bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultraviolet irradiation of plastics. II. Crosslinking and scission
Authors: Stephenson C. V. , Moses B. C. , Burks R. E. , Coburn W. C. , Wilcox W. S. 
Published: April 2003

AbstractUltraviolet irradiation of polyethylen, nylon, Mylar, and Acrilan produces higher scission‐to‐crosslinking ratios when irradiation is performed in a nitrogen atmosphere than it does when irradiation is in a vacuum. Irradiation of polyethylene in nitrogen causes a sharp decrease in molecular weight while irradiation of Acrilan in vacuum causes an equally notable increase in molecular weight.
Polyurethanes. II. Effect of cis‐trans isomerism on properties of polyurethanes
Authors: Lyman D. J. 
Published: April 2003

AbstractThe cis and trans isomers of 1,4‐cyclohexanediol and 1,4‐cyclohexanedimethanol were reacted with methylene bis(4‐phenyl isocyanate), using solution polymerization techniques, to form the corresponding cis and trans polyurethanes. The properties shown by these polyurethanes indicate that enhanced flexibility due to inclined rotating bonds is responsible for differences in polymer melting points. The polymer chain shape, or configuration, has also been shown to influence the polymer properties. This approach has been extended to include differences in polymer solubilities, molecular weight/inherent viscosity ratios, initial modulus, and water absorption.
N‐Carboxyglycine anhydride polymerization with p‐bromoaniline
Authors: Moos Gilbert E. , Merritt Paul E. , Chen Francis P. 
Published: April 2003

AbstractThe presence of a p‐bromoaniline initiator fragment in polyglycine formed from N‐carboxyglycine anhydride has been confirmed by bromine and infrared analyses. Carius halogen analyses, sodium fusions, and Beilstein halogen tests prove the presence of bromine in the polymer. Both the per cent bromine and the per cent amino nitrogen data specify essentially the same molecular weight, 1500–1700, for the polymer. Per cent yield of polymer data provide a second‐order catalytic constant for p‐bromoaniline‐initiated polyglycine in dioxane at 37°C. of 1.8 × 10‐3 l. mole‐1 sec.‐1 for the first 51% of the reaction, and the calculated constant beyond that falls off rather rapidly.
Laterally ordered polymers: Polyacrylonitrile and poly(vinyl trifluoroacetate)
Authors: Bohn C. R. , Schaefgen J. R. , Statton W. O. 
Published: April 2003

AbstractThe structure and properties of two laterally ordered (directionally crystallized) polymers are discussed, namely, polyacrylonitrile and poly(vinyl trifluoroacetate). Evidence from x‐ray diagrams, infrared measurements, thermal expansion data, and fiber properties are interpreted in terms of molecular structure. It is concluded that the existence of only chain‐to‐chain order (lateral order) in polyacrylonitrile and poly(vinyl trifluoroacetate) is principally due to steric and dipolar intramolecular repulsions. These lead to a chain stiffening effect, regardless of tacticity, which is so great in the former case that the backbone chain is forced to assume a twisted, kinked configuration. The stiff molecular chains may be thought of as rigid rods which pack in a lattice array. The side groups, nitrile or trifluoroacetate, assume varying angles with the respect to the rod axis in order to minimize the steric and dipolar repulsion forces. This variation gives rise to diffuse off‐equatorial scattering in the x‐ray diagram of the oriented polymers and low values of the dichroic ratios of selected bands in the infrared. The chain stiffening effect is greater in polyacrylonitrile and this polymer exhibits a higher “melting point”, higher fiber tenacity at equivalent orientation, less solubility, more general diffuse scattering in the x‐ray diagram, and lower dichroic ratios in the polarized infrared spectrum than does poly(vinyl trifluoroacetate). In fact, polyacrylonitrile, in contrast to poly(vinyl trifluoroacetate), acts as if it were all ordered and contained no amorphous regions in the usual sense, as judged from thermal expansion data and the lack of a definite amorphous halo in the x‐ray diagram. Poly(vinyl trifluoroacetate) is concluded to be no more syndiotactic than conventional poly(vinyl acetate), since laterally ordered poly (vinyl trifluoroacetate) can be derived from commercial poly (vinyl alcohol) by esterification. Therefore, the observed lateral order in poly (vinyl trifluoroacetate) is not due to a predominantly syndiotactic structure. These laterally ordered polymers have a properties intermediate between those of normally crystalline polymers and those of amorphous polymers.
Phase equilibrium of polydispersed polymer solution and fractionation
Authors: Okamoto H. , Sekikawa K. 
Published: April 2003

