bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerisation du chlorure de vinyle par les systèmes Ti(OR)y Cl4–y–AlRxCl3–x en milieu CCl4
Authors: Guyot A. , Rocaniere P. 
Published: April 2003

AbstractVinyl chloride polymerizations by Ti(OR)yCl4–y–AlRxCl3–x systems, using carbon tetrachloride as solvent, obey a radical mechanism. Free radicals are generated from alkyl aluminum by way of decomposition of an organometallic compound of tetravalent titanium; the latter is formed either by direct reaction between aluminum and titanium compounds, or after reoxidation by CCl4 of a compound of trivalent titanium. The organometallic compound so obtained contains organic groups more complex than the alkyl group initially bond to aluminum.
The effect of impulsive preloadings on the behavior of quartz phenolic
Authors: Perkins R. D. , Babcock S. G. , Schierloh F. L. , Jones A. H. 
Published: April 2003

AbstractUniaxial strain and uniaxial stress preloadings were performed on quartz phenolic in order to assess the effect of an impulsive preload on the subsequent uniaxial stress behavior of a composite material. In these tests observable damage was limited to the phenolic matrix. As a result, postpreload experiments on the specimen under uniaxial stress correlated the dependence of the fracture strength with the extent of the damage to the phenolic matrix as well as the direction of the reload relative to the fiber layup.
Graft copolymerization of styrene with carbon black‐alkali metal complex
Authors: Minoura Yuji , Katano Masahide 
Published: April 2003

AbstractIt was found that an ion radical complex is formed by the reaction of carbon black with an alkali metal (Li, Na, K) in tetrahydrofuran. The graft copolymerization of styrene with carbon black was carried out using the ion radical complexes as initiator, and free polystyrene and carbon black‐polystyrene graft copolymer were obtained. The identification of the graft copolymer with carbon black was carried out by fractionation and thermal degradation. The initiation activity of the alkali metals increased in the order Li < Na < K. The effect of the particle size of the carbon black on the graft copolymerization was studied.
The pyrolysis of acrylic fiber in inert atmosphere. I. Reactions up to 400°C
Authors: Turner W. N. , Johnson F. C. 
Published: April 2003

AbstractThe pyrolysis of acrylic fiber up to 400°C in an inert atmosphere at 1° and 6°C/min was studied by means of thermogravimetric and differential thermal analysis. The exothermic reaction occuring at 180–300°C was shown to be due to the reaction of nitrile groups by comparing the extent of exotherm with the number of nitrile groups present, determined by infrared spectroscopy. In addition, results of single‐fiber tensile measurements, density, and elemental analysis of the pyrolyzed fibers are interpreted in terms of possible molecular structures. The gases evolved on pyrolysis were analyzed for both ammonia and hydrogen cyanide and the liberation of ammonia was attributed to a termination reaction of the polymerization of nitrile groups. The critical conditions necessary for the production of high strength and modulus carbon fiber are discussed briefly in ralation to the chemical changes occurring on pyrolysis.
Activated gas plasma surface treatment of polymers for adhesive bonding
Authors: Hall J. Richard , Westerdahl Carolyn A. L. , Devine Andrew T. , Bodnar Michael J. 
Published: April 2003

AbstractPolyethylene, polypropylene, poly(vinyl fluoride) (Tedlar), polystyrene, nylon 6, poly(ethylene terephthalate) (Mylar), polycarbonate, cellulose acetate butyrate, and a poly(oxymethylene) copolymer were treated with activated helium and with activated oxygen. Mechanical strengths of adhesive‐bonded specimens prepared from treated and from untreated coupons were compared. Polyethylene (PE) and polypropylene (PP) showed the greatest increases in bond strength. Oxygen and helium were both effective with polyethylene, but polypropylene showed no improvement when treated with activated helium. The results with excited helium parallel the effects of ionizing radiation on these two polymers, as does the appearance of unsaturation bands in the infrared (965 cm−1in PE, and 887 and 910 cm−1in PP). Active nitrogen produced excellent bond strength with polyethylene but not with polypropylene. Of the remaining polymers examined, Tedlar, polystyrene, and nylon 6 showed the greatest improvement in bondability after treatment, and Mylar showed moderate improvement. Polycarbonate, cellulose acetate butyrate, and the poly(oxymethylene) copolymer gave approximately two‐fold increases in lap‐shear bond strength. In several cases, significant differences in response to time of treatment and type of excited gas were found.
Supercooling of polydimethylsiloxane
Authors: Helmer J. D. , Polmanteer K. E. 
Published: April 2003

