bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaction of natural rubber with hydrofluoric acid
Authors: Tom D. H. E.
Published: April 2003

In 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

Intrinsic 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

During 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

The 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

In 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

Studies 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

Vinyl 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

Increasing 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

A 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

1‐ 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

In 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

The 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

Unusual 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

Two 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

A 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

The 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.
Hydrodynamic properties of polyelectrolytes. Part II. Poly‐4‐vinylpyridine
Authors: Jordan D. O. , Mathieson A. R. , Porter M. R.
Published: April 2003

The hydrodynamic properties of fractionated samples of poly‐4‐vinylpyridine have been studied. The intrinsic viscosities and the Huggins' constant (k′) have been obtained. The effect of shear on the viscosity disappears at high dilution. The sedimentation constants (S0) have been measured, and the streaming birefringence has been investigated at various concentrations and shear gradients. The Peterlin theory for concentrated solutions is in good agreement with the results for the orientation angle, but is not so well in accord with the magnitude of the birefringence. The partial specific volume is low (0.685). Molecular weights have been calculated for the fractions, and it is concluded that the shape of the molecules in solution approximates to that of a stiff coil.
The stress relaxation of sulfur vulcanizates of natural rubber
Authors: Berry J. P.
Published: April 2003

An experimental study is reported of the stress relaxation behavior of sulfur vulcanizates of natural rubber maintained at constant extension. Of particular interest is the effect of oxygen pressure on the shape of the force–time curves, and the relaxation proceeding in absence of oxygen. The results are interpreted according to a two‐stage process: (1) oxidation at the crosslinks and (2) scission of oxidized crosslinks.
The molecular weight‐viscosity relation for polyacrylonitrile
Authors: Onyon P. F.
Published: April 2003

A number of low‐conversion unfractionated polymers of acrylonitrile have been prepared by polymerization of the monomer alone and in solution in dimethylformamide. Number‐average molecular weights (28,000 to 1,000,000) were determined by osmometry and intrinsic viscosities measured in dimethylformamide at 25°C. The equation:

was obeyed within the limits of experimental error over the whole range. This relation is derived from one previously obtained by Cleland and Stockmayer from light‐scattering measurements on low‐conversion transfer polymer.
Molecular weights in acrylonitrile polymerization
Authors: Onyon P. F.
Published: April 2003

The rates of polymerization of acrylonitrile at 25°C., initiated by azobisisobutyronitrile, have been measured, together with intrinsic viscosities of the polymer formed. Ratios have been derived for kinetic constants involving transfer to monomer, transfer to dimethyl formamide, propagation, and termination. Molecular weights were obtained using the recently confirmed relation:

The results are consistent with the occurrence of radical termination by disproportionation, and an initiator efficiency of 55%.
Interaction of trifluoroacetic acid with cellulose and related compounds
Authors: Geddes A. L.
Published: April 2003

The reaction of cellulose, cellobiose, and their acetyl derivatives with trifluoroacetic acid has been studied by the method of infrared spectrophotometry. Changes in optical density were measured at 25°C. as a function of time. Band assignments are adequate for the present study, although some uncertainties exist, especially in the 8 to 10 μ region. Trifluoroacetic acid effects the solution of cellulose by an initial process of swelling, rupture of hydrogen bonds, and micellar dispersion of the cellulose structure. Esterification takes place, possibly by a mechanism involving the formation of an intermediate addition compound. Cellobiose reacts in a similar manner. Partially acetylated cellulose is subject to further esterification by trifluoroacetic acid under similar conditions. The results suggest a more rapid rate of esterification of primary than of secondary hydroxyls.
Young's modulus of semicrystalline polymers
Authors: Bueche F.
Published: April 2003

