bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progress in Polymerization Theory of Interest in Synthetic Rubber Production
Authors: Morgan L. B. 
Published: February 2011

Abstract
During the last few years considerable advances have been made in the theory of polymerization processes, and these have a direct bearing on the manufacture of synthetic rubbers and plastics and the properties of the various products of this type that are now handled by the rubber industry. The most important industrial process involves emulsion polymerization. This is used in the production of types, such as GR-S, Perbunan, and Neoprene, and also in the production of polyvinyl chloride. World production of these emulsion polymeric materials is in the region of hundreds of thousands of tons per annum, and the process is probably one of the more important chemical manufactures developed in the last decade. No large manufacture of synthetic rubber has been developed in Great Britain, mainly because of war-time exigencies and economic considerations, and the only significant contribution made by British chemical industry to alleviate the war-time scarcity of natural rubber was to develop a large-scale production of polyvinyl chloride to satisfy the requirements of the cable trade. There has, however, been some research activity on synthetic rubber in this country since 1935 in the laboratories of the Dyestuffs Division of Imperial Chemical Industries, Ltd. Activity in the main was concentrated on the diene emulsion interpolymer types and a large number of second components were examined for interpolymerization with both butadiene and chloroprene. Comparatively few interpolymerize to give rubbers with reasonably good vulcanizate properties. These have been disclosed in the patent literature. Parallel work was being carried out in the laboratories of I. G. Farbenindustrie and later in America, and the results of much of this have now appeared in the technical literature and in the accounts that are now available on German war-time activities. The general conclusions were similar.
Refractometric Determination of Second-Order Transition Temperatures in Polymers. IV. Butadiene-Acrylo-Nitrile Copolymers
Authors: Wiley Richard H. , Brauer G. M. 
Published: February 2011

Abstract
A previous study of the low-temperature properties of a series of vulcanized butadiene-acrylonitrile copolymers indicated an approximately linear relation between composition and brittle temperature. This study provides information relating low-temperature properties to copolymer composition for a series of industrially available butadiene-acrylonitrile copolymers of varying acrylonitrile content. The refractometric technique for determining second-order transition temperatures (Tm) as previously described was used to determine Tm.
Process Problems in Low-Temperature Emulsion Polymerization
Authors: Troyan J. E. 
Published: February 2011

Abstract
When emulsion polymerization of butadiene and styrene is conducted at temperatures in the range of 0° to 41° F, high elastomers possessing greatly improved properties are produced. However, low temperature operation involves several major process problems not encountered in the manufacture of standard GR-S at 122° F. These are the use of activated reaction recipes, the refrigeration of polymerization equipment, and the use of emulsion antifreezes. Redox-type activated systems which have been developed for low temperature runs in the pilot plant result in reaction rates approaching those of normal GR-S even at 14° F. Heat transfer characteristics of typical activated recipes at 41° and 14° F have been investigated in a 260-gallon reactor and compared to similar results for GR-S at 122° F. Variation in overall heat transfer coefficients with conversion has been established at each temperature. Minimum U values of 43, 39 and 23 B.t.u./(hr.) (sq. ft.) (° F) were obtained at 50 to 55 per cent conversion in polymerizations run at 122°, 41° and 14° F. Using experimental heat transfer data, refrigeration requirements for a standard 30,000 ton/year plant operating at 41° F and 14° F are calculated as 450 and 599 tons, respectively. When emulsion polymerizations are conducted at about 0° to 35° F, special antifreezes such as methanol must be included in the reactionrecipe. Methanol is recovered from latex during the usual stream stripping of latex to remove unreacted styrene. A ternary equilibrium solubility diagram for the system styrene-methanol-water has been established to facilitate analysis of the two-phase condensate obtained during stripping.
Effect of Light on Neoprene. I. Discoloration of GR-M Vulcanizates by Direct Sunlight
Authors: Sanders P. A. 
Published: February 2011

