bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal expansion coefficient of polytetrafluoroethylene in the vicinity of its glass transition at about 400°K
Authors: Araki Yoshio 
Published: April 2003

AbstractThe linear thermal expansion of molded PTFE samples of various crystallinities was measured in the vicinity of the transition at about 400°K. In the plot of length of the specimen versus temperature, an inflection of the straight line was observed in the temperature range from 388 to 402°K., the mean value being 396°K. (123°C.) The change of the coefficient of linear thermal expansion at this temperature represents a typical feature of the second‐order transition or the glass transition, designated as Tg. The ratio Tg/Tm is equal to 0.66, in accordance with the so‐called ⅔‐rule between the glass transition temperature (Tg) and the melting point (Tm) of many polymers. The coefficients of linear thermal expansion, below and above Tg, designated α1 and α2 respectively, increased with increasing amorphous fraction, A. The extrapolated values of α1 and α2 at A = 0 were both 0.6 × 10−4 deg.−1, and those at A = 1 were 2 × 10−4 deg.−1 and 3 × 10−4 deg.−1, respectively. The value of TgΔβ/A, where Δβ = 3(α2 – α1), was approximately 0.12 which was closely in agreement with the value of 0.08 or 0.113 predicted by the theories for amorphous high polymers. From these experimental facts, it may be concluded that the transition of PTFE at about 400°K. is the glass transition which occurs in the amorphous region.
Viscoelastic behavior of the polycarbonate of bisphenol A
Authors: Mercier J. P. , Aklonis J. J. , Litt M. , Tobolsky A. V. 
Published: April 2003

AbstractThe viscoelastic properties and thermal expansion properties of bisphenol A polycarbonate have been studied in the neighborhood of the major glass transition temperature. A discussion is given of the possible relation of these properties to the unusual impact resistance of this polymer in the glassy state.
Dielectric behavior and resistivities of polyacrylonitrile and some pyrolyzates
Authors: Van Beek L. K. H. 
Published: April 2003

AbstractDielectric losses in polyacrylonitrile (PAN) and three pyrolyzates were studied between 1 Hz. and 300 kHz. Pure PAN has at 20°C. a very broad loss region with a maximum at 70 Hz. which is ascribed to CN groups. Powdered PAN was pyrolyzed in a nitrogen atmosphere at 170, 220, and 300°C. PAN‐170 has the same loss maximum as the unpyrolyzed polymer, but the maximum had disappeared in PAN‐220. This is attributed to formation of conjugated chains by linking of CN groups above 200°C. However, this does not enhance the conductivity until hydrogen is eliminated above 350°C.
Penetration of water‐soluble solutes into cellulose films
Authors: Aggebrandt Lars , Samuelson Olof 
Published: April 2003

AbstractNonsolvent water determined in very dilute solutions of polymetaphosphate can be used as a measure of the true swelling of cellulose films. From these values and determinations of nonsolvent water under conditions permitting a penetration of the solute into the film, the average molality of trimetaphosphate, polymetaphosphate, and polyglycols inside the film has been determined under equilibrium conditions. With the electrolytes, the molality ratio (film: external solution) is strongly dependent upon the external concentration, which can at least partly be ascribed to the effect of the charged carboxyl groups inside the film. With polyglycols the molality ratio increases with decreasing molecular weight. With dense films there is no detectable penetration of high molecular weight polyglycols. A comparison between various films is made. It is shown that these contain areas of varying packing densities. The dialysis of trimetaphosphate and polymetaphosphate across the cellulose films has also been studied. In dialysis against water there is, within a wide range of concentration, a linear relationship between the rate of dialysis (flux) and the average internal concentration determined in equilibrium experiments. It is interesting to note that this simple relation holds true although the films are inhomogeneous.
Rheological properties of cis‐polybutadiene
Authors: Kraus Gerard , Gruver J. T. 
Published: April 2003

