bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low-Temperature Stiffening of Elastomers
Authors: Gehman S. D. , Jones P. J. , Wilkinson C. S. , Woodford D. E. 
Published: February 2011

Abstract
The generally observed stiffening of elastomers at low temperatures may be supplemented by the occurrence of crystallization if the elastomers have sufficient regularity of molecular structure and other conditions are favorable. To study these effects, observations of the progressive stiffenings of elastomer compounds at low temperatures were made by measurements of the relative torsional modulus of test strips mounted in racks which were stored at low temperature. The periods of observation extended over 30 to 60 days with temperatures in the range from −59° to −18° C. A correlation was found between density changes due to crystallization as determined dilatometrically and torsional stiffness changes. Factors studied in addition to temperature included compounding variables such as cure and plasticizer content. Some data were obtained to show the acceleration of crystallization due to compressive stress. Progressive stiffening due to crystallization was observed for vulcanizates of Hevea, Neoprene Type GN, and Butyl rubber, as well as for an 85-15 butadiene-styrene redox-type copolymer. The results were interpreted in accordance with concepts of crystal nucleation and growth with necessary modifications due to the molecular structure of elastomers. Although the phenomenon of spontaneous crystallization of elastomers was found to be complicated by many factors, a useful degree of generality appears in some of the results.
Stress Relaxation of Some Rubber and Synthetic Rubber Vulcanizates in Compression
Authors: Beatty J. R. , Juve A. E. 
Published: February 2011

Abstract
Vulcanizates of rubber and synthetic rubber find wide and useful applications under conditions of compressive stress in gaskets, seals, suspension systems for vibration isolation, and other uses. In some of these applications the rubber is subjected to a load, either static or dynamic, or a combination of both. In other cases the compression strain is constant, and the resulting stress is utilized as a seal for fluids or gases. It is with this second application of rubber in compression that this work is concerned. In the use of rubber under compression as a seal the service life is dependent on maintaining a value of stress above a minimum necessary for the seal to be effective. It can readily be seen, then, that some method of evaluating materials with respect to service life is highly desirable. Compression set tests, method A or B, of the American Society for Testing Materials, depending on the service conditions, have been widely used for some time in evaluating rubber materials to be used in compression. This test, however, does not give an answer which is directly applicable as to units, and the test time ordinarily used is too short. Test results are reported as percentages secured from the ratio of the unrecovered portion of the amount compressed to the amount the sample is compressed. The unrecovered portion of the amount the sample is compressed is measured after a prescribed interval at room temperature after removing the stress from the sample. A better measure of the property in question, the stress as a function of time, would be to measure this property directly.
Mechanism of Reënforcement. III. Viscosity of Carbon Black Suspensions in GR-S Solutions
Authors: Amborski Leonard E. , Goldfinger George 
Published: February 2011

Abstract
The viscosity of carbon black suspended in GR-S solutions has been investigated in a Stormer-type viscometer at various rates of shear. Relative viscosities thus determined have been extrapolated to zero rate of shear and, by applying Einstein's viscosity equation, the volume of the suspended particles has been calculated. It has been found that, under the conditions examined, the carbon black particles are surrounded by a rubber layer 150 to 200 Ångstroms thick.
Structure of Vulcanized Latex
Authors: Humphreys N. C. H. , Wake W. C. 
Published: February 2011

Abstract
A short theoretical introduction discusses the drying-out of emulsions and some data on electrical conductivity is presented showing that latex probably conforms to the general type. This is used as evidence against the theory that in dried-out films of vulcanized latex the particles are stuck together by the protein which initially surrounds the latex particle. Further experimental evidence concerns the suggestion that the van der Waals' or secondary valencies alone are responsible for the cohesion of the film. This proposed structure for the films is discussed in connection with their physical properties and in the light of modern theories of rubber elasticity.
Vulcanization of Neoprene Type W
Authors: Forman D. B. , Radcliff R. R. , Mayo L. R. 
Published: February 2011

