bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanism of oxidative degradation of ABS resin. Part II. The mechanism of photooxidative degradation
Authors: Shimada Junichi , Kabuki Kimiaki 
Published: April 2003

AbstractThe mechanism of oxidative degradation of ABS resin under ultraviolet irradiation, especially with respect to the wavelength dependencies of the photooxidative rate, has been examined by a spectroweather tester and infrared spectroscopy. The irradiation wave region was 290–800 mμ, and the region was divided into six parts. The changes in each part were examined by infrared spectroscopy. The absorption bands belonging to nitrile and phenyl groups showed no changes, but bands belonging to carbonyl and hydroxyl groups changed markedly, much as in the thermooxidative degradation described in a previous paper. There was a distinct gap between the third and fourth regions, which corresponded to 350 mμ. The graph of the normalized absorbance ratio and the logarithm of the wavelength gave a straight line, and it indicated that the rate of oxidation is proportional to the light intensity and the logarithm of the wavenumber.
Reversible crosslinks in cotton modified with N‐hydroxymethylacetylthioacetamide
Authors: Tesoro G. C. , Sello S. B. , Willard J. J. 
Published: April 2003

AbstractThe reaction of cotton fabric with N‐hydroxymethylacetylthioacetamide (HOCH2‐NHCOCH2SCOCH3) yields acetylthioacetamidomethylcellulose, which can be saponified under mild conditions to the corresponding thiol derivative, mercaptoacetamidomethylcellulose. Some reactions of the thiol group are discussed, including oxidation to disulfide, repeated reduction‐oxidation cycles, and blocking with alkyl halides. Chemical methods were used in establishing the occurrence and extent of the predicted reactions and their dependence on specific variables in the system. Changes in the crease recovery and tensile strength of the cotton derivative obtained in the reactions were found to be qualitatively consistent with the expected structures. The results of this work show that crosslinks can be obtained reversibly in cotton by this sequence of reactions. Intervening side reactions produce a gradual decrease in the yield of the desired products, however, as the number of cycles increases. Mercaptoacetamidomethylcellulose provides a limited but useful model for the investigation of reversible crosslinks in cellulose.
Epoxy resins from dinaphthols
Authors: Burnop V. C. E. 
Published: April 2003

AbstractEpoxy resins were prepared from di‐α‐naphthol(4,4′‐dihydroxy‐1,1′‐dinaphthyl) and di‐β‐naphthol(2,2′‐dihydroxy‐1,1′‐dinaphthyl). The resins consisted mainly of the reaction product of 1 mole of dinaphthol with 2 moles of epichlorhydrin. They contained chlorine, however, and were correspondingly deficient in diepoxide functionality. The resins from di‐α‐naphthol were crystalline, had m.p. 200°C., and were not miscible with conventional curing agents. Di‐β‐naphthol gave resins with softening points in the range 50–70°C., which cured with diethylenetriamine or the anhydrides of dibasic acids, giving hard but brittle products. The brittleness was not removed by curing with plasticizing curing agents, such as tetrapropenyl succinic anhydride. The cured di‐β‐naphthol‐based resins had thermal stabilities similar to analogous epoxy resins based on bisphenol A.
The effect of strain rate on the stress–strain curve of oriented polymers. I. Presentation of experimental results
Authors: Hall I. H. 
Published: April 2003

AbstractThe stress‐strain curves of viscose, nylon 6.6, poly(ethylene terephthalate), polyacrylonitrile, and polypropylene have been determined at a large number of different strain rates between 10−4 and 330 sec.−1. The shape of these stress‐strain curves and its change with strain rate is shown to depend upon whether the material is tested above or below its glass temperature. The stress‐strain curves of materials tested below their glass temperature consists of an initial straight portion followed by a yield point at a few per cent strain. The breaking strain is only slightly affected by strain rate, and the energy to rupture increases with increasing rate. For materials tested above their glass temperature the initial portion of the stress‐strain curves in nonlinear, and the yield strain is much higher than for the other materials. There is a small range of strain rate, in which the breaking strain falls sharply to the yield strain with increasing rate, and the energy to rupture also decreases. Outside this range the energy to rupture increases with increasing rate.
Adiabatic compressibility of polyelectrolytes in aqueous solutions: Poly(methacrylic acid)
Authors: Roy‐Chowdhury Phanibhusan 
Published: April 2003

