bluuebunny/crossref_metadata_2025_split huggingface dataset:
Graft polymerization of vinyl acetate onto starch. Saponification to starch–g–poly(vinyl alcohol)
Authors: Fanta George F. , Burr R. C. , Doane W. M. , Russell C. R. 
Published: April 2003

AbstractGraft polymerizations of vinyl acetate onto granular corn starch were initiated by cobalt‐60 irradiation of starch‐monomer‐water mixtures, and ungrafted poly(vinylacetate) was separated from the graft copolymer by benzene extraction. Conversions of monomer to polymer were quantitative at a radiation dose of 1.0 Mrad. However, over half of the polymer was present as ungrafted poly‐(vinyl acetate) (grafting efficiency less than 50%), and the graft copolymer contained only 34% grafted synthetic polymer (34% add‐on). Lower irradiation doses produced lower conversions of monomer to polymer and gave graft copolymers with lower % add‐on. Addition of minor amounts of acrylamide, methyl acrylate, and methacrylic acid as comonomers produced only small increases in % add‐on and grafting efficiency. However, grafting efficiency was increased to 70% when a monomer mixture containing about 10% methyl methacrylate was used. Grafting efficiency could be increased to over 90% if the graft polymerization of vinyl acetate‐methyl methacrylate was carried out near 0°C, although conversion of monomers to polymer was low and grafted polymer contained 40‐50% poly(methyl methacrylate). Selected graft copolymers were treated with methanolic sodium hydroxide to convert starch–g–poly(vinyl acetate) to starch–g–poly(vinyl alcohol). The molecular weight of the poly(vinyl alcohol) moiety was about 30,000. The solubility of starch–g–poly(vinyl alcohol) in hot water was less than 50%; however, solubility could be increased by substituting either acid‐modified or hypochlorite‐oxidized starch for unmodified starch in the graft polymerization reaction. Vinyl acetate was also graft polymerized onto acid‐modified starch which had been dispersed and partially solubilized by heating in water. A total irradiation dose of either 1.0 or 0.5 Mrad gave starch–g–poly(vinyl acetate) with about 35% add‐on, and a grafting efficiency of about 40% was obtained. A film cast from a starch–g–poly(vinyl alcohol) copolymer in which homopolymer was not removed exhibited a higher ultimate tensile strength than a comparable physical mixture of starch and poly(vinyl alcohol).
Continuous emulsion polymerization. Modeling oscillations in vinyl acetate polymerization
Authors: Kiparissides C. , MacGregor J. F. , Hamielec A. E. 
Published: April 2003

AbstractA theoretical investigation of the emulsion polymerization of vinyl acetate in a continuous stirred tank reactor operating under conditions of sustained oscillations is reported here. Models of two levels of sophistication are developed: a comprehensive model that solves for the age distribution function of polymer particles and a simplified model that assumes discrete nucleation periods. The latter model should find use in adaptive control of latex reactors. These models adequately simulate experimental data after Greene et al.2 for the emulsion polymerization of vinyl acetate under conditions of sustained oscillations.
Mechanical relaxation processes in polyacrylonitrile polymers and copolymers
Authors: Kenyon A. S. , Rayford McC. J. 
Published: April 2003

AbstractThe dynamic mechanical properties of molded and cast polyacrylonitrile and copolymers have been measured by an automatic Rheovibron. The transitions are described for the amorphous, “paracrystalline,” and crystalline phases. Based upon a number of polymer theories of multiple phases in polymeric systems, the transitions have been assigned to specific polymer motions. Three transitions are defined for the alpha transition region. The mechanical response is compared to x‐ray diffraction and infrared to ascertain the transition assignments in decreasing order beginning with the highest temperature transition as (1) the main transition for the amorphous phase (T1), (2) dipole–dipole interaction which is related to the “paracrystalline phase” (T2), and (3) secondary transition for the amorphous phase (T3).
Pulsed‐field gradient NMR measurements of diffusion of oil in rubber
Authors: von Meerwall E. , Ferguson R. D. 
Published: April 2003

AbstractThe pulsed‐gradient NMR method of Stejskal and Tanner was used to measure the diffusion of oil in synthetic cis‐polyisoprene. The diffusion encounters no barriers with spacings at least up to several μm and generally displays free‐volume behavior, obeying the WLF temperature dependence between −10°C and +130°C, and the Fujita‐Doolittle concentration dependence between 10 and 90 vol‐% oil.
Effects of water and moisture on strengths of optical glass (silica) fibers coated with a UV‐cured epoxy acrylate
Authors: Wang T. T. , Vazirani H. N. , Schonhorn H. , Zupko H. M. 
Published: April 2003

