bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dilaminar elastomeric films
Authors: Defries Myron G. , Schneider Louis , Fram Paul , Leonard Fred 
Published: April 2003

AbstractMany applications of rubberlike materials require a combination of bulk and surface properties which may not be attained with a specific elastomeric composition regardless of vulcanization, reinforcement, or other modification by compounding, but may be achieved by combining two materials in a laminated structure. This paper describes a technique for casting hollow laminated elastomeric structures from aqueous dispersions in molds of plaster of Paris. An elastomeric composition which has the properties required of the surface is deposited first, and a second composition having the properties required of the bulk is then cast against original film before the latter dries in the mold. This process, termed “dilaminar” film casting, yields laminated films having resistant surface layers of uniform, controllable thickness that are inherently bound to the substrate. The properties of a series of butyl acrylate‐acrylonitrile copolymers of varying monomer ratios and amounts of organic reinforcing agents were studied. It was found that unreinforced copolymers of approximately 27–30% acrylonitrile had suitable resistance to staining and abrasion, while reinforced compositions of an elastomer copolymer having an acrylonitrile content of about 10% displayed optimum bulk but poor surface properties. Dilaminar films were cast of two compositions having optimum properties for surface and substrate layers. The laminated films retained the surface resistance of the outer laminare and exhibited mechanical properties intermediate between the properties of the two components. Equations relating tensile and flexural properties of laminated elastomeric films to those of the single homogeneous compositions were derived, and calculated tensile and flexural values were found to agree with the experimental data.
Reaction of natural rubber with hydrofluoric acid
Authors: Tom D. H. E. 
Published: April 2003

AbstractIn this article the reaction of natural rubber with hydrofluoric acid is described. It shows that both addition and cyclization occur in a competitive way. By carrying out the reaction at a low temperature, however, and using xylene as a solvent, cyclization could be forced back to a considerable extent. Products were obtained of which 65 to 70% of the double bonds were saturated with hydrofluoric acid. This addition product has a surprisingly good thermal stability and can be cured to a rubber with good mechanical characteristics, limited swelling power in aliphatic hydrocarbons, an absolute resistance to ozone, and a small permeability to gases. Its brittle point is rather high.
Intrinsic viscosities and polymerization speeds in methacrylic ester‐alkyl polymethacrylate systems
Authors: Lal Joginder , Green Richard 
Published: April 2003

AbstractIntrinsic viscosities of solutions of a number of alkyl polymethacrylates in various alkyl esters of methacrylic acid were investigated. Generally speaking, a decrease in the intrinsic viscosity of a given polymer in methacrylic ester took place when the length of the alkyl chain of ester group of the solvent methacrylic ester was increased. This behavior was observed with solutions of methyl polymethacrylate, ethyl polymethacrylate, copolymer of methyl methacrylate und ethyl methacrylate, and copolymer of methyl methacrylate and butyl methacrylate. However, the various alkyl esters of methacrylic acid were found to be almost equally good solvents for butyl polymethacrylate and hexyl polymethacrylate. Peak temperatures and times of polymerization of redox activated slurries obtained from different polymers and alkyl esters of methacrylic acid were studied. The results stressed the fact that compatibility of polymer and monomer in that slurry, indicated by high value of intrinsic viscosity for the polymer in the same monomer, is essential for its successful polymerization in a reasonable time.
Structural changes of alkali cellulose during aging
Authors: Lauer K. , Skark L. 
Published: April 2003

AbstractDuring aging of alkali cellulose the sedimentation volume of the acidified fibers goes through a maximum, indicating a high degree of swelling at this point, which could also be shown by measuring the swelling value and the Canadian freeness of the pulps. Xanthation shows that during aging certain intermicellar bonds are broken up, permitting better accessibility for NaOH and CS2. The sedimentation maximum always was observed at DP values of about 450–500 and viscoses prepared with these alkali celluloses in the specified way had a definite viscosity range. The determination of the sedimentation volume can therefore be used as a short and simple method to find the desired degree of aging in filtrability measurements.
Diffusion and gelation in polyadditions. II. Theory of the viscosity‐conversion curve
Authors: Gordon Manfred , Roe Ryong‐Joon 
Published: April 2003

