Rubber Solutions Research Articles

ゴムの化学構造と分子量がカーボンゲルの量と構造に与える影響

The structure and content of carbon gel in carbon black filled rubber composites were studied as functions of molecular weight and chemical structure of rubber by the pulsed NMR technique. The content of carbon gel was governed by the molecular weight of rubber but was controlled by the viscosity of rubber solutions which were used for the blend and the chemical structure of rubber. The increase of carbon gel content in the composites was mainly from the increase of highly mobile rubber phase, and the gel became soft with the development of this phase. On the other hand, the content and structure of glassy rubber phase were not affected by the size of the carbon gel and chemical structure of rubber, and they showed almost constant value despite the large change in the carbon gel content. The formation mechanism of carbon gel in carbon black filled rubber systems was discussed in connection with the results.

Morphological control of impact toughness in poly(methyl methacrylate) /acrylonitrile‐butadiene rubber blends

AbstractToughening of PMMA by in‐situ polymerisation of methyl methacrylate/acrylonitrile‐butadiene rubber solutions to give blends with a multiple‐inclusion morphology has been achieved This contrasts with the lack of impact toughening observed upon direct blending of PMMA with the same rubber. The toughened blends are analogous to HIPS in terms of the multiple‐inclusion morphology and the observed cross‐linking within the separated elastomeric phase but possess significantly larger separated phase domains.

Studies on the structure and formation mechanism of carbon gel in the carbon black filled polyisoprene rubber composite

The structure and formation mechanism of carbon gel in carbon black filled polyisoprene composites were studied by the pulsed NMR technique. The composites were prepared from a wide range of molecular weights by a solution blend. The carbon gels were extracted from the composites by a solvent-extraction method. The content of carbon gel was not governed by the molecular weight of rubber but was controlled by the viscosity of rubber solutions which were used for the blend. Three rubber phases, having different spin-spin relaxation times, were detected in all the carbon gels. The increase of carbon gel content in the composites was mainly from the increase of highly mobile rubber phase, and the gel became soft with the development of this phase. On the other hand, the content and structure of glassy rubber phases were not affected by the size of the carbon gel, and they showed almost a constant value despite the large change in the carbon gel content. A part of the highly mobile rubber phase in the gels could be removed by solvent extraction at high temperature. These results suggest that the formation of carbon gel is primarily governed by two factors : One is the well-known rubber-carbon black interaction, and the other is a physical crosslink between the carbon gel and unbound rubber molecules during blend.

Effects of environment and composition on degradation of guayule rubber

Bales of antioxidant-stabilized guayule rubber underwent significant losses in bulk viscosity when stored under ambient conditions at an Arizona processing facility. Previous work implicated the unsaturated fatty acid esters present in entrained resin as promoters of such degradation. Aging studies as functions of storage temperature and unsaturated acid ester content were carried out on both bulk rubber and rubber-resin solution (miscella) for cultivar AZ-101. The rate of thermooxidative degradation, determined as a function of Mooney viscosity, was increased by the addition of unsaturated ester. Anaerobic degradation was not affected in this way. The activation energy of chain thermolysis was found to be 116 ± 6 kJ/mol (28 ± 1 kcal/mol). At temperatures above 60°C, chain recombination successfully competed with chain scission in lower viscosity rubber. The rate of thermoox-idative degradation was substantially higher in a typical process miscella. A hindered amine antioxidant significantly reduces chain scission under these conditions. © 1996 John Wiley & Sons, Inc.

Peribiliary plexa--important pathways for shunting of iodized oil and silicon rubber solution from the hepatic artery to the portal vein. An experimental study in rats.

Iodized oil is commonly used in chemoembolization of hepatic tumors, and silicon rubber solution is used for casting studies of hepatic tumor vasculature. Understanding the distribution patterns of iodized oil and silicon rubber solution is of significance in the refinement of iodized oil techniques and proper interpretation of hepatic tumor vascular studies. In this study, the location for iodized oil and silicon rubber solution shunting from the hepatic artery to the portal vein was identified. Iodized oil and silicone rubber solution were injected into the hepatic artery in rats. The porta hepatis and the liver periphery were examined using in vivo microscopy. Iodized oil and silicone rubber solution had identical distribution patterns in the hepatic circulation. Both were shunted in large quantities from the hepatic artery into the portal vein through the peribiliary plexa. Other potential shunting sites did not contribute to the shunting. Though of different chemical natures, iodized oil and silicon rubber solution share similar distribution patterns in the liver. Hepatic arterioportal shunting of these substances occurs via the peribiliary plexa.