Abstract
1. White GR-M vulcanizates discolor differently in direct sunlight from what would be predicted from results obtained with standard light-aging devices. 2. Accelerated light-aging tests are of value for preliminary screening purposes if the control (of known stability to sunlight) is discolored to about the same extent as it would be by sunlight. Under these circumstances accelerated light tests indicate the other stocks to be relatively more stable with respect to the control than does exposure to direct sunlight. 3. Stocks most stable to light are obtained by using high proportions of the rutile crystalline form of titanium dioxide as white pigment. Variations in curing time affect only the initial color of the stock before exposure to light and not its resistance to discoloration by sunlight. 4. The results in this paper apply only to GR-M and to no other Neoprene, and only where outdoor exposures are involved. Preliminary results obtained by aging GR-M in indirect sunlight (behind glass) indicate that the effects produced by direct and indirect sunlight differ.
A Study of Electrostatic Charges Produced during Mastication of Rubber and of GR-S
Authors: Havenhill R. S. , Carlson L. E. , Rankin J. J. 
Published: February 2011

Abstract
A new electrostatic field strength meter has been described which measures and records, not only the magnitude of electrostatic fields, but also their polarity. This device has been used in a study of the mastication of rubber, and has furnished data which indicate that rubber becomes less negative, and may actually become positive, as mastication proceeds ; this indicates in turn an oxidation of the molecules as well as an electronic rearrangement and orientation of the rubber molecular chains. Data on GR-S polymerized at different temperatures show entirely different electrostatic breakdown curves, which, with other physical characteristics, indicate unusual properties of the crude low-temperature polymers; e.g., high molar weight, long-chain molecules, already or easily oriented, which do not oxidize or break up appreciably on mastication. A partial correlation of Mooney viscosity and electrostatic contact-potential and field strength has been shown for rubber and GR-S which have been masticated on a rubber mill. The new electrostatic-field strength meter shows promise as a new tool which can be used in processing control, and also as a research instrument for obtaining fundamental information on mastication, pigment dispersion and incorporation, as well as an aid in forming new concepts concerning the structure of matter.
Physical Properties of Fractions of GR-S and Their Vulcanizates
Authors: Yanko John A. 
Published: February 2011

Abstract
A large-scale precise fractionation of GR-S (X-55) was carried out at 25° C, using a fractional precipitation technique. Nine fractions, each weighing approximately 150 grams and comprising about 11 per cent by weight of the original unfractionated sample, were obtained, with number-average molecular weights varying from 4000 to 1,650,000. High molecular fractions undergo gelation rapidly, even when dried in the absence of light at reduced pressure, and the higher the molecular weight of the fraction, the greater the amount of gel formed. Compared to unfractionated butadiene-styrene copolymers of similar gel contents, the gel portions of the higher molecular fractions had unusually high swelling indices, indicating qualitatively that the average molecular weights between points of effective cross-linking in the three-dimensional gel structure were higher than those found in the past in unfractionated samples of similar gel contents. Through the concentration range studied, the intrinsic viscosity values varied as a straight-line function of the concentration terms for all the fractions. However, the negative slopes of these lines increased as the molecular weight of the fraction increased, demonstrating the greater dependence of the intrinsic viscosity values of the higher molecular fractions on the concentration variable. The relationship between number-average molecular weight, as determined by osmometric measurements, and limiting intrinsic viscosity of the GR-S fractions is given by the equation: [η]0=5.4×10−4 M0.66, which is similar to that obtained by French and Ewart. The μi values calculated from the equation of Huggins were essentially the same (0.35) through the molecular range 12,400 to 723,000.
Plasticization of Natural and Synthetic Rubbers. II. GR-S
Authors: Piper G. H. , Scott J. R. 
Published: February 2011

