bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of γ‐irradiation on the loss properties of dielectrics in vacuum
Authors: Miles J. K. , Newell D. M.
Published: April 2003

Dielectric 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

The 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

The 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

Electrolyte 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

The 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

In 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

1,1,3,3‐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

The 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

The 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

A 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

The 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

Efforts 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

Fiber 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

The 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

In 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

Analytical 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

A 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

The 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

The 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

Attempts 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

It 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

The 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

Ethyl 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

Studies 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

The 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.
Polyblends. III. Correlation of the viscoelastic data for polyblends of NBR and plasticized vinyl chloride compositions with theories of polycomposite behavior
Authors: Jordan Edmund F. , Artymyshyn Bohdan , Riser George R.
Published: April 2003

Viscoelastic data obtained on the polyblends described in the previous two papers together with some new data have been correlated with various theories derived for the viscosity and continuum properties of polycomposites, to gain insight into the nature of compatible domain interactions. Unmodified theories of Mooney, Eilers and Van Dyck, Guth and Smallwood, and Kerner did not correlate with the observed viscoelastic data. However, when the Kerner relation was substantially altered (after allowing for phase inversion following procedures of Halpin and Tsai as modified by Nielsen), an adequate description of torsional modulus behavior at ambient temperature was obtained. To characterize tensile modulus (100%), however, a new expression was necessary. Both procedures invoked in a critical modulus for the blend with respect to composition at which phase inversion was initiated. The critical volume fraction associated with this modulus increased inversely with the Tg of the filler; when the filler Tg was below the ambient temperature, the blends behaved as mixed rubbers, and torsional modulus ratios followed the lower Kerner relation at all blend compositions. It was concluded that polyblends having isochronal modulus–temperature curves that shift with composition over the temperature scale yet are anomalously broad as in the present work should be classified as systems exhibiting restricted molecular mixing. The restricted molecular mixing character exhibited by the polyblends could be explained by a plurality of mixed‐phase responses to deformation produced in a morphology of interlocking microdispersions. Favourable polarity effects and high filler ductility were considered responsible for the domain interactions. No evidence was found for true molecular compatibility in the blends. An analysis of temperature effects on the blend viscoelasticity resulted in a temperature analog of the composition behavior.
Study on ozone treatment of water‐soluble polymers. II. Utilization of ozonized polyethylene glycol by bacteria
Authors: Suzuki Junzo , Nakagawa Hisako , Ito Haruo
Published: April 2003

A bacterium capable of utilizing polyethylene glycol of low molecular weight (less than 300) was isolated from soil and identified as Pseudomonas aeruginosa by biologic characteristics (named P. aeruginosa PEG‐K). The effect of ozone degradation on the utilization of polyethylene glycol of high molecular weight by the bacterium was studied on the basis of the measurement of oxygen uptake by Warburg manometer and of bacterial growth. The polyethylene glycol, which can never be utilized at all because of high molecular weight, became utilizable by the bacterium as a result of ozonization, while the formaldehyde produced by the ozonization inhibited the utilization of the ozonized polyethylene glycol by the same bacterium. However, such inhibition disappeared by treating the aldehyde with hydrogen peroxide. From the results of gas chromatography and measurement of chemical oxygen demand, P. aeruginosa PEG‐K was found to utilize ethylene glycol, diethylene glycol, and triethylene glycol, which were produced by the ozonization.
An examination of the dow and NBS 705 polystyrene standards via gel permeation chromatography
Authors: Fetters L. J.
Published: April 2003

An examination of the molecular weight distribution via gel permeation chromatography of the Dow S‐109 and NBS 705 polystyrenes has revealed that these two samples are the same. Within experimental error, both polystyrenes possess identical number ‐and weight‐average molecular weights. In addition, the molecular characteristics of the Dow S‐102, Dow S‐105, Dow S‐108, and Dow S‐111 polystyrenes were determined. Of the samples examined, the near‐monodisperse NBS 705, Dow S‐102, Dow S‐109, and Dow S‐111 were found to have either low or high molecular weight components in their molecular weight distributions. The characterization results on the Dow S‐109 polystyrene fail, though, to explain the melt viscosity anomalies reported for this polymer.
Stoichiometrically solvated polyalkylbenzimidazole crystals
Authors: Aharoni Shaul M.
Published: April 2003