AbstractThe adiabatic compressibility of dilute aqueous solutions of methacrylic acid, poly‐(methacrylic acid), and three poly(sodium methacrylates) obtained by neutralizing the polyacid with sodium hydroxide to different extents were determined from soundvelocity and density data. The ultrasonic velocity at 25°C. was measured by employing a precision ultrasonic interferometer, and the density was measured with Ostwald‐type pycnometers. The plots of the decrease of compressibility per unit concentration, (β1 − β)/c versus c shows that there is a marked difference between the curves of monomer and of polymer solutions. In case of the monomer there is a proportional decrease with increase in concentration, whereas in polymer in the dilute region (0.1−0.5g./dl.) the curve rises sharply, then shows down, and finally approaches a constant value at comparatively higher concentrations. The nature and number of the free counterions and the shape and the concentration of the polymer molecules are responsible for the compressibility of polymer solutions. However, the contribution of the size and shape and concentration of the polymer seem to be less than that of the nature and number of the counterions. The apparent molal volume ΦV2 and apparent molal compressibility ΦK2 for polymer repeat units show a sharp decrease with increase in concentration and finally attain a constant value at higher concentrations; this has been explained by the fact that in the dilute region the polymer, being extended by coulombic repulsion between similar charges situated on the side chain, enhances the formation of water clusters around it, and the free counterions are solvated, leading to a decrease to these values. The number of free counterions proportionately increases with concentration, causing a proportional decrease of the ΦV2 and ΦK2 values, until the concentration reaches a definite stage, above which the so‐called condensation of ions occurs, and the number of free counterions does not increase further at higher concentrations.
Hysteresis and strength of rubbers
Authors: Harwood J. A. C. , Payne A. R. 
Published: April 2003

AbstractA criterion of tensile failure in terms of energy density and energy loss at break has been developed for several gum rubbers over a wide range of test temperature. A similar description of failure in filled rubbers is related to the gum criterion by a simple elastic interaction term. The upper and lower limits of the failure equation are considered in detail, and the relationships of energy density at break with temperature and ultimate strain are also discussed.
Flow properties of polyethylene melt
Authors: Kataoka Tadao , Ueda Shigeyuki 
Published: April 2003

AbstractFlow properties for low‐density and high‐density polyethylene over a broad range of shear stress are described. Flow equations presented in literatures are tested from the point of view of the extrapolating method for evaluating the zero shear viscosity. It is shown that the method based on the equation of Cross gives relatively good results. The recoverable shear strain calculated from the capillary end correction is practically equal to that determined from the creep experiment at the same shear stress. The effect of shear stress on the elastic property is examined.
Epoxy polymers. III. Factors affecting the cure
Authors: Cuthrell R. E. 
Published: April 2003

AbstractThe rate of cure of epoxy polymers appears to be diffusion‐controlled, and after gelation is dependent upon the capillary dimensions in a floccular matrix. The floccule dimensions and packing determine the size of the interfloccular capillaries and are inversely related to the cure temperature. The degree of cure is inversely related to the pregelation cure temperature (thermal history, including preheat) and directly related to the total cure time.
Studies on polymer blends. II. Butadiene–styrene copolymers and polybutadiene–polystyrene blends
Authors: Shundo Minoru , Hidaka Takashi , Goto Kunio , Imoto Minoru , Minoura Yuji 
Published: April 2003

AbstractThe properties of butadiene–styrene copolymers and of polybutadiene–polystyrene blends were compared. Polybutadiene, polystyrene, and four copolymers having styrene contents of 20, 40, 60, and 80% were prepared. The copolymers were compared with blends having various styrene contents and prepared by means of latex blending and roll blending. Vulcanizates were prepared by three different curing methods, i.e., sulfur cure, peroxide cure, and radiation cure. The results of the benzene extraction of three vulcanizates showed that the polystyrene blended was not cured by any of the curing methods used. The properties of the vulcanizates of the copolymers were markedly different from those of the blends, i.e., in the case of the blends the properties showed a linear relationship with their blending ratio, while in the copolymers the properties showed a curvilinear relationship which had an inflection point at a styrene content of about 60%. From this phenomenon of the copolymers, it was proposed that the second‐order transition point of styrene is the cause of the properties showing this peculiar point. From the results, it was found that the behavior of styrene in copolymers is essentially different from that in blends.
Controllably crazed polystyrene: Morphology and permeability
Authors: Michaels Alan S. , Bixler Harris J. , Hopfenberg Harold B. 
Published: April 2003

