bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new approach to the theory of rubberlike elasticity
Authors: Huggins Maurice L. 
Published: April 2003

AbstractEquations are derived for stress–strain curves for a hypothetical model substance containing a large number of like systems, each assumed to be in equilibrium between two states having different arrangements of the atoms. With this model one can study the dependence of the initial elastic modulus, the limiting strain (for infinite stress), and the over‐all shape of the stress–strain curve on characteristics of the rearranging systems—their number, the initial energy difference between the two states, the shift of atomic positions, etc. Introduction of an assumed proportionality between the shift per rearrangement and the square of the relative length of the sample (in the direction of the shift) leads to stress–strain curves similar to those determined experimentally for natural rubber and other rubberlike materials.
Mechanism of peroxide‐initiated styrene polymerization. Infrared absorption of some polymer samples
Authors: Pfann Harry F. , Williams Van Zandt , Mark H. 
Published: April 2003

AbstractPrevious observations make it probable that one or both ends of a longchain molecule produced by catalyzed vinyl polymerization contain fragments of the initiator. If one uses acid peroxides as initiators, these fragments can contain a carbonyl group. It is the purpose of this paper to investigate whether these carbonyl groups which are present only in a very small amount can be detected by infrared absorption. It seems that in the case of polystyrene initiated with benzoyl peroxide, infrared absorption spectra reveal the presence of a small amount of some carbonyl groups in the polymer. Their amount appears to be in agreement with chemical measurements and with the molecular weight of the material.
Experimental study of copolymerization
Authors: Alfrey T. , Merz E. , Mark H. 
Published: April 2003

AbstractUsing the copolymer composition equation, the critical constants α and β are determined for the systems styrene–2,5‐dichlorostyrene, styrene–methyl acrylate, styrene–diethyl maleate, and styrene–diethyl chloromaleate.
Determination of polymer–liquid interaction by swelling measurements
Authors: Doty Paul , Zable Helen S. 
Published: April 2003

AbstractThe interaction of polymers and liquids can be fairly well characterized by the value of the quantity μ, commonly used in thermodynamics of polymer solutions and usually evaluated from osmotic pressure measurements. The Flory‐Rehner theory of swelling relates the amount of swelling of a slightly cross‐linked polymer in a liquid to μ and a parameter Mc, the average molecular weight between cross links. Mc, may be determined for a cross‐linked polymer from its swelling volume in a solvent in which osmotic pressure measurements with the noncross‐linked polymer have given the value of μ. The cross‐linked polymer, thus calibrated, can be used to obtain the μ value for other liquids by measuring its swelling volume in them. This procedure has been carried out on polyvinyl chloride which can be cross linked by heating. Calibration in three different liquids gave comparable values of Mc, thus checking the Flory‐Rehner theory. The quantity μ was determined at two different temperatures for fifty liquids. The value of μ and its temperature dependence correlate well with the observed properties of the binary systems. Variation of μ with molecular weight in an homologous series is demonstrated.
Density of cellulose fibers. III. Density and refractivity of natural fibers and rayon
Authors: Hermans P. H. , Hermans J. J. , Vermaas D. 
Published: April 2003

AbstractA micromethod is described for density determinations of artificial cellulose fibers by the floating method, in carbon tetrachloride in a dry and air‐free atmosphere, permitting an accuracy of one part per thousand. The density is derived from the temperature at which the samples neither sink nor float. This temperature varies, with the kind of fiber, between 45° and 65°C. Measurements of the refractive power were carried out simultaneously. The refractivity calculated according to Gladstone and Dale yields slightly lower figures than those found for model fibers in the preceding communication (Part II). The average difference amounts to seven parts per thousand and is ascribed to a systematic error in the density determinations, due to a slight absorption of carbon tetrachloride by the fibers at elevated temperatures. This explanation is supported by experiments. The density of native ramie, of contracted and reoriented ramie, and of several series of rayon fibers spun with increasing stretch, is given. The conclusion is reached that the density is a measure of the percentage of crystalline substances in the fiber and it is shown that there is a correlation between density and sorptive capacity toward water vapor. The percentage of crystalline matter is estimated to be 55–60% in native ramie and 20–25% in rayon.
Preparation and properties of rubberlike high polymers. I. Polymerization of dienes and vinyl compounds in bulk
Authors: Koningsberger C. , Salomon G. 
Published: April 2003

