bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of γ‐irradiation on the loss properties of dielectrics in vacuum
Authors: Miles J. K. , Newell D. M. 
Published: April 2003

AbstractDielectric constant and dissipation factor of six types of dielectrics were measured during irradiation in a Co60 source. Tests were made at seven frequencies ranging from 100 cycles/sec. to 100 kcycles/sec. by use of the Schering bridge technique. Polystyrene and polyethylene exhibited no change in loss properties when γ‐irradiated to doses as high as 7.7 × 107 and 3.5 × 107 r, respectively. Poly(methyl methacrylate) decreased slightly in dielectric constant and was essentially unchanged in dissipation factor after 5.7 × 107. TFE underwent the most drastic changes. At a very low dose (106 r) the dissipation factor had increased three orders of magnitude (at 100 cycles/sec.) and one order of magnitude (at 100 kcycles/sec.). After peaking, the loss factor decreased slowly. After removal of the source, the loss factor decreased more; then increased rapidly upon admission of air. Both this and the original increase in dissipation factor are indicative of a dipole with a long relaxation time, in which oxygen plays a role. FEP Teflon increased somewhat less than TFE, and the peak was not reached until a dose of 3 × 107 r. Very little effect was produced by the admission of air after irradiation. Dielectric constant decreased with radiation dose. The dissipation factor and dielectric constant of Rayolin N decreased with dose, until a plateau was reached. Very little effect was seen after irradiation, even upon the admission of air. The changes which took place during the radiation period were, as in the case of the other materials, greater at the lower frequencies than they were at the higher frequencies.
Thermal degradation of poly(phenylene oxides)
Authors: Cox J. M. , Wright B. A. , Wright W. W. 
Published: April 2003

AbstractThe thermal degradation in vacuum of a number of halogenated poly(phenylene oxide) polymers has been studied by a weight loss method. In general the thermal stability decreased as the degree of substitution in the phenylene nuclei increased. The chloro derivatives were relatively more stable than the corresponding bromo derivatives. The majority of the polymers showed an initial rapid loss in weight followed by the formation of a highly stable residue. The good thermal stability of the simpler poly(phenylene oxides), coupled with their fusibility and solubility, indicate that they may be useful starting products for the preparation of practical materials.
Oxidative degradation of poly(ethyl acrylate)
Authors: Conley Robert T. , Valint Paul L. 
Published: April 2003

AbstractThe oxidative degradation of poly(ethyl acrylate) was investigated by infrared spectrophotometric techniques, and the volatile degradation products were determined by vapor‐phase chromatographic analysis. During the course of degradation, no change in the spectrum of the polymer, indicating the formation of other moieties, was detected. There was only a generally uniform decrease of all the existing absorption bands with the exception of the 5.75–5.85 μ ester‐ketone carbonyl region. This decrease of absorption proceeded appreciably slower than the rate previously reported for the degradation of poly(ethylacrylate). The reported formation of carboxylic acid groups detected in the spectrum of degraded polymer was not substantiated in this study. In contrast to degraded poly(ethyl acrylate), the low molecular weight, volatile polymer formed on oxidation was highly oxidized. In addition, the highly volatile degradation products were identified as carbon dioxide, water, ethyl acetate, and ethyl alcohol. No monomer, ethyl acrylate, could be detected among the volatile products. A methanistic pathway was postulated based on these results. Initially, there is attack of molecular oxygen at the tertiary carbon atoms of the polymer chain to form hydroperoxide groups. Subsequent decomposition of the hydroperoxides results in random chain scission eventually giving low molecular weight polymeric units. Further oxidation of the low polymer units leads to the observed product formation.
Studies on cation‐exchange membrane. II. Sorption of electrolyte by rubber‐based cation‐exchange membrane from CNSL resin
Authors: Suryanarayana N. P. , Joshi K. M. 
Published: April 2003

AbstractElectrolyte sorption of a rubber‐based cation‐exchange membrane has been studied for two samples of different rubber contents. The sorption behavior is discussed in terms of the capillary volume between rubber and the resin, and an explanation is provided for the difference in the behavior of the two samples.
The photooxidation of polymers. I. Experimental methods
Authors: Grassie N. , Weir N. A. 
Published: April 2003