AbstractThe effects of n‐heptane and heat treatment on the structural and transport properties of polystyrene films (biaxially oriented and unoriented) were studied to determine whether these treatments improve the film as selective barriers for separation of molecules differing only slightly in size and shape. n‐Heptane treatment of biaxially oriented polystyrene produces a sandwich structure composed of expanded, crazed, surface layers surrounding an apparently unaffected central core. The crazed layers contain a continuous network of interconnected channels. The core provides the total resistance to gas permeation, hence, the overall effect of n‐heptane treatment is fabrication of a thinner more permeable membrane. By restricting the stress‐cracking treatment to one face of the film, it should be possible to make high flux, anisotropic membranes—a type of membrane which is required for successful development of membrane separation processes. n‐Heptane treatment of cast, annealed polystyrene results also in a crazed polymer, but the crazing is in the form of spherical voids, and the films, even with a residual uncrazed core, are too weak to be useful as separation membranes. The crazing process in both types of polymer specimens is characteristic of case II non‐Fickian diffusion in which the kinetics are apparently controlled by polymer relaxation processes. Sorption of isopentane into cast, annealed polystyrene does not cause visible crazing but the kinetics are again non‐Fickian. Desorption of isopentane into n‐heptane‐treated polystyrene releases the appreciable residual n‐heptane in the film which could not be removed by long‐term exposure to vacuum. Analysis of D(0) values for isopentane in n‐heptane treated films indicates that the polymer surrounding the visible voids in the film is essentially unaltered polystyrene with only a small fraction of the voids being interconnected by open channels.
Sorption and diffusion in asymmetric membranes
Authors: Sternberg S. , Rogers C. E. 
Published: April 2003

AbstractPolyethylene membranes with nearly linear gradients of grafted poly(vinyl acetate) from one surface to the other have been prepared by radiation‐initiated polymerization of sorbed vinyl acetate monomer. Transport of methanol through the modified membrane proceeds at different rates, depending on the direction of flow relative to the gradient of grafted PVAc. A mathematical model has been derived, which gives a quantitative description of the directional transport process. The relationship can be used to predict the transport behavior for single penetrants through asymmetric membranes from knowledge of the properties of the individual components.
Modification of butadiene–acrylonitrile and styrene–acrylonitrile copolymerizations in emulsion systems
Authors: Uraneck C. A. , Burleigh J. E. 
Published: April 2003

AbstractModification of acrylonitrile in copolymerizations with butadiene and with styrene in hot and cold emulsion recipes has been studied. Series of primary, secondary, and tertiary mercaptans in addition to several miscellaneous modifiers were tested. Kinetically the rate data for the monomer pairs containing acrylonitrile better fit first‐order plots than the curves obtained for an ideal emulsion polymerization. In this study all modifier depletions in nitrile systems were plotted as log mercaptan versus log conversion and the slope of the curve was taken as the transfer constant. Normal mercaptans were inefficient modifiers in nitrile systems as determined in polymerization and depletion experiments. Secondary mercaptans, 2‐nonyl, 2‐decyl, and mixtures in this molecular weight range, were promising modifiers for low temperature (5°C.) nitrile systems. 2‐Nonyl mercaptan gave enhanced modification by incremental addition of the modifier indicating this procedure could be used to advantage in preparing nitrile rubbers. The series of tertiary mercaptans from C13 to C7 showed an improvement in modification of low temperature nitrile systems as the molecular weight decreased. A plot of the data on a molar basis shows that the optimum modifier falls in the C9–C8 range. The optimum transfer constant for the most efficient modification of 70/30 and of 80/20 butadiene–acrylonitrile polymerizations at 5°C. terminated at 60% conversion is 2. Depletion data show that the transfer constant for a mercaptan decreases as the nitrile content in mixtures with butadiene increases. The properties of the vulcanizates of the 70/30 and 80/20 butadiene–acrylonitrile polymers prepared in the presence of low molecular weight mercaptans were equivalent to or better than those of the controls. These data show that nitrile polymers could be modified with a lower molecule weight mercaptan with no loss of properties but with a considerable saving in amount of modifier. Mercaptans are essential for the initiation of butadiene–acrylonitrile in the presence of persulfate at 50°C. For the hot nitrile rubber preparations, the series of mercaptan from t‐C10 to t‐C7 are efficient modifiers. However, the heptyl and octyl mercaptans are retarders, and the t‐C9 and t‐C10 are the preferred modifiers for efficiency and unretarded polymerization. The modification with a series of mercaptans ranging from t‐C13.2 to t‐C8 of 75/25 styreneacrylonitrile at 50°C. in presence of persulfate–bisulfite showed a consistent behavior. The transfer constant decreased in a regular manner as the molecular weight of the mercaptan increased, and for the series of tertiary modifiers the t‐C10 mercaptan was the most efficient as judged by a melt flow test.
Influence of molecular weight on some properties of poly(vinyl chloride)
Authors: Pezzin Giovanni , Zinelli Giuseppe 
Published: April 2003