The measurement of crystallinity and Young's modulus for two widely different polyethylenes at temperatures between 30 and 140°C. are reported. A theory is presented which accounts fairly well for the observed values of the modulus. By comparing the theory with experiment it is found that the crystallite sizes in slowly cooled polyethylene vary from about 250 to 400 angstrom units depending upon the linearity of the constituent molecules. The theory is also applied to the data of Leitner for natural rubber. It is found that in this material the crystallites were about 4300 A. long. An observed discrepancy between theory and experiment indicates that the amorphous regions between the crystallites are somewhat ordered.
Vinyl polymerization. XVI. Effect of dimethylaniline on rate of polymerization of vinyl monomers initiated by 2,2′‐azobisisobutyronitrile
Authors: Imoto Minoru , Otsu Takayuki , Ota Tadatoshi , Takatsugi Hiroshi , Matsuda Minoru
Published: April 2003

A study has been made of the effect of dimethylaniline on the polymerization of styrene, methyl methacrylate, butyl acrylate, vinyl chloride, and acrylonitrile initiated by 2,2′‐azobisisobutyronitrile at 50°C. It was found that the rate of polymerization decreased with addition of dimethylaniline, but the rate of decomposition of 2,2′‐azobisisobutyronitrile remained constant. The chain transfer constants for the polymerization of these monomers were determined according to Mayo's equation. It was observed that the values of the chain transfer constant for dimethylaniline were proportional to those of the retardation by the latter. From these results, it is assumed that the decrease in rate of polymerization by addition of dimethylaniline is due to the chain transfer reaction.
Molecular weight distribution of a vinylidene cyanide/vinyl acetate copolymer
Authors: Yanko John A.
Published: April 2003

A copolymer of VCVA (vinylidene cyanide/vinyl acetate) was fractionated into twenty‐five fractions ranging in Mn values from 7,000 to 535,000. The differential weight molecular weight distribution curve for this copolymer exhibited two maxima, one occurring at a Mn value of 100,000 and the other at 340,000. The original copolymer had a Mn value of 89,000 and after extraction with acetone the Mn value was increased to 137,000. Molecular weights varying from 7,000 to 24,000 were determined for the acetone‐soluble fractions. At 25.00°C. the relationship between intrinsic viscosity measurements in DMF and molecular weight is given by the equation [η]0 = 1.536 × 10−4 M0.78. Using the equations of Huggins, a μ1 value of 0.373 ± 0.019 and a k′ value of 0.373 ± 0.025 were determined for the VCVA fractions solubilized in DMF at 25.00°C. The μ1 values decreased slightly with decreasing molecular weight, indicating a small change in chemical structure or composition of the VCVA molecules as a function of decreasing molecular weight. Approximately 23% of the original VCVA copolymer was in the molecular weight range of 84,600 to below 7,000 and here with decreasing molecular weight the VA component (per mole of VC) present in the copolymer increased from 1.075 to 2.32 moles. Using the Flory equation, root mean square end‐to‐end values of the VCVA fractions in DMF at 25.00°C. were calculated. Assuming the absence of branching or crosslinking, the degree of coiling of the VCVA chain appeared to increase as the molecular weight increased. The cohesive energy density of the VCVA copolymer was calculated to be 122.8 cal./cc.
Copolymers of allyl alcohol and acrylonitrile produced by dye‐sensitized photopolymerization
Authors: Oster Gerald , Mizutani Yoshimasa
Published: April 2003

Relatively high molecular weight copolymers of acrylonitrile and allyl alcohol have been produced using dye‐sensitized photopolymerization. The chemical constituent of the copolymers was determined by nitrogen analysis and by infrared spectrum. The calculated reactivity ratios of copolymerization were r1 = 3.96 and r2 = 0.11. The copolymers obtained beyond 0.70–0.75 mole fraction of allyl alcohol are soluble in acetone.
Ozonolytic degradation of interpolymers of natural rubber with methyl methacrylate and styrene
Authors: Barnard D.
Published: April 2003