Unlike most crystallizable polymers, some polyalkylbenzimidazoles do not crystallize when pure but do crystallize with ionized solvent molecules to produce solid stoichiometrical, solvated crystals. The polymer–solvent interaction is strongly exothermic, and a crosslinked polymer swells in the solvent over hundredfold. This leads to a negative χ1 value for the system. The cocrystallization with stoichiometric amounts of ionized solvent cannot be examined on the assumption that it is a polyelectrolyte gel since ion mobility is precluded. It also cannot be treated according to the corresponding states theory since the latter does not allow for negative χ1. A theoritical derivation, originating from Flory's semiflexible chain treatment, apparently predicts and explains the behavior of the polyalkylbenzimidazole–solvent system.
Aspects of vapor pressure osmometry
Authors: Morris C. E. M.
Published: April 2003

Three aspects of vapor pressure osmometry were examined: drop size, solute volatility, and the constancy of the calibration factor. It was shown that there is a drop size effect which is dependent on the solute concentration. Solutes having vapor pressures as low as 0.3 mm Hg under the operating conditions were found to give unsatisfactory results. The calibration factor was determined using eight compounds in the molecular weight range of 128 to 883 in chloroform, toluene, and methyl ethyl ketone at several temperatures; a small but significant dependence of the calibration factor on molecular weight was demonstrated. The results fitted, with a high degree of accuracy, the relation log M̄n = a + b log (ΔV/C)C = 0, where a and b are constants for a given solvent/temperature combination. However, measurements with standard polystyrene samples, using extrapolations of this relationship to higher molecular weights, revealed considerable discrepancies in results for the one compound under different solvent/temperature combinations.
Gel permeation chromatography: Dispersion effects on molecular weight monitor‐installed gel permeation chromatograph
Authors: Kotaka Tadao
Published: April 2003

Computer simulation was carried out to examine the performance of a molecular weight (MW) monitor‐installed gel permeation chromatograph (GPC), by taking account of the effects of limited column resolution according to Tung's phenomenological scheme. Efficiency of GPC fractionation was discussed also in the same light. For simulated GPC fractionation results of model polymers having log‐normal distribution, various average MW's and MWD functions were calculated from the data obtained by the MW monitor method as well as the conventional MW calibration methods, and compared with the given true values. The MW monitor method generally tends to predict narrower distributions than the true ones, as opposed to the conventional calibration methods which usually predict broader distributions. For certain simple cases, semiquantitative relation between the extent of column resolution and these deduced average MW's was derived. The efficiency of GPC fractionation (as judged, for example, by the polydispersity of recovered fractions) is limited by such factors as fraction size, column resolution, and polydispersity of the original sample itself.
Photosensitized degradation of polyolefins. II
Authors: Mantovani E. , Mazzei M. , Robertiello A. , Zanobi A.
Published: April 2003

The oxydative photodegradation of polyethylene sensitized by aromatically substituted dienes such as 1,6‐diphenyl‐1,3,5‐hexatriene (DPH) and 1,4‐diphenyl‐1,3‐butadiene (DPB) has been investigated. The rate of degradation has been monitored by following the change of the mechanical properties of the polymer during accelerated indoor aging tests. It was found that both additives are efficient sensitizers of the photodegradation of polyethylene. The mechanism of photo‐oxidation has been investigated by ESR and IR spectroscopy and it has been interpreted on the basis of a complex mechanism which includes excited singlet oxygen (1O2) and the products of photodegradation of the additives.

Singlet oxygen, produced by DPB and DPH and/or by impurities present in the polymer, reacts with the additives themselves and, directly, with polyethylene. In turn, the products of photodegradation of the additives react with the polymer via hydrogen atom abstraction, further promoting the photodegradation.

Irradiation carried out in absence of air seems to rule out the possibility of direct hydrogen atom abstraction by DPB and DPH.
Iodine‐initiated, solid‐state copolymerization of tetraoxane with 1,3‐dioxolane in the presence of methylal. I. Fundamental study on beaker‐scale copolymerization
Authors: Ishigaki Isao , Watanabe Yuhei , Morita Yosuke , Takada Kiyoshi , Ito Akihiko
Published: April 2003

The iodine‐initiated, solid‐state copolymerization of tetraoxane with 1,3‐dioxolane in the presence of methylal has been studied on a beaker scale. It was found that tetraoxane can be easily copolymerized with 1,3‐dioxolane by a small amount of iodine as initiator and gives oxymethylene copolymer with excellent thermal stability in a high yield. The copolymerization was largely influenced by the concentrations of iodine, 1,3‐dioxolane, and methylal, i.e., the polymerization rate increased with increase not only in iodine but also in 1,3‐dioxolane, and the thermal stability and the molecular weight of the copolymer were mainly affected by 1,3‐dioxolane and methylal concentration, respectively.
Diffusion of radioactively tagged penetrants through rubbery polymers. I. Penetrants with very low solubility
Authors: Rhee Chong‐Kon , Ferry John D.
Published: April 2003