AbstractSeveral fractions obtained from a large‐scale fractionation and several unfractionated PVC polymers and blends have been processed both as rigid and plasticized compounds. The latter have been studied by stress–strain, creep, and recovery tests. The recoverable character of the creep results show that a relatively stable network must be present in the samples. The crosslink density is little influenced by molecular weight, as shown by the modulus and compliance results. On the contrary, the ultimate tensile properties depend strongly on molecular weight, which is interpreted as evidence that the stability of the crosslinks increases with increasing chain length of the polymers.
Thermal degradation studies of several pyrrone films
Authors: Jewell Robert A. 
Published: April 2003

AbstractThe thermal degradation of several polyimidazopyrrolone (pyrrone) films was studied in air and in vacuum over the range of 100–1000°C. by thermogravimetric analysis (TGA), with the use of both isothermal heating and programmed heating rates of 2, 3, 5, and 7.5°C./min. At pressures of 10−6 torr or less, maximum weight losses average 30% at 800°C. Rates of volatilization and activation energies were derived to provide comparison between these ladder‐type polymers. Mass spectrometric analysis of the pyrolysis gases evolved under vacuum conditions showed that CO, CO2, and H2O were the primary volatile products and that they were formed throughout the period of weight loss. Approximate correlation between changes in weight and changes in the total pressure for the vacuum tests indicates that mass spectrometric results could provide quantitative as well as qualitative data. The importance of sample history prior to heating and of sample geometry in developing meaningful and reproducible TGA results is aptly demonstrated. The ability of these materials to absorb readily 5–7 wt.‐% of water under ambient conditions and the effect of this property upon weight loss measurements are shown.
Single specimen determination of Young's and bulk moduli
Authors: Warfield Robert W. , Cuevas Joseph E. , Barnet F. Robert 
Published: April 2003

AbstractA new method is presented for the rapid and consecutive determination of the Young's and bulk moduli of polymeric materials. Usually these properties are determined by separate measurements. However, by using an undersized specimen in a standard compressibility device it has been found possible consecutively to determine both moduli on the same specimen in a single test procedure. The initial loading of the undersized specimen results in a decrease in length and an increased diameter. From these changes Young's modulus may be calculated. Once the bore of the tester is filled, the application of additional pressure results in a decrease in the volume of the polymer, from which the bulk modulus may be calculated. Both of these determinations may be made within minutes, and the values of the moduli are in agreement with published values.
The chemistry of sulfur curing. Part I. Kinetics of vulcanization of an EPDM elastomer accelerated by zinc dimethyldithiocarbamate
Authors: Wolfe James R. 
Published: April 2003