A simple ozonolytic method has been developed which enables the natural rubber trunk chains of rubber‐polymethyl methacrylate and rubber‐polystyrene interpolymers to be degraded into low molecular weight fragments from which the liberated polymer may be easily separated for characterization purposes. A dialkyl sulfide is used as a protective agent to prevent the attack of ozone on the polymer and the marked drop in molecular weight which would otherwise result.
Sound velocity, young's modulus and transition temperature in polythenes with different degrees of crystallinity
Authors: Baccaredda M. , Butta E.
Published: April 2003

Mechanical dynamic properties of some polythenes with different degrees of crystalinity have been measured over a temperature range from −70°C. to above room temperature, at frequencies in the range 5–30 kcps. At room temperature Young's modulus and resonance coefficient increase with increasing crystallinity. A transition temperature, independent of the degree of crystallinity, at about −24°C. is found in partially amorphous polythenes. The transition region is sharper for more amorphous samples. The modulus increases with increasing degree of crystallinity at temperatures above the transition point but appears to decrease somewhat with increasing degree of crystallinity below the transition point.
Copolymerization of methyl trans‐β‐benzoylacrylate with butadiene
Authors: Marvel C. S. , Farrar Ralph C.
Published: April 2003

A further study of the copolymerization of methyl trans‐β‐benzoylacrylate has been made. The copolymer prepared in a neutral recipe at 66% conversion contains 15.4% of combined ester from a charging stock which contains 20% of ester. The copolymer has some increased resistance over GR‐S to special solvents but in general is an inferior rubber.
Polyvinyl trifluoroacetate
Authors: Haas Howard C. , Emerson Eugene S. , Schuler Norman W.
Published: April 2003

Vinyl trifluoroacetate and its homopolymer have been investigated. In copolymerization, the monomer behaves normally, having a Q similar to that of vinyl acetate and a positive e value resulting from fluorine substitution. Unlike the vinyl acetate system, polyvinyl trifluoroacetate is insoluble in its monomer and polymerization leads to no increase in DP with conversion. It is suspected that substitution of CH3 by CF3 has greatly reduced chain transfer and branching. Infrared spectra of vinyl trifluoroacetate and its polymer are presented and solubilities of the latter reported. Polyvinyl trifluoroacetate is very unstable to the hydrolytic loss of the perfluoro acid. The fluoropolymer is much harder than polyvinyl acetate and higher values are obtained for its softening point and apparent second‐order transition temperature. Although no difference can be found by infrared measurements between authentic polyvinyl alcohol and that obtained by hydrolysis of the fluoropolymer, a large difference in their water solubilities exists. Polyvinyl trifluoroacetate is readily oriented by stretching and some polarized infrared absorption data are presented. X‐ray diffraction photographs of stretched specimens indicate moderate order and considerable orientation. These results are surprising when considered in the light of the general concepts regarding polymer structure and crystallinity. Extremely highly ordered and highly birefringent polyvinyl alcohol can be obtained readily from stretched polyvinyl trifluoroacetate by conversion of the latter with gaseous ammonia.
Pectic substances–water. I. Structural changes in the polygalacturonide chains during water adsorption
Authors: Bettelheim Frederick A. , Sterling Clarence , Volman David H.
Published: April 2003

An apparatus suitable for studying adsorption of water vapor both volumetrically and gravimetrically is described. Water vapor isotherms of highly esterified pectin, sodium pectate and pectic acid were determined. Equatorial and meridional spacings of the x‐ray diffraction patterns were measured as a function of equilibrium water content in these materials. The interchain separations, as measured by the changes in the equatorial spacings of x‐ray reflections, follow the shape of the adsorption isotherms. In esterified pectin and sodium pectate, the fiber repeat period increases until 5 molecules of water content per 3 galacturonide residues are adsorbed, thereafter remaining constant. The fiber period of pectic acid is constant throughout water adsorption.
Pyrolysis of crosslinked styrene polymers
Authors: Winslow F. H. , Matreyek W.
Published: April 2003