Toughened polystyrene composites by the concentrated emulsion pathway

AbstractRubber–styrene solutions of various compositions and containing a suitable initiator have been polymerized starting from concentrated emulsions in which the above solutions constitute the dispersed phase and solutions of sodium dodecylsulfate in water the continuous phase. Latexes of rubber‐modified polystyrene composites have been thus obtained. Solutions of rubber–styrene have been also polymerized by bulk polymerization for comparison purposes. The molecular weights have been determined from intrinsic viscosity measurements, and the mechanical properties of the composites have been studied via tensile testings. Because of the lower mobility of the high‐molecular radicals in the concentrated emulsions, higher molecular weights have been obtained by the concentrated emulsion polymerization than by the bulk polymerization method. The tensile properties and toughness of the composites have been determined. While the two polymerization methods provide high, comparable toughness, the concentrated emulsion method generates latexes that can be easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc.

Effect of rubber–plasticizer interaction on temperature and concentration dependence of viscoelastic properties

Linear viscoelastic properties of polymer solutions depend on the solvent power even at high polymer concentrations. In this work, solutions of a commercial nitrile rubber in a homologous series of plasticizers were used. The rubbery plateau modulus is higher for the better solvent, the solvent power being assessed from the dilute solution viscosity.

Non‐newtonian liquid flow through globe and gate valves

AbstractExperimental data on the pressure drop across 1/2‐in. globe and gate valves in the horizontal plane for non‐Newtonian pseudoplastic fluids in laminar flow are presented. Generalized correlations in terms of the various physical and dynamic variables of the system have been developed for prediction of the frictional pressure drop for each valve. Statistical analysis of the correlations suggest that they are of acceptable accuracy.

Diffraction of acoustic waves by parallel cylindrical piezoceramic systems of coaxial shells filled by a viscous fluid

Calculations were carried out for the cases in which the interior shells are made of the piezoceramic material TsTCNV-1 with a radial polarization, while the exterior shell are made of polyvinyl chloride. As viscous fluid we selected an octane solution of silicon organic rubber

Low-molecular-weight guayule natural rubber as a feedstock for epoxidized natural rubber

The low-molecular-weight fraction of guayule rubber ( M w 2.68 × 10 5) can be modified to yield a low-viscosity analog of epoxidized natural rubber. A hexane or cyclohexane solution of rubber is treated at 23–63°C with peracid formed in situ from hydrogen peroxide and formic acid. The epoxidized polymer enhances the physical properties of cured rubber compositions, particularly abrasion and oil resistance properties. Low-molecular-weight natural rubbers from other temperate zone plants could be similarly modified.

Microsurgical anatomy of the lower basilar artery.

This study was designed to study the microvascular anatomy of the basilar artery between the superior cerebellar artery and the vertebrobasilar junction (i.e. the lower basilar artery). Twenty unfixed brains were injected with silicone rubber solution and studied with a Zeiss OPMI microscope. The length of this segment of the basilar artery was 28.1 + 1.35 mm and its course was straight in 9 (45%) brains, curved in 7 (35%) and tortuous in 4 (20%). The total number of perforators found in 20 brains was 340 with an average of 17 per brain. Of these, 118 (34.7%) were median and 222 (65.2%) were lateral. Median branches had a mean length of 5.8 + 1.25 mm, whereas left and right lateral branches had a mean length of 16 + 1.25 mm and 16 + 1.58 mm respectively.

Microvascular anatomy of foramen caecum medullae oblongatae

The foramen caecum (FC) is a triangular-shaped fossa situated in the midline on the base of the brain stem, at the pontomedullary junction. Although this area is known to have a very high concentration of brainstem perforating vessels, its microvascular anatomy has not been studied in detail. The purpose of this study was to detail the microvasculature of this territory. Twenty unfixed brains were injected with silicone rubber solution and dissected under a microscope equipped with a camera. The origin, course, outer diameter, and branching pattern of the perforators were examined. The total number of perforators found in the 20 brains was 287, with an average (+/- standard deviation) of 14.35 +/- 1.24 perforators per brain (range seven to 28). Their origin was as follows: right vertebral artery in 52 perforators (18.11%); left vertebral artery in 35 (12.19%); basilar artery below the anterior inferior cerebellar artery (AICA) in 139 (48.43%); basilar artery above the AICA in 46 (16.02%); AICA in 10 (3.48%); and anterior spinal artery in five (1.74%). Most of the perforators arose as sub-branches of larger trunks; their average outer diameter was 0.16 +/- 0.006 mm while that of trunks was 0.35 +/- 0.02 mm. These anatomical data are important for those wishing 1) to study the pathophysiology of vascular insults to this area caused by atheromas, thrombi, and emboli; 2) to plan vertebrobasilar aneurysm surgery; 3) to plan surgery for vertebrobasilar insufficiency; and 4) to study foramen magnum neoplasms.