Abstract
Neoprene Type W, as a polymer, represents a fundamental departure from Neoprene Type GN in the manufacture of chloroprene polymers. This new Neoprene is more stable than any of its predecessors, and it contains no sulfur or chemicals which may decompose to give free sulfur or a vulcanization accelerator. Although its compounds should include both magnesium oxide and zinc oxide, Type W also requires acceleration. Many conventional Neoprene and rubber accelerators can be used. Certain of the rubber accelerators, such as diphenylguanidine or the butyraldehyde-aniline condensation products, require sulfur. Others, such as 2-mercaptothiazoline and tetramethylthiuram monosulfide, as well as the common Neoprene accelerators, such as the di-o-tolylguanidine salt of dicatechol borate, may be used without sulfur. Neoprene Type W vulcanizates differ from those of Type GN by having a stress-strain curve more nearly approaching that of natural rubber and by having much greater resistance to compression set. The resistance to compression set of Neoprene Type W vulcanizates is greater than that of the best natural rubber stock.
Use of Oxidizing Agents in Rubber Vulcanization. Zinc Oxide-Free Process
Authors: Barton Bernard C. 
Published: February 2011

Abstract
Conventional vulcanization may be considered as a two-step oxidation process in which zinc oxide functions through its ability to form zinc mercaptides by reacting with rubber hydrosulfides formed in the first step. These zinc mercaptides are then oxidized by sulfur to disulfide cross-links. Consideration of this mechanism has led to the development of a new vulcanization process in which various mild organic oxidizing agents replace sulfur in the second step of the oxidation process and thereby make possible the elimination of zinc oxide. Oxidizing materials capable of replacing a portion of the sulfur normally used are considered, and the mechanism of the new vulcanization reaction is discussed.
The Use of Zinc Dibutyldithiocarbamate in the Manufacture of Cellular Rubber
Authors: Haehl Adrien 
Published: February 2011

Abstract
One conclusion to be drawn from the present work is that a combination of zinc dibutyldithiocarbamate and benzothiazolyl disulfide is a particularly advantageous one for the manufacture of cellular rubber. By means of this combination of accelerators it is possible, by proper balancing of their proportions and of the percentage of sulfur, to adjust at will the stability of the rubber mixture with respect to blowing and to the rate of vulcanization as soon as blowing is complete. The good solubility of zinc dibutyldithiocarbamate in rubber guarantees a very rapid onset of vulcanization after the blowing action. It is evident that the most suitable method for manufacturing cellular rubber products is stepwise vulcanization. At the beginning, for example, heating may be at a temperature corresponding to 2 kg. per sq. cm. steam pressure, which allows satisfactory blowing of the rubber mixture; following this the temperature is raised rapidly to a point corresponding to 4 kg. per sq. cm. steam pressure as soon as the blowing effect is complete. At this higher temperature, vulcanization of the cellular rubber becomes very rapid. By this method it was found possible to manufacture cellular rubber shoes by an initial heating of 5 minutes at 2 kg. per sq. cm. steam pressure and a final heating of 5 minutes at 4 kg. per sq. cm. steam pressure. However, even if such a stepwise change in temperature during the heating is impracticable, as is the case when shoe soles are vulcanized in an electrically heated press, it is still possible, by choosing the proper proportions of sulfur, zinc dibutyldithiocarbamate, and benzothiazolyl disulfide, as well as the temperature of vulcanization, to obtain perfect blowing and rapid vulcanization.
Stability of Crude GR-S. Effect of Traces of Antioxidant
Authors: Glazer E. J. , Parks C. R. , Cole J. O. , D'Ianni J. D. 
Published: February 2011

Abstract
Antioxidant-free GR-S is highly unstable toward oxygen. The inhibiting effect of phenyl-β-naphthylamine at a concentration as low as 0.001 per cent could be detected, and the effect became appreciable at an antioxidant content of 0.1 per cent. The activity of antioxidants at such low concentrations is difficult to explain except on the basis that the antioxidant functions as a chain terminating agent. Under the usual conditions of processing or storage, the concentration of antioxidant commonly employed in production of GR-S, 1.25 to 1.5 per cent, appears entirely adequate. When used as criteria of polymer stability, satisfactory correlation was noted between oxygen absorption and deterioration of physical properties.
The Evaluation of Flex-Life and Heat Build-Up Properties of Elastomers
Authors: Storey E. B. 
Published: February 2011