AbstractThe very early stages of the oxidation of polymers at ordinary temperatures must be studied if the ultimate reasons for oxidative instability are to be discovered. To this end apparatus which will allow the absorption of small amounts of oxygen to be measured with high precision has been designed and built. Its design is such that both photoinitiated oxidation and pure photolysis may be studied. Experimental manipulation of the apparatus and the calculation of results are discussed, as well as the preparation of polystyrene films for photooxidation and photolysis investigations.
The photooxidation of polymers. III. Photooxidation of polystyrene
Authors: Grassie N. , Weir N. A. 
Published: April 2003

AbstractIn the photooxidation of polystyrene films at 28°C. under 2537 A. radiation, water and carbon dioxide are the only significant volatile products. The intensity exponent of the reaction is unity under 600 mm. O2 but zero under 20 mm., the quantum yield for oxygen absorption is 8.73 × 10−2, the overall energy of activation is 6.0 kcal./mole, and the rate is independent of molecular weight. In addition, the rate is directly proportional to oxygen pressure, whether or not the total pressure is made up to 600 mm. with nitrogen. Investigation of the effect of film thickness shows that neither the nonuniform distribution of initiating radiation in the film nor the diffusion of oxygen influences the reaction rate abnormally. The free radical inhibitor 2,6‐di‐tert‐butyl‐4‐methylphenol has no influence on the reaction, but the ultraviolet absorber 2‐hydroxy‐4‐methoxylbenzophenone accelerates oxygen absorption, having a maximum effect at approximately 3% concentration. It appears that the effect of ultraviolet absorbers is to protect the bulk of the polymer at the expense of the surface layer. Under 3650 A. radiation the oxygen absorption is much slower and the reaction exhibits an induction period. From these results it appears that while the initially formed radicals react with oxygen to form ROO· and HOO· radicals, the next step in the Bolland hydroperoxidation mechanism, RO2 · + RH → ROOH + R ·, is effectively suppressed by the lack of mobility of the long chain radicals within the solid polymer. The kinetic behavior described above can be accounted for qualitatively in terms of three competing processes, namely: (a) direct recombination of the primary radicals, R· and H·, (b) reaction of these primary radicals with oxygen, and (c) diffusion of the hydrogen atoms from the site of their formation.
Catalytic effects of 1,1,3,3‐tetramethylguanidine for isocyanate reactions
Authors: Geoghegan J. T. , Roth R. W. 
Published: April 2003

Abstract1,1,3,3‐Tetramethylguanidine was found to be a more effective catalyst than triethylamine or 1,1,3,3‐tetramethyl‐1,4‐butanediamine and poorer than diazobicyclooctane for the reaction of phenyl isocyanate with 2‐ethylhexanol. Similar catalysis was found for the phenyl isocyanate‐water reaction. It is postulated that the actual catalyst is the reaction product between 1,1,3,3‐tetramethylguanidine and phenyl isocyanate, 1‐phenyl‐3‐[bis(N,N‐dimethylamino)methylene]urea.
Hydrolytic degradation of polymeric insulation materials as measured by infrared absorption spectroscopy
Authors: Pobiner Harvey , Jawitz Martin W. 
Published: April 2003

AbstractThe hydrolytic degradation of certain polymeric insulation materials can be monitored by an infrared band–ratio spectroscopic method. These polymers, used in the precision electronic components of the aerospace industry, were a polyester (Mylar), a polyvinyl fluoride (Tedlar), and a polyimide (H–film). The polymer films were synthetically aged under selected conditions of temperature, moisture, and time. As ingrowth infrared bands appeared, assignments of the functional group bands of the degradation products were made. The band–ratio data gave a quantitative indication of the extent of degradation. The polyimide film showed the greatest resistance to hydrolysis, followed by the polyvinyl fluoride, and lastly, the polyester.
Comments on dielectric relaxation in solutions and moisture sorption in cellulose acetate
Authors: Barker R. E. 
Published: April 2003

AbstractThe model of Fuoss and Boyd which interprets the Stokes' radius rs of an ion in solution as a sum (r + s/ε) of the ionic radius r and a dielectric interaction term s/ε is shown to be at least semiquantitatively applicable to alkali halides in aqueous solutions. Possible applications of the model to amorphous hydrophilic polymers are suggested. This note also contains several corrections to a previous paper.
Theory of rotational dynamic measurement of plastics
Authors: Kaelble D. H. 
Published: April 2003