The diffusion of radioactively tagged n‐hexadecane, 1,7‐heptanediol, and ethylene glycol has been studied in one polar and six nonpolar rubbery polymers. The penetrant–polymer pairs included some in which the two components were miscible in all proportions and some in which they were nearly incompatible (solubility of penetrant in polymer of the order of 1%). The theory for the thin smear method for measuring the diffusion coefficient was evaluated for incompatible pairs with two cases: case 2, when the rate‐limiting step is diffusion through the polymer; and case 3, when the rate‐limiting step is entry into the polymer across the penetrant–polymer interface. They are easily distinguished experimentally from each other and from case 1, which refers to completely miscible pairs. In examples of case 3, e.g., ethylene glycol with butadiene or styrene–butadiene rubbers, the half‐time for saturating the polymer surface in contact with the penetrant was found to be several days at 25°C. The diffusion coefficients, when compared in four hydrocarbon rubbers, of n‐hexadecane and 1,7‐heptanediol were similar in magnitude even though in each rubber the hexadecane was soluble in all proportions and the diol only very slightly. The diffusion coefficient of ethylene glycol, despite its extreme thermodynamic incompatibility, appeared to be somewhat larger than those of the other penetrants.
Radiation degradation of α‐substituted acrylate polymers and copolymers
Authors: Helbert John N. , Caplan Philip J. , Poindexter Edward H.
Published: April 2003

Radiation degradation is observed in poly(methyl α‐chloroacrylate), poly(methyl α‐cyanoacrylate), and poly(α‐chloroacrylonitrile) homopolymers and their respective MMA copolymers when γ‐irradiated in vacuo. Polymer degradation susceptibilities are quantified in terms of G(scission radicals) and G(scission) − G(crosslinks), measured by EPR and membrane osmometry, respectively, values by these two methods are compared. Higher G(rads) values ranging from 2 to 6 and [G(s) − G(x)] values ranging from 2 to 11 are obtained for the substituted polymers and copolymers relative to the values for PMMA (1.6; 1.9), a standard e‐beam positive resist, which suggests that these modified polymers are more sensitive e‐beam resists than PMMA.
Accelerated photo‐oxidation of polyethylene. I. Screening of degradation‐sensitizing additives
Authors: Taylor Lynn J. , Tobias John W.
Published: April 2003

Numerous simple compounds have been shown to be capable of accelerating the photo‐oxidation of polyethylene upon exposure to wavelengths near 300 nanometers. Probable mechanisms of photo‐initiation by the principal classes of degradation‐promoting additives are discussed.
Preparation and properties of phenolic resin laminates. I. Laboratory evaluation
Authors: Meier J. F. , Bellott E. M. , Frank P. P.
Published: April 2003

The preparation and properties of sodium carbonate and sodium hydroxide‐catalyzed phenolic resins polymerized in 1‐liter glass reactors over a broad range of F/P mole ratios are described. Laminates produced from selected sodium carbonate‐catalyzed resins coated on kraft paper are discussed and compared with laminates prepared from standard sodium hydroxide‐catalyzed resins. Several apparent advantages of the sodium carbonate‐catalyzed resin systems over the sodium hydroxide‐catalyzed resins are presented. The superior performance is attributed to the high degree of crosslinking resulting from the high concentration of methylolated phenols present in the sodium carbonate‐catalyzed resin.
A new method of determination of the permeability of vapors of volatile liquid substances through polymer membranes
Authors: Izydorczyk Jan , Podkówka Józef , Salwiński Janusz , Grzywna Zbigniew
Published: April 2003

A new apparatus for the determination of vapor permeability of volatile liquid substances through polymer membranes has been described. The permeability of the vapor is calculated from the measurements of the depression rate of the liquid meniscus in a calibrated capillary tube. The conditions of the measurements by means of the described method are very close to those of the average and practical application of foils. The method is characterized by a simple design of the apparatus, easy handling, and simplicity of the determinations, so it may constitute the basis of vapor permeability determination standards. The results obtained by means of the described method were compared with those derived from the partition cell method.
Radiation yield of hydrogen chloride in gamma‐irradiated poly(vinyl chloride) stabilized by epoxy compounds
Authors: Lerke I. , Szymański W.
Published: April 2003