Abstract
Continuing the work described in Part I, experiments have been made to determine the separate effects of heat, oxidation, mechanical working on rolls or in an internal mixer, peptizing agents (used in hot milling), and absorption of softener on the softness, elastic recovery, and plastic flow relation (between applied force and rate of flow) of GR-S. Heat alone, without oxygen or mechanical action, does not soften GR-S, but makes it harder and more elastic, presumably by inducing cross-linking of the chain molecules; GR-S thus differs fundamentally from natural rubber, which can be softened by heat. Absorption of softener (mineral oil) softens GR-S and reduces its recovery, but these effects are too small to form a practicable plasticizing method. Either oxidation or mechanical working softens GR-S considerably, reduces its elastic recovery, and brings its plastic flow relation nearer to that of well masticated natural rubber, i.e., approaching ordinary viscous or Newtonian flow (flow rate proportional to stress). Peptizing agents such as benzaldehyde phenylhydrazone or iron naphthenate promote the effect of hot milling, presumably by accelerating oxidation, which is shown to occur during hot, but not appreciably in cold, milling. Of the methods tried, those which plasticize GR-S most quickly are (1) hot milling with a peptizing agent, and (2) oxidation at 125° C and 15 lb. per sq. in. oxygen pressure ; if the latter is continued too long, however, hardening sets in. The results show that GR-S, like natural rubber, can be plasticized by mechanical breakage of the chain molecules by the shear stresses set up during mastication, as well as by oxidation, which presumably causes breakage of the molecules at the double bonds. Mechanical and oxidative treatments, however, do not give the same properties ; mechanical breakdown in the cold gives a product completely soluble in benzene, whereas oxidation does not, and is less effective in reducing recovery, and there may be other differences not yet revealed. In view of these differences and the fact that heat has effects opposite to oxidation or mechanical working, it follows that the various possible ways of plasticizing GR-S, since they involve heat, oxidation, and mechanical action in different combinations and degrees, give plasticized batches with very different properties, even if the length of the treatments is so adjusted as to give, say, the same Williams or Mooney plasticity reading. These differences are fully discussed in the present paper; the main conclusions are:
Stability of Accelerators as Affected by High Processing Temperatures
Authors: Holbrook F. L. , Fitzgerald T. H. 
Published: February 2011

Abstract
In high-speed Banbury mixing, sufficiently high temperatures may be generated at least to partially damage some rubber accelerators and decrease their effective activity. Thus, at a processing temperature of 360° F, the following stability relationships hold. 1. Thiazoles, thiazole derivatives, and activated thiazoles show little loss of activity. 2. Thiurams and dithiocarbamates may be severely affected. 3. Guanidines, as represented by diphenylguanidine, are only moderately affected. 4. Aldehydeamines range in stability from moderate to good. This effect of high temperature on accelerator stability may be considered as constituting a processing hazard. The proper selection of accelerators and the careful consideration of any processing changes which may significantly increase temperature minimize the danger and allow avoidance of harmful results. The fact that some accelerators are relatively unstable at high temperatures does not preclude their use. It is simply necessary to incorporate these materials into the mix at a sufficiently low temperature, such as that at which it is normally considered safe to add sulfur.
Analysis of Natural and Synthetic Rubber by Infrared Spectroscopy
Authors: Dinsmore H. L. , Smith Don C. 
Published: February 2011

Abstract
This report describes an investigation of the applicability of infrared spectro-scopic methods to the quantitative determination of the elastomer composition of industrial rubber products. Generally satisfactory techniques for obtaining a valid spectrum of the elastomer content of any rubber specimen have been developed and evaluated and have been applied to the development of detailed analytical procedures for the identification and qualitative analysis of elastomer mixtures, to the quantitative analysis of natural-GR-S blends, and to the determination of the nitrile content of nitrile copolymers. An accuracy corresponding to ° 1 per cent average error has been obtained in these determinations. The methods can be extended to analogous problems with a minimum of alteration, and the same order of accuracy can be expected in general. A discussion of the correlations between spectral absorption and molecular structure is also included. Infrared spectroscopy is finding increasing application as a means for the identification of organic materials and the analysis of complex mixtures. Spectroscopic methods are not only rapid and generally conservative in sample requirements, but the results are often more specific than those obtained by chemical analysis, distillation, etc., and in many cases furnish detailed structural information of importance to research and development. The advantages of infrared analysis are that : (1) the spectrum of a molecule is a unique physical property which is not altered by any changes in which molecular identity is maintained, and (2) the individual features of the spectrum relate in a definite manner to the chemical bonds comprising the molecule and can thus be interpreted, regardless of the total configuration.
Properties of Ebonite. XXXIV. Influence of Organic Accelerators of Vulcanization
Authors: Fisher D. G. , Newton R. G. , Norman R. H. , Scott J. R. 
Published: February 2011