AbstractPhase equilirium of a polydispersed polymer solution was investigated. Experiments on the system of linear polyethylene, xylene, and ethylene glycol were found to be approximately described by Flory's theory. To obtain a more precise description, the authors give a modification of Flory's relation. Methods by which the molecular size distribution of the fractionated polymer can be calculated from that of the unfractionated are proposed. Conditions favorable to effective fractionation are also briefly discussed.
Radiation‐induced graft polymerization: The trommsdorff effect of methanol
Authors: Odian George , Sobel Marjorie , Rossi Albert , Klein Robert 
Published: April 2003

AbstractThe radiation‐induced graft polymerization of styrene to low density polyethylene was investigated. It was found that dilution of the styrene monomer with methanol accelerates the rate of graft polymerization with a maximum effect occurring at approximately 70 vol.‐% methanol. Both the accelerated and unaccelerated graft polymerizations yield volumetric or homogeneous graft copolymers. Experiments in which n‐octane was substituted for methanol as the diluent showed that the accelerative effects of methanol are best explained by the incursion of a Trommsdorff‐type effect. The kp2/kt values for the grafting reaction in the various styrene‐methanol solutions were calculated. It was found that the kp2/kt term is larger in grafting than in homopolymerization by a factor of 103, and that it increases as the methanol concentration of the monomer solution increases.
Diffusion of gases and vapors through polyvinyl chloride‐polyvinyl acetate copolymer films I. Glass transition effect
Authors: Kumins C. A. , Roteman J. 
Published: April 2003

AbstractThe specific volume of a polyvinyl chloride‐polyvinyl acetate copolymer was studied as a function of temperature. It was found that two second‐order transition temperatures exist, one at 30°C. and the other at 77°C. The lower transition temperature has not been reported previously. Diffusion coefficients for several gases of varying van der Waals diameters were measured at several different temperatures and the activation energies for diffusion calculated. It was found that the activation energies were exponential functions of the gas diameters. For the smaller‐sized gases, plots of log diffusion coefficient against 1/T unexpectedly did not change slope at either of the two transition temperatures. On the other hand, the transport processes for carbon dioxide and water vapor were affected by the glass transition temperatures of the copolymer. For the former the slope changed at the lower transition temperature of 30°C. In contrast, the water vapor diffusion coefficients increased normally with temperature until the second transition temperature of 77°C. was reached. At this point the diffusion coefficients exhibited a marked increase with temperature. An explanation for the anomalously high diffusion values for water vapor is offered.
Polymerization of acrylamide with persulfate‐metabisulfite initiator
Authors: Rodriguez F. , Givey R. D. 
Published: April 2003

AbstractThe redox system ammonium persulfate–sodium metabisulfite (I1‐I2) was used to initiate polymerization of acrylamide (M) in water. Up to 50 to 70% conversion, the rate equation is:
where Rp is the rate of polymerization and the bracketed quantities are concentrations. [Mo] is the monomer concentration at time t = 0. In the range investigated, K (30°C.) = 1.20 1. moles‐1 sec.‐1. Activation energy is 26 kcal./mole‐1 and K depends on ferrous ion concentration, [Fe++] (mole 1.‐1):
The number‐average degree of polymerization, x̄n is independent of [Fe++], temperature, or [I1]. However:
The range of concentrations (mole 1.‐1) for which these generalizations hold at 30–50°C. and pH 7.0 are: [Mu] 0.4 bis 2.0; [Il], 0.2 to 3.2 × 10–3; [I2], 0.13 to 2.8 × 10‐3; [Fe++], 0 to 19 ×10‐6; [Il][I2], 0.16 to 3.2 ×10‐6; [Mu]/[M], 1 to 3.5.
Diffusion in a crosslinked acrylamide polymer gel
Authors: White Malcolm L. , Dorion George H. 
Published: April 2003