AbstractThe polymerization of dienes under the influence of heat, of diazoaminobenzene, and of benzoyl peroxide, has been studied. Diazoaminobenzene probably acts as a slow, but continuous, source of free radicals giving quantitative yields of methyl rubber of good quality from dimethylbutadiene after a few days to a few weeks at 100–125°C. The effect of diazoaminobenzene on butadiene is the same, but the rate of the uncatalyzed dimerization of butadiene at 100°C. is as fast as that of dimethylbutadiene at 150°C. and, therefore, dimerization interferes much more strongly with the polymerization of butadiene. Only 60% of polybutadiene has been obtained. A few experiments with isoprene showed its position between the two other dienes. The effect of benzoyl peroxide on the polymerization of the dienes appeared to be much smaller than was expected from its known catalytic action on the polymerization of vinyl compounds, e.g., styrene, for in this case its activity is about 100–1000 times greater than that of diazoaminobenzene. It is assumed that a larger number of radicals, produced by the fast decomposition of benzoyl peroxide, causes this difference. Diazoaminobenzene has about the same effect on the polymerization of styrene and acrylonitrile as on that of the dienes. The catalytic effect of benzoyl peroxide on the polymerization of the dienes is, on the contrary, 10,000–100,000 times smaller than on that of the vinyl compounds. This difference can be understood by the assumption that the catalyst is quickly used up by oxidizing the dienes and their polymers. While methyl rubber and the polyisoprene resemble raw natural rubber, polybutadiene, prepared under comparable conditions, is hard, swells moderately, and has a tendency to become brittle as a result of oxidation (aging). Abbreviations used are DAB (= diazoaminobenzene) and BP (= benzoyl peroxide).
Modern views on the chemistry of vulcanization changes. III. Reaction of sulfur with squalene and with rubber
Authors: Bloomfield George F. 
Published: April 2003

AbstractSqualene containing six isoprene units is more free of end‐group effects and less limited in the range of space‐distributional contortions of its carbon chain than mono‐ and diolefins. Hence it is more comparable with rubber than the latter group where matters of chemical reactivity are concerned. Nevertheless, in its reaction with sulfur, squalene pursues a course very similar to that followed by the diisoprene, dihydromyrcene, in that intramolecular sulfide linkages as well as intermolecular polysulfide linkages are formed. Taking into consideration the amount of sulfur which would suffice for the establishment of some given number of the simplest possible intermolecular linkages (i.e., monosulfide linkages), the efficiency of sulfur as a cross‐linking reagent during the vulcanization of squalene is seen to be of a rather low order; this condition might be expected to hold for rubber in the absence of auxiliary mechanisms. So far as can be determined by direct experiment the action of sulfur in forming cross links is not essentially different from that encountered with squalene, since there are indications that both intra‐ and intermolecular sulfide linkages are formed—the latter being of both dialkenyl and dialkyl sulfide type, and, possibly also of alkenyl alkyl type. Under the influence of small amounts of zinc oxide or of various nitrogen‐containing organic accelerators, sulfur reacts with the thiol groups of organic mercaptans forming di‐ and polysulfides, together with hydrogen sulfide. In the presence of rubber the same reaction occurs without actual liberation of hydrogen sulfide and it thus appears that if any thiol groups are formed as intermediates in vulcanization reactions, they will undergo ready conversion into intermolecular di‐ and polysulfide linkages. This may well represent an important auxiliary mechanism of cross linking.
Preparation and properties of rubberlike high polymers. III. Polymerization of mixtures in emulsion
Authors: Salomon G. , Koningsberger C. 
Published: April 2003