AbstractFurnace‐drawn optical silica fibers coated with a uv‐curable epoxy acrylate (V1F) were subjected to long‐term tests in water and in humid environments. Results of stress‐free aging tests showed a progressive reduction of strength both in water and in the atmosphere of 90% r.h. at 32.6°C. Stressing the fibers up to 517 MN/m2 (75 kpsi) during aging did not result in additional loss of strength. Static fatigue tests in 90% r.h., 32.6°C, showed that the fatigue strength decreased monotonically with time of exposure in accordance with the power law of Charles. However, there were indications that Charles' theory might not be obeyed over an extended test period.
Effect of carboxylic monomers on acid distribution in carboxylated polystyrene latices
Authors: Vijayendran B. R. 
Published: April 2003

AbstractA study was made of the effect of carboxylic monomers, such as itaconic acid, acrylic acid, and methacrylic acid, on the relative distribution of acid in the aqueous serum phase to that on the latex surface to that buried in the particle of carboxylated polystyrene latices prepared by emulsion polymerization. The relative acid distribution of the carboxylated latices was determined by the conductometric titration method of Hen. Effect of carboxylic monomer levels and latex particle size on acid distribution ratio are given. It is shown that itaconic acid, being the most hydrophilic and having the least solubility in styrene, tends to distribute itself in favor of the aqueous serum phase, while acrylic acid, which has limited solubility in styrene and being sufficiently hydrophilic, tends to prefer the particle surface predominantly. Methacrylic acid, being the most hydrophobic of the three carboxylic monomers studied and having good solubility in styrene, is shown to be concentrated inside the particle core. The observed results are compared with other similar findings in the literature and analyzed in the light of accepted mechanisms for emulsion polymerization of carboxylated styrene systems.
Effect of coagulation conditions on crystal modification of poly(p‐phenylene terephthalamide)
Authors: Haraguchi Kazutoshi , Kajiyama Tisato , Takayanagi Motowo 
Published: April 2003

AbstractPoly(p‐phenylene terephthalamide)(PTTA) films were prepared from sulfuric acid solution with various coagulants. X‐ray diffraction and infrared absorption measurements revealed that the crystal structure of the film coagulated with water showed a new crystal modification II, which was different from the one previously reported by Northolt and Tadokoro et al. The latter structure is called here modification I. Modification II coagulated with water from a solution of lower polymer concentration irreversibly transformed to modification I upon annealing, whereas modification II prepared from highly concentrated solution was thermally stable and scarcely transformed to modification I upon annealing. A liquid crystal‐like swollen structure was found in the intermediate stage of the formation of modification II. In this swollen state, x‐ray diffraction revealed that water molecules are included in hydrogen‐bonded planes and the intermolecular spacing along the van der Waals force direction was unaffected by the existence of the water and remained constant throughout the process of regeneration. Both modifications I and II were found to be stable on treatment with boiling solvents. The transformation of the swollen structure to modification I took place in boiling methanol and acetone.
Bulk polymerization of acrylonitrile. I. An experimental investigation of the kinetics of the bulk polymerization of acrylonitrile
Authors: Garcia‐Rubio L. H. , Hamielec A. E. 
Published: April 2003

AbstractA comprehensive experimental investigation is reported of the bulk polymerization of acrylonitrile (AN) to limiting conversion using 2,2′‐azobisisobutyronitrile (AIBN) as initiator at 40°, 60°, and 80°C. Molecular weight development was followed by gel permeation chromatography (GPC).
Thermal degradation of cellulose in air and nitrogen at low temperatures
Authors: Shafizadeh F. , Bradbury A. G. W. 
Published: April 2003

AbstractThermal analysis and kinetic studies have shown that oxidative reactions are responsible for acceleration in the rates of weight loss and depolymerization of cellulose on pyrolysis in air at temperatures below 300°C. The oxidative reactions include production of hydroperoxide, carbonyl, and carboxyl groups, which have been investigated at lower temperatures along with the rates of depolymerization and production of carbon monoxide and carbon dioxide. The experimental results are consistent with an autoxidation mechanism involving initiation, propagation, and decomposition reactions. At temperatures above 300°, the rate of pyrolysis is essentially the same in both air and nitrogen, indicating that thermal degradation is independent of the oxidative reactions.
Characterization of polyethyleneimine modified with organotin halides. Thermal, solubility, and fungal properties
Authors: Carraher Charles E. , Giron David J. , Woelk William K. , Schroeder Jack A. , Feddersen Mary F. 
Published: April 2003