AbstractThe curve governing the viscosity as a function of conversion in the system methyl methacrylate (95% moles)/ethylene dimethacrylate (5% moles) up to the gel point is predicted theoretically. The classical theory of gelation enters critically into the theory. The excellent experimental verification of the curve thus confirms the applicability of the classical theory and the absence of interference by diffusion control. As the gel point is reached at just over 1% conversion, these experiments require further refinements in the viscodilatometric technique used. The reproducibility during the induction period preceding polymerization of the constant initial volume is attested by a standard deviation of 0.5% calculated on the subsequent shrinkage up to the gel point. The standard deviation of the viscosity during the induction period was 1%. The theory of the viscosity/conversion curve makes a correction for nonideal solution behavior, but this is small here. No allowance is required for chain transfer effects or ring formation within a primary polyaddition chain, which are serious obstacles when at tempting to predict the critical conversion absolutely from the classical theory. Formation of rings involving several primary polyaddition chains is neglected, and this seems justified by the agreement between theory and experiment, and by the statistical theory to be given in the fourth paper of this series. The initial intrinsic viscosity of the system is found to be substantially lower than for pure methyl methacrylate polymerization. This reduction can be formally evaluated in terms of a chain transfer constant to ethylene dimethacrylate monomer. However, the value obtained is too high in comparison with suitable model compounds for this monomer, including ethylene diacetate and difumarate. A large part of the reduction in viscosity is, therefore, attributed to the compacting of the primary chains through formation of internal rings of substantial size.
Diffusion and gelation in polyadditions. III. Statistical‐kinetic theory of the trommsdorf rate acceleration
Authors: Gordon Manfred , Roe Ryong‐Joon 
Published: April 2003

AbstractIn a polyfunctional polyaddition system, such as methyl methacrylate/ethylene dimethacrylate (MMA/EDMA), the first elementary reaction step to become affected by diffusion control is the termination step. This is true also in absence of EDMA (pure MMA polymerization), but in the presence of EDMA this diffusion control occurs at much lower conversions. It becomes manifest as the usual Trommsdorf effect (over‐all rate acceleration), and begins after the gel point. A general statistical kinetic theory is developed for the Trommsdorf effect. Surprisingly, the theory is more readily applied to crosslinked systems such as MMA/EDMA than to linear systems such as MMA alone. This happens because crosslinking causes useful discontinuities both in the viscosity/time curve and in the size distribution curve of the radicals, whose diffusion behavior determines the Trommsdorf effect. The theory divides these radicals by a size barrier into small radicals which freely diffuse and large radicals which are immobilized. A successful termination step is taken to require at least one mobile radical. To assume that all the radicals are mobile, or that all are immobile, is neither sound in theory nor successful in practice. Theory leads to the conclusion that uncrosslinked radicals should be mobile, while those bearing crosslinks are immobilized beyond the gel point. This conclusion determines the rate curve, and no reasonable amendment will make any difference to the theoretical curve. The curve lends itself to reduction to dimensionless form. Experimental plots are successfully brought to mutual coincidence by this reduction, but not into quantitative coincidence with the theoretical curve. This is attributed to incomplete efficacy of the size barrier, in that even pairs of nominally frozen radicals will occasionally succeed in mutual termination. The theoretical rate curve lies closer to experimental results if radical combination rather than disproportionation is the assumed termination mechanism. The rate theory furnishes an improved explanation of kinks, previously observed in rate curves going through a gel point. The success of the treatment confirms the classical network theory of gelation, and the diffusion control theory of the Trommsdorf effect.
A light scattering investigation of the retrogradation of amylose
Authors: Foster Joseph F. , Sterman Melvin D. 
Published: April 2003