Abstract
1. An investigation was made of the influence of several organic accelerators, of the types commonly used in soft rubber, on the vulcanization of ebonite and the properties of the product. This includes the study of zinc and magnesium oxides as activators, and of variation in the proportion of accelerator used. 2. Most of the accelerators are effective in the vulcanization of ebonite, and it is definitely established that they accelerate the final “hard rubber” phase of the rubber-sulfur reaction. The degree of acceleration, however, is much less than in soft rubber, and the different accelerators do not show the same relative efficiencies. 3. Neither zinc oxide nor magnesium oxide functions as an accelerator activator in the hard-rubber reaction. 4. The effects of accelerators and metallic oxides on the maximum safe rate of vulcanization, i.e., consistent with avoiding excessive exothermic temperature rise, have been examined. All the accelerators improved the maximum safe rate of vulcanization; the most effective were butyraldehyde-aniline and diphenylguanidine, the former being considerably the better. Zinc oxide reduced the maximum safe rate when added to an accelerated mixing ; magnesium oxide caused a further improvement. Butyraldehyde-aniline plus magnesium oxide was thus the most effective combination for enabling the vulcanizing period to be reduced without risk of overheating due to the exothermic hard-rubber reaction. The fact that certain accelerators or accelerator metallic oxide combinations make possible quicker vulcanization without increased exothermic temperature rise suggests the possibility of developing special ebonite accelerators possessing this useful characteristic in an enhanced degree. 5. For speedy set-curing, a mixing containing either diphenylguanidine or butyraldehyde-aniline with magnesium oxide appears best, particularly the latter, since it can be used at a higher vulcanizing temperature without excessive overheating. The activating effect of zinc oxide in the early (soft-rubber) stage of vulcanization is of no use in speeding up set-curing ; indeed, zinc oxide usually delays the formation of a satisfactory set-cured product. 6. Accelerators do not alter the relationship between combined sulfur content and physical properties, as they do in soft rubber ; their function is simply to increase the rate of the rubber-sulfur reaction, and, perhaps as a consequence of this, to enable more of the added sulfur to become combined. 7. The technically important effects of accelerators on the properties of ebonite are : increase in resistance to plastic yield, decrease in impact strength, increase in resistance to swelling liquids, and increase (usually) in dielectric loss at normal temperatures, though the loss at elevated temperatures may be reduced. The first three of these effects result from the more complete combination of sulfur noted above.
The Molecular Structure and Arrangement in Stretched Natural Rubber
Authors: Fisher Dorothy G. 
Published: February 2011

Abstract
Although there are still some minor discrepancies to be resolved, the appearance of the diffuse-zone electron-diffraction pattern arising from thin films of stretched natural rubber is adequately explained on the basis of the thermal oscillations of the long-chain rubber molecules in the crystalline regions, this pattern being analogous to that which would be given by a stream of oriented molecules in a pseudo-gaseous condition. As Charlesby, Finch and Wilman pointed out, the diffuse-zone pattern has distinct advantages in the examination of complex molecules, since it gives a direct indication of the configuration of the molecule, independent of its mode of fitting into any particular crystalline lattice. In spite of the diffuseness of the patterns with which we are dealing a study of the diffuse zone or molecular pattern has shown that it is possible to discriminate decisively between two postulated atomic configurations which do not differ greatly. In the case of natural rubber, neither of the two configurations investigated agrees in every respect with experiment, but the evidence brought forward above supports the view that the atomic arrangement in the stretched rubber molecule approximates to a simple form having planar units and standard bond lengths and angles, rather than to the more complex form hitherto considered.
Elastomers from Fluoroprene
Authors: Mochel W. E. , Salisbury L. F. , Barney A. L. , Coffman D. D. , Mighton C. J. 
Published: February 2011

