bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultraviolet spectroscopic studies on aqueous polyvinyl alcohol solutions. Part I. Characterization of chromophores
Authors: Lloyd D. G. 
Published: April 2003

AbstractThe ultraviolet spectra of aqueous solutions of polyvinyl alcohol have been examined with a view to identifying the chromophores present. The spectrum may be modified by reduction with hydrogen over Raney nickel at room temperature, which is specific for ethylenic unsaturation, and by reduction with sodium borohydride, which is specific for carbonyl groups. An analysis of the resulting spectra supports the proposal that the ultraviolet absorption of aqueous polyvinyl alcohol solutions arises from polyene‐carbonyl chromophores of empirical formulas: (CHCH)nCO, where n may vary from 0 to 3.
The relationship between structure and properties of crystalline, high‐melting polyhydrocarbons
Authors: Campbell Tod W. , Haven A. C. 
Published: April 2003

AbstractTwenty‐two α‐olefin monomers with varying degrees and types of branching in the lateral group have been polymerized and the polymers characterized. In general, the closer the branching in the side chain is to the polyethylene trunk, the higher the degree of crystallinity and the crystalline melting point. The degree of branching and the symmetry of the branches also affects the melting point and crystallinity markedly. Relationships have been drawn between type and position of the branch and melting point.
The aging of thiuram disulfide vulcanizates and their mechanism of vulcanization
Authors: Dunn J. R. , Scanlan J. 
Published: April 2003

AbstractThe aging of sulfurless tetraalkylthiuramdisulfide vulcanizates has been studied by the stress‐relaxation technique, the general behavior being independent of the nature of the alkyl group. The aging in air at 100°C. of fully cured vulcanizates is excellent before acetone extraction but rapid after it, due to removal of zine dialkyldithiocarbamates which are powerful antioxidants. In undercured vulcanizates, the network breakdown at 100°C. after extraction is much less than in fully cured samples, and there is considerable crosslinking during the aging. This behavior is attributed to the presence of a vulcanization intermediate which, at 100°C., brings about crosslinking with formation of zine dialkyldithiocarbamate and which cannot be removed by acetone extraction. The presence of such an intermediate is confirmed by the ability of extracted undercured thiuram vulcanizates to be further crosslinked in the press at 140°C. Previous theories regarding thiuram vulcanization are discussed in the light of these observations. The rapid initial relaxation of unextracted undercured vulcanizates may be due to the breakdown of this vulcanization intermediate. During the thermal aging of apparently fully cured samples, some crosslinking occurs which is considered to be due to a direct oxidative reaction of dithiocarbamates. Unextracted thiuram vulcanizates degrade very little on illumination with ultraviolet light (wavelength 365 mμ), but, after extraction, the photolytic aging becomes more rapid. There is no variation in the rate of this type of aging with degree of cure, presumably because the vulcanization intermediate is light stable.
Orientation in extruded polyethylene films
Authors: Aggarwal Sundar L. , Tilley George P. , Sweeting Orville J. 
Published: April 2003

AbstractA discussion of the methods for studying orientation of crystalline and amorphous regions in polyethylene films is given. Extruded polyethylene films and films after having been stretched approximately 200% were studied by the methods of x‐ray diffraction and absorption of polarized infrared radiation. It is shown that in extruded polyethylene films the a‐axes of the crystallites are oriented parallel to the extrusion direction. The amorphous regions in these are either not oriented or show only to a slight degree the orientation of chains perpendicular to the extrusion direction. When the polyethylene films are stretched, both the crystallites and the amorphous regions become oriented. In stretched films, the orientation of the crystallites is with c‐axis parallel to the stretching direction, and the chains in the amorphous regions are also oriented parallel to the stretching direction. Two mechanisms by which a‐axis orientation may arise during extrusion of polyethylene films, and a convenient method for determining the relative degree of a‐axis orientation in polyethylene films are given. The relative degrees of a‐axis orientation as determined by x‐ray diffraction and dichroism of absorption at 13.70 μ are compared for a number of film samples.
Mastication of rubber. VII. Mechanical degradation of polymers during mastication
Authors: Ceresa R. J. , Watson W. F. 
Published: April 2003