AbstractThe steady‐state viscosity of a number of cis‐polybutadienes was determined as a function of shear rate and temperature by use of a capillary rheometer. Polymers investigated differed in molecular weight distribution and long chain branching. None of the polymers exhibited Newtonian behavior, even at the lowest shear rates attainable. Nevertheless, for polymers of similar molecular weight distribution and minimum branching, all the capillary viscometer data could be reduced to a single curve by a reduced variable treatment. The molecular weight shift function was found to be the same as for polymers exhibiting a Newtonian flow range, i.e., a 3.4th power law in weight‐average molecular weight. Broadening the molecular weight distribution or increasing the degree of long‐chain branching led to increasingly pronounced non‐Newtonian behavior. Tensile creep experiments showed nonlinear viscoelastic behavior for all polymers studied, even at small strains. This behavior was most pronounced in the more highly branched polymers. At very low stresses some of these polymers exhibited extremely high viscosities, the strain being almost completely recoverable. Under larger stresses the viscosity of these rubbers dropped several decades and in the capillary extrusion experiments these polymers flowed readily. This is the same behavior observed previously in high molecular weight branched (multichain) narrow distribution polybutadienes. It is tentatively explained by a constraint of the branch points on the slippage of chain entanglements. The fact that all cis‐polybutadienes exhibit this behavior, while linear polybutadienes made by organolithium initiation do not, suggests that all cis‐polybutadienes may be branched to some extent.
Transient techniques for determining the thermal conductivity of homogeneous polymeric materials at elevated temperatures
Authors: Nagler Robert G. 
Published: April 2003

AbstractLinear thermal conductivity relations at temperatures above room temperature were found from transient temperature–time data for polyethylene, polytetrafluoroethylene, and poly(methyl methacrylate). The relations agree well with literature data for the same temperature ranges, but the computer time and cost of obtaining data points are significantly greater when compared to other measuring techniques of equivalent accuracy.
Separation of elastic and viscous effects in polymer melt extrusion
Authors: Schreiber H. P. , Rudin A. , Bagley E. B. 
Published: April 2003

AbstractViscosity and elasticity of polymer melts respond differently to changes in extrusion conditions and to thermal and shear history of the polymer sample. Some reasons for this difference in behavior are summarized in this communication, which also presents new data on the topic. The results are rationalized on the basis of chain flexibility and interaction concepts, permitting the prediction of certain experimentally verifiable aspects of polymer melt rheology.
The mechanical fatigue limit for rubber
Authors: Lake G. J. , Lindley P. B. 
Published: April 2003

AbstractInvestigations of the dynamic cut growth behavior of vulcanized rubbers indicate that there is a minimum tearing energy at which mechanical rupture of chains occurs. The limiting value is characteristic of each vulcanizate, but is in the region of 0.05 kg./cm. The mechanical fatigue limit, below which the number of cycles to failure increases rapidly, is accurately predicted from this critical tearing energy. Characteristics of cut growth at low tearing energies, and effects of polymer, vulcanizing system, oxygen, and fillers on the critical tearing energy and fatigue limit are discussed.
Studies on blend polymers. mixing of cis‐ and trans‐ 1,4‐polybutadiene
Authors: Minoura Yuji , Iino Hirokazu , Tsukasa Masahiro 
Published: April 2003

Abstractcis‐1,4‐Polybutadiene and trans‐1,4‐polybutadiene were mixed at the ratio in weight of 100/0, 75/25, 50/50, 25/75 and 0/100, and various problems related to the mixing were studied. The mixing was carried out by the three methods, i.e., (1) by rolling, (2) by filler batch polymer, and (3) by coprecipitation of the solution. For the mixed compound and vulcanized rubber, such characteristics as the viscosity of the solution, the Mooney viscosity, x‐ray diffraction, infrared spectra phase separation of the solution, tensile strength, and the swelling ratio in benzene were observed. No marked difference in the state of mixing was noted, regardless of the method of mixing. However, the mixing of filler batch polymer was accomplished more easily than by the rolling method. A 50/50 blend rubber was microheterogeneous and contained particles about 0.5 μ in length, but these did not affect the crystallization, as judged from the observation of the state of dispersion, by means of electron microscopy, x‐ray diffraction, and infrared analysis. The trans‐4 polymer, vulcanized at a much slower rate than Cis‐4. This was revealed by comparing infrared spectra of extracts obtained from the unvulcanized portion after various vulcanization times. The Cis‐4 vulcanizate did not show any crystalline pattern even at 550% elongation.
Measurement of brittleness temperature of neoprene by proton magnetic resonance: Effect of plasticizers
Authors: Smith George W. 
Published: April 2003