AbstractModified polyethyleneimine products are hydrophobic with products from monohalotin reactants soluble in HMPA, DMSO, CHCI3 and 2,4‐pentanedione, while products from dihalotin reactants are insoluble in all solvents. Antifungal activity varies markedly with the nature of the tin moiety. For products from triphenyltin chloride, antifungal activity is widespread and suitable to about 40 ppb of the polymer, which is clearly acceptable for medical and industrial uses. Thus, such modified polymers can be used as retarders of fungi related rot and mildew. The products show moderate high‐temperature stabilities.
A novel approach to viscometric parameters of polymer solutions
Authors: Chee K. K. 
Published: April 2003

AbstractA three‐parameter equation is put forward to evaluate the [η] of polymer solution from a wide range of concentrations, up to a relative viscosity of 100. The equation is tested by viscometric data of polystyrene, poly(vinyl chloride), poly(1‐vinylnaphthalene), poly(2‐vinylnaphthalene), and poly(4‐vinylbiphenyl) at different temperatures and in a variety of solvents including mixed solvents. A statistical method is employed to analyze the experimental data. It is found that the values of [η] obtained by the new equation are consistently lower than those derived from the Huggins equation. However, the discrepancy is not more than 3% on average, and it does not affect the values of Mark‐Houwink constants significantly. Other parameters of the equation are also computed.
The characterization of nylon 6 filaments by x‐ray diffraction
Authors: Stepaniak R. F. , Garton A. , Carlsson D. J. , Wiles D. M. 
Published: April 2003

AbstractA method is described for calculating crystallinity indices and crystalline orientation functions for the α and γ components of the crystalline phase of nylon 6 filaments using wide‐angle x‐ray diffraction (WAXS) analysis. The method is shown to be applicable to a wide range of filament samples (“conventional” as‐spun, fast spun, drawn, and annealed) even when only a single broad diffraction maximum is observable from the WAXS photograph. The component indices can be used to illustrate differences present in the filament microstructure which would be unobservable if a total crystallinity index, such as that determined by density, were determined alone. For example, the initially mixed α–γ structure is retained in low‐temperature drawing (75–150°C) of nylon 6 fiber, but the predominantly α form is produced at higher draw temperatures.
Durable flame resistance via reaction of cotton cellulose bearing aromatic amino groups with tetrakis(hydroxymethyl)phosphonium chloride
Authors: Hebeish A. , Waly A. , El‐Kashouti M. A. 
Published: April 2003

AbstractChemically modified cotton fabric samples having different amounts of aromatic amino groups were prepared. These modified samples were reacted with tetrakis(hydroxymethyl)phosphonium chloride (THPC) under a variety of conditions using the pad‐dry–thermofixation technique. The extent of the reaction (expressed as %P) was dependent of the degree of chemical modification of cotton, temperature and time of heating, and pH of the treating bath as well as incorporation of Lyofix CHN (N‐methylol finishing agent), MgCl2·6H2O (catalyst), and urea at various concentrations. THPC did react with the modified cotton having a nitrogen content over a range of 0.4%–1.3% even in the absence of catalyst at a temperature as low as 30°C for 10 min to impart durable flame resistance to cotton. Increasing the temperature up to 80°C enhanced considerably the extent of reaction; he latter remained practically constant upon further increase in temperature. The reaction was favored in acidic media (pH 4–6), whereas alkaline media (pH 9–11) inhibited it. Incorporation of Lyofix CHN (9%), MgCl26H2O (1%), and urea (5%) along with THPC (25%) in the treating bath required a curing temperature of 120°C and a curing time of 5 min to achieve a fabric containing as much as 2.7% phosphorus with excellent durable flame resistance. A tentative mechanism of the reaction between THPC and the modified cotton was also elicited.
Comparisons of the cure of phenol–formaldehyde novolac and resol systems by differential scanning calorimetry
Authors: Chow S. , Steiner P. R. 
Published: April 2003

