficiency decreased with increasing acrylonitrile content in acrylic rubber, while the chain transfer constant of St for acrylic rubber remained practically unchanged.
Characterization of NBR networks from stress–strain and swelling equilibrium measurements
Authors: Hassan A. M. , Ray L. N. 
Published: April 2003

AbstractAn improved stress–strain (S/S) method based on rubber elasticity theory and swelling equilibrium measurements was used to investigate the S/S behavior and the solvent swelling properties of nitrile–butadiene rubber (NBR) and also to study the effects of varying the cure agent and the curing conditions on the crosslinking efficiency in NBR vulcanizates. The S/S curve of completely swollen NBR vulcanizates is, as expected, in agreement with rubber elasticity theory, while that of dry or partially swollen vulcanizates is well described by the Mooney‐Rivlin equation. Determined in benzene, χ was 0.494, compared to 1.338 in cyclohexane and 2.124 in n‐heptane. The degree of crosslinking and the crosslinking efficiency in the NBR vulcanizates, moles of crosslinks produced per mole of crosslinking agent employed in the formula, are largely dependent on the nature of the crosslinking agent used and increase in the following order: peroxide, sulfur tetramethylthiuram disulfide, sulfur N‐cyclohexyl‐2‐benzothiazolesulfenamide, sulfur benzothiazyl disulfide, and finally tetramethylthiuram disulfide.
Preparation and properties of a diaryl sulfone‐containing unsaturated polyester
Authors: Spitsbergen J. C. , Loewrigkeit P. , Kim Y. K. , Lauzé W. L. 
Published: April 2003

AbstractThermoset poly(dipropoxylated bisphenol S–fumarate) showed an increase in heat deformation resistance over thermoset poly(dipropoxylated bisphenol A–fumarate). However, the poly(dipropoxylated bisphenol S–fumarate) required the incorporation of about 20 mole‐% of dipropoxylated bisphenol A into the polyester molecule to be styrene compatible. Condensation polymerization of various ratios of the dipropoxylated bisphenols with fumaric acid was employed to prepare the polyesters. The polyesters were then thermoset by crosslinking with styrene using a peroxide initiator. The thermoset of a poly(dipropoxylated bisphenol S–fumarate), into which 20 mole‐% of the dipropoxylated bisphenol A had been incorporated, had a heat distortion temperature 13°C higher than the poly(dipropoxylated bisphenol A–fumarate) thermoset.
Asymmetric oxidation of poly(vinyl sulfides) with percamphoric acid, aspergillus niger, and penicillium notatum
Authors: Yamaguchi Hidemasa , Minoura Yuji 
Published: April 2003

AbstractThe asymmetric oxidation of poly(phenylvinyl sulfide) (poly‐Ph VS) and poly(t‐butylvinyl sulfide) (poly‐t‐BuVS) was carried out with optically active percamphoric acid, and the optically active polysulfoxides were obtained. The values of the specific rotation for the oxidation products of poly‐PhVS and poly‐t‐BuVS were + 1.0 (having 56% of sulfoxide unit contents) and +9.1 (49%), respectively. The specific rotation of the product increased with increasing the contents of sulfoxide units. The optical rotatory dispersion curves of the oxidation products of poly‐PhVS and poly‐t‐BuVS were positive curves and were found to fit the simple Drude equation. The λc values of the oxidation products (poly‐PhVS, 271 mμ; poly‐t‐BuVS, 212 mμ) suggested that the chromophore which caused optically activity was the sulfoxide group. Similarly, the asymmetric oxidation of t‐BuVS–MMA copolymer, t‐BuVS–styrene copolymer, and PhVS–MMA copolymer was carried out, and the optically active copolysulfoxides were obtained. Furthermore, the biosynthetic oxidation of poly‐PhVS and PhVS–maleic anhydride copolymer treated with aqueous KOH was carried out using Aspergillus niger or Penicillium notatum in Czapeck solution, and the optically active polymers were obtained.
Preparation and properties of some poly(alpha‐olefin sulfones)
Authors: Crawford James E. , Gray Don N. 
Published: April 2003

AbstractThe properties of alpha‐olefin–sulfur dioxide copolymer prepared from the series C8–C18 (even‐numbered) alpha‐olefins and sulfur dioxide are described. These polymers undergo clean thermal degradation and have high permeabilities to oxygen and carbon dioxide. Maximum permeabilities, maximum per cent elongation at the yield point, and minimum density are obtained with the C16‐based polymer. An explanation is proposed involving a competitive plasticizing/side chain crystallization effect.
Graft copolymers of starch with mineral acid salts of dimethylaminoethyl methacrylate. Preparation and testing as flocculating agents
Authors: Fanta George F. , Burr Robert C. , Russell C. R. , Rist C. E. 
Published: April 2003

AbstractMineral acid salts of dimethylaminoethyl methacrylate (DMAEMA) have been graft polymerized onto starch with ferrous ammonium sulfate–hydrogen peroxide initiation. The nitric acid salt was used in most reactions, and graft polymerizations were run in both water and aqueous–organic solvent systems. Increased monomer concentration in water led to an increase in both the percentage of poly(DMAEMA · HNO3) in the graft copolymer (percent add‐on) and the molecular weight of grafted branches. Variations in initiator concentration altered the percent add‐on only slightly but affected the molecular weight of grafted polymer significantly. When swollen starch, in contrast with unswollen starch was used in graft polymerization reactions run in water, the product had a higher per cent add‐on and a larger number of grafted branches of lower molecular weight. The efficiency of starch–poly(DMAEMA · HNO3) graft copolymers as flocculants for diatomaceous silica increased with per cent add‐on; however, variations in grafting frequency and graft molecular weight had less effect on the behavior of these materials as flocculants.
NMR studies of urea–formaldehyde resins
Authors: Kambanis S. M. , Vasishth R. C. 
Published: April 2003

AbstractA procedure used for analyzing urea–formaldehyde resins by NMR spectroscopy was developed. Using this procedure, the condensation of dimethylolurea under acidic and alkaline conditions was sudied. It was confirmed that polymerization under acidic conditions proceeds via the formation of methylene linkages and under alkaline conditions, via the formation of dimethylene ether groups. The more highly condensed water‐soluble urea resins were found to contain hemiformal groups, which could be quantitatively determined. Two butylated urea–formaldehyde resins with varying degrees of butylation were also studied and were found to differ in the number of methylene and dimethylene ether groups and degree of butoxylation. Both were found to contain hemiformal groups. The resin with lower degree of butylation was also found to contain dimethyl ether linkages. None of the resins studied showed any detectable amounts of fully substituted amide groups.