AbstractThe diffusion coefficients of sucrose, urea, potassium chloride, and heavy water (D2O) in an acrylamide–methylenebisacrylamide gel were determined as a function of total polymer concentration and degree of crosslinking, and found to decrease with increasing polymer concentration but to be relatively independent of the degree of crosslinking. Extrapolation of the values to 0% polymer gave diffusion coefficients that checked well with the known values for the solutes in pure water, indicating that there are no specific interactions of the gel with either electrolytes or nonelectrolytes. Equilibrium values for the diffusion after infinite time showed that all of the water in the gel is available for diffusion, indicating the absence of “bound” water. Calculation of average pore sizes from the diffusion data gave values that agreed with previously reported results obtained from water permeability measurements. These data confirm the hypothesis that the gel has a “brush‐heap” type of structure.
Intramolecular rearrangements of polyketones
Authors: Michel R. H. , Murphey W. A. 
Published: April 2003

AbstractA number of polymeric ketones with the carbonyl groups in the polymer backbone (ethylene‐carbon monoxide copolymers) have been converted to polyamides by means of Schmidt and Beckmann rearrangements. The high degree to which these reactions are intramolecular has permitted conversion with little loss in molecular weight.
Crystallization kinetics of polycapramide
Authors: Inoue Masakazu 
Published: April 2003

AbstractThe kinetics of the isothermal crystallization of polycapramide (nylon 6) is discussed. Temperature changes in specimens during the course of crystallization are measured. For specimens at 200–210°C., the temperature is 2–3°C. higher than that of the crystallization bath. Below 200°C., strict isothermal crystallization cannot be obtained because there are no stable supercooled states. The isothermal crystallization proceeds in two stages. In the first stage, in which the Avrami equation is appliable, n is 4 at temperatures of 210–215°C. and is 2.5 below 207°C.; it changes rapidly between 207 and 210°C. In the second stage, the relaxation of the entanglement of molecules and the perfection of crystals takes place, and the rate of density change increases with crystallization temperature, contrary to the first stage of crystallization. However, the first‐ and second‐stage processes overlap to some degree. Higher molecular weight polymer crystallizes at a lower rate than does low molecular weight polymer. The rate depends on the activation energy of melt flow, and its effect is greater at higher crystallization temperatures. If we assume n equal to 4, log k is in linear relation to Tm/(ΔT)T or T2/(ΔT)2T, where Tm is the melting point; Tm increases with crystallization temperature, especially above 210°C.
Heterogeneous hydrolysis of cellulose with high polymer acids. Part 2. Determination of acid hydrolysis effects by means of inversion of sucrose
Authors: Hartler Nils , Hyllengren Kari 
Published: April 2003

AbstractThe acid hydrolysis effects of polystyrenesulfonic acid and sulfuric acid have been determined for the inversion of sucrose. “Equivalent” acid concentrations which have been determined may be applied to the heterogeneous hydrolysis of cellulosic material. Observed differences in the rate of hydrolysis can be attributed to the diffusion effects of the high polymer acid over that of the low molecular weight acid.
Preparation of copoly(carbonate/urethanes) from polycarbonates
Authors: Foldi Veronika S. , Campbell Tod W. 
Published: April 2003

AbstractWhen solutions of high molecular weight poly(diphenylolpropane carbonate) were treated with aliphatic primary and secondary diamines in a homogeneous system, degradation to hydroxyl‐terminated copoly(carbonate/urethane) macrosegments occurred. This observation led to a novel method for the preparation of high molecular weight copoly(carbonate/urethanes). This involved (1) preparation of high molecular weight polycarbonate, (2) degradation of the polycarbonate to a low molecular weight urethane‐bisphenol, (3) repolymerization with phosgene. The composition of the final copolymer could be regulated by the amount of diamine empolyed in step (2). High molecular weight copolymers were thus prepared from poly(diphenylolpropane carbonate) and piperazine, ethylene diamine, hexamethylene diamine, p‐xylylene diamine and hydrazine. These copolymers could be converted to tough drawable films which showed greatly improved hydrolytic stability over unmodified poly(diphenylolpropane carbonate).
A study of the mechanism of emulsion polymerization of styrene and chloroprene by means of reaction heat
Authors: Maňyásek Z. , Řežábek A. 
Published: April 2003

AbstractInvestigation of the polymerization process was carried out on emulsions placed in water‐thermostatted flasks. The temperatures of the central part of the flask and of the thermostat were measured with the aid of thermocouples. The heat balance of the reaction system under investigation is given by the differential equation:

