bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological properties of cis‐polybutadiene
Authors: Kraus Gerard , Gruver J. T.
Published: April 2003

The 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

Linear 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

Viscosity 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

Investigations 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

cis‐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

Proton 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

The 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

The 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

The 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

The 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

The 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

Acetylenic 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

Hydrophilic 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

It 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

Previous 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

The 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

Rates 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

Some 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.
Diffusion of dye mixtures in nylon 6. Binary mixtures of disperse dyes
Authors: Kim Jin‐Woo , Iijima Toshiro
Published: April 2003

The diffusion of binary dye mixtures of markedly different chemical constitutions (4‐nitro‐4′‐aminoazobenzene and 1‐amino‐4‐hydroxyanthraquinone) and of similar ones (1‐amino‐4‐hydroxyanthraquinone and 1,4‐dihydroxyanthraquinone) into nylon 6 film was examined. Apparent diffusion coefficients of dyes in the mixture within a single dyeing were determined by the film roll method at 60°, 70°, 80°, and 90°C. Diffusion coefficients of individual dyes used in a mixture of chemically dissimilar dyes are found to change little in comparison with single dyeings, while diffusion coefficients of dyes of similar structures are decreased appreciably. It is suggested that the latter effect is due to the interaction between two dyes in the fiber substrate.
Reactivity of poly(vinyl chloride) containing N‐methyl‐N‐carboxymethyl dithiocarbamate toward metal ions in heterogeneous system and effect of γ‐irradiation on the reactivity
Authors: Nakagawa Tsutomu , Taniguchi Junichi , Fujiwara Yukihiko
Published: April 2003

The reaction of poly(vinyl chloride) containing N‐methyl‐N‐carboxymethyl dithiocarbamate (PSDC) with metal ions in a heterogeneous system and the effects of γ‐irradiation on the reactivity were studied. Slurried PSDC has an affinity for a number of metal ions in aqueous solutions. On the basis of analyses for nitrogen and sulfur and on infrared spectra, a possible chelating structure for PSDC was deduced. The gaseous products evolved during the gamma radiolysis of PSDC under vacuum were measured. Although the dithiocarbamate group bonded to the main chain gave some protection against the dehydrochlorination of poly(vinyl chloride) component, a small amount of the carboxymethyl group was decomposed. It was found that with γ‐irradiation doses up to 30 Mrad, only about 1 mole‐% out of 17.6 mole‐% of N‐methyl‐N‐carboxymethyl dithiocarbamate in the polymer was decomposed. It was shown that the reactivity of the irradiated PSDC in water toward metal ions was almost the same as that before irradiation.
The determination of the addition variation and geometrical isomerism of a polybutadiene as a function of molecular weight by preparative gel permeation chromatography and infrared analysis
Authors: Mirabella Francis M. , Barrall Edward M. , Johnson Julian F.
Published: April 2003

The addition variation, 1,2 and 1,4 units, and the geometrical isomerism, 1,4‐cis and 1,4‐trans units, of a fractionated polybutadiene were determined as a function of molecular weight using preparative gel permeation chromatography followed by infrared analysis of the fractions. Both the addition variation and geometrical isomerism remained essentially constant across the molecular weight distribution.
Ultrahigh molecular weight polyethylene as used in articular prostheses (a molecular weight distribution study)
Authors: Crugnola Aldo M. , Radin Eric L. , Rose Robert M. , Paul Igor L. , Simon Sheldon R. , Berry Mark B.
Published: April 2003

Currently there is widespread use of ultrahigh molecular weight polyethylene (UHMWPE) acetabular components in total joint replacement prostheses. What has been most surprising about the wear of UHMWPE under such circumstances is the occurrence of brittle fracture. Such fracture had not been observed in the usual engineering tests done in the laboratory on UHMWPE. It was only when prosthese which had been removed from patients were examined or run in hip joint simulators with serum or synovial fluid as the lubricant, that brittle fracture was encountered. The problem of environment‐enhanced brittle fracture in plastics dates back to 1946. Interestingly, the phenomenon was first described in polyethylene. The prime variables involved are polymer molecular weight, sensitizing environment, stress filed, and temperature. Other things being equal, brittle behavior in polyethylene is extremely sensitive to the amount of low molecular weight polymer present. In the light of the foregoing we have studied the molecular weight distribution in six commercially available UHMWPE components. These were obtained from six different manufacturers. The specimens were characterized both on their bearing (wear) surfaces and in their interior bulk. The results obtained indicate that:

The UHMWPE components contain substantial amounts of low molecular weight polymer.