AbstractStudies of the rate of retrogradation (precipitation) of amylose from aqueous solution utilizing turbidity studies, are reported. A marked dependence of rate on the prior physical state of the amylose preparation is demonstrated. In particular it is concluded that retrogradation is retarded by increased perfection of the helical crystalline form. It is suggested that the rate of retrogradation is primarily governed by the rate of disruption of the intramolecularly hydrogen‐bonded helical form of amylose. The process of retrogradation is thus akin to the prevalent picture of protein denaturation.
Vinyl epoxystearate: Preparation, polymerization and properties of polymers and copolymers
Authors: Silbert Leonard S. , Jacobs Zelda B. , Palm William E. , Witnauer Lee P. , Port William S. , Swern Daniel 
Published: April 2003

AbstractVinyl epoxysterate was synthesized by the reaction of vinyl oleate and percarboxylic acids. An investigation of the kinetics of the epoxidation of the two unsaturated bonds in vinyl oleate showed that the epoxidation of the internal double bond proceeded at 220 times the rate of the vinyl bond. Polyvinyl epoxystearate was prepared by conventional methods. Like polyvinyl esters of other long‐chain fatty acids, polyvinyl epoxystearate exhibited low intrinsic and specific viscosities. The mechanical and thermal properties of copolymers of vinyl chloride and vinyl epoxystearate were compared with those of compositions of polyvinyl chloride and butyl epoxystearate. Vinyl epoxystearate had a greater effect of the milling temperature of the copolymer than butyl epoxystearate had on that of the composition, but the opposite effect was observed on the temperature coefficient of the torsional modulus. In heat and light stability studies, it was found that butyl epoxystearate (or other external epoxy plasticizers) was more efficient than vinyl epoxystearate.
Effect of crystallinity on the properties of nylons
Authors: Starkweather Howard W. , Moore George E. , Hansen John E. , Roder Thomas M. , Brooks Richard E. 
Published: April 2003

AbstractIncreasing the degree of crystallization of unoriented 66 or 610 nylon increases the stiffness, yield point, tensile strength, and hardness, but reduces the impact strength, particularly in the high crystallinity range. The impact strength was increased by increasing the molecular weight, but the other properties were substantially unchanged. The effect of varying water content was independent of the effect of varying crystallinity and generally acts in the opposite direction.
Polymer characterization: A typical copolyamide system
Authors: Beaman Ralph G. , Cramer Francis B. 
Published: April 2003

AbstractA characterization scheme for small‐scale evaluation of fiber‐forming polymers is presented. Tests are described for bulk polymer (visual observations, toughness, viscosity number, polymer melt temperature, and solubility), films (visual observations, toughness, water absorption, glass transition temperature, and crystallinity), and fibers (tenacity, elongation, initial modulus, compliance ratio, tensile recovery, work recovery, fiber stick temperature, zero strength temperature, crystalline melting point, orientation, and crystallinity). The copolyamide system poly(tetraethylene adipamide‐co‐hexamethylene sebacamide) was evaluated over the whole composition range by this scheme. In general, maxima or minima were obtained at an intermediate composition for the properties studied. The point of greatest copolymer effect, however, was found to depend upon the specific property studied. Water absorption and glass transition temperature appeared to be more nearly linear functions of composition.
Copolymerization of 1,3‐butadiene with 1‐ and 2‐chloroanthracenes
Authors: Marvel C. S. , Johnson J. W. 
Published: April 2003

Abstract1‐ and 2‐Chloroanthracenes have been copolymerized with butadiene in the Mutual recipe and in the Mutual recipe with some added benzene. Using charging ratios of 90 parts of butadiene and 10 parts of chloroanthracene in the absence of benzene, the incorporation of the 1 isomer at 62% conversion is 16.9% and the incorporation of the 2 isomer at 80% conversion is 7.3%. In the presence of added benzene (5 ml. to 84 g. charge) the incorporation of the 1 isomer is 21.2% at 39% conversion and the incorporation of the 2 isomer is 9.4% at 53% conversion. The anthracene derivative is incorporated in the polymer chain through the meso positions.
Methylation of secondary cellulose acetate with diazomethane
Authors: Rebenfeld L. , Pacsu E. 
Published: April 2003