The GHCI values of γ‐irradiated PVC mixtures were studied after addition of various amounts of three epoxy stabilizers: diglycidyl ether of 2,2‐bis(4‐hydroxy‐3‐methylphenyl)propane (I); diglycidyl ether of 1,1‐bis(4‐hydroxyphenyl)cyclohexane (II), and butyl‐cis‐9,10‐epoxystearate (III). The results indicated that two processes are essential for the stabilization: HCI capture by the epoxy groups, and an external protective effect, due to the remaining part of the stabilizer molecule. The role of the benzene rings in stabilizers I and II, as compared with the protective effect due to the long chains of stabilizer III, is not as dominant as one would expect.
Dyeing of chemically modified celluloses. II. Effect of chemical modification of cellulose on the dyeing properties of some direct dyes
Authors: Hebeish A. , Moursi A. Z. , Khalil M. I. , Abdel‐Mohdy F. A.
Published: April 2003

The behavior of partially acetylated cellulose, partially carboxymethylated cellulose, cyanoethylated cellulose, and cellulose grafted with polyacrylontrile toward three direct dyes, namely, Chlorantine Fast Red 6 BLL, Solophenyl Orange T4RL, and Diphenyl Brilliant Flavine 7GFF, was studied. Partially acetylated cellulose having 2.06% combined acetic acid showed higher dye uptake than the unmodified cellulose. The amount of dye uptake increased as the acetyl content increased up to 4% combined acetic acid. Beyond this, enhancement in the dye uptake was not significant. Whereas partially carboxymethylated cellulose showed a lower dye uptake than the control. The dye uptake decreased considerably as the carboxymethyl groups increased. The same holds true for cyanoethylated cellulose where increasing the cyanoethyl content caused a substantial reduction in the dye uptake. On the other hand, cellulose grafted with polyacrylonitrile up to 18.3% graft yield showed much higher dye uptake than the ungrafted cellulose.
Determination of compositional heterogeneity in butadiene–styrene copolymers by density gradient ultracentrifugation
Authors: Stacy C. J.
Published: April 2003

Sedimentation equilibrium in a density gradient gives a sensitive intermolecular composition analysis of styrene–butadiene copolymers. This information is sometimes unobtainable by other analytical techniques. The density gradient is formed by action of the centrifugal field upon a carbon tetrachloride–cyclohexane mixture, and the equilibrium position of each polymeric solute in the gradient depends upon its effective buoyant density. The large difference in styrene and butadiene densities makes possible accurate composition calibrations which are independent of molecular weight and branching.
Preparative gel permeation chromatography. I. Polypropylene
Authors: Vaughan M. F. , Francis M. A.
Published: April 2003

Preparative gel permeation chromatography was used to produce a number of polypropylene reference samples, within the molecular weight range of 10,000–600,000, from commercial materials. Some of these materials were degraded in a controlled manner to give base materials having suitable molecular weight characteristics. A procedure has been developed using a single preparative column packed with equal quantities of Styragel with nominal exclusion limits of 102, 103, 104, and 105 nm. The volume of solvent for recovery was minimized by use of higher loading factors than in analytical GPC (some 2–20 times more polymer was thus fractionated in each experiment). Under these conditions the fractions first eluted were sharpest having polydispersities of about 1.5. First fractions, from different base materials, were characterized by analytical GPC, and those of similar molecular weight and polydispersity were combined to give the reference samples. Refractionation was necessary with the highest molecular weight base material because the first stage fractions were not sharp enough. Some of these fractions were recovered at elution volumes where much lower molecular weight material was expected. Comparison with results from the other base materials indicates that the primary cause of the spreading is not overloading. This spreading is explained in terms of slower partitioning of the larger molecules between the interstitial fluid and the gel particles.
Stress–strain behavior, hardness, and thermomechanical properties of butadiene–styrene block copolymers as a function of processing technique
Authors: Leblanc Jean L.
Published: April 2003

Stress–strain properties of star‐shaped butadiene–styrene block copolymers were carried out on extruded sheet and injection molded samples. A striking “plastic‐like” behavior was observed during the first extension, with a marked yield point, a drawing process, and an important hysteresis. These phenomena disappeared on the second elongation, but annealing below the polystyrene glass transition temperature gave again the initial behavior. A marked processing technique dependence was observed in the stress–strain experiments. An important variation in hardness was observed before and after stretching, and annealing experiments permitted the study of hardness recovery. A logarithmic relation between recovered hardness and the annealing time at constant temperature was deduced from the experimental data. Thermomechanical analysis curves show singular transitions between 20° and 85°C, which disappear on stretching. An important discrepancy occurs in TMA curves of extruded and injected samples. A comparison is made of thermomechanical behavior of linear and star‐shaped SBS block copolymers. A modified model is proposed for a reversibly deformable structure composed of polybutadiene and polystyrene linked ends at the diffuse interfacial region between the PS domains and the PB matrix.
The effects of flow rate and column combination on the separation efficiency in multicolumn gel permeation chromatography
Authors: Ambler M. R. , Fetters L. J. , Kesten Y.
Published: April 2003