AbstractThe degradation on mastication of polymers brought into a rubbery state by incorporation of liquids or rise in temperature is accounted for by the mechanicochemical mechanism previously advanced to explain the degradation of rubbers. The dependence of the reaction on shear rate has been shown indirectly, as with rubbers, by the negative temperature coefficient of reaction, and also directly by variation of masticator rotor speed and design. A further new feature is the influence of the nature as well as concentration of plasticizer on the rate of degradation and a correlation with the softening of the polymer. A limiting molecular weight is reached on prolonged mastication from whatever initial molecular weight.
The deformation of foamed elastic materials
Authors: Gent A. N. , Thomas A. G. 
Published: April 2003

AbstractA theoretical treatment is given which predicts the behavior of a foamed elastic material on the basis of a model consisting of a network of thin threads. Two cases are considered: (1) small strains, and (2) finite compressions, when the major part of the deformation of the threads is attributed to buckling. The behavior is given in terms of Young's modulus of the matrix and the density of the foam. Measurements of the load‐deformation relations for small tensile strains and finite compressions are described for natural rubber foams prepared from latex. A wide range of density is covered (0.09–0.57), giving a variation of compression hardness of about 100:1. Satisfactory agreement with theory is found for both the cases considered, indicating that the basic concepts of the structure and mode of deformation are correct.
Thermal expansion measurements and transition temperatures, first and second order
Authors: Dannis Mark L. 
Published: April 2003

AbstractTransitions in polymers have been studied with the use of a differential expansion apparatus modified from a design described by K. L. Floyd. Materials ranging from uncured, soft rubbers to hard, waxy solids have been studied from above room temperature down to liquid air temperatures. Both the first‐order transition temperature, Tm and the second‐order transition temperature, Tg, can be identified. Multiple changes in slope of the expansion curves indicate the possibility of additional second‐order transitions. Expansion curves for several diene rubbers are presented, illustrating typical transition phenomena. Expansion curves for several polyolefin materials are presented which illustrate changes in Tg and in the low temperature expansion coefficient with changes in the structure of the polymer.
Resistance to ozone cracking in elastomer blends
Authors: Andrews E. H. 
Published: April 2003

AbstractThe phenomenon of ozone cracking has been investigated for elastomer blends containing an ozone‐reactive phase (natural rubber) and an ozone‐inert phase (ethylene–propylene rubber). Electron microscopical studies reveal phase separation in the blend and the locus of ozone attack. Ozone cracks traverse the reactive phase and occasionally jump across inert particles without severing them. This mechanism provides the basis of a theory which correctly predicts the dependence of both the critical stored energy for ozone cracking and the crack density upon the blend composition.
Diffusion of liquids in cellulose membranes
Authors: Arnowich B. , Carangelo S. 
Published: April 2003

AbstractDiffusion of small quantities of liquids in porous polymeric substrates has been studied by means of a radiotracer technique. The procedure has been applied to the permeation of five different types of paper stock by ethylene‐1,2‐C14 glycol. Data obtained indicate that under the experimental conditions the diffusion analogy is valid for solvent penetration in the systems studied. The method should have general applicability to studies of diffusion rates in cellulosic and other membranes and to investigations where only small quantities of diffusant are available.
The steady flow shear modulus of polymer melts
Authors: Blyler L. L. , Huseby T. W. 
Published: April 2003

AbstractRelaxation times of polyethylene melts have been measured by Aloisio, Matsuoka, and Maxwell. One implication regarding their observations is that the elastic properties of polymer melts must be time‐dependent. In particular, the steady‐flow shear modulus depends on the strain rate. Some interpretations of data in the literature have been based on concepts in rubber elasticity where the steady‐flow modulus is an equilibrium value, independent of strain rate. We have used Pao's theory for viscoelastic flow together with measurements of relaxation times to discuss the strain rate dependence of the steady‐flow shear modulus of melts. The existence of a strain rate‐dependent shear modulus leads naturally to a nonlinear relation between shear stress and recoverable shear strain. The conclusions regarding the molecular weight dependence of the modulus also differ from interpretations based on rubber elasticity.
Emulsion polymerization of ethylene. III. Factors affecting the stability of polyethylene latexes
Authors: Stryker Harry K. , Helin Arthur F. , Mantell Gerald J. 
Published: April 2003