AbstractIn an attempt to determine the acetyl group distribution in a commercial secondary cellulose acetate, it was desired to methylate fully the remaining free hydroxyl groups of the cellulose. In order to accomplish this, etherial diazomethane was used as the methylating agent. An anomalous effect was observed during the methylation reaction which was ascribed to a neighboring acetyl group participation. It consists of deacetylation accompanied by the introduction of methoxyl groups on the cellulose. The rate of reaction is controlled by the moisture content of the sample; however, a simple hydrolytic mechanism is not postulated since diazomethane is also required. Kinetic data are presented and two alternative mechanisms for the observed reaction are postulated.
Dipole moments and the structures of polyethylene glycols
Authors: Uchida Tadashi , Kurita Yukio , Koizumi Naokazu , Kubo Masaji 
Published: April 2003

AbstractThe dipole moments of polyethylene glycols (from a monomer to a heptamer) were measured in dioxane solution. Measurements were made also of the infrared absorptions of these compounds in carbon tetrachloride and in dioxane. Unlike the case of polyoxymethylene dimethyl ethers, the moment of the series of polyethylene glycols increases progressively with the degree of polymerization. This fact cannot be explained by assuming a helical structure of the chain molecule. Such a structure could result from the gauche minima of the internal rotation about single bonds in the case of a polyoxymethylene chain. The free rotation model, in the sense that the trans and the gauche minima are equally important, is suitable for the polyoxyethylene chain, presumably because the chain has CC bonds of a vanishing bond moment. A systematic increase of the theoretical moment for the free rotation model over the experimental data was observed for the higher members of this series of compounds. This effect is attributable to the volume effect. Infrared absorption measurements made in carbon tetrachloride and dioxane solutions revealed that in the latter solution all the OH groups are hydrogen‐bonded with the ether‐type oxygen of the solvent. This explains the fact that the theoretical moments of the lower members of polyethylene glycols are slightly lower than the observed ones.
Studies of orientation phenomena in crystallizing polymers
Authors: Keller A. 
Published: April 2003

AbstractUnusual orientation effects encountered during the formation of filaments of polyamides (nylon 6,6, 6,10, and 6 (polyhexamethylene adipamide, sebacamide, and polycaproamide)), polythene, and Terylene (polyethylene terephthalate) are described and discussed. The paper is divided into two parts: (I) extrusion, (II) drawing. (I) It was found that, under certain conditions, the extrusion process can produce a characteristic perpendicular orientation of the crystallites. This type of orientation can correspond to two types of structures in the extruded samples: (1) the row structure, which consists of aggregates of partially developed spherulites forming along flow lines; (2) a new structure, in which the crystalline fibrillar units (helices in our interpretation) grow in the extrusion direction only, instead of forming the normal spherulites. Both structures occur in all the polymers investigated, but their relative frequency depends on the material and on the conditions of extrusion. (II) It was found that polyamides have a perpendicular orientation in the first stages of elongation corresponding to a strong elastic distortion of the spherulites, and further, that rupture occurs within the crystalline region during the later stages of drawing. It was shown that, under certain conditions, drawing can consist in the gliding past of crystal aggregates which themselves possess perpendicular orientation. Attention is drawn to some unusually pronounced relaxation phenomena observed in polyamides and to the variety of crystallographic tilts, which can occur in Terylene. These experimental findings are discussed. In the course of this discussion the usefulness of the morphological approach in the treatment of these types of phenomena is clearly brought out.
The size and configuration of some soluble wool keratins
Authors: O'Donnell I. J. , Woods E. F. 
Published: April 2003

