bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymerization of ethylene with vinyl acetate. II. Effect of solvent on polymer yield and molecular weight
Authors: Wisotsky M. J. , Kober A. E. 
Published: April 2003

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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