bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo‐optical and differential scanning calorimetric observations of mobility transitions in polystyrene‐poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends
Authors: Shultz A. R. , Gendron B. M.
Published: April 2003

Transition temperatures by thermo‐optical analysis (TOA) and by DSC were measured on films of polystyrene (PS), poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO resin) and nine homogeneous blends of these polymers. The TOA procedure consists of automatically monitoring light transmission through birefringent scratches in a film during heating at constant rate in a microscope hot stage between crossed (90°) plane polarizers. The TTOA transition temperature, defined as the temperature of birefringence disappearance in the scratches, increased monotonically from 113°C for pure PS to 222°C for pure PPO resin at a 10°/min heating rate. The Tg (DSC) similarly ranged from 99°C to 212°C at a 20°/min heating rate. The TOA technique as described should be a useful addition to thermomechanical studies of transparent polymers and polymer blends.
Bound rubber in elastomers: Analysis of elastomer‐filler interaction and its effect on viscosity and modulus of composite systems
Authors: Pliskin Irwin , Tokita Noboru
Published: April 2003

Bound rubber measurement may be very misleading as a measure of elastomer–carbon black interaction because sometimes only part of the apparently bound rubber is truly adsorbed on the carbon black surface. A theory is proposed which utilizes bound rubber measurements, but separates truly adsorbed rubber from other insoluble gel and enables calculation of the adsorbed elastomer layer thickness, a numerical value of interaction. Measurements of interaction were obtained for many different rubbers, including polybutadienes, styrene–butadienes, EPDMs, and butyl, with several different furnace blacks. An equation for viscosity of a rubber–carbon black composite is proposed, based on the degree of interaction obtained from the theory and the possible varying degree of orientation of the composite as the rate of shear is changed. This has been applied experimentally both to soluble elastomers and to an elastomer containing a nonrigid gel. The modulus of a vulcanized composite is shown to be related to the effective volume fraction of filler, which is equivalent to the volume fraction of filler plus adsorbed rubber, at temperatures above the glass transition temperature, regardless of the type of rigid filler. Below the glass transition temperature, the modulus depends only on the filler volume concentration.
Elastic properties and structure of polybutadiene vulcanized with magnesium methacrylate
Authors: Dontsov A. , De Candia F. , Amelino L.
Published: April 2003

The elastic and structural properties of polybutadiene vulcanized with magnesium methacrylate were investigated. Structural information was obtained by x‐ray smallangle diffusion diagrams. Results clearly indicate that in the elastomeric network there is a random distribution of rigid particles. The elastic behavior was analyzed in terms of the Mooney‐Rivlin equation. Experimental evidence for the direct correlation between elastic and structural properties is given.
The effect of molecular weight on the fatigue behavior of polystyrene
Authors: Foden E. , Morrow D. R. , Sauer J. A.
Published: April 2003

Significant improvements in the fatigue life of polystyrene can be realized by increase in molecular weight. In this investigation, samples of polystyrene of varying molecular weight were subject to alternating cycles of axial tension and compression at a test speed of 1600 rpm. One set of fatigue tests was made on samples machined from commercial whole polymer rod. A second set of samples was prepared from a PS standard having an average molecular weight of 160,000 and a narrow molecular weight distribution. A third set of samples had a high average molecular weight of 860,000. For a whole polymer, the S–log N curves tended to have the same general shape as for metals, and the endurance limit appeared to be about 1400 psi. The test results show that the average fatigue life, at any given stress amplitude, is significantly increased by increase in molecular weight. For example, the average life of the high molecular weight standard at any given stress level was found to be more than tenfold that of the low molecular weight standard.
Long‐term stiffening of neoprene pads for the Poseidon missile launch system
Authors: Meier J. F. , Rudd G. E. , Rosenblatt G. B.
Published: April 2003

In a previous paper1 the development of neoprene formulations and mechanical designs to meet operational requirements for the Poseidon launch tube liner pads were presented. Subsequently, it was found that early development pads aged for three months at room temperature were ∼10% stiffer than the vendor's qualification compression–deflection (CD) test values. The increase was attributed to a combination of normal elastomer recovery and continued crosslinking due to the original low state of cure of the pads. A program was designed to study the effect of postcure time and temperature on CD recovery, the effect of carbon black loading on the CD recovery, and room temperature and accelerated aging at elevated temperature on these effects. Values of the molecular weight between crosslinks (M̄c) were determined experimentally to establish the state of cure. The results of these experiments are presented and discussed. Recommendations are given for reducing CD variation by modifying carbon black loading and/or postcure conditions.
Protection against intense light. II. The role of the gaseous decomposition products
Authors: Prosser R. A. , Stapler J. T.
Published: April 2003

Screening studies have shown that of a series of halogenated vinyl polymers, poly(vinylidine fluoride) gives comparatively good thermal protection when exposed to the intense light energy of the carbon are‐image furnace. Results indicate that this protection is undoubtedly provided by polyenes, (CHCF)n, formed during pyrolysis. Decomposition products containing these structures are expelled by the gases formed into the region between the light source and the target where they intercept photons from about 200 to 500 mμ and dissipate the energy to the air as heat and/or reradiate it. Instrumental evidence for polyene formation is given. The concept of polyene formation clarifies the relative thermal protection offered by a series of vinyl polymers.
A new approach to coagulation phenomena in wet‐spinning
Authors: Rende A.
Published: April 2003