The effect of network density on pyrolysis of polymers and copolymers of styrene, divinylbenzene, and trivinylbenzene was studied over a wide range of temperature. Thermal stability of polymers and size of carbon residues increased with crosslink concentration as volatilization rates declined. Rate of gas evolution was dependent on particle size, but was unaffected by catalyst content and moderate pressure changes. The results indicate extensive alteration of monomer units, possibly by a hydrogen transfer process which favors carbon formation rather than vaporization.
Copolymerization of styrene and acrylonitrile in aqueous dispersion
Authors: Mino G.
Published: April 2003

The bead copolymerization of styrene‐acrylonitrile, in the presence of 1‐azobis‐1‐phenylethane, was investigated at high temperature (90–100°C.). The initial distribution of acrylonitrile between styrene and the aqueous phase was determined and the change of this distribution during the copolymerization. The concentration of acrylonitrile in the aqueous phase remains fairly constant up to 20–25% conversion, then it decreases rapidly up to about 90% conversion. The over‐all rate of copolymerization following an induction period, remains constant up to about 30–35% conversion, then it increases slightly only to decrease rapidly at about 90% conversion. In a system of this type the mole fraction of acrylonitrile in the oil phase increases through the polymerization, partly because acrylonitrile reacts at a lower relative rate, partly because the acrylonitrile dissolved in the aqueous phase diffuses continuously into the beads. The reactivities of styrene and acrylonitrile in aqueous dispersion are the same as in bulk if the partition of acrylonitrile between the two phases is taken into account. The initial rates of copolymerization, in bulk, increase with the acrylonitrile content of the mixture. At high conversion, a marked acceleration in rates takes place. This autoacceleration is due to the increased viscosity of the medium and to the variation of the comonomer composition with conversion.
Crystallite regularity and void content in cellulose fibers as shown by small‐angle x‐ray scattering
Authors: Statton W. O.
Published: April 2003

Long spacing order in the fiber axis direction is found for the majority of viscose rayon yarns, varying in repeat spacing from about 170 to 220 A. This order is interpreted as a regularity of crystallite placement such that the crystallites themselves act as diffracting centers to form a line lattice with long spacings. The diffraction found for different rayons varies in intensity and perfection as well as repeat spacing. This new structural feature can be related to the periodic length determined by the limiting degree of polymerization after hydrolysis. Current interpretations in the literature regarding the diffuse scattering at small angles are extended to include scattering due to micro‐voids or regions of low electron density. Since it is known that the materials are so dense that interparticle interference arises for the particle scattering, the reciprocity rule dictates that the voids are the source of the major amount of the scattering, not the crystallites. This interpretation is in agreement with the concepts of polymer structure from other techniques and can be used to explain the changes in scattering with swelling or the very small changes with crystallization. The micro‐voids are elongated in the fiber axes direction. For a dry cellulose fiber a distribution of sizes of the axes of the ellipsoidal voids can be obtained for relative comparisons.
Factors influencing removal of pentosan from birch wood: Evidence on the lignin‐carbohydrate bond
Authors: Nelson Russell , Schuerch Conrad
Published: April 2003

The effect of particle size, alkali concentration, and temperature on the rate of extraction of pentosans and on the amount of pentosans extractable from birch wood meal has been studied. In general, a very rapid extraction of accessible pentosans is followed by a slow, almost negligible, diffusion of inaccessible pentosans. There is, therefore, almost a limiting amount of pentosans not extractable under each given set of conditions. The effect of decreasing particle size is to increase the amount of pentosan extractable under any given set of conditions. The optimum sodium hydroxide concentrations at 0, 20, 40, 60 and 80 degrees are about 2, 4, 7, 10 and 12%, and under the last of these conditions at least 80% of the pentosans can be extracted rapidly from the wood meal. Pentosan is made more accessible by increasing the alkali concentration up to these levels, but thereafter the amount of accessible pentosan is decreased by an increase in alkali concentration. The decrease in extractability has the same concentration and temperature dependence as the increase in cellulose swelling under the same conditions. Therefore, pentosan removal is inhibited by excessive swelling restricted within the rigid lignin and fiber structure. Similar but less marked inhibition by swelling occurs even after lignin removal.