AbstractA theory which postulates a condition of combined constraints of constant stress and constant strain is developed for the rotating cantilever beam measurement of dynamic mechanical properties of rigid plastics. The theory provides operating equations for the rotating beam instrument of Maxwell equipped with a biaxial strain gage dynamometer. The storage component of the dynamic Young's modulus E′ = 64 L3F1/3πd4(ΔXt − K1F1) and the mechanical loss tangent tan γ = [F2(δXt − K1F1) + K2F1F2]/[F1(ΔXt − K1F1) − K2(F2)2] are expressed in terms of the length L and diameter d of the circular rod specimen; the bending spring constants of the biaxial dynamometer K1 K2; the imposed dynamometer displacement (ΔXt); and the cantilever beam storage and loss response forces F1, F2.
Crosslinking of cis‐polybutadiene by co60 γ‐rays
Authors: Jankowski Bogdan , Kroh Jerzy 
Published: April 2003

AbstractThe radiation‐induced vulcanization of cis‐polybutadiene (Europrene Cis, 92% cis‐configuration) was investigated. The crosslinking density of irradiated rubber was determined by two methods: equilibrium swelling and equilibrium compression modulus. The inhibition and acceleration of radiation‐induced crosslinking by addition to Europrene Cis of sulfur, Thiurame, Elastopar, Arubrene, paraffin oil, or barium sulfate was studied. The chemical resistance of radiation vulcanizates to 10% nitric acid was determined.
Polymers of acetylenic nitriles
Authors: Lee S. M. 
Published: April 2003

AbstractEfforts to prepare 1,6‐dicyano‐2,4‐hexadiyne resulted in the formation of insoluble, chemically inert, high‐melting “brick dust” type polymeric materials. Similar appearing products arose from the dihalo‐, ditosyl‐, and dihydroxy‐ hexadiyne derivatives as well as propargyl halide starting materials. It appears that diacetylenic diols and their propargylic precursors undergo direct nitrilation.
Properties of fibers and films of a thiazole polymer: Poly(2‐tetramethylene‐4‐phenylenethiazole)
Authors: Sheehan W. C. , Cole T. B. , Picklesimer L. G. 
Published: April 2003

AbstractFiber formation of tetramethylenephenylenethiazole polymers has been investigated by melt‐, wet‐, and dry‐spinning methods. The effects on fiber properties, the molecular weight of the polymer, the method of spinning, and the amount the fiber is drawn after spinning have been studied. The stability of the fibers to strong acids and alkali was also determined. The physical properties and the resistance to ultraviolet and gamma radiations of films of tetramethylenephenylenethiazole polymers were determined and compared with similar properties of some commercial films.
Polymerization rates of monochlorostyrenes
Authors: Rubens L. C. 
Published: April 2003

AbstractThe polymerization rates of o‐ and p‐chlorostyrenes have been determined under a variety of reaction conditions. These monomers polymerize much more rapidly than styrene thermally with peroxide, or high energy radiation. With no initiator the polymerization of chlorostyrene follows a behavior similar to styrene, i.e., the reaction exhibits a maximum rate during the initial stage of the reaction. With initiator, the form of the rate curve changes and acceleration is observed in the midconversion range. The ratio of the accelerated rate to the initial rate increases with initiator concentration. Mixtures of chlorostyrene with small amounts of certain difunctional monomers (e.g., divinylbenzene, ethylene dimethacrylate, and biacrylophenone) copolymerize much more rapidly than the chlorostyrene polymerizes alone. Polyester resins containing maleic or fumaric unsaturation copolymerize much more rapidly with chlorostyrene than with styrene under identical reaction conditions.
Curing ethylene–propylene rubber terpolymers with dimethacrylate monomers. II. Effect of unsaturation
Authors: Cornell John , Howarth J. T. , Olson L. Raymond , Winters Albert J. , Ellis Sylvia J. 
Published: April 2003

AbstractIn a previous paper it was shown that the vulcanization obtained with ethylene‐propylene‐diene terpolymer is equivalent or superior to that obtained with ethylene‐propylene copolymer when a peroxide‐dimethacrylate coagent cure system was used. In order to determine the effect of the unsaturation on the physical properties in the terpolymer, the terpolymer had been hydrogenated to remove the double bonds. Infrared spectra and bromination were used to check the extent of hydrogenation. Tensile strength, Shore A hardness, per cent elongation, and modulus indicated no decrease in vulcanization efficiency after hydrogenation. The data show that the unsaturation in the terpolymer does not contribute to the vulcanization cure with the peroxide‐dimethacrylate coagent curing system.
Surface tension and viscosity studies of molten resins for thermoplastic recording
Authors: Toy Madeline S. 
Published: April 2003