A new physicochemical model was built to describe the phenomena occurring during wet‐spinning of polyacrylonitrile, in order to relate the integral time of coagulation to the major variables of the spinning bath. According to this model, counterdiffusion of solvent and coagulant leads the system to overcome the thermodynamic equilibrium conditions, so that precipitation of polymer occurs, at a distance from the fiber axis variable with time. This causes a moving‐interface dope‐coagulated polymer to build up. The integral time required by this interface to reach the fiber axis, i.e., the coagulation time, is related, by simple equations to initial radius, to temperature via diffusional coefficients, to “bath hardness” (i.e., coagulant content), and to thermodynamic phase equilibrium conditions.
Photo‐oxidation of polypropylene films. VI. Possible UV‐stabilization mechanisms
Authors: Carlsson D. J. , Suprunchuk T. , Wiles D. M.
Published: April 2003

The effects of the chemical nature, concentration, stability, and location of various additives on the ultraviolet stability of polypropylene are discussed. It is shown that effective stabilizers of thin films do not depend on UV absorption for their protective action, whereas some relatively inefficient additives operate solely as UV screeners. Adequate UV protection was observed when small amounts (∼0.01 wt‐%) of effective stabilizers were concentrated in or on the surfaces of commercial films, and the remaining bulk of the film contained only a very low concentration (∼0.01 wt‐%) of uniformly blended additive. Previous attempts at demonstrating energy‐transfer stabilization of the polymer are discussed with reference to the present data; it is concluded that effective polypropylene stabilizers probably operate by a combination of chromophore quenching, radical scavenging, and hydroperoxide decomposition.
Effect of solvents on the degradation of polymers by high‐speed stirring
Authors: Nakano Akihiko , Minoura Yuji
Published: April 2003

The effect of solvents on the degradation of poly(methyl methacrylate), polystyrene, and polyisobutylene by high‐speed stirring (30,000 rpm) at 30°C was studied. From the intrinsic viscosities of polymers stirred for given times, the viscosity‐average degree of polymerization, P̄v was obtained and the number of scissions per molecule, B/n0. was calculated. Ovenall's equation

could be applied to the results, where dBi/dl is the rate of breakage of molecules of ith degree of polymerization, ni is the number of molecules present, PI is the limiting degree of polymerization, and ki is a rate constant; k and PI were changed with solvents, and were found to have no relation to the physical properties of the solvents but to the intrinsic viscosities the polymers showed in the solvents used for the stirring. k was smaller and PI larger for solvents where polymers had larger intrinsic viscosities. This relation implies that the degree of expansion of a polymer coil in a solvent is closely related to the rate constant of scission and to the limiting degree of polymerization.
Radiation crosslinking of poly(vinyl chloride)
Authors: Salmon W. A. , Loan L. D.
Published: April 2003

The mechanism of the electron irradiation crosslinking of poly(vinyl chloride) (PVC) with polyfunctional acrylic monomers has been investigated as part of a program to develop an insulation for distributing‐frame wire. These monomers were found to undergo rapid polymerization to form a rigid, three‐dimensional network onto which PVC was grafted. Polyfunctionality was necessary for crosslinking to occur, since butyl methacrylate, containing only a single unsaturated bond, did not crosslink readily. On the other hand, trimethylolpropane triacrylate and trimethylolpropane trimethacrylate, each containing three unsaturated groups, gave extremely rapid crosslinking. Trimethylolpropane triacrylate showed 40 times the radiation sensitivity of tetraethylene glycol dimethacrylate, a diunsaturated compound. The rate of disappearance of unsaturation was related inversely to the rate of gel formation. This was attributed to immobilization of unreacted pendant double bonds in the rigid crosslinked network. In the triunsaturated monomers, half the vinyl groups were left unreacted when all of the PVC was insoluble.
The thermal degradation of hydrofluoro polymers
Authors: Knight G. J. , Wright W. W.
Published: April 2003

The evolution of hydrogen fluoride (or other degradation products giving rise to Fions in aqueous solution) from a number of hydrofluoro polymers has been studied in nitrogen or air over a range of temperatures using a fluoride ion selective electrode to monitor the process. The results in an inert atmosphere illustrate the effect of chemical structure upon the relative ease of hydrogen fluoride elimination.
The action of tridecyl phosphite in the stabilization of poly(vinyl chloride) with metal soaps
Authors: Hybart F. J. , Rowley G. N.
Published: April 2003

The effect of tridecyl phosphite on the stabilization of the thermal degradation of poly(vinyl chloride) under nitrogen by cadmium and zinc stearates has been studied. The rate of evolution of hydrochloric acid from solutions of the polymer with stabilizers in dioctyl phthalate at 190°C has been measured. Tridecyl phosphite absorbs HCl and is converted into the phosphonate which reduced the deleterious action of the cadmium and zinc chlorides formed from the stearates.
Free volume and the annealing and antiplasticizing of bisphenol A polycarbonate
Authors: Robertson Richard E. , Joynson Catherine W.
Published: April 2003