Even under conditions of low alkali concentration, when no inhibition of solution by restricted swelling occurs, neither the temperature nor alkali dependence of rate is typical of a chemical process. The factors which inhibit the removal of pentosan are therefore physical and the inhibition of solution of pentosan from birch wood gives no support to the concept of a lignin‐carbohydrate bond.
A recording apparatus for measuring the dynamic mechanical properties of polymers
Authors: Kline Donald E.
Published: April 2003

An apparatus for measuring the dynamic mechanical properties of polymers is described. Rodlike specimens are driven through a transverse resonant mode by changing the driving frequency. The specimen response is obtained and automatically plotted by a recorder. Resonant frequency and width of the resonance curve constitute a measure of the dynamic mechanical properties. The temperature range of the apparatus is 4°K. to more than 600°K., and the frequency range is at least 50 to 5000 cps. Damping values have been measured from 10−4 to 5 × 10−1.
Light scattering and viscosity studies on poly‐4‐vinylpyridine
Authors: Boyes Allan G. , Strauss Ulrich P.
Published: April 2003

Seven fractionated and three unfractionated samples of poly‐4‐vinylpyridine, ranging in molecular weight from about 7 × 104 to 2 × 106, were investigated by light scattering and viscosity studies at 25°C. Intrinsic viscosity‐molecular weight relationships in 86:14 butanone‐isopropanol and in 92.01 weight per cent ethanol were [η] = 3.80 × 10−4 M0.57 and [η] = 1.20 × 10−4 M0.73, respectively. Flory's constant K, defined by the relation [η]θ = KM0.5, was determined by two independent methods to be 8.1 × 10−4. The close agreement of this value with that obtained for polystyrene confirms Flory's hypothesis that the unperturbed molecular dimensions are controlled by steric effects. The relationship between molecular dimensions and second virial coefficient is in fair agreement with recently proposed theoretical relations. The negative temperature coefficient of the solubility of poly‐4‐vinylpyridine in tert‐butanol‐benzene mixtures indicates strong solvation through hydrogen bonding between pyridine and hydroxyl groups.
Light scattering and viscosity study of electron‐irradiated polystyrene and polymethacrylates
Authors: Shultz Allan R. , Roth Paul I. , Rathmann George B.
Published: April 2003

The solution viscosity behavior of polymers previously irradiated by high‐energy sources is treated theoretically by a combination of existing random crosslinking and degradation theory and branched‐polymer solution viscosity theory. The derived relations are applied to data on polystyrene, polymethyl methacrylate and poly‐tert‐butyl methacrylate irradiated as films in air with 1000 kvp. electrons. Polystyrene films underwent gelation exhibiting an energy dissipation per crosslinked unit Ec = 855 electron volts and a main‐chain scission to crosslinked unit ratio α/β = 0.35. Pregelation light‐scattering molecular weights of the irradiated polystyrene predicted an incident gelation dose (9.4 megareps) in good agreement with that (10.3 megareps) observed by gel measurements. Theory satisfactorily reproduced the solution viscosity data over a wide range of pregelation radiation doses. A combination of light‐scattering and intrinsic viscosity data proved conclusively that no appreciable crosslinking occurs during the degradation of polymethyl methacrylate under 1000 kvp. electrons. The apparent energy dissipation per main‐chain scission, Ed = 58–62 e.v., determined by viscometry is therefore the true Ed in this instance. Reactions leading to crosslinking in polyacrylates are either blocked or diverted by the methyl group on the polymethacrylate backbone. Poly‐tert‐butyl methacrylate degrades under electron bombardment with an Ed = 43 e.v.
Sorption of water vapor by water‐soluble polymers: Kinetic, equilibrium, and glass temperature data
Authors: Hughes L. J. Thompson , Fordyce D. B.
Published: April 2003

