bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress crazing of transparent plastics. Computed stresses at a nonvoid craze mark
Authors: Knight Alan C. 
Published: April 2003

AbstractThe mechanism of the stress crazing of transparent plastics is discussed in terms of a model suggested by recent publications in which the interior of the craze mark contains tenacious, elongated fibrils connecting the parallel faces. Internal and external stress distributions have been computed for a two‐dimensional model of equilibrium crazes. Three shape parameters are used; the length of a uniform section, the thickness of the uniform section, and the length of a tapered tip section. The configuration of the tapered tip is determined in the model by the requirement that stresses remain finite. Stabilization of the craze is attributed to reduction of stress intensity by an increase in the ratio of tip length to thickness as the craze propagates. Two conditions are noted where craze stability is not predicted. Qualitative agreement was found between the model and growth kinetics reported in the literature, but the simple equilibrium model does not provide a basis for explaining the effects of stress level and temperature on the size of craze marks. The occurrence of crazing rather than general elongation is explained in this model by the stress intensification which occurs when the fibrils of the craze materials are elongated.
Concentration dependence of the reduced viscosity of dilute aqueous polyelectrolyte solutions
Authors: Darskus R. L. , Jordan D. O. , Kurucsev T. , Martin M. L. 
Published: April 2003

AbstractThe concentration dependence of the reduced viscosity has been studied for several polyelectrolytes in conductivity water. It is shown that the viscosity maximum previously reported for polyelectrolyte solutions without added electrolyte can be explained either by the presence of ionic impurities in the solvent or by the contamination of the solutions. It is concluded that the folding chain theory of polyelectrolyte solutions requires amendment to account for the experimental results on counterion association. A suggested amendment to the theory implies that the application of the Huggins equation to the concentration dependence of polyelectrolyte solutions in the presence of added electrolyte may not lead to information concerning the interactions between the polyions in solution.
Temperature dependence of dye diffusion
Authors: Rosenbaum Shlomo 
Published: April 2003

AbstractThe temperature dependence of the diffusion of cationic dyes in polyacrylonitrile fibers has been examined over a wide range of temperatures. The results were found to accord well with a free volume model of dye diffusion. Apparent activation energies increased with decreasing temperature above the glass transition temperature Tg, and became extremely high near Tg. The course of the dependence could be described by a relation of the form of the Williams, Landel, and Ferry equation.
Contribution à l'etude de la cinétique de formation de polymères séquencés par voie radicalaire
Authors: Vuillemenot Jacques , Barbier Bernard , Riess Gérard , Banderet Albert 
Published: April 2003

AbstractIn order to study some aspects of radical polymerization initiated by a polymer, hexanediol sebacates in different degrees of polymerization were prepared. The endgroup was the tert‐butyl perester which was used to polymerize the styrene. With such compounds, it is easy after the polymerization to take off the polyester backbone by hydrolysis. One can then study the mixture of polystyrene sequences and homopolystyrene made at the same time. It appears that if the speed of thermal decomposition of the tert‐butyl perester group on the polyester is of the same order as that of the tert‐butyl perbenzoate, the efficiency factor, i.e., the fraction of free radicals which effectively initiates the polymerization, is much smaller with a polymeric initiator. Moreover, the average degree of polymerization is much smaller in this case (even in the presence of a nonperoxidized polyester). It is believed that these two results can be explained by assuming each polyester backbone to act as a cage for the free radicals produced by its own perester group which aids their recombination and intramolecular transfer.
Fracture processes in polymeric materials. VII. The nature of local inelastic processes in glassy polymers
Authors: Berry J. P. 
Published: April 2003

AbstractThe nature of the response to the local stress in the vicinity of a flaw in a glassy polymer is considered in the light of recent work on the nature and structure of craze marks. It is concluded that the response is similar to that which gives rise to a craze mark and that the structure of the layer at the fracture plane responsible for optical effects is likewise similar to that of a craze mark. This hypothesis resolves some of the inconsistencies in the earlier concept of the layer structure as a domain of oriented molecules.
Test of theories of flory, ptitsyn, and kurata for dilute polymer solutions
Authors: Patel R. S. , Patel R. D. 
Published: April 2003