AbstractComparisons were made of differential scanning‐calorimetric (DSC) thermograms of both liquid and powdered commercial phenol–formaldehyde resins. By a combination of the results from analyses under a variety of conditions, such as ambient pressure, high pressure, using freeze‐dried samples, and also by direct observation of the resin‐curing process in wood‐veneer assemblies, the curing reactions of phenol–formaldehyde resins were found to differ for resol and novolac systems. At a heating rate of 10°C/min, the resol resin showed endothermic curing reactions at temperatures of about 150°C, while the novolac‐type resin showed an exothermic peak maximum at about 160°C. Results are presented to show how DSC can be used to differentiate between a resol and novolac system.
Thermoelastic properties of urethane elastomers
Authors: Nierzwicki W. , Szpilewicz E. 
Published: April 2003

AbstractSeveral polyurethanes based on poly(ethylene adipate), 4,4′‐diphenylmethane diisocyanate, 1,4‐butanediol, and 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane were prepared. The thermoelastic properties of these polyurethanes depend on compositional variables and are interpreted in terms of the extent and stability of microphase separation.
Kinetics of the base‐catalyzed reactions of cyclo‐octameric and catenapolymeric sulfur with dithiol
Authors: Bordoloi Binoy K. , Pearce Eli M. 
Published: April 2003

AbstractThe base‐catalyzed sulfur‐1,2‐ethanedithiol reactions appear to follow pseudo first‐order kinetics as determined by TGA. The activation energy has been determined to be 26.1 kcal/mol with either cyclo‐octameric or catenapolymeric sulfur.
Polymers with pendant isocyanate groups. III. Synthesis and properties of poly(styrene‐co‐acrylonitrile‐co‐styrylisocyanate)
Authors: Liebersohn Aharon , Kohn David H. 
Published: April 2003

AbstractThe terpolymer poly(styrene‐co‐acrylonitrile‐co‐styrylisocyanate) was synthesized by radical initiation directly from styrene, acrylonitrile, and cinnamoyl azide. The monomer feed–terpolymer composition relationship was determined by Slocombe's triangular graph. The solubility, intrinsic viscosity, and melting range of the various terpolymers and the chemical reactions of the pendant isocyanate groups toward alcohol and amines were investigated.
Composite reverse osmosis membranes prepared by plasma polymerization of allylamine. Evaluation of membrane performance for the treatment of washwater and its components
Authors: Hinman P. V. , Bell A. T. , Shen M. 
Published: April 2003

AbstractReverse osmosis membranes prepared by plasma polymerization of allylamine–nitrogen mixtures over a porous substrate were evaluated for the rejection of components present in washwater. The membranes exhibited high rejections for sodium chloride, potassium chloride, detergent, and dextrose. High rejections of urea could be achieved, but only at a sacrifice of water flux. Lactic acid could also be rejected but caused a degradation of the plasma‐deposited layer.
Influence of curing agent concentration and curing temperatures on the thermostability of styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate copolymer systems
Authors: Zeldin Arkady N. , Kukacka Lawrence E. , Fontana Jack J. , Carciello Neal R. , Reams Walter 
Published: April 2003

AbstractThermogravimetric (TGA) and infrared (IR) analyses were used to determine the thermal stability of a polymer system consisting of styrene–acrylonitrile–acrylamide–trimethylolpropane trimethacrylate. This study indicates that increases in curing temperature and the use of two initiators with different activities decreases the percentages of unreacted monomers. This increases the thermal stability of the polymer. To prove this, dynamic and isothermal TGA were used. The change in typical functional groups found by IR spectra also confirms this observation.
Compressive creep of flexible polyurethane foam
Authors: Campbell Gregory A. 
Published: April 2003

AbstractThe compressive creep rate of polyurethane foams was found to be a complex function of deflection and time. The complexity has been shown to be related to the buckling of the cell struts as the foam is compressed. Of the parameters normally varied in the foam formulation, both the polyol molecular weight and the water content of the foam formulation seemed to have a measureable effect on the creep rate.
Ionically crosslinked poly(acrylic acid) membranes. II. Dry technique
Authors: Habert A. Claudio , Burns Charles M. , Huang Robert Y. M. 
Published: April 2003