Abstract
A method has been developed whereby the separate indices may be obtained for the flex life and heat build-up properties of elastomers. These indices are independent of the state of cure, but depend on the test recipe and the dispersion of the compounding ingredients. The method may be used to examine the effect of polymerization variables, compounding ingredients and procedures, or ambient temperature, on these two properties.
Dynamic Compression Test for Adhesion of Rubber to Cord Fabric
Authors: Pittman G. A. , Thornley E. R. 
Published: February 2011

Abstract
An improved laboratory method has been developed for the purpose of evaluating rubber-cord adhesions. The test-piece consists of a single cord surrounded by a thin cylindrical layer of casing compound which, in turn, is enclosed and protected by a thicker layer of rubber of standard composition. Such test-pieces are subjected to cyclic compression and bending, under controlled conditions of cord tension and ambient temperature, in a specially designed machine. The apparatus simulates the primary stresses and strains which occur in the crown and shoulder regions of a giant tire running under load, and it has been established that the cord bond in the test-pieces breaks down in a manner analogous to that in an overloaded tire. The degree of bond deterioration is determined by comparing the load required to pull the cord axially through that part of the rubber which has been subjected to compression after a specific number of cycles with that required to do so in a similar untreated test-piece. Data show the rate at which the rubber-cord bond deteriorates with various degrees of compression and temperature, and examples are given of the use of the method for evaluating bonding agents for cotton and rayon cords. A general comparison is made between the Henley test and other adhesion tests known to be in use.
Tack of Butyl and Natural Rubbers
Authors: Beckwith R. K. , Welch L. M. , Nelson J. F. , Chaney A. L. , McCracken E. A. 
Published: February 2011

Abstract
A comparative study of the tack of Butyl and natural rubbers was made by contacting freshly cut surfaces of the compounds under various time-temperature-pressure conditions and measuring the force required to separate the splice. The temperature of the knife used to cut the samples was found to be of primary importance. The tack of Butyl compounded with 50 parts of semireën-forcing carbon black (no curatives) decreases regularly with increasing knife temperature. Both longer time and higher pressure of contact favor better splicing. Data are presented on the effect of various plasticizers and carbon blacks on the tack of Butyl compounds.
Rubber Bonding
Authors: Buist J. M. , Naunton W. J. S. 
Published: February 2011

Abstract
Bonding in this paper is limited to the formation of bonds of considerable strength, and little attention is paid to the numerous agents which can be used for sticking rubber (usually cured rubber) to various materials. For many purposes a good stick, such as that obtained by the use of cyclized rubber, is sufficient, especially where service conditions tend to maintain the bond rather than to break it. Two other aspects of bonding, namely, bonding by brass-plating and the discussion of the nature of the bond do not enter into the subject matter of this paper. Brass-plating is a whole subject in itself, and is of technical interest only to those who have sufficient bonding work to maintain a plating unit in active condition. The question of whether a given bond is chemical or physical appears to the authors a futile controversy since, as with most rubber problems, both chemical and physical factors play their simultaneous parts. For the early history of the bonding of rubber to metals, the reader is referred to the paper by B. J. Habgood.
Determination of Copper in Raw Materials Used in the Rubber Industry
Authors: Genova J. , Addobbati A. 
Published: February 2011

Abstract
Because of its catalytic action on the deterioration of rubber, the presence of copper in rubber products, even in very small quantities (0.001 per cent), may lead to serious difficulties which shorten the useful life of the products. Most of the raw materials used in the manufacture of these products contain small percentages of copper, and its determination is best made by the colorimetric method. Various reagents can be used for this purpose, among them dithizone (phenylazothionoformic acid phenylhydrazide) and sodium diethyldithiocarbamate. The use of the latter was proposed by Callan and Henderson. The method specified by the A.S.T.M. for the determination of copper in rubber products is based on their work. This method may be briefly described as follows. The destruction of the organic matter and dissolution of the sample is effected by digestion with sulfuric acid in a Kjeldahl flask, followed by treatment with fuming nitric acid and hydrogen peroxide. Repeated treatment and final evaporation to the point where white fumes are evolved eliminates any colored substances and any excess of oxidizing agents. The sesquioxides are precipitated by ammonium hydroxide, and an aliquot part of the filtrate obtained is transferred to a Nessler tube. One cc. of 5 per cent solution of gum arabic, 10 cc. of ammonium hydroxide (d. 0.90), and 10 cc. of 0.1 per cent solution of sodium diethyldithiocarbamate are added. The presence of copper is indicated by the formation of its gray colored carbamate, which, because of its colloidal nature, remains in suspension.
Polarographic Determination of Zinc in Compounded Rubber
Authors: Poulton F. C. J. , Tarrant L. 
Published: February 2011