Annealing below the glass transition temperature and the addition of an antiplasticizer are each known to increase the yield stress and the density of glassy bisphenol A polycarbonate. We have studied the combined effects of annealing and antiplasticizing to see if the individual effects would interfere with one another, as might be expected if the same free volume were involved in each. We find that the effects, even when they individually approach saturation, remain additive. This suggests that the free volume in the glass has at least two parts, one of which is affected by annealing and the other by antiplasticization. The available data indicate that the rate at which the yield stress changes with measured volume is different for the two parts.
The thermal degradation of perfluoro polymers
Authors: Knight G. J. , Wright W. W.
Published: April 2003

A number of perfluoro polymers were heated at a constant rate of temperature rise in an atmosphere of nitrogen or air, and the volatile degradation products were passed into an aqueous solution, where the F− ions produced were monitored with a fluoride ion‐selective electrode. Compounds giving rise to F− ions were formed in both nitrogen and air, but in larger amounts in the latter atmosphere. For the formation of appreciable quantities of F− ions, temperatures greater than 500°C were normally necessary.
Thermal polymerization of styrene at high conversions and temperatures. An experimental study
Authors: Hui Albert W. , Hamielec Archie E.
Published: April 2003

An experimental study of thermal polymerization of styrene in the temperature range 100–200°C and conversion range 0–100% is reported. Conversions, molecular weight averages, and molecular weight distributions were measured. A kinetic model with third‐order initiation gives a satisfactory fit of conversion and number‐ and weightaverage molecular weights over the ranges of temperature and conversion investigated. This model should find use in the design, simulation, and optimization of polystyrene reactors.
The role of membrane pressure in reverse osmosis
Authors: Paul D. R.
Published: April 2003

Liquid transport occurs through reverse osmosis membranes as a result of an applied pressure differential. The pressure within the membrane continuum is an important thermodynamic parameter in the formulation of solution‐diffusion models for this process. It is shown that this membrane pressure is the same throughout the membrane for supported flat and tubular membranes and for hollow fibers. The use of this parameter in calculating the induced concentration differential is discussed.
Spectroscopic examination of ethylene–propylene–norbornenic diene terpolymers
Authors: Tosi C. , Ciampelli F. , Cameli N.
Published: April 2003

Infrared methods for the analysis of the third monomer in ethylene–propylene–norbornenic diene terpolymers were developed. They are based either on the CC stretching vibration near 6 μ or on the CH out‐of‐plane deformation vibration between 11 and 12 μ. Calibration was made by NMR on selected samples with high unsaturation content. Particular emphasis was laid on terpolymers with ethylidene norbornene, for which the reliability of the analysis for the third monomer was checked by several techniques, and the transferability to the determination of propylene of the calibration curves set up for the analysis of composition in ethylene–propylene copolymers was studied.
Effect of stirring on the emulsion polymerization of styrene
Authors: Nomura Mamoru , Harada Makoto , Eguchi Wataru , Nagata Shinji
Published: April 2003

The purpose of this paper is to clarify the effect of stirring on the course of emulsion polymerization of, for example, styrene. It establishes the existence of an optimum range of stirring speed and three important factors which must be considered in carrying out emulsion polymerization. (1) Stirring significantly affects the course of reaction in the presence of an imperfectly purified nitrogen atmosphere. Consequently, the number of polymer particles produced and the polymerization rate per particle will be affected. (2) At higher stirring speeds, polymer particles coagulate and coalesce. At lower stirring speeds, the reaction rate is controlled by the monomer transport rate from monomer droplets to the aqueous phase. (3) Stirring contributes to the reduction of the number of micelles because emulsifier molecules are adsorbed onto the surfaces of monomer droplets finely dispersed by the stirring. At low emulsifier concentrations near the critical micelle concentration, this effect cannot be neglected.
Copolymerization of ethylene with vinyl acetate. II. Effect of solvent on polymer yield and molecular weight
Authors: Wisotsky M. J. , Kober A. E.
Published: April 2003

In the free‐radical solution copolymerization of ethylene and vinyl acetate, polymer yield and molecular weight were found to vary considerably with the solvent used. Solvents were toluene, benzene, hexane, heptane, and cyclohexane. Molecular weights were highest in benzene and lowest in toluene and were readily explained by different solvent chain‐transfer constants. Polymer yields were highest in aliphatic solvents and lowest in aromatic solvents including benzene. This was attributed to different types of interactions of the solvents with radical species. The saturated aliphatic solvents undergo hydrogen abstraction reactions, but these give reactive alkyl radicals which reinitiate polymer growth. Toluene also undergoes hydrogen abstraction reactions, but the resultant benzyl radical is resonance stabilized and does not readily reinitiate polymerization. Benzene does not undergo hydrogen abstraction reactions. The low yields are attributed to complex formation. A consideration of kinetic theory indicates that complex formation with both initiator and growing polymer radicals is involved. Differences in viscosity, ethylene solubility, and initiator half‐life in the different solvents, as well as induced decomposition of the initiator, were not determining factors.
Flow of water through highly swollen membranes
Authors: Peterlin A. , Yasuda H. , Olf H. G.
Published: April 2003