Abstract
As the first member of the haloprene or halogen-substituted butadiene series, fluoroprene (2-fluoro-1,3-butadiene) occupies a position between butadiene and chloroprene in most of its properties and characteristics. For example, it polymerizes at a rate approximately twenty-five times that of butadiene under comparable conditions, but it is somewhat slower than chloroprene in its rate of polymerization. However, fluoroprene resembles butadiene in that it copolymerizes readily in wide proportions with most 1,3-dienes and many monovinyl compounds, whereas chloroprene copolymerizes only incompletely with many monomers. In sharp contrast to the other haloprenes, fluoroprene polymers, like those of butadiene, have an amorphous rather than crystalline structure in the stretched state, and they require reinforcement with fillers to develop high tensile properties in their vulcanizates. Polyfluoroprene rubbers obtained in 85 to 90 per cent conversions using selected emulsion systems have exhibited tensile strengths of 2800 to 3200 pounds per square inch at 400 to 500 per cent elongation in tread type of vulcanizates. These vulcanizates are highly freeze resistant and have the good oil resistance of corresponding chloroprene polymers. The resilience of the vulcanizates is excellent and their resistance to ozone and sunlight is good although not so outstanding as that of corresponding polychloroprene products. Polyfluoroprene vulcanizates, unlike those of polychloroprene, propagate a flame when ignited, but they burn at a much slower rate than GR-S or natural rubber. In electrical properties they are superior to polychloroprene vulcanizates, and approach natural rubber in resistivity and power factor.
The Structure of Neoprene. I. The Molecular-Weight Distribution of Neoprene Type GN
Authors: Mochel W. E. , Nichols J. B. , Mighton C. J. 
Published: February 2011

Abstract
Polychloroprene rubber (Neoprene Type GN) was fractionated by partial precipitation from dilute solution in benzene and the fractions were examined both osmotically and viscometrically in benzene solutions. The molecular-weight distribution curve for Neoprene Type GN based on osmotic pressure measurements shows a pronounced maximum at 100,000, but has a long extension to molecular weights of over one million, indicating the presence of branched or cross-linked material which is still soluble. The uniformity is somewhat less than that of sol natural rubber, while in shape the Neoprene distribution curve resembles more closely that of peptized natural rubber than fresh sol rubber. Observed variations in the slopes of the π/c vs. c and the ηsp/c vs. c curves also indicate the presence in solution of complex, branched and (or) cross-linked molecules. Calibration of the intrinsic viscosity-molecular weight relationship by osmotic pressure measurements gave good agreement with the equation: [η]=KMa, where K=1.46×10−4 and a=0.73.
Have Mechanical Stresses Any Effect on the Oxidizability of Rubber?
Authors: Le Bras Jean , Salvetti André 
Published: February 2011

Abstract
Subjection of rubber to mechanical stresses, whether static or dynamic, does not change its inherent oxidizability, at least within the limits of stress which were applied in the experiments described. Perhaps changes would have been observed if the range of stresses had been reached where crystallization phenomena became pronounced, for sufficient distortion or change in molecular state might have a certain influence on the oxidizability. For example, Williams and Dale, in a study of infrared absorption by rubber, pointed out that linear extensions greater than 400 per cent are necessary to bring about any appreciable increase in the vibration frequency of the C — C groups. However, the elongations employed in the present work cover, in general, the range of deformations to which vulcanized rubber products are normally subjected in service; hence there seemed to be no advantage in attempting to carry out the tests under more severe conditions. From another point of view, it would appear of interest to record the following observation. In all the oxidation tests under dynamic conditions, the test-specimens broke either by being cut through near the points where they were fastened, at random points where rupture began, or when the tensile strength was lowered too much by oxidation; but in no case was actual flexcracking observed. Although this is only negative evidence, the view of Eccher that ozone is indispensable to the formation of cracking would appear to be confirmed.