Abstract
Reasons are advanced for the unsatisfactory nature of some of the older methods for the determination of very small amounts of zinc in compounded rubber, particularly in latex mixings. The polarographic technique offers a possible solution, but most of the commoner electrolytes for the electroreduction of this metal are alkaline, and give rise to similar errors as are met in the gravimetric procedure. The development of a suitable acid electrolyte was therefore undertaken, and ways of dealing with likely interferences were examined. The electroltye finally recommended is a potassium thiocyanate-ammonium acetate buffer solution; iron, when present, is reduced to the ferrous condition by potassium iodide. The method was used to determine zinc oxide in a series of mixings of known composition ranging from 0.8 to 40 per cent. In all except the highest proportions of zinc oxide, the figures obtained agree well with the theoretical.
Fractionation of Purified Hevea Rubber
Authors: Verghese G. T. 
Published: February 2011

Abstract
Resolution of high polymers into fractions of different molecular weights has proved to be of great value in the study of the fundamental properties of polymers. Such fractionation is generally effected by fractional adsorption, fractional precipitation, or fractional solution. Of these, the last two methods have been largely used for the fractionation of rubber. Hauser and coworkers prepared a series of fractions from smoked sheet, while Bloomfield and Farmer obtained different fractions from crepe rubber and partially purified latex rubber. There are no data available on the fractionation of highly purified rubber. An investigation was, therefore, undertaken to obtain a series of fractions from purified rubber hydrocarbon prepared by a method described in an earlier paper, and to compare the molecular weights of these rubber fractions with the molecular weights of the corresponding fractions of unpurified rubber. Fractionation was effected by progressively dissolving out rubber in n-hexane containing 10 per cent methyl alcohol. Kemp and Peters, and also Gauser and colleagues, used n-hexane alone for fractionation. These authors pointed out that n-hexane is a poor solvent for rubber and would give a more efficient fractionation, but Kemp and Peters observed later that the addition of polar substances like acetone or alcohol to n-hexane makes it a more efficient solvent, and Gee found the same effect by the addition of 10 to 15 per cent of methyl alcohol to the hexane.
Effect of tall oil fatty acids content on the properties of novel hyperbranched alkyd resins
Authors: Murillo Edwin A. , Vallejo Pedro P. , López Betty L. 
Published: February 2011

AbstractHyperbranched alkyd resins (HBRA) were synthesized by modification of hydroxylated hyperbranched polyester (HBP1‐4) with tall oil fatty acids (TOFA). The core is a hydroxylated hyperbranched polyester of fourth generation with OH groups in the periphery (18), which is endcapped with tall oil fatty acids. The occurrence of these reactions, HBP1‐4 and TOFA, was determined by making use of acid value, nuclear magnetic resonance, and hydroxyl values. The effects of TOFA and HBP1‐4 on properties of the HBRA resins were investigated by vapor pressure osmometry, differential scanning calorimetry, thermogravimetric analysis, friction resistance, and hardness. The resins with higher modification percentage (HBRA4) presented the best thermal and hydrolytic stability, but lower friction resistance and hardness. All HBRA resins presented amorphous characteristics, OH groups, and double bonds in the periphery. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Synthesis and characterization of new aliphatic polyesters containing methanodinaphtho[1,3]dioxocin part
Authors: Rahmatpour Ali 
Published: February 2011