The quantity of heat dq evolved during the time dτ in the course of the reaction raises the temperature of the system by d(ΔT), part of the heat being removed by the cooling bath. The constant K expresses the overall heat transfer, and C is the overall heat capacity of the polymerizing system. The left side of eq. (1) contains the time function of the reaction. We investigated the cases for zero‐, first‐, and second‐order reactions and derived the corresponding solution of the basic equation for ΔT = f(τ). For a zero‐order reaction:

For a first‐order reaction:

For a second‐order reaction:

K0, K1, and K2 in eqs. (2), (3), and (4) are the zero‐, first‐, and second‐order rate constants, respectively, ΔH is the heat of polymerization; Mp and ΔTp, the number of moles and the temperature difference at the start of the reaction, respectively; the difference

is the so‐called reduced exponential integral. The constants K and C may be calculated from the experimental curve ΔT = f(τ) and from two–three value for the degree of conversion in the course of polymerization. From this any number of values may be obtained for the degrees of conversion with time. For such values we derived the relation

where Δp/Δτ is the overall reaction rate expressed by the increase with time of the amount of polymer. Expression (5) has a convenient linear plot, and from the slope and the intercept on the ordinate axis the reaction order i and the rate constant Ki may be determined directly. The theory was applied to a kinetic study of the emulsion polymerisation and styrene and chloroprene. An aqueous solution of potassion laurate served as emulsifier and potassium persulfate as initiator. The reaction was carried out at 40°C. The method permits accurate determination of the overall polymerization rate and of the monomer concentration in the latex particles. In a number of experiments the reaction rates and quantity of latex particles as function of initiator concentration were determined. The results were compared with conclusions following from the Smith‐Ewart quantitative theory of emulsion polymerization. The constants of chain growth of polystyrene and polychloroprene were determined.
Electron exchange polymers. XVII. Some new methylated poly(vinylhydroquinones)
Authors: Kun Kenneth A. , Cassidy Harold G. 
Published: April 2003

Abstract2,5‐Dimethoxy‐3,6‐dimethylstyrene was prepared by dehydration of 2'‐hydroxyethyl‐2,5‐dimethoxy‐3,6‐dimethylbenzene and 2,5‐dimethoxy‐3,4,6‐trimethylstyrene was prepared by dehydration of 2'‐hydroxyethyl‐2,5‐dimethoxy‐3,4,6‐trimethylbenzene and by dehydration of the 1'‐hydroxyethyl isomer. Preparation of the intermediates is described. These two relatively stable vinyl monomers were polymerized by cationic initiation to the corresponding polystyrenes, which were demethylated under acid conditions to the corresponding poly(vinylhydroquinones). Some crosslinking occurred during demethylation of the poly(2,5‐dimethoxy‐3,6‐dimethylstyrene). These methyl‐substituted polyvinylhydroquinones are new redox (electron exchange) polymers. They were prepared in order to obtain redox polymers more stable to oxidation than polyvinylhydroquinone. Oxidation of poly(3,4,6‐trimethylstyrene) yielded the flattened potentiometric titration curve characteristic of electron exchange polymers.
Polymerization of acrylonitrile with n‐butyllithium at −78°C.
Authors: Miller M. L. 
Published: April 2003

AbstractThe polymerization of acrylonitrile with n‐butyllithium in toluene at −78°C. was studied at three monomer concentrations, 5.7, 13, and 27%, and at butyllithium concentrations from 0.5 to 1.5 × 10−2 m./1. With high concentrations of monomer the conversion was reduced by a gel effect. At low monomer concentrations the dependence of polymerization rate on monomer and catalyst concentration was similar to the dependence observed by other workers in the polymerization of styrene with butyllithium at 20–30°C. At −78°C. in toluene there was no evidence for termination of polyacrylonitrile chains by monomer. Cyanoethylation and reactions which produce yellowing at higher temperatures were absent. The initial polymerization was rapid and the initial catalyst efficiency low. Molecular weights were from 250,000 to 1,300,000.
Glass transition and melting point of poly(vinyl chloride)
Authors: Reding F. P. , Walter E. R. , Welch F. J. 
Published: April 2003