The difference between the hydraulic permeability K under a pressure gradient and the diffusive permeability P under a concentration gradient can be explained by the incipient viscous flow at high degree of swelling. This flow is opposed by the friction resistance of the macromolecules of the highly swollen membrane. It comes to an end at a critical swelling Hc when the number of permeant molecules is not more sufficient for a complete solvation of the macromolecules of the membrane. Below this swelling, K equals PV1/RT, where V1 is the molar volume of the permeant, and above it the difference K − PV1/RT is proportional to H/(1 − H) − Hc/(1 − Hc). The proportionality factor depends on the friction coefficient of the macromolecular segments and on the average lateral chain clustering. The data on poly(glycerol methacrylate) suggest that on the average the aggregates contain two chains.
Graft copolymerization of acrylic acid to nylon 6 by mutual irradiation. II. The influence of cupric ions
Authors: Huglin M. B. , Johnson B. L.
Published: April 2003

In the γ‐irradiation in vacuo of nylon 6 film in the presence of aqueous acrylic acid and different concentrations of cupric chloride, the following relationships have been obtained: RH ∝ [CuCl2]−1.0 and RG ∝ [CuCl2]−0.3 Here [CuCl2] is the concentration of cupric chloride in the bulk solution, and RH and RG denote the initial rates of homopolymerization and grafting, respectively. The values of −1.0 and −0.3 for the exponents indicate that the cupric ion is a less effective chain terminator in the film on account of its lower concentration there. Analyses of films grafted in different media demonstrate the copper content of a film to be independent of both the concentration of monomer in the solution and the degree of swelling. The copper content is primarily a function of the total poly(acrylic acid) present, i.e., (grafted species plus occluded homopolymer). Thus, at high doses, where the total poly(acrylic acid) associated with a film is significant, the grafting curves exhibit a falling off, and complex formation between cupric ion and a growing chain is considered a likely contributory factor.
Caprolactam polymerization. Polymerization in backmix flow systems
Authors: Nagasubramanian K. , Reimschuessel H. K.
Published: April 2003

A reactor system consisting of a cascade of N perfectly mixed stirred tanks followed by a plug flow reactor was analyzed. Compared with a single‐stage closed system, a substantial reduction in the total reaction time was indicated for systems using cascades of three or more stirred tanks. Calculations for both the micromixed and the segregated systems showed no significant difference between the respective total residence times.
Crosslinking of cotton in the presence of poly(vinyl alcohol). Analysis and composition of products
Authors: Andrews B. A. Kottes , Frick J. G.
Published: April 2003

The spectrophotometric method developed by Finley for the determination of poly(vinyl alcohol) in paper coatings has been adapted for analysis of cotton fabrics crosslinked with finishes containing a poly(vinyl alcohol) additive. The effect of time and pH of hydrolysis on the analysis, and the dependency of the durability of the poly(vinyl alcohol) on the crosslinking agent are established. Evidence of chemical attachment to the cellulose of the cotton fiber through the crosslinking agent is offered.
Catalytic action of metallic salts in autoxidation and polymerization. VI. The inhibitive effects of transition‐metal N,N‐diethyldiselenocarbamates on the thermal oxidative degradation of isotactic polypropylene
Authors: Osawa Zenjiro , Ishizuka Takashi , Ogiwara Yoshitaka , Suzuki Hideo , Ishikawa Hisao
Published: April 2003

Transition‐metal (Zn, Ni, Pd, Cu, Cr, Co) N,N‐diethyldiselenocarbamates were prepared, and the inhibitive effects of these compounds on the thermal oxidative degradation of isotactic polypropylene, both in the presence and absence of copper stearate as oxidation accelerator, were examined by conventional oxygen uptake. In both cases, all metal selenocarbamates showed a pronounced inhibitive effect on the degradation of the polymer, especially Zn and Ni selenocarbamates. The inhibitive action of these metal selenocarbamates was discussed from the viewpoint of viscosity change and carbonyl and hydroperoxide contents.
Photo‐induced graft copolymerization of methyl methacrylate on poly(vinyl alcohol)
Authors: Kubota Hitoshi , Ogiwara Yoshitaka
Published: April 2003

Photo‐induced graft copolymerization of methyl methacrylate on poly(vinyl alcohol) (PVA) was examined in aqueous solutions. In unoxidized samples, only a few percent of PVA used took part in the formation of grafts, and the percent grafting was very low. However, if Fe2+, Fe3+, anthraquinone‐2,7‐disulfonate, or oxalic acid was used as sensitizer, the percent grafting was somewhat improved. Among them, the effect of Fe3+ was most remarkable. Oxidized PVA showed a higher initiating activity and was more susceptible to the sensitizing action of Fe3+ than unoxidized PVA. As Fe3+ has an ability to accelerate the photo‐induced scission reaction of PVA chains for both oxidized and unoxidized PVA, it is thought to be very probable that the copolymer formed in the photo‐induced systems has a block polymer‐type structure like that in systems initiated by ceric ion or hydrogen peroxide.
Characterization of the collagen–vinyl graft copolymers prepared by the ceric ion method. II. Infrared spectra and electron microscopy
Authors: Rao K. Panduranga , Joseph K. Thomas , Nayudamma Y.
Published: April 2003