AbstractTwo soluble wool proteins, S‐carboxymethylkerateine 2 (SCMK) and α‐keratose, have been studied by viscosity, sedimentation, and diffusion methods. In aqueous buffers both proteins exist in an aggregated state with a wide distribution of particle size depending on the pH and ionic strength of the buffer. SCMK gives one peak in the ultracentrifuge except in the presence of 2 M guanidine hydrochloride, where two are observed. α‐Keratose gives two polydisperse components under most conditions studied. Increase of ionic strength causes aggregation and increased heterogeneity of both SCMK and α‐keratose. When stored at 25°C. both proteins show a decrease in viscosity and this has been shown for α‐keratose to reflect an aggregation process which is more rapid a t pH 7.0 than a t pH 11. Disaggregation of both proteins can be brought about by either 8 M urea or by sodium dodecyl sulfate in amount equivalent to 2 moles of detergent per positive site on the protein, to give a more homogeneous protein of particle weight 45,000–50,000, both proteins under these conditions yielding one peak in the ultracentrifuge. Even further reduction in molecular size can be brought about by alkali at pH 13.0. The hydrodynamic parameters have been calculated where possible and interpreted on the basis of a spheroidal model for the molecule. In 8 M urea the molecules appear to be in a greatly expanded state, whereas the complexes with sodium dodecyl sulfate are more compact, having smaller axial ratios and hydrodynamic volumes. The possibility that the molecules exist as random coils in solution has been discussed.
Determination of primary adsorbed water in cotton fibers by drying techniques
Authors: Ayer James E. 
Published: April 2003

AbstractA number of techniques for the determination of nonsolvent, or hydrate, water upon the cellulose molecule have been advanced. The results have been expressed as both maximum and stoichiometric amounts of water as hydrate. The values determined have been limited, however, to a system in which the fiber was dried prior to reaction and determination of the adsorbed water. The existence of hydrate has been attributed to chemical combination of water at the hydroxyl groups of the cellulose. It is well known that during the drying of many materials two rates of drying are encountered, a constantrate period and a falling‐rate period. The constant‐rate period is devoted to the evaporation of free water and the falling‐rate period to the removal of “bound” or capillary water. Since the moist fiber may contain two types of “bound” water, it was theorized that a second falling‐rate period should be in evidence during the drying of a fibrous material. Experimentation showed a definite second falling‐rate period, which was attributed to the evaporation of primary adsorbed or hydrate water. The method utilized in this work was a drying technique employing a convection type oven over which was mounted a torsion balance making it possible to take continual weight change readings while maintaining the sample in the conditioning atmosphere. The determinations were made at a temperature of 105°C. Six fiber–water systems were investigated which included combinations of drying and mercerizing of alcohol–benzene extracted cotton fibers. The data obtained were plotted as drying rate versus per cent dry fiber and the results were expressed as the molar ratio of H2O: C6H10O5 at the point of intersection of the two falling‐rate lines. The molar ratio found for the several systems investigated were: extracted cotton 1.65; extracted, dried, cotton 0.52; extracted, mercerized cotton 2.12; extracted, mercerized, dried cotton 1.08; extracted, dried, mercerized cotton 1.04; and extracted, dried, mercerized, dried cotton 0.89. The values obtained agree closely with the known quantities advanced by other authors employing different techniques. From the values obtained it appears that drying greatly reduces the ability of cellulose to sorb water. Mercerization results in increased primary adsorbed water uptake. However, drying prior to mercerization reduces the number of hydroxyl groups available for hydrate formation over that of a fiber which is undried before mercerization. It seems that regardless of subsequent treatment in a fiber–water or fiber–water‐NaOH system, prior drying reduces the water taken up as hydrate over that taken up by a fiber which has not been dried. The results indicate that this method permits a quantitative determination of primary adsorbed water in fiber–water systems which was impossible to determine by methods previously employed.
Hydrodynamic properties of polyelectrolytes. Part I. Poly‐4‐vinyl‐N‐n‐butylpyridinium bromide
Authors: Jordan D. O. , Mathieson A. R. , Porter M. R. 
Published: April 2003

AbstractThe viscosity, streaming birefringence, and sedimentation of a sample of poly‐4‐vinyl‐N‐n‐butylpyridinium bromide have been measured in aqueous and in sodium chloride solutions. The theory of Peterlin for concentrated solutions has been found to be in agreement with the results. Values of the molecular weight have been calculated by different methods and a value of 9 × 105 has been chosen.