AbstractBoth the glass transition temperature and the melting point of poly(vinyl chloride have been found to increase as the temperature at which the ample is polymerized is decreased). The glass transition temperature changes from about 70°C. for polymer prepared at 125°C. to about 100°C. for polymer prepared at −80°C. It is believed the increase in percentage of syndiotactic structure which results from decreasing the polymerization temperature is responsible for the change in glass transition temperature. The effect of polymerization temperature on melting point is even more striking. The melting point changes from approximately 160 to above 300°C. on lowering the polymerization temperature from 125 to −80°C. X‐ray diffraction studies show that polymers prepared at low temperature form crystals which have a substantial increase in perfection along the chain axis. It seems probable that this increase in crystalline perfection along the chain axis is responsible for the very marked increase in melting point.
Esters of polyvinyl alcohol and sulfuric acid
Authors: Fingauz I. M. , Vorob'Eva A. F. , Shirikova G. A. , Dokuchaeva M. P. 
Published: April 2003

AbstractThe alcoholysis of polyvinyl acetate in ethyl alcohol solution catalyzed by sulfuric acid is accompanied by a side reaction leading to formation of a certain amount of polyvinyl sulfate. Aqueous solutions of the polyvinyl monosulfates possess a comparatively high emulsifying capacity, which increases with increase in the bound sulfur content, comprising 0.06–0.08% for 1–5% sulfuric acid in the reaction medium. Attempts to incorporate the sulfate group to a great degree with the objective of obtaining sulfated polymers of specific properties (efficient emulsifiers, stabilizers, ion exchangers etc.) did not yield satisfactory results when methods described in the literature were employed. Direct sulfation of polyvinyl acetate with subsequent conversion to polyvinyl alcohol or the sulfation of polyvinyl alcohol, to obtain a derivative with a large ester content, is impossible, owing to stereochemical hindrance. Because of this we investigated the possibility of sulfating the polymer during the process of alcoholysis of polyvinyl acetate in ethyl alcohol. It was found that under the reaction conditions for various amounts of acetate residual groups polyvinyl alcohol may be obtained with a varying content of acid or neutral esters. Under the chosen conditions a hitherto undescribed acid sulfuric acid ester of polyvinyl alcohol with 10–15% bound sulfur content was obtained. In contrast to the original polyvinyl alcohol soluble in water this sulfur‐containing product dissolved in ethyl alcohol, water or aqueous alcohol. Neutral sulfates of polyvinyl alcohol are soluble only in ethanol but not in water. The acid sulfates possess high emulsifying and stabilizing properties. If the reaction is carried out in methanol, esterification of the acid sulfuric acid ester of polyvinyl alcohol takes place as a side reaction. The resultant products are devoid of emulsifying properties.
Titanium tetrafluoride as a catalyst for some organic reactions
Authors: Latham Ross , Drago Russell S. 
Published: April 2003

AbstractTitanium tetrafluoride has been successfully employed in combination with triisobutyl aluminum (TBA) as a Ziegler type of catalyst to polymerize butadiene. The resulting polymer has a higher cis to trans ratio and a higher degree of crosslinking than one prepared with the titanium tetrachloride–TBA catalyst. It is of interest that vinyl chloride, a monomer containing a donor atom, was polymerized with the TiF4–TBA catalyst. Titanium tetrafluoride is not a very effective catalyst for the Friedel‐Crafts type of reactions.
Free energies of formation of fluorocarbons and their radicals. Thermodynamics of formation and depolymerization of polytetrafluoroethylene
Authors: Bryant W. M. D. 
Published: April 2003

AbstractEnthalpies and free energies of formation of a group of aliphatic fluorocarbons and their radicals for 298.15°K. and the ideal gaseous condition are calculated from the available experimental heat and entropy data, extended by means of empirical series treatments. The polymerization of tetrafluoroethylene and the thermal breakdown of the resulting polymer are recognized as thermodynamically equivalent processes, differing only in the sign of the thermal quantities involved. Free energy changes attending various intermediate steps in the free radical‐initiated polymerization are calculated. The heat and free energy of polymerization are highly exothermal at 298.15°K., compared with those for other olefinic compounds. At high temperatures reversal of the synthesis steps is to be expected. Initiation of degradation need not occur merely by reversal of the termination process, although this possibility is not excluded.
Light scattering studies on unfractionated poly(n‐docosyl methacrylate)
Authors: Levi D. W. , Valles R. J. , Schramm E. C. 
Published: April 2003

AbstractPoly(n‐docosyl methacrylate) was prepared by emulsion polymerization. Since the weight‐average molecular weight of the unfractionated material appeared to be unusually large, light scattering measurements were made in three solvents and at several temperatures. No evidence of association in solution was found. Values of average molecular weight, dimensions, and second virial coefficients are reported.