The UHMWPE components differ significantly in molecular weight distribution.

The UHMWPE components contain substantial amounts of crosslinked polymer.
Polymer flow through capillaries of variable diameter
Authors: Chee K. K. , Yap Y. H. , Rudin A.
Published: April 2003

A polystyrene melt has been extruded through successive capillaries arranged to produce converging and diverging flow patterns through the twin orifices. Applied pressure at fixed mass flow rate through the combined dies is equal to the sum of the pressure drops in the single capillaries in both flow modes. The Bagley end correction was found to apply to each die in the sequence. Bagley plots were linear with a particular upper capillary at given apparent shear rate in the lower die. No effect of shear history could be detected on the viscous behavior of the polymer, but preshearing in converging flow produced a slight reduction in die swell.
Stress growth and relaxation of a molten polyethylene in a modified weissenberg rheogoniometer
Authors: Nazem F. , Hansen M. G.
Published: April 2003

A Weissenberg rheogoniometer was modified1‐3 to improve sample temperature uniformity and constancy (to within ±0.5°C) and to give a quicker response to normal thrust changes (estimated gap change ≤0.1 μm/kg thrust; gap angle = 8.046°; gap radius = 1.2 cm; servomechanism replaced by an open‐loop cantilever spring of 10 kg/μm stiffness). Low‐density polyethylenes (IUPAC samples A and C, melt index at 190°C = 1.6) at 150°C were used in step‐function shear rate experiments. Inspection of marked sectors in the samples showed substantial uniformity of shear at values of Ṡ = 0.1, 2, and 5 sec−1; for Ṡ = 10 sec−1 and S ≤ 2 shear units (S = Ṡt), the shear was highly nonuniform at and near the free boundary. Using selected premolded samples A, scatter in seven replicate tests at Ṡ = 1.0 sec−1 did not exceed ±6% for N1(t) and ±5% for σ(t) (N1 = primary normal stress difference; σ = shear stress; t = time of deformation from the initiation of experiment at zero time). N1(t) and σ(t) data agreed with Meissner's1; for Ṡ = 0.1, 2.0, 5.0, and 10.0 sec−1, torque maxima occurred at S = 6 shear units, and thrust maxima occurred in the range of 10 to 20 shear units. σ(t) and N1(t) data do not satisfy the van Es and Christensen4 test for rubber‐like liquids with strain rate invariants included in the memory function. On cessation of shear (after a shear strain S at constant shear rate Ṡ), initial values of −dσ(t)/dt and −dN1(t)/dt were found to depend strongly on S, in some cases passing through maxima as S was increased. After shearing at Ṡ = 0.1 sec−1 for 500 sec, such that stresses became constant, stress relaxation data satisfied Yamamoto's5 equation of dN1(t)/dt = −2Ṡσ(t).
Development of an autographic falling‐weight impact system
Authors: Gonzalez Henry , Stowell W. J.
Published: April 2003

The objective of this project was to develop a system that would allow the determination of the energy absorbed during fracture in a falling‐weight impact test. Equipment was developed which would allow the force exerted by the impact tup on the specimen to be determined during the test. Using this information and the equations developed, it was possible to convert force‐versus‐time traces on an oscilloscope to energy absorbed. Tests were conducted to compare the autographic method with the normal falling‐weight method. The system was shown to give results which are similar to results from normal falling‐weight impact tests, but requires much fewer specimens. Tests can be made and results can be obtained on small sample sizes, since results are obtained for each specimen tested. Also, a more representative value of falling‐weight impact strength can be determined in cases where there are mixed failure modes. The autographic system may be used in those instances where there are limitations of material, and with further use it may eventually replace the normal falling‐weight impact determination.
Behavior of cellulose grafted with poly(methyl methacrylate) and polyacrylonitrile toward some direct and reactive dyes
Authors: Kamel M. M. , Hebeish A.
Published: April 2003