AbstractA semiquantitative method for assessing the amount of visible solid matter in polyethylene latexes is described. As judged by this method and by the presence of particles larger than 50 μ, the stability of the latexes was related to (1) the type and concentration of post‐emulsifier added to the latex, (2) the average size of the polymer particles, and (3) the concentration of solids. Generally, the appearance was better when the latexes had a low (30%) concentration of solids, a large (800 A.) average particle diameter, and enough post‐emulsifier to cover most of the polymer surface. Specific samples, however, having a high (36%) concentration of solids and a small (300 A.) average particle diameter also showed good storage stability. According to tests on selected latexes, good resistance to coagulation by mechanical shear was obtained only if the surface of the polymer was completely covered with emulsifier. When polyethoxylated alkylphenols were used as post‐emulsifiers, an inverse relation appeared to exist between latex stability and average number of ethylene oxide units per emulsifier molecule. Moreover, the addition of each ethylene oxide group increased the apparent area of the emulsifier molecule by about 4 A.2
Thermally induced solid‐state polymerization in nylon 66
Authors: Griskey Richard G. , Lee Byong Il 
Published: April 2003

AbstractThe thermally induced solid‐state polymerization of 66 nylon was investigated. It was found that the rate‐controlling step in the process is chemical reaction. A mechanism of the form, rate = ktn was shown to hold. The reaction rate constant was found to be k = 1.53 × 1010 exp [ − 12,960/RT]. Units of k are (hours)−0.51. Activation energy determined in this work compared closely to that determined for nylon 6 solid‐state polymerization.
Application of the theory of elasticity and viscosity of two‐phase systems to polymer blends
Authors: Uemura Shinsaku , Takayanagi Motowo 
Published: April 2003

AbstractAn attempt was made to evaluate the apparent elastic constant of a two‐phase system G from those of the components of the system. The modulus G is expressed as follows:

where G1 and G2 are the shear moduli of the suspending medium and the suspended particles, respectively, v1 is the Poisson ratio of the medium, and v is the volume fraction of the particles. The results for modulus were extended to dynamic viscoelasticity by the corresponding principle. Experimental verifications with dynamic viscoelasticity data were conducted for the system of styrene‐acrylonitrile copolymer interpolymerized with polybutadiene particles. For shear viscosity comparisons with experiment were made for the system linear polyethylene‐polybutene‐1.
Radiation‐induced graft copolymerization of butadiene to polyethylene and polypropylene
Authors: Furuhashi Akira , Kadonaga Masao 
Published: April 2003

AbstractPolyethylene and polypropylene films were irradiated by γ‐irradiation from a Co60 source in butadiene gas flow and in liquid butaidne. Irradiating in the butadiene gas flow is particularly convenient because the gas state monomer is available directly and little homopolymer is produced. In this case, there is a retardative effect on the grafting near the surface of the film and the grafting rate shows the maximum values at 50–60°C. for high‐density PE (PEH) and PP. Irradiating in the liquid butadiene decreases the retardative effect near the surface. The effect of dose rate I on the grafting rate Rp is represented by Rp ∞ I1/4 in this case. The grafting rate is always higher in PEH than in low‐density PE (PEL). Results of x‐ray diffractometry and electron microscopy indicate that the grafting reaction occurs predominantly near the surface of the crystallite (lamella) of PE and the grafting rate is not affected by the overall crystallinity of the trunk polymer but by the configurational structure, such as the degree of branching or side‐chain length.
Physical and electrical properties of polyethylene radiation crosslinked via polyfunctional monomers
Authors: Bernstein Bruce S. , Odian George , Binder Sidney , Benderly Asaf A. 
Published: April 2003

