bluuebunny/crossref_metadata_2025 huggingface dataset:
Fresh Hevea Latex. A Complex Colloidal System
Authors: Homans L. N. S. , Van Gils G. E.
Published: February 2011

Fresh Hevea latex is a complex system, containing two dispersed phases : (1) rubber globules; (2) lutoids, i.e., small irregularly shaped, viscous colloidal bodies. The lutoids dissolve in ammonia and other alkalies, coagulate when the latex is diluted with water but retain their form if the latex is diluted with salt solutions of certain concentrations. By centrifuging, the lutoids are collected at the bottom of the tube as a separate layer with a sharp boundary. After separation, the fractions (now called the yellow and the white fractions) may be examined separately. Their properties are reviewed. The importance of the lutoids for the general properties of the latex is discussed.
Alteration of Neoprene by Polymerization Temperature
Authors: Walker H. W. , Mochel W. E.
Published: February 2011

Changes of the temperature at which 2-chloro-1,3-butadiene (chloroprene) is polymerized, with other variables held constant, gives Neoprenes with marked differences in the rate of crystallization and dispersion in solvents of the raw polymer and in the physical properties of the vulcanizates. For example, plastic polychloroprene formed at 10° C crystallizes quickly, forms homogeneous solutions, and exhibits high tensile strength; whereas polymer produced at 100° C fails to crystallize, only swells in solvents, and has low tensile strength. These changes in properties appear to be caused by alterations of the structure of the polymer, notably the side-branching, cross-linking, spacing of the chlorine atoms, and possibly cis-trans-isomerism. The structural differences are small in magnitude and difficult to detect. Ozonolysis reveals that a soluble form of polychloroprene, as well as highly insoluble “popcorn” polymer, is at least 93 to 95 per cent 1,4-addition product and x-ray diffraction shows the polymer chains to have essentially a transconfiguration. Infrared spectroscopy indicates the absence of side vinyl groups. Branching and cross-linking explain the decreased rate of crystallization and other properties of the less soluble polymers, and it is considered that varying minor portions of 4,1-1,4 or 1,4-4,1 addition or of intramolecular cis-isomers are a factor in the crystallization of the soluble polymers. Technical advantages of the variations in Neoprene effected by polymerization temperature are outlined.
Refractive Index of Natural Rubber for Different Wave Lengths
Authors: Wood L. A. , Tilton L. W.
Published: February 2011

The refractive index of natural rubber and its variation with temperature and wave length are those which would be predicted for a similar hydrocarbon of low molecular weight. A two-constant equation of the Cauchy or Sellmeier type is inadequate to express the relation between refractive index and wave length for rubber. For convenient reference the best values resulting from the present investigation are recapitulated in Table VI.
The Control of Undesirable Viscosity Increases in Latex Compounds
Authors: Flint C. F.
Published: February 2011

A latex stabilizer of the nonionogenic class, consisting of a fatty alcoholethylene oxide condensate, similar in chemical type and technological properties to Emulphor-O (I.G.), is shown to be effective in controlling zinc oxide effect thickening and similar undesirable increases in the viscosity of compounded latex mixes, e.g., in the presence of active accelerators under conditions where an older and better known stabilizer of the anionic synthetic detergent class is not adequately effective. The proposed stabilizer may be effective in as low an amount as ¼ per cent on the rubber, and the material actually used in the experimental work was Vulcastab-LW.
Latex-Reclaim-Casein Mixtures for Rubber-Cord Fabric Adhesion
Authors: Gardner E. R. , Williams P. L.
Published: February 2011

A good bond, resistant to flexing, is afforded between rubber and rayon cord by the interposition of a mixed casein-rubber film. In a series of solutions in which the proportion of rubber solids was kept constant and the quantity of casein varied progressively, it was found that there was an optimum amount of casein for maximum adhesion. Taking into consideration also the handling of the solution and the stiffening of the cord, it would appear that for an adhesive with the usual total solids content of 15 to 20 per cent, the ratio of casein to rubber hydrocarbon should be approximately 1:6. When the rubber hydrocarbon is supplied by dispersed reclaim, the adhesion is a little higher than when latex is used. The most satisfactory solution from all points of view, however, contains approximately equal quantities of rubber hydrocarbon derived from the two sources. Wetting agents may be employed to improve the uniformity of application of the adhesive. The amount used must be very small, otherwise the adhesion is impaired. By dipping cord successively in casein and latex solutions and vice versa in the adhesive film, casein acts as a specific adhesive for rayon, whereas the rubber in the film gives the necessary affinity for the casing rubber which surrounds it. Treating a cord successively in a casein-rich mixture and then in a rubber-rich mixture appears to give a slightly better bond than the conventional treatment. The subsequent application of a rubber cement to a cord dipped in latex-reclaim-casein solution results in an improvement in the bond.
A Combustion Method for the Estimation of Carbon Black in Compounded Rubber
Authors: Bauminger B. B. , Poulton F. C. J.
Published: February 2011