Collagen powder and goat skins were grafted with different vinyl monomers using the ceric ion technique. The graft copolymers were characterized by infrared spectra and electron microscopy. The collagen–vinyl graft copolymers were hydrolyzed by both acid and enzymatic hydrolysis, and the grafted vinyl polymer side chains were isolated. In the grafted poly(methyl methacrylate) (PMMA) side chains isolated by acid hydrolysis, the characteristic amide absorption bands at 1550 and 1660 cm−1 were not seen prominently. However, in PMMA side chains isolated by enzymatic methods, the amide absorption bands were more prominent as these isolated side chain polymers contained longer fragments of the peptide backbone attached to them. Electron‐microscopic observations of grafted collagen fibrils and ultrathin sections of grafted goat skin fibrils did not show any cross‐striations. These various evidences indicate that the polymers formed on collagen have penetrated into the fibrils and that they were chemically bound to the collagen molecules.
Treatment for improving flame retardancy of wool and minimizing toxic gas evolution in burning
Authors: Gilbert S. , Liepins R.
Published: April 2003

A treatment involving formaldehyde, a reducing agent, and a boron‐containing compound of a wool shag carpet imparted to it a flame‐retardancy effect that was effective after the seventh but not the eighth shampoo. This treatment also decreased the concentration of carbon monoxide and hydrocyanic acid generated in the products of combustion by at least a factor of 2. Analogous treatment of a wool flannel fabric produced a 15–22% sample area shrinkage and imparted a flame‐retardancy effect that was still effective after a 2‐hr cold water rinse.
Liquid transport through membranes prepared by grafting of polar monomers onto poly(tetrafluoroethylene) films. I. Some fractionations of liquid mixtures by pervaporation
Authors: Aptel P. , Cuny J. , Jozefowicz J. , Morel G. , Neel J.
Published: April 2003

The separation of various liquid mixtures including systems of chloroform–hydrocarbons or ethyl ether, water–alcohols and water–nucleophilic organic solvents have been investigated by the pervaporation technique. Membranes were obtained by grafting Lewis base onto poly(tetrafluoroethylene) (PTFE) films. The PTFE backbone has been chosen for its mechanical and chemical resistance. N‐Vinylpyrrolidone and 4‐vinylpyridine were selected because of their great affinity for the electrophilic compounds. In all cases, the compound which has the greatest affinity for the membrane pervaporates selectively through modified PTFE films. Selectivity and rates were studied. It is concluded that because selectivity is very important, total separation of different mixtures is possible at a good yield, with a faster rate when the temperature is increased or the thickness of the membrane is decreased.
Some aspects of nonisothermal crystallization of polymers. I. Relationship between crystallization temperature, crystallinity, and cooling conditions
Authors: Nakamura K. , Watanabe T. , Katayama K. , Amano T.
Published: April 2003

The changes in temperature and crystallinity of polymer during nonisothermal crystallization were theoretically analyzed assuming a cooling condition under which heat transfer occurs at a rate proportional to the difference in temperature between polymer and the environment. When a plateau appears in the temperature change during crystallization, crystallization temperature can be predicted by a simple method. This method gives nearly the same value as that obtained by successive calculations of temperature and crystallinity throughout the whole process. In addition, a graphic method is presented to predict crystallization temperature. By using the plateau temperature observed in melt‐spinning experiments, the crystallization rate under molecular orientation is evaluated. Furthermore, a method applicable to estimating the ultimate crystallinity is proposed. A rough estimation of the increase in the rate of crystallization under molecular orientation was carried out for very high‐speed spinning of poly(ethylene terephthalate).
Heterogeneous nucleation and crystallization of polyethylene with gold: Dilatometry
Authors: Hara Katsuyuki , Schonhorn Harold
Published: April 2003

Heterogeneous nucleation and crystallization data for polyethylene at a gold interface are reported. Isothermal crystallization is investigated by dilatometry. Avrami plots of the crystallization data suggest that the gold surface acts as a suitable nucleating agent resulting in heterogeneous nucleation and two‐dimensional crystal growth at the polyethylene melt–gold interface. The deviation of measurements from Avrami's equation suggests the presence of intercrystalline links during the final growth stages of isothermal crystallization. A closely packed lamellar model is given for heterogeneous nucleation and two‐dimensional crystallization which results in high density and rod‐like crystals.
Studies on heterogeneous polymeric systems. I. Influence of morphology on mechanical properties
Authors: Baer Massimo
Published: April 2003

Polybutadiene rubbers of well‐defined and varying molecular weight were prepared by anionic polymerization and used in the preparation of mass‐polymerized polystyrene blends. The particle size of the dispersed rubber phase was varied by (1) controlling the relative viscosity, at phase inversion, of the two liquid phases composed of polystyrene and polybutadiene in styrene monomer; (2) by varying the intensity of mixing, and (3) by adding preformed polystyrene to the prepolymer, prior to phase inversion. The mechanical and dynamic properties of the resulting blends are found to be determined mainly by the particle size of the dispersed rubber phase, independently from the method used to obtain such size. The weight fraction of rubber phase, rather than the weight fraction of rubber charged, is found to correlate with the blend modulus and may also affect its level of toughness. Low molecular weight rubbers are found capable of efficient blend reinforcement, if the excessively small rubber particle size obtained by conventional processes is enlarged by incorporation of preformed polystyrene prior to phase inversion.
The grafting of methyl methacrylate onto cotton by tri‐n‐butylborane
Authors: Kojima Kuniharu , Iwabuchi Susumu , Murakami Kunio , Kojima Koichi , Ichikawa Fumio
Published: April 2003