AbstractThe linear expansion factor α for the fractions of amylose acetate in various solvent–nonsolvent mixtures at different temperatures have been determined using Kurata's relationship. The validity of the Flory, Kurata, and Ptitsyn theories has been tested in terms of the dependence of the function of α on molecular weight. It has been found that Flory's theory is not applicable while the Kurata and Ptitsyn theories are in good agreement.
Kinetic study of cyclopolymerization
Authors: Minoura Yuji , Mitoh Motonori 
Published: April 2003

AbstractKinetic studies of cyclopolymerization have been reported in several papers to date, but the overall kinetics is not yet established. Therefore, divinylformal was synthesized and polymerized as a difunctional monomer, and the overall rate equation, Rp = k[I]3/4[M]3/2−2, was obtained. To interpret this irregular rate equation, elementary reactions were considered and the theoretical rate equation, Rp = k[I]1/2−1[M]2−1, was obtained. The overall activation energy of polymerization was 27.7 kcal./mole, and this value, together with the result of the measurement of residual unsaturation in the polymer, yielded a value for the difference of activation energy between cyclization and propagation reaction of 2.6 kcal./mole. The results of measurements of intrinsic viscosities and residual unsaturation in the polymer at various conversions suggest that the branching reaction occurs to some extent during polymerization. The polydivinylformal was hydrolyzed to poly(vinyl alcohol) with hydroxylamine hydrochloride, and the 1,2‐glycol structures in the poly(vinyl alcohol) were determined. The result showed a higher content of 1,2‐glycol structures than that in commercial poly(vinyl alcohol).
Effect of atomic oxygen on polymers
Authors: Hansen R. H. , Pascale J. V. , De Benedictis T. , Rentzepis P. M. 
Published: April 2003

AbstractA stream of atomic oxygen, produced by passing oxygen at low pressure through a radio‐frequency coil, was allowed to impinge on films prepared from several dozen different polymers. The flow of oxygen radicals was regulated so that the reaction temperatures were between 40 and 70°C. The rapid reactions which occurred at the polymer film–oxygen radical interface were essentially unaffected by the presence of phenolic antioxidants over a wide range of concentrations but rate of reaction was greatly affected by the structure of the polymer. Bulk properties of the polymers were unchanged because the attack by atomic oxygen is limited to the surface of the polymer. In many instances a simple ablation of the surface was observed, but in some cases, especially polyethylene and polypropylene, a highly oxidized surface layer was created. These oxidized surface layers had remarkably low contact angles with water and should be of great interest in improving adhesion and other surface‐dependent properties of polymers.
Solvent effects in anionic copolymerization. III. Reactivity of dienes
Authors: O'Driscoll K. F. 
Published: April 2003

AbstractThe effect of monomer configurations (s‐cis or s‐trans) on the observed rate of propagation of butadiene, isoprene and 2,3‐dimethylbutadiene is considered. It is shown that this effect can be separated from the electronic effect of methyl substitution. Equations and numerical values are derived which can serve as a basis for quantitative treatment of the effect of solvent on diene reactivity and microstructure.
Effect of film thickness on the dynamic elastic modulus of cellophane
Authors: Gipstein Edward , Marker Leon , Wellisch Eric , Sweeting Orville J. 
Published: April 2003

AbstractThe effect of film thickness on the dynamic modulus of cellophane has been investigated to inquire into structural differences that may exist in cellophane, resulting from different conditions of regeneration. Modulus measurements on different types of platecast and commercial films at first indicated a decrease in modulus with an increase in film thickness. For all films a limiting stiffness was approached with increasing thickness which appeared to be independent of the type of film. This result, however, was proved to be an artifact introduced by an instrumental effect; the dynamic modulus apparatus was found to behave as a spring in series with the film. The moduli of all films were corrected for this effect and the mean values of the moduli in the machine and transverse directions were averaged for all films separately by types and by thicknesses. The values were found to be independent of film thickness, for all types of cellophane. Cellophane by this method of study shows no indication of a point‐to‐point variation in structure in the thickness dimension. Differences in modulus do exist among different types of cellophanes, however, and are undoubtedly the result of structural differences that arise during different methods of preparation.
Cationic copolymerization of isobutene. III. Solvent effect in cationic copolymerization of isobutene with styrene in mixed solvents
Authors: Imanishi Yukio , Higashimura Toshinobu , Okamura Seizo 
Published: April 2003