AbstractProton magnetic resonance (PMR) line widths, δH, have been determined as a function of temperature for a number of neoprene (polychloroprene) samples. The measurements were made on raw neoprenes (type W, WRT, and GNA) and on neoprenes with plasticizers in both the unvulcanized and vulcanized states. An excellent correlation of the temperature of line narrowing with brittleness temperature found by mechanical tests is reported. The results indicate that PMR may be of value in studying plasticizer properties and in measuring glass temperatures in a manner dependent only on molecular motions rather than on the nature of a mechanical test or on sample statistics.
Irradiation stability of sulfonated styrene resins crosslinked with various divinylbenzene isomers and mixtures thereof
Authors: Wiley Richard H. , Devenuto Giovanni 
Published: April 2003

AbstractThe Co60γ‐irradiation‐induced degradation of sulfonated styrene resins crosslinked with 4 and 8 mole‐% m‐ or p‐divinylbenzene isomers, or mixtures thereof including commercial divinylbenzene have shown a loss in capacity of 5–12.8% at radiation intensities of ca. 290,000 r./hr. and total doses of 0.91–1.90 X 108 rad in the presence of water. The loss is less for the 8% crosslinked resins and is less (2–6%) if irradiated dry. The resins crosslinked with commercial divinylbenzene show a slightly higher loss of capacity (11.2–11.9%) than do others (10.2–10.7%), presumably due to the ethylphenyl contamination. The moisture content also increases on irradiation; 13–16% for the 8% and 2.7–3.0% for the 4% resins at 1.90 X 108 rad. The meta crosslinked resin shows somewhat lower moisture content increase (1.5% for 8%; 0.8% for 4%), indicative of a more stable cross‐linkage. The results are discussed in terms of the reactions involved: desulfonation, hydroxylation, and cleavage of crosslinkages.
Studies on the drawing of polyamide fibers. III. Change of dye‐diffusion behavior into polyamide fibers with drawing
Authors: Takagi Yasuo , Hattori Hiroshi 
Published: April 2003

AbstractThe diffusion constants of an acidic dye (Xylene Fast Blue P) into nylon 6 monofilaments of various draw ratios have been measured at several temperatures by measuring the distance of dye penetration into the cross‐sections of the sample. The results are as follows. The diffusion coefficient of dye increases, reaches a maximum at a draw ratio near 1.6, and then decreases as the draw ratio increases. The activation energy of dye diffusion obtained from the temperature dependence of dye diffusion coefficient remains nearly constant in the initial and middle stages of drawing and increases above a draw ratio of about 3, as the draw ratio increases. The change in the polymer structure during drawing is discussed on the basis of these results.
Mechanical shear relaxation spectroscopy in experimental viscoelasticity
Authors: Miles D. O. , Knollman G. C. , Hamamoto A. S. , Norstrom G. C. 
Published: April 2003

AbstractThe applicability of experimental viscoelastic techniques involving sinusoidal mechanical shear is examined for several types of rheological systems. Data are first presented for NBS polyisobutylene to establish validity for the approach used. General categories that are investigated include elastomers, filled systems, pure liquids, slurries or suspensions, solutions and gels, foodstuffs, and polymer melts. A modification of the familiar time‐temperature superposition routine is proposed by which both entropy and energy relaxation processes can be treated for liquids and polymers alike.
Induction period in the aging of polypropylene
Authors: Tamblyn J. W. , Newland G. C. 
Published: April 2003

AbstractThe ordinary methods for obtaining a rapid estimate of the useful life of a plastic, extrapolations from tests conducted at higher temperatures or at lower stabilizer concentrations than those of actual use, lead to serious errors in estimating the useful life of some stabilized polypropylene compositions. Two methods for obtaining more reliable rapid estimates of useful life have been explored and are reported here: (1) measurement of physical and chemical changes, such as weight loss, stabilizer loss, density increase, dyeability increase, and formation of carbonyl or hydroperoxide groups, which occur during the prefailure stages of oxidative deterioration at the temperature of interest (of these, measurements of stabilizer loss appear the most promising); (2) thermal development of the prefailure oxidative damage initiated at the temperature of interest. This method needs further exploration.
Modification of crosslinking effects in cotton fabrics by swelling and methylation
Authors: Frick J. G. , Kullman Russell M. H. , Reinhardt Robert M. 
Published: April 2003