AbstractThe ionic crosslinking of poly(acrylic acid) for dialysis and reverse osmosis applications has been studied. A new dry technique has been developed that is faster than the wet technique reported in the previous paper to synthesize aluminum/poly(acrylic acid) membranes. It is based on casting a solution containing both the aluminum salt and the unneutralized poly(acrylic acid) (PAA) and subjecting the cast film to a heat treatment (curing step) to promote ionic crosslinking. Postcuring treatment in nonsolvents for PAA such as acetone induced structural modifications in the membrane. Membranes with optical clarity ranging from colorless and transparent to white and opaque were obtained and were characterized by their water and aluminum contents. Transport properties of these membranes were investigated and indicated a selective rejection of ionic solutes such as NaCl compared to organic solutes such as ethylene glycols. Typical results for reverse osmosis under static conditions at fluxes of 1250 g/hm2 (0.75 U.S. gallons/ft2‐day) gave rejections of 85% for a feed of 0.1% (by wt.) NaCl at 600 psi. Much lower rejection (28%) for ethylene glycol suggests the possible use of these membranes in the fractionation of mixtures of ionic and nonionic solutes by reverse osmosis.
Radiation‐induced polymerization of ethylene in a pilot plant. II. Development of wet‐wall process
Authors: Takehisa Masaaki , Watanabe Hiromasa , Kurihara Hirondo , Takasaka Yoshio , Maruyama Yoshio , Miyanaga Kazukiyo , Suwa Takeshi , Nakajima Hayato , Yamaguchi Kouichi , Tohei Masamichi , Kawakami Waichiro , Watanabe Terutaka , Senrui Shiro , Machi Sueo 
Published: April 2003

AbstractRadiation‐induced polymerization of ethylene using tert‐butyl alcohol aqueous solution as a medium was carried out in a pilot plant with 10 liter reactor at pressures of 100 to 400 kg/cm2, ethylene feed rates of 1.2 to 11.8 kg/hr, medium feed rates of 0 to 100 liter/hr, dose rates of 0.6 × 105 to 1.4 × 105 rad/hr, and at room temperature. The space‐time yield and molecular weight of polymer were in the range of 1.2 to 16.7 g/liter hr and 6 × 103 to 2 × 105, respectively. The space‐time yield and molecular weight increased with pressure and mean residence time. The space‐time yield was the maximum at an ethylene molar fraction of 0.5. The produced polymer was continuously taken out from the high‐pressure system as a slurry. The amount of deposited polymer to the reactor wall was markedly decreased, and five full days continuous operation was successfully performed with the space‐time yield of 13.5 g/liter hr.
The kinetics of polyesterifications. IV. Polyol from BHET and adipic acid and its urethanes
Authors: Lin Chen‐Chong , Yu Ping‐Chang , Huang Li‐Chau 
Published: April 2003

AbstractNew polyol containing aromatic rings was prepared from BHET, or BHET/ethylene glycol mixtures and adipic acid. In this new system, the kinetics of polyesterification were investigated and were shown to follow the kinetic equations proposed by Lin and his co‐workers which were obtained by modifying Flory's theory. Polyurethane elastomers were prepared by reacting these polyols and toluene diisocyanate (TDI) in DMF solution with NaCN as a crosslinking catalyst at room temperature. Their physical properties such as density, gel fraction, swelling ratio, mechanical properties, etc., were measured. High values of elastic modulus are due to the rigid segment of BHET. By varying the molar ratio of diisocyanate and polyester, polyurethanes with different crosslinking densities can be obtained. The relationship between physical properties and crosslinking density was shown to follow the general theory of rubber elasticity.
Permeability of phenol through cellulose acetate membranes by reverse osmosis in various alcoholic systems
Authors: Nomura Hiroshi , Senō Manabu , Takahashi Hiroshi , Yamabe Takeo 
Published: April 2003

AbstractReverse osmosis separation of phenol in various alcoholic solutions using porous cellulose acetate membranes was investigated. The permeation behavior of phenol was measured for cellulose acetate membranes having various pore size distributions which were prepared by annealing at four different temperatures. Some differences were found between the aqueous and the alcoholic solutions in solute permeabilities and product rates. Membranes annealed at 90°C showed higher permselectivity than membranes annealed at lower temperatures. The pore character was classified into two types according to the relation of the product rate of 1‐propanol and that of water. It was found in a series of alcoholic solutions that the permeability of phenol, the product rate, and the apparent partition coefficient are closely related to the carbon number of the alcohols, but the values of Jv × η (ca. 1.25 × 10−4 poise·m3/m2·day) and of the permselectivity coefficient (ca. 0.83) remain constant. The result was analyzed by using the three‐dimensional solubility parameter to obtain some information for the partition mechanism of solutes in aqueous and alcoholic solutions.