Methyl Methacrylate was grafted onto cotton by tri‐n‐butylborane in the presence of water. No graft was obtained in organic solvents, i.e., in the absence of water. The percentage of grafting increased with increases in reaction time, cotton amount, and initiator concentration. Pretreatment of cotton with pyridine also enhanced the percentage of grafting. Glycidyl methacrylate and ethyl acrylate were grafted onto cotton by tri‐n‐butylborane, while no grafting occurred when vinyl acetate and 4‐vinyl pyridine were used. Usual radical initiators, such as azobisisobutyronitrile and benzoyl peroxide/dimethyl‐p‐toluidine, were not effective under the same conditions.
The determination of network chain density and the chemical stress relaxation of crosslinked polymers
Authors: Tamura Saburo , Murakami Kenkichi
Published: April 2003

Both initial network chain densities nM(0) and ns(0) of dicumyl peroxide‐cured natural rubbers were determined from the tensile stress and swelling method, respectively. The difference between nM(0) and nS(0) was usually constant, independent of the magnitude of network chain density. That is, it was found that the number of entanglement network chains in the crosslinked natural rubber was usually constant, independent of network chain density. The entanglement network chain density nII(0) was 0.7 × 10−4 mole/cc. This led to the supposition that the molecular weight between entanglement points (Me) would be about 9000. Although this value is far from exact, it does not differ too greatly from the value found for noncrosslinked natural rubber. Next, in order to calculate the number of main‐chain scission of crosslinked polymers from their chemical stress relaxation, we proposed our modification of Tobolsky's equation. Using our equation, it was found that the scission of dicumyl peroxide‐cured natural rubber occurred in the main chain only. Furthermore, this value agreed with the one obtained from the oxidation of toluene solution of noncrosslinked rubber under the same conditions.
Dynamic mechanical behavior of highly filled polymers: Dewetting effect
Authors: Lepie A. , Adicoff A.
Published: April 2003

This paper describes the results of simultaneous dynamic measurements in tension and torsion made on propellant samples. The complex dynamic moduli E′, E″, G′, and G″ at low frequencies were determined within a temperature range from room temperature to −90°C. Time temperature shift factors and reduced master curves for both tension and shear properties are discussed. The effect of dewetting on the dynamic properties in tension and shear was also investigated. A preliminary attempt is made to compute the degree of dewetting in a propellant by applying Beer‐Lambert's law.
Effect of vulcanization on the low‐strain dynamic properties of filled rubbers
Authors: Payne A. R. , Whittaker R. E. , Smith J. F.
Published: April 2003

A change in the degree of vulcanization in a carbon black‐filled rubber is shown not to affect the change of in‐phase shear modulus with strain amplitude, provided the amount of filler is kept constant. Similar results are found with the change of out‐of‐phase modulus and phase angle with strain amplitude. A similar value of change of in‐phase shear modulus with strain amplitude (G′0 – G′∞) is found for a vulcanized and unvulcanized tire tread rubber; this behavior is attributed for the breakdown of the secondary three‐dimensional carbon black aggregated network. Detailed consideration is given to other factors such as hydrodynamic, shape factor, and relaxation effects which contribute to the difference between the shear modulus of the gum rubber and the filled rubber when all the carbon black structure has been broken down. The consequence of the breakdown of the secondary aggregated structure of carbon black are considered in terms of factors affecting heat build‐up in tires.
Urethanes. II. The effect of amine bases on the thermal degradation of carbanilates
Authors: Abbate F. William , Farrissey William J. , Sayigh A. A. R.
Published: April 2003

The amine‐catalyzed, low‐temperature (< 200°C) thermal degradation of aromatic urethanes, specifically carbanilates, was studied to determine the primary reactions responsible for the loss of starting material and the resultant products. The primary degradation reactions are (1) the reversible dissociation of the urethane to isocyanate and alcohol and (2) the nonreversible nucleophilic attack by a basic species on the carbon attached to the carbamate oxygen to yield amine, carbon dioxide, and an alkylated base. Secondary products fall into two categories, neutral and basic species. The neutral components consist of carbanilide, dialkyl carbonate, isocyanurate, and N‐alkylated carbamates. The basic components, derived from starting materials, are pseudoureas and guanidines. Their formation depends solely on the presence of carbanilide in the reaction mixture. When the amine catalyst is 1,4‐diaza[2.2.2]bicyclooctane, novel piperazine compounds are formed. In general, quarternized triethylenediamine species undergo nucleophilic displacement reactions to form N‐alkyl‐N′‐ethylpiperazine derivatives.
The skin‐core morphology and structure–property relationships in injection‐molded polypropylene
Authors: Kantz M. R. , Newman H. D. , Stigale F. H.
Published: April 2003

Tensile bars of an isotactic propylene homopolymer and an ethylene–propylene copolymer were prepared by injection molding under a variety of melt temperatures and injection pressures. The effects of these processing variables on morphology and crystalline orientation were studied using optical microscopy and x‐ray diffraction. Microscopy of microtomed thin sections of the tensile bars revealed the presence of three distinct crystalline zones, namely, a highly oriented nonspherulitic skin, a row or shear‐nucleated spherulitic intermediate layer, and a typically spherulitic core. The thickness of the oriented skin layer is a function of the polymer melt temperature and varies inversely with temperature. The thickness of the intermediate layer varies with injection pressure, but in a complex manner. Preferred crystallite orientation in the skin and intermediate layers exerts profound effects on mechanical properties. Tensile yield strength, impact strength, and shrinkage increase with increasing combined thickness of the two oriented outer layers.
Experimental and theoretical study of the extrusion of two‐phase molten polymer systems
Authors: White James L. , Ufford Raymond C. , Dharod Khushal R. , Price Robert L.
Published: April 2003