Equilibrium and kinetic studies of the sorption and desorption of water vapor by poly(acrylic acid), poly(sodium acrylate), sodium carboxy methyl cellulose, methyl cellulose, and a series of poly(methyl acrylate) hydrolyzates in acid and sodium salt forms were made at 30°C. It was found, as expected, that equilibrium sorption increased and was greater for polymers containing strong‐electrolyte type substituents than for those containing an equivalent number of weakly ionizable units. In general, the diffusion is somewhat slower than in the case of water‐insoluble polymers. It was also found that water solubility of a polymer does not per se result in anomalous water sorption. In Methocel, for example, water diffusion is both Fickian and concentration‐independent. All of the results, particularly those on the poly(methyl acrylate) hydrolyzates which ranged from completely water‐soluble to insoluble systems, support the following conclusion: For water‐soluble polymers both anomalous diffusion and relatively high glass temperatures are associated with high concentrations along polymer chains of very polar or ionic groups, such as OH, COOH, and CO2−Na+. Presumably both the anomalies and high transition temperatures are associated with restricted segmental mobility resulting from strong chain‐chain interactions which originate in the highly polar and ionic, water‐solubilizing chain substituents.
Dilute solution studies on polystyrene by light scattering and viscosity
Authors: Chinai S. N. , Scherer P. C. , Bondurant C. W. , Levi D. W.
Published: April 2003

Polystyrene was fractionated and refractionated to obtain essentially homogeneous fractions. The constants K and a in the conventional equation [η] = KMa were determined. The intrinsic viscosity in an ideal solvent fitted the relation [η]θ = KM1/2 over the molecular weight range 0.04 × 106 to 1.46 × 106. The degree of flexibility of polystyrene chains in solution is compared with those of polymethyl and polyethyl methacrylates.
Cellulose derivative‐solvent interaction
Authors: Moore W. R. , Epstein J. A. , Brown A. M. , Tidswell B. M.
Published: April 2003

Osmotic pressure, initial phase separation, and viscosity results are presented for dilute solutions of cellulose nitrate, cellulose acetate, and ethyl cellulose, using polymers of similar molecular weight and degree of substitution. A fairly wide range of solvents has been used in each case. Osmotic pressure results suggest molecular dispersion of polymer in most solvents but there is evidence for association of ethyl cellulose in aromatic hydrocarbons. Values of the Huggins μ are obtained and, for systems involving cellulose nitrate and ethyl cellulose in homologous series of ketones and acetates, seem to fall to a minimum and then increase on ascent of each series. It is suggested that the heat term in μ should include an exothermic contribution arising from solvation in addition to an endothermic contribution resulting from mixing of solvated polymer and solvent. It is tentatively suggested that, in a homologous series of solvents, the entropy and exothermic contributions may not vary much and that the variation of μ may arise from varying endothermic contributions. The volumes of hexane required to cause initial phase separation of the nitrate and acetate from solution increase with solvent power, as estimated from μ, but with ethyl cellulose the volumes tend to decrease. It is suggested that solvated polymer may separate from solutions involving polar solvents and, making certain assumptions, estimates are made of the solubility parameters of the polymers separating. Those for cellulose nitrate vary markedly with solvent. The variation of solubility parameter with solvent is less with cellulose acetate and ethyl cellulose but in the latter case values for polymer separating from polar solvents are less than from nonpolar. Comparison of these estimated solubility parameters with those of the solvents and hexane suggests that the volumes of hexane required to cause initial phase separation will only serve as measures of solvent power if the solubility parameters of solvents and precipitant all lie on the same side of that of the polymer separating. This seems to be so for cellulose acetate and possibly the nitrate but not for ethyl cellulose. Comparison of viscosity parameters and values of μ suggests that in certain cases both [η] and the initial slope of the plot of ηsp/c against c increase with solvent power. Other suggested viscosity measures of solvent power do not seem to be generally applicable. Some variation of chain configuration with solvent seems probable. Solvation, solvent type and association of polymer may also affect the viscosities of dilute solutions of cellulose derivatives.