AbstractThis study was undertaken to determine the quenching rates necessary to supercool polydimethylsiloxane. A technique was developed that allowed controlled quenching rates up to 52°C/see and a modified DTA apparatus was used to obtain thermograms during the warm‐up cycle. No supercooling was observed for a cooling rate of 1.6°C/sec; 56% supercooling was found for a 9.6°C/sec cooling rate; 65% for 10.6°C/sec and 85% for a 52°C/sec cooling rate. Evidence was also presented showing that the crystals in polydimethylsiloxane consist of two forms.
Dielectric relaxation and crosslinking in unsaturated polyester resins
Authors: Learmonth George S. , Pritchard Geoffrey 
Published: April 2003

AbstractThe properties of crosslinked thermosetting resins depend markedly on the completeness of the crosslinking process. Determination of the degree of cure of an unsaturated polyester resin has been studied previously by mechanical, spectroscopic and volume resistivity methods. In this respect the effect of cure time and temperature on the ac dielectric constant and dissipation factor at 1 kc/s and 10 kc/s is considered. The dissipation factor appears to be a most useful parameter for detecting changes in the degree of cure in the later stages of reaction.The electrical properties of the cured resin are discussed, and values for the energy of activation for electrical conduction are compared with literature reports on similar materials.
The glass transition temperature of filled polymers and its effect on their physical properties
Authors: Droste D. H. , Dibenedetto A. T. 
Published: April 2003

AbstractThe glass transition temperature, dynamic shear moduli, and bulk viscosities of Phenoxy PKHH (a thermoplastic polymer made from bisphenol‐A and epichlorohydrin) filled with glass beads and Attapulgite clay were investigated. The glass temperature of the polymer increased with increasing filler concentration and with increasing specific surface area of the filler. The data were interpreted by assuming that interactions between filler particles and the polymer matrix reduce molecular mobility and flexibility of the polymer chains in the vicinity of the interfaces. From the measured moduli and the viscosities of the filled and unfilled materials, the modulus reinforcement ratio in the glassy state and the relative viscosity in the viscous state were obtained as functions of the filler type and concentration. The relative modulus for the glass bead composite system follows the Kerner equation, while the clay‐filled systems exhibit slightly greater reinforcement. The relative viscosities are strongly temperature dependent and do not follow conventional viscosity predictions for suspensions. It is suggested that the filler has a twofold effect on the viscosity of the composite materials; one is due to its mechanical presence and the other is due to modifications of part of the polymer matrix caused by interaction. Using the WLF equation to express all modifications of the matrix, one can isolate a purely mechanical contribution to the viscosity reinforcement. This mechanical part is approximately bounded by the theoretical predictions of Kerner,32 Mooney, 36 and Brodnyan,41 for suspension viscosities.
Studies on disulfide‐crosslinked nylon. II. Stress relaxation of disulfide‐crosslinked polycaprolactam fibers in water
Authors: Miyauchi Shin'Nosuke , Sakamoto Munenori , Tonami Hiroaki 
Published: April 2003

AbstractThe stress relaxation at 100% elongation in water was investigated for disulfide‐crosslinked polycaprolactam (DSPC) fibers prepared from N‐mercaptomethyl polycaprolactam. The stress decreased faster with increasing temperature and with increasing mercaptan content of the fiber. Little stress decay took place when the fiber was treated with a mercaptan‐blocking reagent. It was concluded that the controlling mechanism of the stress relaxation was the mercaptan/disulfied (SH/SS) interchange reaction. The remanent stress observed for the stress relaxation was fairly high and increased with decreasing mercaptan content of the fiber. The stress decay curve was not Maxwellian. It has been suggested that the concentration of mercaptan that could not participate in the interchange with stressed disulfide bonds increased with increasing cycles of the interchange reaction. A kinetic equation is presented and the activation energy of the SH/SS interchange reaction was evaluated as 22.3–23.9 kcal/mole. The stress relaxation of DSPC fibers in dilute β‐mercaptoethanol was also studied. The stress decreased more rapidly to almost zero and the decay curve was Maxwellian. The activation energy of the reaction was 17.1 kcal/mole. These results were compared with the stress relaxation of wool fibers.
Oxidation of bisphenol a polymers
Authors: Gesner B. D. , Kelleher P. G. 
Published: April 2003