AbstractCopolymerizations of isobutene (M1) and styrene (M2) were carried out at −78°C. with the use of titanium tetrachloride as the catalyst in n‐hexane‐methylene chloride mixed solvents of various compositions. A great variation of r1, r2 was observed. In n‐hexane r1 < 1 and r2 > 1, in methylene chloride r1 > 1 and r2 ≃ 1, and in the mixed solvents both r1 and r2 were greater than unity. These experimental facts were interpreted on the basis of a large difference between the reactivities of isobutene cation and styrene cation. A values, on which the discussion of the decrease in the degree of copolymer polymerization can be based, were maximal in n‐hexane and decreased with increasing ratio of methylene chloride in the mixed solvent. This is characteristic of the styrenetype monomer transfer reaction.
Relaxation response of polyurethane elastomers
Authors: Theocaris P. S. 
Published: April 2003

AbstractThe transient extension relaxation modulus E(t) and the lateral contraction ratio vr(t) for a polyurethane elastomer have been simultaneously measured in the transition region from the glassy to the rubbery consistencies of the material. The differential moiré method was used in these measurements and yielded simultaneous values of the longitudinal extension and the lateral contraction principal strains of the tension specimen. Composite curves of E(t) and vr(t) reduced to a standard temperature were obtained by applying the method of reduced variables. The time factors KT in both curves were coincident and they followed the WLF equation. The shear and bulk modulus characteristic functions were determined from the extension modulus and lateral contraction ratio functions. The values of the lateral contraction ratio in relaxation were determined by using data of the extension relaxation modulus along the whole viscoelastic range and the initial value of the lateral contraction ratio at the rubbery state and applying an indirect method. The results obtained by the indirect method coincided with the experimental values. The shear modulus function was evaluated from the extension relaxation modulus and the lateral contraction ratio functions and compared with the shear dynamic compliance determined by Landel. The experimental data indicated that a linear relationship holds between the lateral contraction ratio in relaxation and the bulk modulus along the whole response spectrum. The same relationship was previously shown to hold for a series of various polymeric substances.
Polymerization of adsorbed monolayers. I. Preparation of the clay–polymer complex
Authors: Blumstein Alexandre 
Published: April 2003

AbstractMonomolecular layers of methyl methacrylate adsorbed on the surface of sodium montmorillonite clay were prepared by saturation of the clay with the monomer, followed by desorption of the excess monomer by means of repeated washings with nonpolar hydrocarbons. No spontaneous polymerization was observed. The polymerization of these monolayers was initiated with γ‐ray irradiation or by free radical catalysts. The doses of γ‐rays and the concentration of free radical catalysts required to initiate polymerization are much higher than for the polymerization of methyl methacrylate in bulk. Complexes containing 25% MMA gave inserted polymer only; complexes containing more than 25% of MMA gave inserted and external polymer. The yields of polymerization of the inserted polymer were found to be below 50%. The inserted polymer is strongly retained by the surface of the clay. X‐ray data show that its segments are oriented horizontally (lying flat) on the surface.
Synthesis of condensation polyesters containing the bis(halomethyl) group
Authors: Miyake Hideo , Hayashi Koichiro , Okamura Seizo 
Published: April 2003

AbstractMethods of preparing polyesters from 2,2‐bis(halomethyl)‐propanediols were investigated. Linear solid polyesters were obtained by the reaction with dicarboxylic acid chlorides, and this was the most suitable method of preparing polyesters from these diols. The polyoxalate, polysuccinate, and polyadipate of 2,2‐bis(chloromethyl)‐1,3‐propanediol were crystalline, but the poly(o‐, m‐, p‐)phthalates were amorphous. Polyadipates of 2,2‐bis(bromomethyl)‐and 2‐chloromethyl‐2‐bromomethyl‐propanediol were also crystalline, and polyadipates of 2,2‐bis(iodomethyl)‐ and 2‐chloromethyl‐2‐iodomethylpropanediols were amorphous.
Raman spectra of polymers in solution
Authors: Yoshino Tsuneo , Shinomiya Masayasu 
Published: April 2003