AbstractThe copolymerization in emulsion of butadiene with varying amounts of styrene and acrylonitrile and of dimethylbutadiene with the latter vinyl compound has been studied on a laboratory scale. An essential difference between polymeric vinyl compounds and polydienes is the olefinic character of the latter, which leads to typical secondary changes in the polymers originally formed during the completion of the reaction. Such changes are of fundamental importance for the ultimate mechanical properties of polymers and copolymers based on dienes. After a brief discussion of the general theoretical line of thought serving as a base for our experiments, the influence of various factors on the rate of polymerization is pointed out and demonstrated by experiments. The changes in the nitrogen content of copolymers from acrylonitrile and the yields as a function of the reaction time have also been studied. From an investigation of some physical properties, such as solubility and swelling, the existence of true copolymers (of unknown irregularity) has been established. Copolymers from dimethylbutadiene and acrylonitrile represent a new class of olefinic thermoplastics resembling gutta‐percha. Abbreviations used are BP (benzoyl peroxide) and DAB (diazoaminobenzene).
Determination of polystyrene in GR‐S rubber
Authors: Kolthoff I. M. , Lee T. S. , Carr C. W. 
Published: April 2003

AbstractA convenient procedure for the determination of polystyrene in GR‐S is given. The method depends upon degradation of the GR‐S by tert‐butyl hydroperoxide in the presence of a trace of osmium tetroxide. Polystyrene is not attacked and is separated by precipitation with ethanol.
Polymerization of methyl methacrylate in aqueous emulsions
Authors: Baxendale J. H. , Evans M. G. , Kilham J. K. 
Published: April 2003

AbstractThe kinetics of the polymerization of methyl methacrylate in emulsions has been examined. The initial rate of polymerization is independent of the amount of discontinuous monomer phase present and it is concluded that initiation occurs in the aqueous phase. Monomer is observed to disappear from the discontinuous phase more quickly than it polymerizes, and probably forms a monomer‐polymer mixture with the polymer produced. An increase in the subsequent rate of polymerization is attributed to the fact that propagation of the growing polymer chains occurs in this monomer–polymer mixture and this entails a decrease in the velocity of termination due to the high viscosity of such mixtures.
Investigation of potato proteins
Authors: Jirgensons B. 
Published: April 2003

AbstractBy treating potato juice with acid it was found that potato globulin is converted to albumin and an insoluble casein‐like protein. Potato albumin, salted out with ammonium sulfate and purified by dialysis, is very similar to ovalbumin; it is reconverted into a globulin‐like protein by alkali. Solutions of potato albumin in water, as well as in acids and alkali, have a very low viscosity. Alkaline solutions of globulin have a greater viscosity than those of albumin; the viscosity numbers of the difficulty soluble protein are even greater. On the basis of the viscosity data, it was concluded that the albumin particles are corpuscular, the globulin molecules are longitudinal, and that the dissymetry is greatest for the difficulty soluble protein particles. On the basis of the different solubilities of all three proteins (which apparently have approximately the same chemical composition), it was concluded that the albumin molecule was the smallest and the difficulty soluble protein molecule the largest. An aqueous solution of potato albumin is denatured when heated to 50–60°, the viscosity thereby increasing more than 100‐fold. The solutions become only slightly turbid, but do not flocculate. This unusual viscosity rise can be explained by the transformation of globular albumin molecules into fibrous, elongated particles. Only a slight viscosity increase is observed when alkaline solutions of albumin are heated. Albumin, in the presence of small amounts of salt, is precipitated at 50–60°; the salts also lower the turbidity point. However, very small concentrations of calcium chloride have a stabilizing effect. Albumin is not coagulated at room temperature by 1–2 N salt solutions. The experiments on the effect of cold on potato albumin showed that albumin, after congealing and thawing out, was more easily precipitated than the control solution. The viscosity of the cold‐damaged albumin was somewhat less than that of the control solution. It was ascertained that the deaminated product of potato albumin was very similar to deaminated ovalbumin (solutions of high viscosity; linear colloid).
Heat polymerization of nonconjugated vegetable oils
Authors: Bernstein I. M. 
Published: April 2003