AbstractAnalytical and experimental studies of surface tension and viscosity properties of Dow resins PS‐2 and 276V‐2 are described. This investigation was undertaken to provide information on materials of interest for thermoplastic recording. It was found that external plasticization lowered the surface tension of the polystyrene while greatly decreasing the viscosity. Typical values for a 25% mixture of PS‐2 in 276V‐2 are γ = 35 dynes/cm. and η = 20 poise at 80°C.
Heptane‐soluble material from atactic polypropylene. I. Fractionation and characterization of fractions
Authors: Moore W. R. , Boden G. F. 
Published: April 2003

AbstractA sample of commercial atactic polypropylene was extracted with ether and the residue extracted with boiling n‐heptane. Six fractions of the heptane‐soluble material, which is very similar to that obtained by heptane extraction of isotactic polypropylene, were obtained by stepwise addition of acetone to a solution in cyclohexane. Densities, melting points, and x‐ray photographs of the fractions and the unfractionated material were obtained and infrared absorption spectra used to estimate tacticity. Molecular weights, determined by means of a vapor pressure osmometer, ranged from about 3000 to about 25,000. That of the fraction of highest molecular weight was in good agreement with a separate determination by means of osmotic pressure measurements. Separation in fractionation occurred in order of decreasing molecular weight and increasing crystallinity as estimated from densities and x‐ray photographs. Tacticity also seems to increase with decreasing molecular weight. Melting points of the fractions were not entirely in the order expected from their molecular weights and estimated crystallinities, and it is possible that low DP isotactic material may be preferentially concentrated in the highest molecular weight fraction. It is emphasized that the unfractionated material may contain polymers possessing a range of order intermediate between those of purely atactic and purely isotactic polymer and that refractionation may be required in order to characterize the material completely.
Studies in hard rubber reaction. Part IV. Effect of fillers
Authors: Bhaumik M. L. , Banerjee D. , Sircar Anil K. 
Published: April 2003

AbstractThe effects of the different fillers i.e., china clay, light magnesium carbonate, Pliolite S6E, and ebonite dust, on the exothermic hard rubber reaction has been studied with the help of differential thermal analysis. The data for heat evolution show some unexpected features in that china clay, a more or less inert filler, lowers heat evolution. The behavior of magnesium carbonate also can not be fully explained. Attempts have been made to explain the data for Pliolite S6E and ebonite dust on the basis of their composition and effects of the individual components on heat of reaction. The differences in initiation temperature and slope values have been explained.
Anionic heterogeneous polymerization of acrylonitrile by butyllithium. I
Authors: Feit Ben‐Ami , Mirelman David , Zilkha Albert 
Published: April 2003

AbstractThe anionic heterogeneous polymerization of acrylonitrile in petroleum ether by n‐butyllithium was studied under various experimental conditions. The dependence of the molecular weight on the total concentrations of the monomer and initiator was strongly affected by the momentary concentration of monomer in the polymerization mixture and by the order of their addition to it. Two polymerization mechanisms were found to operate simultaneously. When monomer was added to the catalyst solution at low rates, nonterminated “living” polymerization was essentially dominant, as was evident from the linear dependence of DP on [monomer] and 1/[BuLi]. Under such conditions DP was independent of the rate of monomer addition. Chain transfer to monomer was the dominant mechanism at high rates of monomer addition, as was evident from the independence of the degree of polymerization of both monomer and initiator concentrations. At intermediate rates of monomer addition the extent of each of the two mechanisms was appreciable, and DP increased with decreasing the rate of monomer addition. A two‐stage propagation step in which the growing carbanion of the C−Li+ ion‐pair was solvated by monomer, was suggested to be responsible for the dependence of the polymerization mechanism on the momentary concentration of monomer in the polymerization mixture.
Radiation‐induced block or graft copolymers of methyl methacrylate with isobutylene and ethylene–propylene rubbers
Authors: Pellon Joseph , Valan Kent J. 
Published: April 2003