The method described in this paper is based on the removal of volatile organic ingredients of the compound by heating in a current of purified nitrogen and, on the subsequent combustion of the carbon black to carbon dioxide, which is collected and weighed. The effect of the adsorptive nature of the carbon black has been studied, and the volatile components of many of the standard grades of carbon black used in the industry have been determined under the experimental conditions used.
A Tackmeter for Rubber Testing
Authors: Beaven E. W. J. , Croft-White P. G. , Garner P. J. , Rooney G.
Published: February 2011

In the hand test for tackiness commonly used, two surfaces of the compound are pressed together for a short time and are then separated, the force required for separation giving a measure of the tackiness of the compound. The magnitude of the separating force depends largely on such factors as the load applied to the contacting surfaces, the duration of application ef the load, and the surface area in contact, but none of these factors can be controlled within reasonable limits of reproducibility. Moreover, the results of this test can be recorded only in rather general terms such as “fair”, “good”, so recorded results may vary from one operator to another and they depend very largely on the experience of the individual operator. It thus becomes evident that in any investigation which calls for the evaluation of the tack properties of a fair number of different compounds, some method of test is required in which the personal element is entirely eliminated. In the course of an investigation into the tackiness of GR-S compounds, Busse, Lambert, and Verdery (J. Applied Physics 17, 376 (1946)) designed an apparatus which enabled the measurement of tack values to be put on a quantitative basis, and the principles of the apparatus reported by them have been embodied in the tackmeter described below.
The Direct Determination of Oxygen in Rubbers. Application of the Unterzaucher Method
Authors: Chambers W. T.
Published: February 2011

The direct determination of oxygen in organic compounds by reduction with carbon on a microscale by the Unterzaucher method is described, together with criteria of purity for the carbon and iodine pentoxide reagents employed. The method has been applied to rubbers and a relative precision of 2 per cent has been obtained i.e. : ±0.01 in the range 0 to 0.5% oxygen, ±0.02 in the range 0.5 to 1.0% oxygen, ±0.04 in the range 1.0 to 2.0% oxygen. For compounds containing larger percentages of oxygen, the method gives an absolute accuracy of ±0.2 or better. The method is speedier and yields more accurate results than when oxygen is determined by difference or by hydrogenation. A single determination requires but 30 minutes.
Thixotropic Behavior of Carbon Black in Rubber
Authors: Mullins L.
Published: February 2011

The addition of carbon black may cause considerable changes in the physical properties of rubber. Often rubbers compounded with carbon black or other fillers show evidence of thixotropic behavior—their properties depend on the past history of the rubber and may be changed on the one hand by continuous standing and on the other hand by working. This paper describes investigations into the behavior of both unvulcanized and vulcanized rubbers, and discusses the thixotropic build-up and breakdown of colloidal carbon black structures which are shown to exist in rubber. The importance of this build-up and breakdown of structure has not been adequately appreciated in many measurements on compounded rubbers; for example, the terms viscosity, plasticity, and stiffness (modulus) can only be defined when complications due to thixotropy are carefully controlled before and during the actual measurement. A knowledge and understanding of this behavior enables the significance of the results of various tests on these materials to be more correctly assessed and accounts for behavior which has previously appeared to be anomalous. The deficiencies of earlier theories of the reënforcement of rubber produced by carbon black are indicated, and modifications which make allowance for thixotropic filler structure are proposed.
Elongation Hysteresis of Hevea and Synthetic Elastomers
Authors: Mooney M. , Black S. A.
Published: February 2011