Using general‐purpose multicolumn sets, it was found that separations could be increased by increasing analysis time, either by decreasing flow rate or increasing column length. Several examples are shown illustrating the influence of these system variables. The generation of linear calibration curves over extended molecular weight ranges is discussed. In particular, the desirability of using high molecular weight standards to extend the calibration curve and eliminate extrapolation of the curve is shown. Not using all available gel porosities, i.e., gapped column sets, is shown to be detrimental to the resolution of molecular species. It was found that with the use of sufficiently long column lengths and flow rates, accurate molecular weights of both narrow and broad molecular weight distribution samples are directly calculable from the chromatogram without the need for peak spreading corrections.
Semiconductor properties of polyamide‐6 containing dispersed copper or zinc additives
Authors: Czekaj Tadeusz , Kapko Jerzy
Published: April 2003

It was expected that elemental copper or zinc introduced into polycaproamide would interact with amide groups of the polymer and that the materials would be characterized by semiconductor properties. To prove this theory, resistivity at several temperatures was determined and thermal activation energies calculated. As the metal contents were relatively low, metallic conductivity was avoided. Temperature‐resistivity dependence and a negative temperature coefficient of the resistivity prove that polyamide–metal compositions can be classified as semiconductors.
Polymerization of styrene with n‐butyllithium in a batch reactor. A mathematical model
Authors: Tanlak Tayfun , Ahmad Abu , Treybig Michael N. , Anthony Rayford G.
Published: April 2003

Sytrene was polymerized in a 0.8‐liter vessel which was operated as an isothermal and a nonisothermal batch reactor. Styrene and n‐butyllithium conversions were determined for different reaction times. Rate equations were developed by use of the isothermal data and then used to estimate the conversions for the nonisothermal experiments. The importance of using nonisothermal data in the development of rate equations is illustrated.
Reclamation of vulcanized rubbers by chemical degradation. VIII. Absorption of oxygen and degradation of cis‐1,4‐polyisoprene by phenylhydrazine–iron(II) chloride system
Authors: Yamashita Shinzo , Kato Shin'Ichi , Kawabata Nariyoshi , Okamoto Takao
Published: April 2003

Absorption of oxygen and degradation of cis‐1,4‐polyisoprene by the phenylhydrazine–iron(II) chloride system was investigated at 30°C in connection with the mechanism of reclamation of vulcanized rubbers by the system. In the presence of iron(II) chloride, phenylhydrazine rapidly absorbed an equimolar amount of oxygen and evolved an equimolar amount of nitrogen. Gas‐chromatographic analysis of the reaction mixture showed the presence of benzene, phenol, and biphenyl in 37%, 35–60%, and 4–8% yields, respectively, based on phenylhydrazine. When cis‐1,4‐polyisoprene was added to the reaction mixture, additional absorption of oxygen was observed. Molecular weight of the polymer decreased during the oxygen absorption, and the scission efficiency (i.e., number of mole scissions/mole oxygen) was 0.14–0.26.
The continuous measurement of the damping and fatigue properties of high‐impact polystyrene with a controlled‐amplitude torsion pendulum
Authors: Bartesch H. , Williams D. R. G.
Published: April 2003

Torsional damping and fatigue studies were made on high‐impact polystyrene using a controlled‐amplitude, continuously recording torsion pendulum. The damping behavior was measured as a function of the angular displacement, axial tensile stress, and the number of repeated cycles. At a critical axial tensile stress, the damping behavior changed from amplitude‐independent to amplitude‐dependent behavior. Damping measurements on high‐impact polystyrene specimens that had been previously crazed in tension showed that both the damping and the tensile stress necessary to produce amplitude‐dependent damping varied with the orientation of the craze. Repeated cycling of HIPS specimens produced crazing and amplitude‐dependent damping at a tensile stress below that expected from simple static tensile loading. Scanning electron micrographs of fracture surfaces from these specimens revealed that the rubber particles could be clearly distinguished from the surrounding matrix.