AbstractThe effects of crosslinking on cotton fabric are changed when the cotton has been chemically modified before crosslinking with an inert substituent, such as the methyl group. The main action of the inert substituent is to preserve swelling ability by hindering fiber deswelling after methylation and during crosslinking. At the levels of modification used, the crosslinking reaction appears to proceed normally, with no effects from reduction in the number of reactive cellulosic hydroxyl groups.
Acetylenic polyesters
Authors: Feit Ben‐Ami , Raucher Daniel , Zilkha Albert 
Published: April 2003

AbstractAcetylenic polyesters containing either residues of 2‐butyne‐1,4‐diol, acetylenedicarboxylic acid, or both of them, were prepared and characterized. Polyesters of 2‐butyne‐1,4‐diol with succinic, adipic, and phthalic acids were obtained as soluble polymers by use of known methods. The polymaleate ester of 2‐butyne‐1,4‐diol was obtained either as a soluble or as an insoluble polymer, depending on the experimental conditions. Relatively high temperature or long reaction periods led to the formation of insoluble polymers. Polyesters of acetylenedicarboxylic acid with diethylene glycol, tetra‐ and hexamethylene glycols, 2‐butene‐1,4‐diol, and 1,4‐cyclohexane dimethanol were prepared by melt polycondensation in bulk. These polyesters were obtained as insoluble, rubbery materials, except those of 2‐butene‐1,4‐diol and 1,4‐cyclohexane dimethanol, which were obtained both as linear or as nonlinear polymers. The insolubility of the polyesters of acetylenedicarboxylic acid was due to crosslinking reactions involving the conjugated system CCCO. While the melt polycondensations in bulk involving either 2‐butyne‐1,4‐diol or acetylenedicarboxylic acid were entirely controlled reactions, those carried out between acetylenedicarboxylic acid and 2‐butyne‐1,4‐diol were very often associated with highly exothermic decompositions involving carbonization. The decompositions could be eliminated when the melt polycondensation in bulk was preceded by a fore‐condensation in solution. Solid, soluble, powdery low polymers (DP = 2–3) having softening temperatures of about 150–175°C. were thus obtained.
Hydrogels from 2‐hydroxyethyl methacrylate and propylene glycol monoacrylate
Authors: Refojo M. F. , Yasuda H. 
Published: April 2003

AbstractHydrophilic three‐dimensional polymer networks (hydrogels) were prepared from 2‐hydroxyethyl methacrylate (HEMA) and propylene glycol monacrylate (PGMA). By wet crosslinking, hydrogels which maintain their original shape and volume relatively well, compared with the dry‐cross‐linked polymer networks, were obtained. The maximum amount of water which can be maintained in transparent hydrogels depends on the hydrophilicity of the monomers, e. g., about 40% for HEMA gels, about 50% for PGMA gels, and 40–50% for HEMA–PGMA copolymer gels depending on the monomer composition. When the water content exceeds this maximum in transparent gels (homogeneous hydrogels), they become opaque and/or spongy (heterogeneous hydrogels). Effects of the amount of crosslinking agent and the initial dilution of the monomer solution upon the swelling behavior of hydrogels were investigated. The temperature dependence of the swelling of these hydrogels and the water permeation through them were also studied.
Strain energy functions for filled elastomers
Authors: Shinozuka M. , Freudenthal A. M. 
Published: April 2003

AbstractIt is the purpose of this research to investigate possible forms of elastic strain energy functions which reproduce the fundamental behavior of compressible, isotropic filled elastomers as observed in experiments. Three different forms of the strain energy function are considered, although they can be classified into two essentially different classes: in the first case, the function is assumed to be the sum of the distortional and the volumetric strain energy, while in the second it represents a possible modification of Mooney's strain energy function. For these three strain energy functions, the relations between axial and lateral deformations under uniaxial tension are plotted together with the result of experiments performed on dumbbell‐shaped specimens of a KCI‐filled polyurethane. The relations in uniaxial tension and compression between the axial stress and deformation are also plotted.
Limiting shear dependence of the intrinsic viscosity of deformable polymer molecules
Authors: Van Oene H. 
Published: April 2003