AbstractThe intensity and the depolarization ratio of a Raman line measured on a turbid polymer solution were related to the true intensity and the depolarization ratio, and the relations were confirmed by experiments. Apparent depolarization ratios measured on a polymer rod or solution are different from the corrected values obtained by using these relations, especially for polarized lines. The intensity per monomer unit of a polymer Raman line is equal to the intensity of the corresponding line of a model compound. No effect of polymer tacticity on Raman spectra was found.
Preparation and polymerization of vinyl esters of nonhydroxy carnuba wax acids and acrylic esters of carnuba wax alcohols
Authors: Marvel C. S. , Griffith J. H. , Comp J. L. , Cowan J. C. , O'Donnel J. L. 
Published: April 2003

AbstractThe acrylic esters of carnuba wax alcohols and the vinyl esters of nonhydroxy carnuba wax acids have been synthesized. The acrylic and vinyl esters have been homopolymerized and copolymerized with vinyl chloride. Acrylonitrile–acrylic ester copolymers also have been prepared. The copolymers were quite brittle when molding was attempted.
Polymerization of vinyl monomers by organoaluminum initiators
Authors: Wexler Herman , Manson John A. 
Published: April 2003

AbstractTriethyl aluminum, triisobutylaluminum, and diisobutylaluminum hydride have been utilized to polymerize vinyl acetate, methyl methacrylate, and styrene at temperatures from −80 to 25°C. Linear high polymers were obtained in reasonable yields. Based on kinetic experiments studied in dilatometers, it was possible to observe: (a) the rate decreased steadily with time from an initially high value; (b) the initial rate depended upon catalyst concentration and upon the square of the monomer concentration; (c) the overall energy of activation was 13 kcal./mole, and the energy of activation for the degree of polymerization was about 2 kcal./mole. The copolymerization of methyl methacrylate and styrene produced a polymer that was rich in methyl methacrylate. The polymerization is not clearly free‐radical nor ionic, and some form of coordination may take place.
Poly(vinylene fluoride), synthesis and properties
Authors: Durrell W. S. , Westmoreland G. , Moshonas M. G. 
Published: April 2003

AbstractA new synthesis of vinylene fluoride by means of the dehalogenation of 1,2‐dichloro‐1,2‐difluoroethane is reported. Both the pure cis and pure trans isomers of vinylene fluoride were found to polymerize quite readily. This polymer differs from the known polyfluoroolefins in having little crystallinity and fair solubility in a number of common solvents. While it is not markedly unstable thermally, it is the least stable of the polyfluoroethylenes in this respect. Several copolymers were prepared to further elucidate the polymerization behavior of vinylene fluoride, and some of the properties of these copolymers were examined.
Surface energetics, adhesion, and adhesive joints. IV. Joints between epoxy adhesives and chlorotrifluoroethylene copolymer and terpolymer (aclar)
Authors: Schonhorn H. , Sharpe L. H. 
Published: April 2003

AbstractIt is shown that structural joints can be formed between conventional epoxy adhesives and copolymer and terpolymer of chlorotrifluoroethylene, at temperatures well below the softening points of these polymers, without their prior surface treatment. An explanation of this low temperature behavior is given in terms of the surface tension of the adhesive, surface roughness, and the micro‐Brownian motion of the polymers associated with the glass transition.
Anionic polymerization of vinylmesitylene
Authors: Bhattacharyya D. N. , Smid J. , Szwarc M. 
Published: April 2003

AbstractAnionic polymerization of vinylmesitylene was investigated in THF (counterion Na+) at temperatures ranging from +25° to −70°C. The homopropagation is slow (kp ∼ 11./mole‐sec. at 25°C.), indicating the basically low reactivity of the monomer. Studies of conductivity and the retardation of the polymerization by the addition of Na+BPh4− demonstrate that free ions and ion pairs participate in the process. At 25°C. the kp of the free ion appears to be about 1000 times greater than that of ion pair. The outstanding feature of the polymerization is the proton transfer from the monomer to living end, producing an inert ion

(or its isomer) which does not propagate. This reaction leads to retardation of the polymerization. Its contribution decreases on lowering the temperature, and the effect of Na+BPh4− indicates that the free ion, and not the ion‐pair, acts as a base in the proton transfer.
Catalyst and solvent effects in the terpolymerization of ethylene, propylene, and dicyclopentadiene
Authors: Cunningham Robert E. 
Published: April 2003