An experimental and theoretical study of two‐phase flow of molten polymers has been carried out. The theoretical analyses apply the theory of nonlinear viscoelastic fluids to consider stress and velocity profiles and interface shape in stratified flow between parallel plates and in a tube. The second normal stress difference is predicted to influence interface shape. Experimental studies have been made of stratified two‐phase flow of a low viscosity but elastic low‐density polyethylene and a high‐viscosity polystyrene in a capillary rheometer. In the stratified flow experiment, velocity fields and interface shape in the reservoir approaching capillary die and the emerging extrudate were investigated, the former being observed through visual experiments. The emerging extrudates possessed convex polystyrene surfaces at the interface. A strong tendency toward the collection of bubbles near the capillary entry was found. We have made an experimental study of the extrusion of disperse mixtures of polystyrene and different polyolefins. The morphology of the disperse two‐phase emerging extrudates has been investigated.
Optical properties and orientation of thermally treated acrylic fibers
Authors: Thorne D. J. , Marjoram J. R.
Published: April 2003

Acrylic fibers containing methyl acrylate copolymer have been thermally treated in the temperature range 473°–573°K in an inert, oxygen‐free environment. The optical properties and an x‐ray diffraction orientation parameter have been studied in these fibers, with special attention to correlation with the essential chemical reactions and to the behavior of polymer chain orientation. Densification of the fibers, illustrated by specific gravity and refractive index changes during the thermal treatment, is interpreted as a more efficient packing of the polymer chains in addition to the development of more highly refractive and dense chemical species. An extrapolated value of refractive index of 1.70 for 100% nitrile polymerization supports the presence of naphthyridine structures. Birefringence changes from −0.003 to +0.27 imply a high degree of retention of the preferred orientation of polymer chains, despite the severe change in the chemical identity of the chains. The contrary behavior of the orientation parameter from the 100 arc of the x‐ray diffraction of polyacrylonitrile as the thermal treatment proceeds indicates that the residual polyacrylonitrile sequences have reduced orientation.
Yielding, crazing, and fracture of polymers. II. Studies of the retraction of crazed and drawn films
Authors: Legrand D. G.
Published: April 2003

Optical, mechanical, and thermal data on cold‐ and hot‐drawn as well as crazed films of bisphenol A polycarbonate suggest that three separate processes occur during deformation. These processes are a volume change, a preferential orientation of the molecules along the deformation axis, and a configurational change within the molecules (ordering). An attempt is made to correlate these processes with the various types of experimental data. It is suggested that the ordering process is activated by surface, bulk, or external stresses, which are dependent upon molecular weight, processing history, and sample geometry.
Total applied shear in capillary extrusion
Authors: Rudin Alfred , Chee K. K.
Published: April 2003

Viscoelastic properties of polymer fluids are single‐valued functions of shear stress or shear rate only at high total applied shear. These parameters may vary with applied shear under milder shear histories. The mean total shear in capillary extrusion is shown to be a function of orifice geometry. Apparent flow curves can be measured at various total shear values by changing the length/radius ratio of the capillary. The true shear stress and true shear rate at the orifice wall correspond to infinite total shear conditions. The true flow curve and elastic parameters like die swell are not measured at equivalent total shear unless the capillary is extremely long.
Dynamic shear modulus of polystyrene bead foams
Authors: Rinde J. A. , Hoge K. G.
Published: April 2003

The shear storage modulus has been determined for 0.05, 0.10, and 0.22 g/cc polystyrene bead foams and for the full density polymer at frequencies from 0.005 to 0.5 Hz at temperatures from −5° to 84°C. These data are superposed to form master curves of log modulus versus log temperature‐reduced frequency, using shift factors calculated by the Arrhenius equation. A plot of log modulus versus log density is linear for the three density foams; however, the modulus value for the solid polymer does not follow this relationship.
Reaction of formaldehyde with cellulose in the presence of sulfuric acid
Authors: Nabar G. M. , Shenai V. A. , Shenai V. A.
Published: April 2003

The extent and rate of reaction between cotton yarn before and after slack mercerization and slack mercerization followed by stretching and formaldehyde, in the presence of various amounts of sulfuric acid (5–60% by weight) were studied. Beyond a concentration of 45% sulfuric acid, the reaction takes place very rapidly, and an explanation is put forward in terms of the extent of swelling of the fiber in sulfuric acid solutions. The reaction was also studied in the presence of glycerin, when the combined formaldehyde value is shown to decrease with an increasing concentration of glycerin.
Influence of chain length on the rate of hydrolysis of polyoxymethylene ethers
Authors: Stanonis David J. , King Walter D. , Vail Sidney L.
Published: April 2003