AbstractPolysulfone, polycarbonate, and phenoxy resins were aged under thermal and ultraviolet light conditions. Thermoxidative processes in polysulfone and polycarbonate are of such minor significance as not to impart noticeable losses in these materials below 125°C. In phenoxy, however, thermal oxidation above 100°C results in rapid deterioration of all physical properties. This probably results from the low glass transition temperature of this polymer. Photo‐oxidation rapidly degrades polysulfone. This appears to be a consequence of scission at the sulfone link. In polycarbonate, however, the only serious result of short‐term irradiation is discoloration. For phenoxy resin, crosslinking through reactions at the hydroxyl group is the principal result of photo‐oxidation. In all processes the bisphenol A portion of the three polymers appears to play only a small role.
Failure mechanisms in peeling of pressure‐sensitive adhesive tape
Authors: Aubrey D. W. , Welding G. N. , Wong T. 
Published: April 2003

AbstractStudies on the peel behavior of pressure‐sensitive tape comprising a polyester backing and polyacrylate adhesive have shown that, in peeling from a plane glass surface, three fundamentally different modes of peeling may be distinguished, depending upon the rate of pulling. At low rates, deformation by flow of the adhesive appears to determine the peel behavior and the peel force is strongly rate dependent. At high rates, little or no viscous deformation of the adhesive occurs and the peel force is independent of rate. At intermediate pulling rates, cyclical instability of made of failure involving alternate storage and dissipation of elastic energy in the backing, results in the phenomenon of “slip‐stick” peeling, in which failure is jerky and regular. Results have been obtained which show how the pulling rates at which transitions from one mode of peel to another occur, and the peel force values for a given type of failure, depend upon such factors as molecular weight of adhesive, thickness of backing film, and angle of peeling.
Measurement of diffusion coefficient and partition coefficient of sodium in nonionic polymer membranes
Authors: Yasuda H. , Lamaze C. E. 
Published: April 2003

AbstractThe difficulties involved in the measurement of the partition coefficient and diffusion coefficient of NaCl in hydrophilic polymer membranes are examined by the initial rate and late‐time analysis of desorption data for three nonionic polymer systems. The late‐time analysis, based on the plot of the logarithmic relative desorption versus time, was found to be useful when the diffusion is Fickian and the magnitude of D2/l2 is small. Depending on the magnitude of D2/l2, an accurate measurement of k2 and determination of D2 cannot be achieved without correction for the effect of surface salt solution, impossible with late‐time analysis. The initial rate measurement was found more versatile for general non‐Fickian diffusion and it gave a means of correction of the errors involved in estimating the partition coefficient. In general, the diffusion of NaCl in hydrophilic polymers is not ideal Fickian and the discrepancy between the two analyses is appreciable.
Photocrosslinking of stilbene‐modified polymers
Authors: Stuber F. A. , Ulrich Henri , Rao Durvasula V. , Sayigh A. A. R. 
Published: April 2003

AbstractThe reactions of trans‐2,5‐dimethoxy‐4′‐aminostilbene with poly(maleic anhydride‐co‐methylvinyl ether) and trans‐2,5‐dimethoxy‐4′‐isocyanatostilbene with poly(oxy‐1,4‐phenyleneisopropylidene:1,4‐phenyleneoxy‐2‐hydroxytrimethylene) yield polymeric systems which undergo rapid crosslinking upon short exposure to ultraviolet light. The extent of photocrosslinking as a function of exposure time was determined by the decrease of the trans‐stilbene ultraviolet absorption at 350 nm.
Radiation chemical studies of protein reactions: Effect of amino acids on optical rotation
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractMonosodium 1‐glutamate, disodium inosine‐5′‐monophosphate, disodium guanosine‐5′‐monophosphate, calcium d‐pantothanate, 1‐arginine, and 1‐aspartic acid were found to protect the changes in the internal relationships of the atoms in the protein molecule from radiation damage. The behavior of the optical rotation was determined. The empirical equation for the protective effect is given by [α] f = b − a log X, where [α] f is the final specific rotation of the solution, X is the concentration of the amino acids, and a and b are adjustable constants.
Radiation chemical studies of protein reactions: Effect of protectors on the breaking of secondary bonding in protein
Authors: Nisizawa Mizuho 
Published: April 2003