Viscose rayon fibers modified with polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) were dyed with some direct and reactive dyes. Exhaustion rate of the dye onto fibers was governed by the amount and nature of the polymer grafted. In general, the dye affinity for cellulose and dye exhaustion onto fibers decreased as the graft yield increased. Dye affinity for the PAN–cellulose graft copolymers was greater than that found with PMMA–cellulose graft copolymers. Except in a few cases, the tendency of cellulose graft copolymers of ca. 13% graft to accept direct dyes was more than that of the untreated cellulose, whereas the affinity of reactive dyes for cellulose graft copolymers of up to ca. 43% polymer was more than that of untreated cellulose. The dye fixation, based on the weight of cellulose component, increased as the graft yield increased. The dyeability of cellulose oxidized with ceric ammonium nitrate was also examined. Oxidation of cellulose prior to dyeing reduced the affinity of the dye for cellulose.
Investigation of high‐density polyethylene film surface treated with chromic acid mixture by use of 2,4‐dinitrophenylhydrazine
Authors: Kato Koichiro
Published: April 2003

High‐density polyethylene films were treated with chromic acid mixture. 2,4‐Dinitrophenylhydrazine was reacted on the treated films. The changes in amounts of 2,4‐dinitrophenylhydrazones formed in the films were inferred by comparing the absorptions in the ultraviolet spectra. The changes in the film surfaces by chromic acid mixture treatment were investigated by comparing the changes in the amount of the hydrazones with changes in water wettability of the treated films. Scanning electron micrographs of the treated film surfaces were taken. Oxidation of the film surface zone, partial breakdown of polymer in the film surface zone, and oxidation of surface zone bared from the film inner zone seem to have occurred with increase in treatment time. When the treatment temperature was raised, the increase in carbonyl groups in the surface of the high‐density polyethylene film with rise in treatment temperature seems to have been prevented by an increase in partial breakdown of polymer in the film surface.
Polyblends. I. Mechanical properties of polyblends of butadiene–acrylonitrile elastomers and copolymers of vinyl stearate and vinyl chloride
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Riser George R. , Wrigley A. N.
Published: April 2003

Several nitrile rubber elastomers were polyblended, across the composition range, with selected polymeric compositions containing vinyl chloride. The compositions incorporated were (a) bulk poly(vinyl chloride) (PVC); (b) copolymers of vinyl stearate and vinyl chloride containing, respectively, 0.21, 0.36, and 0.47 weight fraction of the vinyl ester; and (c) mixtures containing the same weight fractions of di‐2‐ethylhexyl phthalate (DOP) with PVC. Mechanical, viscoelastic, optical, and volatility properties were studied on all blends in this first paper. To accurately compare the mechanical properties of polyblends of different systems, a criterion of mechanical equivalence was taken as the observance of similar stresses at break for compositions selected to have identical 100% moduli. Optimum mechanical equivalence, therefore, occurred at the largest ratios of 100% modulus to break stress for all systems compared. Optimum mechanical property equivalence was observed for NBR blends with PVC and for similar blends of both internally and externally plasticized systems containing 0.21 weight fraction of plasticizer. However, considerably more nitrile rubber was needed for PVC blends to acquire the properties of the plasticized systems. Mechanical equivalence was observed, but was not optimum for systems having more plasticizer because tensile strengths were lower. Polyblending with NBR improved the toughness and low‐temperature properties of starting vinyl stearate copolymers. Improved toughness was indicated by the expansion of areas under stress–strain curves. Refractive index matching appeared to explain the transparency of the best films and their relative freedom from haze. On heating at 85°C, poly(vinyl chloride) and the copolymer polyblends suffered no volatility loss. Volatility of DOP from the blends was 1.5 times greater than for PVC–DOP mixtures. Because modulus–temperature curves and mechanical Tg values of the filler component shifted with composition, the mechanical behavior of these blends was in harmony with an accepted standard of interdomain compatibility.
Polyblends. II. Isochronal viscoelastic parameters for polyblends of butadiene–acrylonitrile elastomers and copolymers of vinyl stearate and vinyl chloride
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Riser George R. , Wrigley A. N.
Published: April 2003