AbstractThe maximum cure rates of an EPDM rubber were determined by using the Monsanto oscillating disk rheometer and correlated against the initial concentrations of curing ingredients. Unaccelerated and ZnDMDC‐accelerated sulfur curing systems were used. The results were interpreted to indicate that both unaccelerated and ZnDMDC‐accelerated curing reactions proceed simultaneously in ZnDMDC‐accelerated stocks. The maximum cure rates of the ZnDMDC‐accelerated crosslinking reactions were found to be first‐order in initial ZnDMDC concentration, second‐order in initial cure site concentration, variable fractional order in initial sulfur concentration, and approximately zero‐order in initial zinc oxide concentration. The maximum cure rates of the ZnDMDC‐accelerated reaction were shown to be limited by the low solubility of ZnDMDC in the polymer. The maximum cure rates of the unaccelerated crosslinking reaction were found to be 0.6‐order in initial sulfur concentration, 1.2‐order in initial cure site concentration, and of a positive variable order in initial zinc oxide concentration.
Aging of polyblends
Authors: Boyle D. J. , Gesner B. D. 
Published: April 2003

AbstractMethyl methacrylate–styrene–acrylonitrile copolymers, alone and with polybutadiene modification, were examined for changes in impact strength and yellowness after thermal and light aging. The copolymer displayed no change in strength or clarity, while the butadiene‐modified material showed increase in yellowness and loss in impact resistance. It is apparent that these changes are primarily due to the decomposition of the butadiene phase in the impact material, and this conclusion might be applied to diene‐containing blends in general.
Thermal and photo‐oxidation of polysulfone
Authors: Gesner B. D. , Kelleher P. G. 
Published: April 2003

AbstractProlonged heating at temperatures below 140°C. causes only slight changes in the properties of polysulfone. Exposure to ultraviolet light, however, results in substantial changes as evidenced by broad absorption in both the hydroxyl and carbonyl regions of the infrared spectrum, evolution of carbon monoxide and dioxide, decrease in polymer elongation and intrinsic viscosity, and pronounced yellowing. A free‐radical mechanism is proposed in which chain scission occurs with the formation of low molecular weight, oxidized fragments as the predominant oxidation products.
Elastomers based on cellulose fibers. II. Ethyl acrylate grafting onto disulfide‐crosslinked cellulose
Authors: Negishi Michiharu , Nakamura Yoshio , Hosoi Masahiro 
Published: April 2003

AbstractPartially disulfide‐crosslinked viscose rayon fibers (SS 2.3 mole/104 g. cellulose) were prepared by means of mercaptoethylation and successive oxidation and then grafted to the extent of 200–1200% graft‐on of ethyl acrylate with or without preswelling by zinc chloride, by using the ceric ion method. The tensile strength, breaking elongation, initial modulus, elastic recovery, and extension energy loss of the modified fibers were measured. In the disulfide‐crosslinked, about 1000% ethyl acrylate‐grafted fibers with preswelling, typical rubber elasticity was found. The disulfide crosslinkage in the grafted fibers was found generally to be capable of cleaving and re‐forming by the reduction and successive oxidation treatments, and the properties were also well reversible. Therefrom, it was confirmed that intermolecular crosslinking between cellulose molecules plays an important role for developing of elastomeric properties, as was found for the methylene‐crosslinked and grafted fiber reported previously. Most of elastomeric properties in our grafted fibers seem to be essentially attributable to the random conformation of the decrystallized, disoriented, and weakly crosslinked cellulose chains which are embedded in a matrix of flexible graft polymers.
Effects of substitution of triphenylmethyl groups into cellulose on the fine structure and thermal properties of the products
Authors: Conrad C. M. , Stanonis D. J. , King W. D. , Harbrink P. 
Published: April 2003

AbstractMercerized cellulose in the form of 7/2 yarn was reactivated with 17.5% sodium hydroxide and then heated at 100°C. with 5 moles of trityl chloride, in pyridine, per anhydroglucose unit. The time of reaction was varied, giving ether derivatives of the cellulose containing 0.31–0.79 triphenylmethyl groups (DS) per anhydroglucose unit. Controls consisted of (1) the untreated cellulose yarn and (2) a portion subjected to all the reaction conditions except the reactant. The density of the product decreased hyperbolically with increasing substitution. The mixed x‐ray pattern of the untreated control cellulose (35% cellulose I, 43% cellulose II) was largely converted by the activation treatment (10% cellulose I, 53% cellulose II). As reaction proceeded the crystal structure largely disappeared. The assumption is that substitution was confined almost exclusively to the primary hydroxyl position. The behavior of tensile stiffness, elastic recovery, and work recovery was explored at temperatures from about 25 to 225°C. Considerable improvement, which generally increased with increasing substitution, was observed in both elastic and work recovery at all temperatures studied.