AbstractA general theory is proposed to account quantitatively for the heat polymerization and gelation of the nonconjugated vegetable oils. This is based on a direct approach to polyfunctionality as developed from quantitative considerations of partial random distribution of the fatty acid components in the triglyceride molecules. The differing polymerization rates of linseed and soybean oils are accounted for on the basis of the assumed influence of certain cis‐trans geometric isomers. The theory accounts for the anomalous extensive linear polymerization and nongelation of olive oil. Calculations from the theory agree substantially with experimental results on average molecular weight, iodine value, and the percentage of insoluble, infusible cross‐linked polymers.
Theory of rolling plastics. II. Thermal effects
Authors: Eley D. D. 
Published: April 2003

AbstractIn the rolling of Plastic sheet the viscous work gives rise to heating of the plastic sheet. The maximum temperature reached in the interior of the sheet during shearing is of the interest, both in the theoretical calculation of roll pressure, and from the point of view of possible thermal decomposition effects. A calculation is given for a simple, some‐what artificial, model, which leads to an upper value for this maximum temperature if a measurement of the average temperature of the emergent sheet is given. The model taken is that of an infinite sheet, of thickness 2δ, in which heat is continuously liberated at the rate of 4ηϕ2 cal. cc. −1 sec. −1, where ϕ is the relevant value of the rate of compression (assumed constant across the sheet). The curve giving the temperature distribution across the sheet is calculated numerically for two cases; it is relatively flat, as would be expected on physical grounds, since the viscosity, η, decreases as the temperature rises. It is concluded that these thermal effects may be neglected in the calculation of roll pressure in Part 1.
Photolysis of rubber
Authors: Bateman L. 
Published: April 2003

AbstractRubber hydrocarbon irradiated in vacuo is decomposed by ultraviolet light of wave length less than 4000 Å. The rubber very rapidly becomes insoluble, and liberates a gaseous mixture which consists mainly of hydrogen when the irradiation temperature is less than 150°C. The reaction characteristics have been investigated and point to the occurrence of dissociation processes similar to those deduced for comparable simple olefins. When irradiated above 150°C., small but significant amounts of isoprene appear in the volatile product, thereby providing an experimental means of determining the activation energy for the separation of isoprene from a polyisoprene chain terminated by an allyl radical.
Polyelectrolytes. I. Picrates of 4‐vinylpyridine‐styrene copolymers
Authors: Fuoss Raymond M. , Cathers George I. 
Published: April 2003

AbstractThe conductance in diphenyl ether at 35°C. and 60 cycles of the picrate of a 4‐vinylpyridine‐styrene copolymer (10:90) has been measured. The equivalent conductance, based on the nitrogen content, is of the same order as that of picoline picrate, and varies with concentration in accordance with the law of ion association.
Effect of silver salts on emulsion polymerization systems containing butadiene
Authors: Rainard L. W. 
Published: April 2003

AbstractThe addition of silver nitrate to polymerizable systems containing butadiene can result in increased over‐all rates of conversion. When butadiene is the only monomer and a cationic soap is used the addition of silver nitrate causes* a significant decrease in rate. The most active system studied was one which contained butadiene, styrene, a cationic soap, a peroxide, and silver nitrate. Comparison runs in a GR‐S type formulation with silver nitrate and potassium ferricyanide indicate that the silver salt is the more effective in producing higher over‐all rates of conversion.
Intrinsic viscosities and molecular weights of polyvinyl acetates
Authors: Wagner R. H. 
Published: April 2003

AbstractA polyvinyl acetate polymer of medium viscosity was fractionated into sixteen fractions (first series) and three of the larger of these further separated into twenty subfractions (second series). The intrinsic viscosities and the osmotic pressure molecular weights were determined at 25°C. and the relation between them was found to be expressed by the equations: first series: [η] = (1.88 × 10−4) M0.69; second series: [η] = (1.76 × 10−4) M0.68. The data indicate that little, if any, increase in homogeneity is to be expected by further successive fractionations and that the equations applicable to the second fractionation series are representative of essentially homogeneous polyvinyl acetates in acetone. An equation applicable to fractionated and unfractionated vinyl acetate polymers is described that is useful in obtaining the intrinsic viscosity from a single viscosity measurement. Several unfractionated materials from different sources were also studied and the calculated ratios of the viscosity‐average to the number‐average molecular weight indicate that the degree of heterogeneity of chain‐length distribution increases with increasing average molecular weight.
Mercaptans as promoters and modifiers in emulsion copolymerization of butadiene and styrene using potassium persulfate as catalyst. III. Calculation of molecular weights and intrinsic viscosities of polymers from mercaptan consumption data
Authors: Harris W. E. , Kolthoff I. M. 
Published: April 2003