A hysteresis test has been developed which measures directly the energy loss per cycle of elongation. Six samples are stretched, like the spokes of a wheel, between a small disk and a large disk. The large disk is motor driven, and the small disk, mounted on a ball-bearing, is displaced eccentrically with respect to the larger disk. In the elongation cycle which each sample undergoes with each revolution, the hysteresis causes an average force on the small disk, which is normal to the eccentric displacement and is proportional to the energy loss per cycle. A lever and balance system makes it possible to measure this force continuously while the machine is running. Measurements were made on gum stocks of Hevea and five commercial synthetic elastomers. Testing conditions included temperatures, T, of 0°, 35°, 70°, and 105° C; frequencies, f, of 5 and 50 c.p.s.; mean elongations, e, of 50, 100, and 200 per cent and elongation amplitude, A, 25 per cent. Absolute hysteresis, H (loss/cycle-(amplitude)), at first decreases with increasing e and then flattens or goes through a minimum. Hysteresis decreases with increasing T. The temperature coefficient between 0° and 35° C is very large for Hycar. Hysteresis usually increases with f, but only slightly in most cases; and Hevea at e=400 per cent shows a reversal of frequency effect, which is presumably associated with crystallization effects. Under the same conditions, the hysteresis of the synthetics is 10 to 20 times that of Hevea. When the hysteresis data for all synthetic stocks at various temperatures are plotted against T−Ts, Ts being the second-order transition temperature of the respective elastomer, the data lie within a rather narrow band. From this it is concluded that the hysteresis of synthetic elastomers arises from the same molecular forces which cause hardening and embrittlement at and below Ts.
Low-Temperature Behavior of Butadiene-Styrene Copolymers. Effect of Compounding Variables
Authors: Juve R. D. , Marsh J. W.
Published: February 2011

Synthetic rubbers and natural rubber increase in stiffness at low temperatures and tend to lose their elastic characteristics. This stiffening and hardening phenomenon occurs in varying degrees with various elastomers. Natural rubber and certain synthetic rubbers crystallize during extended exposure at low temperature, whereas other synthetic rubbers such as GR-S remain amorphous. In a general review of the low temperature properties of synthetic rubber, Liska has shown that decreased styrene in butadiene-styrene copolymers improves the flexibility at low temperature. The low temperature flexibility of vulcanized articles made from any particular rubber or synthetic rubber is influenced by the compounding ingredients admixed with the elastomer. This paper shows the results of some studies of the effect of these compounding ingredients on the low temperature serviceability of butadiene-styrene copolymers. Somewhat similar work on the effect of a large number of plasticizers in GR-S has been conducted at the Rubber Laboratory, Mare Island Naval Shipyard, with particular emphasis on compression set at low temperature.
Low-Temperature Stiffening of Elastomers
Authors: Gehman S. D. , Jones P. J. , Wilkinson C. S. , Woodford D. E.
Published: February 2011

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Hyperbranched 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

A 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

Andrographolide (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

Composition 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.
Penta‐1,2,3,4,6‐O‐galloyl‐beta‐D‐glucose induces senescence‐like terminal S‐phase arrest in human hepatoma and breast cancer cells
Authors: Yin Shutao , Dong Yinhui , Li Jinhua , Lü Junxuan , Hu Hongbo
Published: February 2011

Senescence is a permanent growth arrest and has been implicated as an efficient anti‐carcinogenesis mechanism. The purpose of this study was designed to test the hypothesis that penta‐1,2,3,4,6‐O‐galloyl‐beta‐D‐glucose (PGG), a naturally occurring polyphonolic gallotannin compound, might induce this type of permanent growth arrest in cancer cells. Our results show, for the first time, that PGG‐induced senescence‐like S‐phase arrest in HepG2, Huh‐7 human hepatoma cells, and SKBr3 human breast cancer cells at sublethal doses, judged by cellular morphological changes, increased senescence‐associated β‐galactosidase (SA‐β‐gal) activity, together with loss of proliferative capacity after being released from the treatment. This senescence‐like response was mediated by intracellular ROS generation, but was not attributed to p53 Ser15 phosphorylative activation and was uncoupled from the p21cip1 axis, which has been shown to mediate Pten loss‐induced cellular senescence or oncogene‐driven senescence. The findings of the present study implicate a novel mechanism of PGG action to induce an atypical cellular senescence, adding to its promise as a potential chemopreventive agent. ©2011 Wiley‐Liss, Inc.
Impulsivity and compulsivity in drug‐naïve patients with Parkinson's disease
Authors: Antonini Angelo , Siri Chiara , Santangelo Gabriella , Cilia Roberto , Poletti Michele , Canesi Margherita , Caporali Alessandra , Mancini Francesca , Pezzoli Gianni , Ceravolo Roberto , Bonuccelli Ubaldo , Barone Paolo
Published: February 2011

Background:

Abnormal repetitive behaviors have been reported in Parkinson's disease (PD) during dopamine replacement therapy (DRT) and associated with individual predisposing features, including impulsivity. However, impulsivity and compulsive symptoms have never been explored in PD patients before initiation of DRT. We previously reported a 20% of impulse control disorders (ICD) in an Italian cohort.