AbstractRadiation protective effect of the breaking of secondary bonding in protein was examined with sodium benzoate, monosodium 1‐glutamate, 1‐arginine, and thiourea, and the behavior of viscosity against the protector was obtained. An experimental equation for the viscosity change is given by ηred = b − a log X, where ηred is the reduced viscosity of the solution, X is the protector concentration, and a and b are adjustable constants.
The shear modulus of flowing polyethylene melts
Authors: Cooper Winifred M. , Pollett W. F. O. 
Published: April 2003

AbstractTests on three low‐density polyethylene melts over a range of temperatures and shear rates, using a Weissenberg rheogoniometer, have enabled the reduced shear modulus to be obtained as a function of shear rate at the initiation of shearing and at various subsequent stages. For the two polymers which gave plateau values of modulus during the course of shearing these were in good agreement with figures quoted in the literature, but the initial modulus (measured on one polymer) was an order of magnitude higher. This supports the view that a network structure exists in the polymer at rest and is disrupted in the early stages of shearing. It was not possible to obtain unequivocal evidence that the equilibrium modulus decreases with amount of shearing, as required by the hypothesis that rheological breakdown is caused by a reduction in molecular entanglements.
Poly(α,α,α′,α′‐tetrafluoro‐p‐xylylene)
Authors: Chow S. W. , Loeb W. E. , White C. E. 
Published: April 2003

AbstractPoly(α,α,α′,α′‐tetrafluoro‐p‐xylylene) was prepared by the pyrolysis of cyclo‐di‐(α,α,α′,α′‐tetrafluoro‐p‐xylylene) and by the pyrolysis of α,α′‐bis(alkylsulfonyl)‐α,α,α′,α′‐tetrafluoro‐p‐xylene. The pyrolysis of α,α′‐dibromo‐α,α,α′,α′‐tetrafluoro‐p‐xylylene also gave the polymer, but the method is less satisfactory. Poly(α,α,α′,α′‐tetrafluoro‐p‐xylylene) shows remarkable thermal and oxidative stability at elevated temperatures. Useful mechanical and electrical properties are retained after aging for 3000 hr at 250° in air. After initial change due to crystallization, tensile strength remains near 10,000 psi, elongation above 5%, and dielectric constants and dissipation factors at approximately 2.4 and .001, respectively.
Multiple detectors for molecular weight and composition analysis of copolymers by gel permeation chromatography
Authors: Runyon J. R. , Barnes D. E. , Rudd J. F. , Tung L. H. 
Published: April 2003

AbstractThe use of a single detector in gel permeation chromatography (GPC) for samples of varying composition leads to erroneous conclusions. With certain simplifying assumptions, a gel permeation chromatograph equipped with properly selected dual detectors yields composition and molecular weight distribution information that is meaningful. Examples discussed are a mixture of homopolymers and a sample supposed to have been a styrene–butadiene block copolymer. The ultraviolet absorption is used in conjunction with the refractive index trace to give qualitative information that is much more informative than could be obtained with one detector. Calibration of the relative responses of the detectors to each of the components of the mixture is described, and these calibrations are used to calculate point‐by‐point composition, molecular weights, and molecular weight averages.
Calibration of instrumental spreading for GPC
Authors: Tung L. H. , Runyon J. R. 
Published: April 2003