AbstractAn empirical equation is described which predicts the intrinsic viscosities of 75:25 butadiene‐styrene emulsion copolymers from data on mercaptan consumption. The form of the equation is as follows:

where [η] is the intrinsic viscosity, P is the conversion, R is the fraction of mercaptan consumed, R0 is the mercaptan charged, and a, b, and c are constants equal to 0.22, 1.12, and 0.66, respectively. Evidence is given that the intrinsic viscosity of mutual‐recipe polymers can be described satisfactorily in terms of mercaptan consumption.
Mercaptans as promoters and modifiers in emulsion copolymerization of butadiene and styrene using potassium persulfate as catalyst. IV. Definition and calculation of modifier efficiency
Authors: Harris W. E. , Kolthoff I. M. 
Published: April 2003

AbstractThe calculation of the “theoretical” minimum modifier requirement, TMMR, for butadiene‐styrene (75:25) copolymers of given intrinsic viscosities at various conversions is described. The TMMR of 75% conversion polymer of intrinsic viscosity 2.0 is R0 = 0.28, which is only about 60% of the value of R0 for commercial primary dodecyl mercaptan (C.M.) in large‐size reactors. The efficiency, E, of a modifier for 75:25 butadiene‐styrene copolymerization using soap as emulsifier and persulfate as catalyst has been defined by and calculated from the equation:

where Mv is the intrinsic viscosity molecular weight of the polymer at conversion, P, with an amount of mercaptan, R0, charged with the monomers. For all modifiers the efficiency is low at low conversions and gradually increases to a maximum with increasing conversion. For different modifiers this maximum may be as at low as 10% conversion or at higher than 80% conversion. After the maximum the efficiency decreases with further increase of conversion. The most efficient modifier for the production of polymers of intrinsic viscosity, [η], at conversion, P, will meet the following conditions, R = 1 at conversion, P, and dP/dR is constant. Inefficient modifiers may be made more efficient by changing the conditions or procedure of polymerization in such a way that the modifier more nearly complies with the above conditions.
Internal plasticization: The effect of chemical structure
Authors: Simril V. L. 
Published: April 2003

AbstractThe elastic and plastic properties of high polymeric materials are functions of the forces holding the molecules together and the ability of small segments of the chains to move about, relative to other segments. Internal plasticization is accomplished by introducing structural features which reduce intermolecular and intramolecular forces and which, in general, decrease the order of the polymer. Physical techniques used to determine the effect of such structural features have been discussed. The results of numerous investigations into the relations between structure and properties have been considered in an attempt to present a simple and consistent physical picture of these relations.
Effect of plasticizers on second‐order transition points of high polymers
Authors: Boyer R. F. , Spencer R. S. 
Published: April 2003

AbstractThis is a review article concerned with the effect of plasticizers on the second‐order transition point and related phenomena in high polymers. The second‐order transition temperature behavior of plasticized polymers can be described by a linear relationship between the square root of the weight fraction of polymer and the reciprocal transition temperature. For certain temperature regions and plasticizer contents, this is mathematically equivalent to the linear decrease of transition temperature with plasticizer content which is also observed experimentally. This latter result is in accord with Zhurkov's theory of the softening action of solvents, which predicts a linear decrease in softening temperature with solvent content, and no dependence on the nature of the solvent. Neither the second‐order transition approach nor Zhurkov's theory permits conclusions about the nature of the plasticizer. However, it is shown empirically that brittle temperature can be represented as a function of the solvent‐polymer interaction constant μ by a curve having a maximum at μ ≈ 0.4. Since μ is also the parameter which measures compatibility, it is seen that the efficiency and the compatibility of a plasticizer are intimately related. Moreover, correlation can be made with older observations showing the relation between efficiency and the temperature coefficient of viscosity of the plasticizer.