Methods:

103 consecutive newly diagnosed drug‐naïve PD patients (means: age = 60.5 ± 9.2 years; duration = 15.4 ± 15.3 months) were screened for compulsive sexual behavior, compulsive buying, intermittent explosive disorder (Minnesota Impulsive Disorders Interview, MIDI), and pathological gambling (South Oaks Gambling Screen, SOGS). Barratt Impulsiveness Scale (BIS‐11) and Maudsley Obsessional‐Compulsive Questionnaire (MOCQ/R) assessed impulsivity, obsessive‐compulsive symptoms, respectively. Depression (GDS‐15) and general cognitive status were additionally assessed. We also compared ICDs frequency with our healthy controls.

Results:

17.5% of PD patients screened positive for at least one ICD at MIDI (17/103) and SOGS (1/103), though none had a disorder based on DSM‐IV criteria. These frequencies were similar to healthy controls. There was a trend toward higher scores in BIS‐11 attentive‐impulsivity subscale (15.2 ± 4.8 vs. 18.7 ± 4.9; P = 0.007) and in MOCQ/R‐Doubting subscale (0.67 ± 1.1 vs. 1.5 ± 1.2; P = 0.007) in PD with ICD. We also observed a positive correlation between GDS‐15 and BIS‐11.

Conclusions:

Similar to our healthy control population, we found a significant proportion of early PD patients positive for ICDs before starting treatment. We also found a relationship between impulsivity and depression. A detailed behavioral assessment before starting dopaminergic therapy is recommended. © 2011 Movement Disorder Society
Cortically evoked responses of human pallidal neurons recorded during stereotactic neurosurgery
Authors: Nishibayashi Hiroki , Ogura Mitsuhiro , Kakishita Koji , Tanaka Satoshi , Tachibana Yoshihisa , Nambu Atsushi , Kita Hitoshi , Itakura Toru
Published: February 2011

Responses of neurons in the globus pallidus (GP) to cortical stimulation were recorded for the first time in humans. We performed microelectrode recordings of GP neurons in 10 Parkinson's disease (PD) patients and 1 cervical dystonia (CD) patient during surgeries to implant bilateral deep brain stimulation electrodes in the GP. To identify the motor territories in the external (GPe) and internal (GPi) segments of the GP, unitary responses evoked by stimulation of the primary motor cortex were observed by constructing peristimulus time histograms. Neurons in the motor territories of the GPe and GPi responded to cortical stimulation. Response patterns observed in the PD patients were combinations of an early excitation, an inhibition, and a late excitation. In addition, in the CD patient, a long‐lasting inhibition was prominent, suggesting increased activity along the cortico‐striato‐GPe/GPi pathways. The firing rates of GPe and GPi neurons in the CD patient were lower than those in the PD patients. Many GPe and GPi neurons of the PD and CD patients showed burst or oscillatory burst activity. Effective cathodal contacts tended to be located close to the responding neurons. Such unitary responses induced by cortical stimulation may be of use to target motor territories of the GP for stereotactic functional neurosurgery. Future findings utilizing this method may give us new insights into understanding the pathophysiology of movement disorders. © 2011 Movement Disorder Society
Symptomatology and markers of anxiety disorders in Parkinson's disease: A cross‐sectional study
Authors: Leentjens Albert F. G. , Dujardin Kathy , Marsh Laura , Martinez‐Martin Pablo , Richard Irene H. , Starkstein Sergio E.
Published: February 2011

Anxiety is understudied in Parkinson's disease (PD), which is not justified by the prevalence and impact of anxiety disorders on quality of life in PD patients. In this cross‐sectional study, 342 patients suffering from idiopathic PD underwent a research‐based assessment including DSM IV criteria for anxiety disorders, the Hamilton anxiety rating scale (HARS) and the beck anxiety inventory (BAI).