AbstractA novel dinaphthodioxocin‐containing diol monomer, 8,16‐methano‐16H‐dinaphtho[2,1‐d:1′,2′‐g][1,3] dioxocin‐2,14‐diol (MDDD) was synthesized in high yield and purity through the condensation of 2,7‐dihydroxynaphthalene with malonaldehydetetramethyl acetal at room temperature. It is used as a new monomer for the synthesis of a series of novel dinaphthodioxocin‐containing aliphatic polyesters by interfacial polycondensation method. The new diol monomer was fully characterized by IR, NMR, mass spectroscopies, and elemental analysis. Optimal conditions for polyesterification were obtained via study of the model compounds. Polyesters derived from MDDD and four aliphatic diacid chlorides had inherent viscosities ranging from 0.26 to 0.38 dL/g. The chemical structure of the polymers was fully characterized by IR, NMR spectroscopies, and elemental analysis. The physical properties of the polymers were studied. All the new polymers show good thermal stability and very good solubility in most organic solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Critical roles of cellular glutathione homeostasis and jnk activation in andrographolide‐mediated apoptotic cell death in human hepatoma cells
Authors: Ji Lili , Shen Kaikai , Jiang Ping , Morahan Grant , Wang Zhengtao 
Published: February 2011

AbstractAndrographolide (ANDRO), isolated from the traditional herbal medicine Andrographis paniculata, is reported to have the potential therapeutic effects for hepatocellular carcinoma (HCC) in our previous reports. Here, we investigated the mechanism of ANDRO‐mediated apoptotic cell death, focusing on the involvement of cellular reduced glutathione (GSH) homeostasis and c‐Jun NH2‐Terminal kinase (JNK). Buthionine sulfoximine (BSO), an inhibitor of cellular GSH biosynthesis, significantly augmented ANDRO‐induced cytotoxicity in hepatoma Hep3B and HepG2 cells. BSO depleted cellular GSH, and augmented ANDRO‐induced apoptosis, inhibition of colony formation and JNK activation in Hep3B cells. All these effects could be reversed by GSH monoethyl ester (GSH.EE), whose deacetylation replenishes cellular GSH. BSO also augmented ANDRO‐induced activation of apoptosis signal‐regulating kinase 1 (ASK1), mitogen‐activated protein kinase kinase‐4 (MKK4) and c‐Jun, which are all up‐stream or down‐stream signals of JNK. Further results showed that JNK inhibitor SP600125 and 420116 both reversed ANDRO‐induced cytotoxicity, and SP600125 also decreased ANDRO‐increased intracellular GSH and GCL activity. Finally, we showed that in nude mice bearing xenografted Hep3B tumors, BSO improved the inhibition of tumor growth by ANDRO. Taken together, our results suggest that there is a crosstalk between JNK activation and cellular GSH homeostasis, and ANDRO targets this to induce cytotoxicity in hepatoma cells. © 2011 Wiley‐Liss, Inc.
Post‐transcriptional up‐regulation of miR‐21 by type I collagen
Authors: Li Cui , Nguyen Hong T. , Zhuang Yan , Lin Yi , Flemington Erik K. , Guo Weichao , Guenther James , Burow Matthew E. , Morris Gilbert F. , Sullivan Deborah , Shan Bin 
Published: February 2011

AbstractComposition of extracellular matrix (ECM) is crucial to the establishment and maintenance of epithelial apical‐basolateral polarity. Increased ECM rigidity caused by deposition of fibrillar collagen, for example, collagen type I (Col‐1), promotes loss of epithelial polarity and tumor progression. microRNAs are small non‐coding RNAs that regulate gene expression and fundamental cellular processes. The current study explored a link between microRNAs and Col‐1 using organotypic three‐dimensional culture in which epithelial cells are embedded within Matrigel, a mimic of basement membrane matrix (Matrigel 3‐D). Matrigel 3‐D culture of A549, MCF‐7, and mK‐ras‐LE cells (lung and mammary epithelial cell lines) gave rise to acinus, an in vitro equivalent of apical‐basolateral polarity that consists of a polarized monolayer of epithelial cells facing a central lumen. Supplementation of Col‐1 disrupted acinus. Moreover, Col‐1 up‐regulated the expression of miR‐21, a well‐documented oncogenic microRNA, via a post‐transcriptional mechanism. Similar post‐transcriptional up‐regulation of miR‐21 correlated with deposition of Col‐1 in a murine model of lung fibrogenesis. In summary, our findings link altered ECM composition/rigidity and the expression of oncogenic microRNAs. The current study also suggests a novel post‐transcriptional mechanism for regulation of miR‐21 expression at maturation from pre‐miR‐21 to mature miR‐21. Mol. Carcinog. © 2011 Wiley‐Liss, Inc.