AbstractEthylene, propylene, and dicyclopentadiene were terpolymerized to form unsaturated, sulfur‐curable elastomers, by use of catalysts of VCl4 or VOCl3 (with Al2Et3Cl3 cocatalyst) and polymerization solvents of heptane, benzene, or tetrachloroethylene. Of the various possible catalyst–solvent combinations, best overall balance of results was given by VOCl3 catalyst in benzene solvent. All other combinations, except one, also gave good results, however, with some having special points of merit. The exception was VOCl3 in heptane solvent, which produced erratic yields of highly gelled polymer. A limited study was made of the effect of the dicyclopentadiene concentration on polymerization. Increasing the diene concentration decreased polymer yield but increased its unsaturation; it had no gross effect on the inherent viscosities of the polymers. Terpolymers containing more than about 0.30 mole CC/kg. can be cured tightly with sulfur‐based vulcanizing recipe.
Adsorption of poly‐4‐vinylpyridine onto glass surfaces
Authors: Peyser Paul , Ullman Robert 
Published: April 2003

AbstractSome data on the adsorption of poly‐4‐vinylpyridine on a glass surface are presented. The results on the un‐ionized polymer are characteristic of the adsorption of organic polymers; the adsorption isotherm has a flat top and the amount adsorbed depends on the solvent used. The adsorption of ionized poly‐4‐vinylpyridine decreases with increasing ionization and increases with increasing ionic strength. The effect of increased ionic strength is presumably associated with the greater tendency of an ionized polymer to coil in the presence of excess salt. These results tend to confirm the general hypothesis that the coiling of a polymer molecule at a liquid–solid interface reflects the tendency of the polymer to coil in solution.
Silver perchlorate‐initiated polymerization of vinyl monomers
Authors: Hermans J. P. , Smets G. 
Published: April 2003

AbstractThe polymerization of vinyl compounds can be initiated by soluble silver salts. In this paper, the kinetics of the silver perchlorate‐initiated polymerization of styrene and methyl methacrylate in organic solution has been examined. The rates were measured dilatometrically at 70°C.; the solutions were prepared by a high vacuum technique. With respect to the monomer, either styrene or methyl methacrylate, the order of reaction is equal to two. In the case of styrene, the rate of polymerization is proportional to the silver perchlorate concentration when this concentration is ≤ 102 mole/l. Above this value, the rate becomes proportional to the square of the silver perchlorate concentration. For methyl methacrylate, the order with respect to the silver salt concentration varies from 0.5 to 1, depending on the concentration range. These kinetic results are interpreted on the basis of the assumption that a silver perchlorate–monomer complex, instead of a silver perchlorate molecule, participates in the polymerization. Moreover, the examination of styrene and benzene solutions of silver perchlorate indicates a formation of silver salt–aromatic hydrocarbon complexes of the 1:1 and 2:1 types. Consequently, good agreement is found between the kinetics of those two different initiator systems. A coordination polymerization mechanism is proposed, in which hydrogen transfer alternates with each propagation step. The mechanism is corroborated by an isotope effect equal to two, when dideuterostyrene is compared to styrene. The internal structure of the poly(methylmethacrylate) obtained with AgClO4, corresponds to that of a conventional polymer. The presence of traces of water inhibits the polymerization.
Copolymerization of p‐triphenyltinstyrene and p‐triphenylleadstyrene with styrene or vinyltoluene
Authors: Sandler Stanley R. , Dannin J. , Tsou K. C. 
Published: April 2003

AbstractThe reactivity ratios for the copolymerization of p‐triphenyltinstyrene (M1) and styrene (M2) have been determined by the Fineman and Ross method to be r1 = 2.55 and r2 = 0.93. The values for vinyltoluene copolymerization are r1 = 3, and r2 = 0.60. The latter values indicate that p‐triphenyltinstyrene‐copolymers with styrene or vinyl‐toluene contain blocks of the former monomer unit. The rate of homopolymerization of p‐triphenyltinstyrene and p‐triphenylleadstyrene in toluene was shown to be the same at 50°C.