Thirty‐four percent (34%) of subjects met the DSM IV criteria for at least one anxiety disorder; 11.8% met criteria for multiple anxiety disorders; and 11.4% had clinically relevant anxiety symptoms without meeting the criteria for any specific anxiety disorder. Score profiles on the HARS and BAI differed significantly between the disorders, but these differences were associated with different scores on a limited number of items, and the respective symptom profiles were not readily interpretable. Female sex, the presence of motor fluctuations, as well as a previous history of an anxiety disorder were markers for anxiety disorders. The use of a mono‐amino oxidase (MAO)‐B inhibitor was associated with a reduced prevalence of anxiety disorders.

Research into anxiety in PD is hampered by the questionable validity of DSM IV defined anxiety disorders in this population. A first focus for research should therefore be the identification of clinically useful anxiety presentations and their validation in PD. © 2011 Movement Disorder Society
On doing nothing: Descriptions of sleep, fatigue, and motivation in encephalitis lethargica
Authors: Ward Christopher D.
Published: February 2011

Epidemics of encephalitis lethargica (EL), from 1917 to the 1930s, are an important milestone in the history of movement disorders. Today, the two best‐known features of EL are somnolence and parkinsonism but the full clinical picture was variable and complex. States of wakeful inactivity—as opposed to drowsiness—were often described both in the acute and postacute stages and were referred to in the EL literature as “lethargy” or “torpor.” The study described here is based on a survey of clinical descriptions published in English, French, and German from 1917 to 1942. Its focus is on the history of clinical ideas, rather than applying modern pathophysiological concepts retrospectively. Descriptions of lethargy are explored as a way of elucidating concepts of sleep, fatigue, and motivation during the study period.

The literature described many patients who had (1) lethargy without interruption in consciousness; (2) slowness of movement and catalepsy without other prominent parkinsonian features; and (3) apathy and lack of initiative without severe disorders of mood or thought content. Hence observers distinguished a state of wakeful inactivity from primary disorders of sleep, movement and behavior.

Contemporaneous accounts suggest that writers had difficulty in reconciling their observations with preexisting concepts; there still may be limitations in our ability to describe and classify the clinical states connected during the epidemic era with the term “lethargy.” © 2011 Movement Disorder Society
Long‐term clinical outcome in meige syndrome treated with internal pallidum deep brain stimulation
Authors: Reese René , Gruber Doreen , Schoenecker Thomas , Bäzner Hansjörg , Blahak Christian , Capelle H. Holger , Falk Daniela , Herzog Jan , Pinsker Marcus O. , Schneider Gerd H. , Schrader Christoph , Deuschl Günther , Mehdorn Günther M. , Kupsch Andreas , Volkmann Jens , Krauss Joachim K.
Published: February 2011

Deep brain stimulation of the globus pallidus internus (GPi DBS) is effective in the treatment of primary segmental and generalized dystonia. Although limb, neck, or truncal dystonia are markedly improved, orofacial dystonia is ameliorated to a lesser extent. Nevertheless, several case reports and small cohort studies have described favorable short‐term results of GPi DBS in patients with severe Meige syndrome. Here, we extend this preliminary experience by reporting long‐term outcome in a multicenter case series, following 12 patients (6 women, 6 men) with Meige syndrome for up to 78 months after bilateral GPi DBS. We retrospectively assessed dystonia severity based on preoperative and postoperative video documentation. Mean age of patients at surgery was 64.5 ± 4.4 years, and mean disease duration 8.3 ± 4.4 years. Dystonia severity as assessed by the Burke–Fahn–Marsden Dystonia Rating Scale showed a mean improvement of 45% at short‐term follow‐up (4.4 ± 1.5 months; P < 0.001) and of 53% at long‐term follow‐up (38.8 ± 21.7 months; P < 0.001). Subscores for eyes were improved by 38% (P = 0.004) and 47% (P < 0.001), for mouth by 50% (P < 0.001) and 56% (P < 0.001), and for speech/swallowing by 44% (P = 0.058) and 64% (P = 0.004). Mean improvements were 25% (P = 0.006) and 38% (P < 0.001) on the Blepharospasm Movement Scale and 44% (P < 0.001) and 49% (P < 0.001) on the Abnormal Involuntary Movement Scale. This series, which is the first to demonstrate a long‐term follow‐up in a large number of patients, shows that GPi DBS is a safe and highly effective therapy for Meige syndrome. The benefit is preserved for up to 6 years. © 2011 Movement Disorder Society