AbstractAttempts to prepare block or graft copolymers of isobutylene rubbers by radiation in the presence of methyl methacrylate gave low yields of copolymer with only 20% of the rubber entering into the copolymer. The remainder of the rubber is degraded during the process. A single experiment describes the graft copolymerization of methyl methacrylate with ethylene–propylene rubber in which 45% of the rubber is copolymerized.
Thermal degradation of 6‐chloro carbohydrates
Authors: Shafizadeh F. , Lai Y. Z. , Nelson C. R. 
Published: April 2003

AbstractIt has been shown that 6‐chloro sugar derivatives are thermally less stable than the corresponding unsubstituted carbohydrates. When heated, they generate hydrogen chloride which catalyzes a series of heterolytic reactions including transglycosylation, dehydration, inter‐ and intramolecular etherification, and condensation. The latter products are ultimately carbonized through free‐radical reactions producing large amounts of char.
Dynamic rheological properties of polyisobutylene
Authors: Dunlop A. N. , Williams H. Leverne 
Published: April 2003

AbstractThe viscoelastic properties of polyisobutylene melts were investigated as functions of temperature, molecular weight, and molecular weight distribution. The effect of molecular weight distribution was studied through the use of blends of narrow distribution polymers. The Ninomiya and Ferry theory was used successfully to predict the viscosity of the blends. It was observed that the temperature coefficient for flow was independent of molecular weight distribution and of molecular weight. It was shown, at least in the case of polyisobutylene melts, that the temperature dependence of elasticity is less for polymers with greater polydispersity.
Corona‐induced graft polymerization of ethyl acrylate onto cellulose film
Authors: Sakata I. , Goring D. A. I. 
Published: April 2003

AbstractEthyl acrylate was readily grafted from an aqueous solution onto cellophane film previously treated in a corona discharge at atmospheric pressure. The effect was found when the corona treatment was carried out not only in air but also in pure nitrogen. The observed grafting was not promoted but depressed by the presence of ferrous ion, which indicated that peroxide radicals were not initiating the graft. A high grafting efficiency was obtained, and the grafted surface was covered with a smooth uniform layer of polymer.
Thermal degradation of polymers. X. Thermal analysis studies on poly(p‐N,N‐dimethylaminostyrene) homopolymers and copolymers with styrene in nitrogen
Authors: Still R. H. , Whitehead A. 
Published: April 2003

AbstractStudies have been made on the effect of the molecular weight of p‐N,N‐dimethylaminostyrene homopolymers and the composition of its copolymers with styrene on the glass transition temperature. Comparative thermal degradation studies have been made on polystyrene and p‐N,N‐dimethylaminostyrene polymers by thermal analytical methods (TG, DTA, and DSC). The differences in thermal stability and overall thermal degradation behavior of the two systems are discussed in terms of the differences in their degradation mechanisms.
Radiation protection of poly(vinyl chloride) by N,N‐dialkyl dithiocarbamate substitution
Authors: Nakagawa Tsutomu , Fujiwara Yukihiko 
Published: April 2003

AbstractThe effect of N,N‐dialkyl dithiocarbamate substitution on the radiation stability of poly(vinyl chloride) (PVC) film was studied. PVC containing 6.5–15.7 mole‐% N,N‐dimethyl dithiocarbamate (PDM) and PVC containing 8.3–17.5 mole‐% N,N‐diethyl dithiocarbamate (PDE) was irradiated with γ‐rays from a Co‐60 source at room temperature under vacuum. The evolved gaseous products were measured and analyzed with a mass spectrometer. The apparent G values for gas evolution of PDM and PDE decreased remarkably. For example, a G value of 0.10 was obtained for a PDE which contains 17.5 mole‐% diethyl dithiocarbamate group. The mass spectrum of the evolved gas from the same PDE sample with 10‐Mrad irradiation showed no hydrogen chloride to be present. The external protection was studied using polymer‐blended films of PVC and PDE or PDM. The stabilization coefficients for internal protection and external protection in polymer blends were calculated. Although the ESR spectrum of the irradiated PDM, PDE, and PVDE which is synthesized by polymerization of S‐vinyl‐N,N‐diethyl dithiocarbamate (VDE) showed the same sulfur radicals, they were different from those of the irradiated cysteamine hydrochloride and PVC containing N‐methyl dithiocarbamate (PMD). From these results, the protection of a polymer by a covalently bound dithiocarbamate was discussed.