Isochronal viscoelastic parameters were obtained for the polyblends of nitrile rubbers with internally and externally plasticized poly(vinyl chloride) (PVC) whose mechanical properties were studied in the previous paper. Thus, the room‐temperature mechanical properties of the previous paper were extended to included a wide temperature range in this work. Phase immiscibility, indicated by the observance of two glass transition temperatures, using differential scanning calorimetry, was observed for most of the polyblends. In contrast, blend compatibility was indicated by mechanical measurements, because the inflection temperatures of the isochronal curves (Ti) shifted with blend composition. It was concluded that mechanical spectroscopy‐monitored volume elements large enough to include contributions to viscoelastic response from both phases; this caused the curves to shift with composition. On the other hand, the much shorter‐range segmental responses characteristic of Tg produced transitions at the discrete temperature intervals representative of each phase. Using a relation between torsional stiffness at room temperature and tensile strength, failure strengths with respect to temperature were estimated and compared at varied free‐volume increments (T − Tg) up to 50°C. Approximate equivalence was found by this procedure for fillers of bulk PVC and those containing 21 wt‐% of both internal and external plasticizer, in analogy with findings for mechanical property optimization of the previous paper. Low‐temperature properties and viscoelastic response of the polyblends containing vinyl stearate copolymers were greatly improved over their neat state. In addition, data from isochronal temperature–composition diagrams suggested viscoelastic equivalence, but greater ease of processability for the blends containing vinyl ester, compared to the others.
Oxidation behavior of isoprene/styrene copolymer and butadiene/styrene copolymer
Authors: Sakota Kazuyuki , Okuno Kenji , Okaya Takuji , Tsuchiya Shizuo
Published: April 2003

The oxidation behavior of emulsion isoprene/styrene copolymer (SIR) and emulsion butadiene/styrene copolymer (SBR) by heat aging of ultraviolet irradiation in air has been investigated from the change of gel fraction, intrinsic viscosity, molecular weight distribution, and mechanical properties. Upon oxidation by heat aging, SIR predominantly undergoes chain scission and shows only a slight change of mechanical properties, whereas SBR predominantly undergoes crosslinking and sharply becomes brittle. Upon oxidation by ultraviolet irradiation, SIR undergoes both chain scission and crosslinking and shows almost no substantial change in mechanical properties, whereas SBR predominantly undergoes crosslinking and sharply becomes brittle. The probability ratio of chain scission to crosslinking with oxidation by heat aging or ultraviolet irradiation was determined by the method of Charlesby et al. The results can reasonably explain the oxidation behavior of the copolymers described above.
Effects of cyclic loading on the dynamic viscoelastic properties of crosslinked polymers reinforced with randomly distributed short glass fiber
Authors: Kodama Minekazu
Published: April 2003

This study describes the effects of the application of cyclic uniaxial loading on the viscoelastic response properties of two crosslinked copolymers which contain short, randomly distributed glass fibers as reinforcing agents. The additional viscoelastic dispersion, observed with unstressed glass‐filled polymers and which occurs somewhat above the primary glass transition temperature of the matrix resin, disappeared as a result of the applied cyclic loading. A concurrent lowering of the rubbery modulus of the composite was observed.
Oxidative degradation of poly(vinyl chloride)
Authors: Decker Christian
Published: April 2003

Rates of oxygen consumption and formation of oxidation products were determined in γ‐initiated oxidation of poly(vinyl chloride) (PVC) at 25°C. Data are given for five dose rates and correlated on the basis that the overall oxidation is the sum of two reactions that are first order and half order in rate of initiation. The principle oxidation product is hydroperoxide, formed by the half‐order reaction, whereas alcohol and carbonyl compounds result mostly from first‐order reactions. These products account for 77–80% of the total oxygen absorption. The presence of oxygen was found to increase twofold the rate of dehydrochlorination of irradiated PVC. A reaction scheme is developed which assumes that a significant fraction of the interactions of tertiary peroxy radicals is nonterminating and yields alkoxy radicals which propagate or decompose by β‐scission. This decomposition occurs mostly by splitting off a chlorine atom with formation of a ketone and, to a lesser extent, by CC cleavage which accounts for the observed decrease in molecular weight of the oxidized PVC. Polystyrene was found to be much more resistant to oxidation than PVC. A classification of some commercial polymers in function of their susceptibility to oxidation is proposed.
Theoretical predictions of the elastic moduli of polymer‐impregnated hardened cement paste and mortars
Authors: Whiting D. , Kline D. E.
Published: April 2003