AbstractPrevious theories of the shear dependence of the intrinsic viscosity of deformable polymer molecules are reviewed. Most of these theories, except those of Cerf and Kuhn and Kuhn, predict that for a polymer homologous series the shear dependence [η]/[η]0 can be expressed in terms of the reduced parameter (M[η]0/RT)ηsq. Such a representation is not in agreement with experimental findings. In this paper a phenomenological model is presented in terms of the Oldroyd rheological equations of state. This model allows one to take into account the finite deformation of the molecule. In terms of this model finite deformation leads to a retarded elasticity, which can be described in terms of the recoverable shear but which does not influence the shear viscosity. The retarded elasticity results, however, in a shift of the [η]/[η]0 versus (M‐[η]0/RT)ηsq. curve along the reduced stress coordinate. This shift is proportional to the molecular weight and independent of the solvent viscosity. Comparison with experiment shows the existence of the predicted shift factor for series of measurements on fractions of polystyrene in a good solvent. The one series of measurements in a theta solvent reveal that in such a solvent the shift vanishes. The implications of this finding are discussed. The shift factor is also shown to have many properties in common with the inner viscosity as defined by Cerf and experimentally evaluated by Leray from the velocity‐gradient dependence of the extinction angle.
Measurement of plastisol gelation and solution by infrared spectroscopy
Authors: Alter Harvey , Kaufman John E. 
Published: April 2003

AbstractThe rate and extent of solution of polyvinylchloride in ester plasticizers has been measured using infrared spectroscopy. The measurement is based on shifts in the carbonyl stretching frequency of the ester linkage, similar to the familiar infrared solvent shifts commonly observed for low molecular weight materials. Double beam techniques were necessary to record the shifts. The intensity of the shifted band increases up to gelation and the rate of increase depends on the temperature of heating. The intensity of the shifted band is directly proportional to the concentration of polymer dissolved in the plasticizer and can be used to measure this concentration at any time during the gelation process. It is estimated that from 17 to 22 per cent of the polymer was dissolved at the gel point after heating at 65°C. and that about 29 per cent of the polymer was dissolved at the gel point after heating at 75°C., for the plastisols used in this study.
Variations in crosslink organization in formaldehyde‐modified cotton celluloses
Authors: Rowland Stanley P. , Cousins Edwin R. , Mitcham Donald 
Published: April 2003

AbstractRates of decrease in crystallinity, as measured by x‐ray crystallinity index, have been followed throughout periodate oxidations of cotton cellulose and formaldehyde‐treated cotton celluloses. Depending upon the conditions under which the agent was introduced, a low level of formaldehyde crosslinks exerted small or large retardation on the rate of decrease of crystallinity index. The extents of decrystallization per unit of oxidation of cotton and crosslinked cotton celluloses are substantially smaller in the initial phase of oxidation than in the later stage, indicative of preferential oxidative attack in the early stage on chain segments of predominantly noncrystalline regions. Relative to unmodified cotton, crosslinked cotton celluloses are characterized by more extensive decrystallization per unit of oxidation in the early phase of oxidative attack (to approx. 40%). From these data, supplemented by electron micrographs and solubilities in cupriethylenediamine hydroxide, uniformity of distribution of crosslinks is shown to increase in this series of formaldehyde‐modified cotton celluloses (at the same level of agent) in the order: form D cotton (nonaqueous treatment) < form W cotton (aqueous treatment) < form V cotton (vapor treatment). Effectiveness of crosslinking (i. e., composite of number of linkages, ratio of intermolecular to intramolecular bonds, low degree of polymerization in crosslink) is indicated to increase from form W to form D to form V cotton.
Molecular weight and molecular weight distribution control in HDPE with VOCl3‐based Ziegler—Natta catalysts
Authors: Mortimer George A. 
Published: April 2003

AbstractSome characteristics of alkoxylated catalysts derived from VOCl3and trialkylaluminum compounds have been examined for ethylene polymerization. Specifically studied were catalysts resulting from reaction of VOCl3with either an alcohol or an alkylaluminum alkoxide, or both, prior to reduction with a trialkylaluminum compound (R3Al). Although the two methods of preparing alkoxylated catalysts did not give identical results, certain overall generalizations can be drawn. In general, as the alkoxide content was increased, the molecular weight distribution was narrowed (by a simultaneous increase inM̄nand decrease inM̄w), polymerization rate was decreased, and the polymer melt index increased at a constant hydrogen level. Alkoxides had a negative effect on rate which could largely be overcome by raising the R3Al/V ratio or using continuous addition of R3Al. By suitably adjusting the alkoxide and hydrogen amounts, the complete range of molecular weights and molecular weight distribution of current commercial HDPE products can be made.