Four series of polyoxymethylene ethers (polyformals) [RO(CH2O)nR] where R is isopropyl, ethyl, methyl, or methoxyethyl and n = 1–3 have been prepared, examined by GLC, separated by fractional distillation, and characterized by NMR. Rate constants for the aqueous acid hydrolysis of all the compounds have been determined. The isopropyl series appears to be a special case, and as reported in the literature (but in aqueous dioxane), all members of this series hydrolyze at the same rate. In the other series, there is a definite increase in rate, which never exceeds fourfold, in going from n = 1 to n = 2. This increase differs considerably from the 100‐fold increase reported by others in going from CH3OCH2OCH3 to CH3O(CH2O)2CH3. In all series, the n = 3 compound hydrolyses at practically the same rate as the n = 2 compound.
Some effects of emulsion polymerization conditions on molecular polydispersity and rheological properties of poly(methyl methacrylate)
Authors: Guillod M. S. , Bauer R. G.
Published: April 2003

Emulsion polymerization conditions of free‐radical‐polymerized poly(methyl methacrylate) have been examined in relation to the molecular weight and molecular polydispersity of the resulting polymers. In turn, molecular weight and molecular polydispersity have been related to the apparent viscosity and the appearance of the extrudate produced by an Instron capillary rheometer. The length of time for monomer addition to the polymerization medium was found to be a variable of primary concern in the emulsion polymerization. Continuous monomer addition (from 1 to 2 hr) resulted in a poly(methyl methacrylate) with a narrow distribution (∼2.0) and medium molecular weight (∼132 × 103). Both molecular weight and polydispersity were found to significantly affect apparent viscosity and extrudate appearance. Differences in the rheological parameters were most marked at the lowest shear rate run in this study. The poly(methyl methacrylate) samples with medium molecular weight and more narrow molecular polydispersity exhibited the best combination of low apparent viscosity and smooth glossy appearance.
Effect of activated gas plasma treatment time on adhesive bondability of polymers
Authors: Hall J. Richard , Westerdahl Carolyn A. L. , Bodnar Michael J. , Levi David W.
Published: April 2003

The bondability of the following polymers as a function of length of exposure to excited helium or oxygen was investigated: low‐density polyethylene, high‐density polyethylene (two types), poly(4‐methyl‐1‐pentene), poly(vinyl fluoride), poly(vinylidene fluoride), FEP Teflon, poly(oxymethylene) copolymer, nylon 6, nylon 66, poly(ethylene terephthalate), and polystyrene. Generally, the bond strength increase rapidly initially and then remains nearly constant, perhaps decreasing in some cases at long exposure times. A method is presented for calculating bond strength‐versus‐exposure time curves. The calculated curves generally fit the data reasonably well. Polypropylene showed a rapid increase in bondability with exposure to excited oxygen. Helium was ineffective toward this polymer under normal conditions, but could produce good bond strength at higher temperatures.
Rheological properties of molten poly(ethylene terephthalate)
Authors: Gregory D. R.
Published: April 2003

The complete steady‐state flow properties of molten poly(ethylene terephthalate) for shear stresses ≦4.14 × 106 dynes/cm2 were determined. A single, complete master curve had been constructed in earlier work by Gregory and Watson; the curve interrelates the shear stress, shear rate, temperature, and molecular weight (inherent viscosity) by using a temperature superposition scheme from the literature and a similar molecular weight superposition scheme.

Equations in agreement with theory and with other published experimental data were derived from the master curve. Results presented here make possible the direct calculation of the melt viscosity of poly(ethylene terephthalate) at shear stresses ≦4.14 × 106 dynes/cm2. The effects of a unit temperature change and/or a unit change in inherent viscosity (I. V.) on the melt viscosity were determined. For poly(ethylene terephthalate) with a 0.6 I. V., a 0.0025 change in I. V. accounts for about the same change in melt viscosity as a 1°C change in temperature.
Melt viscosities of molten poly(ethylene terephthalate) calculated from modified Bueche‐Harding equation
Authors: Gregory D. R.
Published: April 2003

The semiempirical Bueche‐Harding equation was successfully modified to allow the calculation of experimentally verified melt viscosities of molten poly(ethylene terephthalate) (PET) for shear stresses > 9.65 × 105 dynes/cm2 by accounting for the definite Newtonian region in the flow behavior of PET for shear stresses lE; 9.65 × 105 dynes/cm2. Melt viscosity values calculated from the modified Bueche‐Harding equation agreed within ±12% of the values calculated from the equations based on experimental data.
Reversible crosslinking in cellulose. IV. Reactions of tosylcellulose with potassium thiolacetate
Authors: Sakamoto Munenori , Yamada Yoshio , Ojima Nobuko , Tonami Hiroaki
Published: April 2003

Reactions of tosylated cotton with potassium thiolacetate followed by alkaline hydrolysis yielded products containing both mercaptan and disulfide. The proportion of disulfide in the products depended much on the solvent used for the thiolacetylation. Reactions of tosylcellulose with thiolacetate in various solvents were investigated by polarographic and infrared analyses. Part of the acetylthio groups produced in acetone or in dimethylformamide was found to undergo rearrangement to form mercaptocellulose acetate. On the other hand, acetylthio groups formed in methanol were found to undergo complete methanolysis to form mercaptocellulose, and most of the mercapto groups thus produced were oxidized before hydrolysis treatment to yield the corresponding disulfide. This could account for the high disulfide proportion in the sample obtained through the reaction of tosylcellulose in methanol. Reaction of tosylcellulose with sodium thiosulfate yielded cellulose disulfide without mercaptan formation.