Hardened coment pastes with water‐to‐cement (w/c) ratios of 0.4 and 0.6 and hydration times of one, three, seven, and 28 days were oven dried and subsequently impregnated with an epoxy resin formulation which was then polymerized in situ at 75°C. Portland cement mortars containing Ottawa sand and asbestos fibers as filler were also subjected to this impregnation process. Dynamic elastic moduli (E′) were measured at audio frequencies over a range of temperatures (100–400°K). Experimental values were compared with moduli calculated using various theoretical approaches based on two‐phase composite materials theory. Best agreement between experimental and calculated results occurs when Wu's theory for spherical polymer inclusions was applied to a cement‐based matrix. In the case of polymer‐impregnated mortars, experimental and theoretical results are in closest agreement at low temperatures and at low volume fraction of filler.
Slow release of water‐soluble salts from polymers
Authors: Narkis Nava , Narkis Moshe
Published: April 2003

Release rates of NaCl and NaF from mixtures with polystyrene, polyethylene, thermosetting polyester, and crosslinked polyethylene have been studied. Salt/polymer granules were prepared by melt mixing under different conditions. The release process was studied in batch as well as continuous systems. The salt release from polymer into water depends on such parameters as salt content, temperature, water flow rate, and salt particle size.
Water‐soluble polymers as retention aids in a model papermaking system. II. Poly(vinylpyridines)
Authors: Howard G. J. , Hudson F. Lyth , West Jeremy
Published: April 2003

Three poly(4‐vinylpyridines) and a poly(2‐vinylpyridine) were studied for their effectiveness at increasing the retention of titanium dioxide a model papermaking system at pH 3.8. All the polymers are very efficient retention aids and do not greatly increase the time for the paper sheet to be formed. They are well adsorbed by both cellulose fibers and titanium dioxide. Although fiber suspensions are weakly flocculated by the poly(vinylpyridines), pigment suspensions are stabilized. Flocculation studies on mixed suspensions show that the poly(vinylpyridines) have a powerful heterocoagulation effect which mirrors the retention results. Some results are also reported in which the pH is brought to 6.5; under these conditions, polymer adsorption and its consequent effects compete with polymer precipitation.
Calibration of gel permeation chromatography columns using polydisperse polymer standards
Authors: McCrackin Frank L.
Published: April 2003

Two methods of calibrating gel permeation chromatography columns are given. The first method uses polymer standards that may have broad molecular weight distributions. Either the weight‐, number‐, or viscosity‐average molecular weight of each standard must be known. This method neglects column peak spreading. The second method requires polymer standards of moderately narrow molecular weight distributions for which both the weight‐ and number‐average molecular weights are known. However, the second method determines both the column peak spreading and calibration of the column. The second method is applied to calibration of a column using polystyrene standards. The column peak spreading is found to be small and independent of molecular weight for this column.
Bimodal character of polyester–solvent interactions. III. The effects of morphology on the nature of the interaction of nonaqueous solvents with the aromatic and the aliphatic ester residues of poly(ethylene terephthalate)
Authors: Knox B. H.
Published: April 2003

The extent of solvent‐induced shrinkage, swelling, and crystallization of polyester is found to be dependent on the initial morphology of the material. However, the nature of the interaction of the nonaqueous solvents with the aromatic and the aliphatic ester residues of poly(ethylene terephthalate) is found to be independent of morphology and only dependent on the differences in the stereochemical nature of the given solvent and polyester residue.
The absorption of direct dyes by crosslinked cellulose. I. The equilibrium of dyeing
Authors: Ibe E. Chianakwalam , Valko Emery I.
Published: April 2003

The effect of the degree of chemical crosslinking of cellulose with two bifunctional crosslinking agents dimethylol ethylene are (DMEU) and bis (hydroxyethyl) sulfur (BHES), on the equilibrium absorption of the direct dyes Chlorazol Sky Blue FF (C.I. Direct Blue 1) and Chrysophenine G (C.I. Direct Yellow 12) has been reported. The results show the increasing reduction of equilibrium dye absorption with increasing crosslink density. However, the maximum loss of absorption is about less than half of the amount absorbed by uncrosslinked cellulose. The results have been interpreted by reference to the parameters affecting the free energy of dyeing and the relevant models (pore model and gel model) available for explaining the fine structure of swollen cellulose.
The absorption of direct dyes by crosslinked cellulose. II. Rate of dyeing and diffusivity
Authors: Ibe E. Chianakwalam , Valko Emery I.
Published: April 2003