AbstractThe radiation crosslinking (via Co60) of both high and low density polyethylene in the presence of several tetrafunctional monomers has been studied to observe the effects of the additives on mechanical and electrical properties. The monomers employed were allyl methacrylate, divinylbenzene, and diallyl maleate. Monomer levels were such that the number of moles presented per number‐average mole of polyethylene was 2.2–2.6 for AMA and DVB with Marlex 5003 and 6009, and 9–10 for Marlex 1712. The DAM level was 3–5% of that of the other monomers on the same basis. Gel fractions, tensile strengths (at yield and break) at ambient temperature and tensile strengths, elongations, and moduli measured at a temperature above which no crystallinity remains all undergo more marked changes in the presence of tetrafunctional monomer after only 1–3 Mrad of radiation, regardless of monomer nature. Gels, tensiles, and moduli increase while elongation decreases. The magnitude of the changes depends upon the monomer nature (at the above ratios), the order being AMA>DVB>DAM> Monomer‐free. With increasing does to 8 Mrad, the trends continue. The gel swelling ratios are inversely proportional to the 3/5 power of the crosslink density, as determined by the modulus value in the absence of crystallinity. Straight radiation of monomer‐free polyethylene to higher doses not necessarily yield physical properties values attained at the lower doses with additive. The dielectric constant and dissipation factor of monomer‐containing crosslinked polyethylene are only slightly affected by the presence of the polyfunctional monomer.
Influence of polymer solubilization on latex behavior
Authors: Isaacs P. K. , Edelhauser H. A. 
Published: April 2003

AbstractThe effect of solubilization of latex polymers was investigated in various anionic surfactant solutions. The process of solubilization was studied by measuring the increase in light transmission and viscosity of the latexes. It was found that anionic surfactants differ widely in their ability to solubilize a given polymer, and susceptibility to solubilization is significantly affected by comonomer content of the polymer. If, for example, a poly(vinyl acetate) latex is stabilized exclusivdly by a strongly solubilizing sodium dodecyl benzene sulfonate, it is less stable and hydrolyzes faster than a similar latex made with a polyoxyethylene derivative, which has only a slight solubilizing action. Dibutyl mateate copolymers of vinyl acetate are less susceptible to solubilization than hompolymers of vinyl acetate.
Permeation of water through some heterogeneous hydrophilic membranes
Authors: Refojo Miguel F. 
Published: April 2003

AbstractThe permeation of water through glyceryl methacrylate (2,3‐dihydroxypropyl methacrylate) and 2hyphen;hydroxyethyl methacrylate hydrogels was increased by the incorporation of silica fillers. Both the amount of water at equilibrium and the amount of filler in the gel contribute to increase the permeability of these membranes.
Thermal degradation of polymers. Part I. Thermogravimetric and differential thermal analysis studies of atactic poly‐m‐aminostyrene and related polymers
Authors: Still R. H. , Keattch C. J. 
Published: April 2003

AbstractThermogravimetric and differential thermal analysis have been employed to study the thermal degradation patterns of poly‐m‐aminostyrenes and poly‐m‐acetamidostyrenes of different molecular weights and also the corresponding 2:1 copolymers with styrene. The thermal degradation routes have also been compared and contrasted with that of polystyrene. Experiments have been carried out in static air and dynamic nitrogen, and the different behavior exhibited by these polymers has been reconciled in terms of their differing structures and different mechanisms for pyrolytic degradation.
Pressure–volume–temperature behavior of high density polyethylene
Authors: Foster George N. , Waldman Nathan , Griskey Richard G. 
Published: April 2003

AbstractEquilibrium pressure‐volume‐temperature behavior in both the solid and molten regtions was determined for a high density (ρ = 0.958 g./cm.3) polyethylene. Data were measured with a recently developed compressibility device capable of obtaining precise and accurate data. Residual curve treatment showed that the data were true equilibrium data. Compressibilities calculated from the data of this Work compared favorably to existing data which were limited to 205°C. The presented work extended the compressibility behavior to 250°C. It was also found that differences in compressibility of low and high density polyethylenes were not eliminated. in the molten region, indicating that the effect of differences in morphology was not eliminated. The Spencer‐Gilmore equation was fitted to the data of the present work. The internal pressure (π) term of the equation showed a definite relation to polymer morphology.
Polymerization behavior of silver‐filled epoxy resins by resistivity measurements
Authors: Miller B. 
Published: April 2003