AbstractThe proper use of the method for correcting instrumental spreading in GPC requires a precise calibration of the spreading characteristics of the instrument. Heretofore, such a calibration could be obtained only through the tedious reverse‐flow experiments. A more rapid method of calibrating instrumental spreading is presented in this work. This method uses the leading halves of the chromatograms of several standard polystyrene samples. These chromatograms are normally used in the calibration of molecular weight; additional experimental steps are therefore not required. The calculation of the instrumental spreading characteristics from these chromatograms is also relatively simple. The instrumental spreading characteristics were found to depend on the elution volume but not on the nature of the polymer. Thus, calibration results from using polystyrene standards can be used to treat chromatograms for other polymers. For the present GPC instrument, the spreading was found to reach a maximum at an elution volume near 400,000 in polystyrene molecular weight. The existence of this maximum is in agreement with observations made by other investigators and is and indication that diffusion in the mobile phase is not an important contribution to instrumental spreading. The problem of skewing or tailing is discussed. Indication of skewing was observed for one of the higher molecular weight polystyrene samples but the extent of skewing was not severe at the present flow rate of 2 ml/min.
Viscosity of polystyrene near the glass transition
Authors: Penwell Richard C. , Porter Roger S. 
Published: April 2003

AbstractA quantitative explanation is given for the apparent viscosity increase with increasing capillary shear rate for polystyrene at temperatures approaching the glass transition, Tg. Possible shifts in Tg as a function of the parameters shear rate, frequency, and pressure are interrelated to viscosity changes. Experimentally, the Instron capillary rheometer and the Weissenberg rheogoniometer provided a means for uncoupling the variables for individual consideration. Calculated and experimental data for the apparent viscosity as a function of the given parameters are presented and discussed. The explanation of the apparent viscosity increase in capillary flow can be quantitatively explained through the pressure dependence of Tg. Brief mention is made of the pressure effects on the Bagley and Rabinowitsch corrections normally made in capillary measurements.
A comparison of the dielectric method with density, moisture regain, and x‐ray diffraction methods of determining fine structure in cellulosic materials
Authors: Venkateswaran A. 
Published: April 2003

AbstractA comparison between the dielectric method and density, moisture regain, and x‐ray diffraction methods of estimating crystallinity in cellulosic materials is presented. The merits of the dielectric method compared to the other methods are discussed. Although the permittivities of completely crystalline and completely noncrystalline celluloses are not directly measureable, the use of extrapolated values for completely crystalline and completely noncrystalline celluloses make it possible to assign a percentage crystallinity to a given material from a single permittivity measurement. Capacitance measurements are very sensitive, accurate, and rapid. Therefore, the dielectric method is capable of following small and rapid changes in crystalline content arising from mechanical, chemical, or thermal treatments. In such a study, permittivities of completely crystalline and completely noncrystalline celluloses are not required. Since the relationship between permittivity and crystallinity is linear, it appears reasonable to continue to represent the fine structure of a cellulosic material by a simple model of a mixture or two hyprothetical components: “crystalline” and “noncrystalline” cellulose and to retain the concept of “percentage crystallinity” in its present form.
Stiffness of molecular chain of synthetic rubber
Authors: Furukawa Junji , Yamashita Shinzo , Kotani Teizo , Kawashima Masaaki 
Published: April 2003

AbstractThe principal polarizabilities of rubber molecules including copolymers were evaluated by the arithmetic sum of the polarizabilities of the components. The mean polarizabilities thus calculated are in good accordance with those from the refractive indices. The anisotropic polarizabilities of polymeric units for several kinds of rubbers were calculated and compared with those estimated from stress‐optical coefficients. Length or molecular weight of a statistical link thus estimated is used as a measure of stiffness of rubber molecules. There is a good accordance in statistical links between anisotropic and viscosity measurements in theta solvent. The molecular weight or length of a statistical link thus obtained is found to be compatible with the value calculated from end‐to‐end distance in theta solvent. The ultimate elongation of rubber is correlated with the stiffness and can be estimated from the measure of stiffness of the chain.
Anisotropy of styrene–butadiene rubber
Authors: Furukawa Junji , Kotani Teizo , Yamashita Shinzo 
Published: April 2003

AbstractAnisotropy of styrene–butadiene rubber (SBR) was investigated. The anisotropy of the copolymer varies linearly with the styrene content and the ultimate value coincides with that of polystyrene at elevated temperature. From these facts, the transverse configuration of the pendant phenyl group is estimated irrespective of the styrene content of SBR.