The effect of crosslinking in the dry state on the rate of dyeing of cellophane with two direct dyes, Chrysophenine G and Chlorazol Sky Blue FF, has been studied. Dimethylolethyleneurea and bis(hydroxyethyl) sulfone were the crosslinking agents. It was found that the rate of dyeing was reduced at high degree of crosslinking by more than 90%, whereas the amount of dye absorbed at equilibrium was reduced by only 40%. It was concluded that the major factor in the practical undyeability of the crosslinked cellulose fibers in commerce is the reduction of the rate of dyeing rather than that of the absorption at final equilibrium. The average diffusivities of the dyes in the cellulose film were calculated from the rate data. The diffusion coefficients as functions of the dye concentration in the films were estimated from the diffusivity values. The two models of swollen cellulose, the pore model and the gel model, were applied to explain the effect of crosslinking on the diffusion coefficients. The pore model offers a satisfactory explanation by assuming that crosslinking reduces the average pore diameter and therefore increases the drag and also the tortuosity. The gel model offers an equally satisfactory explanation by assuming that crosslinking reduces the free volume by increasing the rigidity and concentration of the cellulose chains in the cellulose gel.
Acetylene–butadiene copolymer for polymer coatings
Authors: Furukawa Junji , Kobayashi Eiichi , Kawagoe Takahiro
Published: April 2003

Low molecular weight,M̄n1800–2400, and soluble copolymers of acetylene and butadiene were prepared by nickel naphthenate–diethylaluminum chloride catalyst. These copolymers possess high cure tendency to give insoluble and highly crosslinked films. The curing ability can be controlled by the amount of acetylene content in the copolymer and is in the following order: acetylene–butadiene copolymer > tung oil >cis‐1,4‐polybutadiene ≫ linseed oil, 1,2‐polybutadiene, butadiene–isobutylene copolymer. Chemical modifications of the copolymer such as maleic reaction, metallation by lithium or sodium, graft polymerization by methyl methacrylate, 4‐vinylpyridine or vinyl acetate, and epoxidation were also examined. The divinyl methylene in the copolymer gives a high cure tendency and high chemical reactivity.
Iodine‐initiated, solid‐state copolymerization of tetraoxane with 1,3‐dioxolane in the presence of methylal. II. Properties of copolymer obtained by beaker‐scale copolymerization
Authors: Morita Yosuke , Ishigaki Isao , Watanabe Yuhei , Okubo Hiroshi , Ito Akihiko
Published: April 2003

In order to elucidate the copolymerization mechanism, the properties of the copolymer obtained by the iodine‐initiated copolymerization of the tetraoxane–1,3‐dioxolane–methylal system have been studied using gas chromatography, microscopy, scanning electron microscopy, differential scanning calorimetry, and gel permeation chromatography. From the behavior of the thermal stability and gas chromatography of the reaction mixture, it was found that reactivity of 1,3‐dioxolane with active center is larger than that of tetraoxane, i.e., more than 90% 1,3‐dioxolane is consumed at an early stage of the polymerization. The results obtained by microscopy, DSC, and GPC of the copolymer suggested that the copolymerization proceeds from the surface to the center of the tetraoxane crystal as if it were a core model. It was also suggested that the heterogeniety in copolymer properties can be explained not only by heterogeneous dispersion of 1,3‐dioxolane in tetraoxane crystal, but also by the difference of reactivity of 1,3‐dioxolane with the active center.
Iodine‐initiated, solid‐state copolymerization of tetraoxane with 1,3‐dioxolane in the presence of methylal. III. Study on larger‐scale copolymerization
Authors: Ishigaki Isao , Morita Yosuke , Nishimura Koichi , Yokooji Makoto , Ito Akihiko
Published: April 2003

The iodine‐initiated, solid‐state copolymerization of tetraoxane with 1,3‐dioxolane in the presence of methylal has been studied using 15 l kneader‐type reactor. Effects of the addition method of the 1,3‐dioxolane–methylal solution on the copolymerization has been mainly discussed. The copolymerization rate, intrinsic viscosity, and thermal stability of the copolymer were found to be largely dependent on the addition method of the 1,3‐dioxolane‐methylal solution, i.e., if the solution is added all at once, properties of the copolymer are different at the early stage then at the later stage of the copolymerization, while on successive addition of the solution, the copolymer properties become almost constant irrespective of the polymerization time. Therefore, it was suggested that 1,3‐dioxolane and methylal can easily diffuse through the copolymer layer formed on the surface of the tetraoxane particle and reacts with an active center as copolymerization proceeds.