AbstractThe cure of heavily silver‐loaded epoxy resins with several amines has been investigated by resistivity–time measurements under isothermal conditions. For favorable cases activation energies in the range of 14–17 kcal./mole have been derived from slope analyses of the ρ−t plots. The relationship of the technique to similar measurements on unfilled or lightly loaded resins is discussed. Many aspects of the electrical behavior of silver‐based conductive adhesive systems are clarified by the kinetic data.
Degradation of natural rubber during mill mastication
Authors: Harmon D. J. , Jacobs H. L. 
Published: April 2003

AbstractChanges in the molecular weight distribution of natural rubber, after mill mastication, have been studied by using a Water's gel permeation chromatography. This study indicates that as the polymer is milled the distribution is narrowed primarily through the breaking down of large molecular weight molecules. The peak of the distribution curve shifts to lower and lower molecular weight with increased milling time but it appears to be approaching a limiting molecular weight after 76 min. of milling time. One unexpected result is the development of a secondary hump in the distribution curve at the high molecular weight end. This hump gets larger and moves to lower molecular weight with increasing milling time until 76 min. of milling, at which time it disappears entirely.
Synthesis and degradation of poly (alkyl α‐cyanoacrylates)
Authors: Leonard Fred , Kulkarni R. K. , Brandes George , Nelson Joshua , Cameron John J. 
Published: April 2003

AbstractIn order to study structure‐tissue reactivity relationships and ultimately develop a less necrotizing adhesive, this laboratory undertook a study of the synthesis and degradation of the homologous series of α‐cyanoacrylate monomers and polymers. A method for synthesizing high purity cyanoacrylates and some of their chemical and physical properties and presented. In vitro kinetics studies under heterotgeneous and homogeneous conditions indicate that cyanoacrylate polymers degrade by hydrolytic scission of the polymer chain. The products resulting from such a scission are formaldehyde (positively identified by derivative formation) and ultimately and alkyl cyanoacetate. As the homologous series is ascended, the rate of degradation under neutral conditions decreases. In homogeneous solutions, under alkaline conditions, the ràte of degradation is considerably higher than under neutral conditions and the rates obtained with the methyl to the butyl derivative are of the same order. Aproposed mechanism of degradation is presented. Medical evaluation has indicated that as the homologous series is ascended, the greater the tissue tolerance to the monomers and polymers. The relevance of the results of the in vitro studies to this medical finding is presented.
Response of epoxy adhesives when stressed to failure in milliseconds
Authors: Wegman Raymond F. , O'Brien Eugene L. 
Published: April 2003

AbstractThis investigation showed, as did an earlier investigation, that the adhesives tested exhibit greater resistance to rapidly applied stresses than they do to slower or gradually applied stresses. Also, the adhesives were shown to lose strength with test temperature whether tested rapidly or slowly. Within a region bounded approximately by a high‐temperature second‐order transition point (the ASTM heat distortion temperature) and a low‐temperature second‐order transition point, the test data fits an Arrhenius‐type exponential equation, S = AeE/RT, where S is the stress in the joint at failure and the other terms have their usual significance. Energies calculated from this expression are lower for dynamic (fast) than for static (slower) rates of testing. Further, it was shown that little change in bond strength occurs until time to failure is below 100 msec. Plots of stress versus 1/T for a series of test times show a decided discontinuity at 1/T = 0.0039 or −16°C.
Stress softening in natural rubber vulcanizates. Part III. Carbon black‐filled vulcanizates
Authors: Harwood J. A. C. , Payne A. R. 
Published: April 2003

AbstractStress softening (Mullins effect) occurs in rubber vulcanizates during the first and subsequent deformations. This paper shows the similarity of the degree of stress softening in both unfilled and carbon black‐filled vulcanizates of natural rubber when stressed almost to break. This confirms the earlier investigations which were confined to moderate stresses. A simple interpretation of the tensile stress–strain results for filled rubber is that the strain in the rubber is increased by the presence of the filler, so that the ratio of the average strain in the rubber to the measured overall strain is given by a strain amplification factor. The usefulness of this concept is confirmed by showing the similarity of the stress‐softened curves after normalizing the strains, provided the vulcanizates of both gum and filled vulcanizates were subjected to the same initial stress.