Two-Level Factorial Study of the Rheology and Foaming of Bromobutyl Rubber Solutions

Abstract The rheology and foaming properties of BIIR coating slurries were studied. Two-level three-factorial analyses showed that solids content had the main influence on apparent viscosity, and foaming was less persistent at higher concentration of hydrated silica. Bentonite, on the other hand, had no statistically significant contribution.

Electrosurgery-Induced Endotracheal Tube Ignition during Tracheotomy

Electrosurgery was the most common source of ignition for operating room fires prior to the advent of lasers. When combined with volatile anesthetic mixtures, electrosurgery has caused ignition of plastic, rubber, paper, enteric gases, and combustible preparation solutions. We report on an intubated patient whose polyvinyl chloride endotracheal tube ignited during a tracheotomy performed with an electrosurgical unit. The oxygen-rich environment, the polyvinyl chloride tube, and the heat generated by the electrosurgical unit combined to produce a fire. Since otolaryngologists are called upon often to perform tracheotomies on intubated patients, it is imperative that they understand the factors involved in the development of such a fire. This case is presented with an explanation of why this type of fire occurs. A brief review of the literature is included. Different kinds of electrosurgical units, precautions as to their use, and the management of electrosurgery-induced endotracheal tube fires are also discussed.

A preliminary report on a new hydraulic sphincter for controlling urinary incontinence

A new pressure-regulated artificial urinary sphincter (AUS) has been developed which overcomes many of the deficiencies of earlier devices. This implantable AUS comprises a circular occluder cuff and the means to inflate and deflate through a pressure-regulated valve. The device is made from medical-grade silicone rubber and filled with radio-opaque isotonic fluid. A few days before surgery the implant is coated on the outside with an antibiotic-loaded silicone rubber solution. Tests have shown that the regulated pressure was very easily adjusted in situ by injecting or withdrawing the hydraulic fluid through a hypodermic needle penetrating a self-sealing filling port. When set, the regulated pressure remained very stable. The mechanism by which cuff pressure was increased to overcome stress incontinence worked well. Of the five earlier devices (AUS Mk I) implanted, none has survived without mechanical failure. The two latest implants (Mk II), which were rigorously tested for defects before implantation, have been more successful.

The effect of hexane treatment on the permeation of silicone‐coated polyethersulfone membranes

AbstractThe polyethersulfone membranes were cast from casting solutions including poly(vinyl pyrrolidone) additive. The membranes were further dried, silicone‐coated, and used for the permeation study with hydrogen and nitrogen gases. It has been found that solvent hexane which was included in the silicone rubber solution for surface coating increased the pore size on the membranes surface when poly(vinyl pyrrolidone) was present in the membrane. The above effect counteracted the pore size decrease by silicone coating, and, as a result, an H2/N2 permeability ratio of only 8.9 was achieved as compared with 28, which was obtained when the base polyethersulfone membrane was prepared from a casting solution without poly(vinyl pyrrolidone) additive.

Phase equilibria in solutions of butyl rubber in monomer-hydrocarbon solvent mixtures

Types and conditions of phase equilibria existing in solutions of butyl rubber in monomer-hydrocarbon solvent mixtures have been determined over the range −150–+100°. The monomer concentration was varied from 35 to 70%, and the polymer concentration from 2 to 20%.

Foaming characteristics of filled solutions of nitrile butadiene rubber

AbstractDuring the development of nitrile‐butadiene‐rubber‐based coatings, persistent foaming—a grave obstacle in such applications—was encountered, An investigation was undertaken to study the behavior of foams in order to prevent their formation. Both the apparent viscosity and the foam stability were found to attain their minimum values at the same filler level. It is plausible that the observed phenomenon is due to the binding of polymer chains to filler particles, which takes place most effectively at a certain proportion of filler and polymer.

Application of nitrile butadiene rubber for flexible, chemically protective coating

AbstractRheological properties of toluene solutions of nitrile butadiene rubber, of different molecular weights (Mw, 290,000,320,000, and 450,000) and acrylonitrile contents (30 and 40 percent), were investigated at low (0.1 S−1) to medium (20,0 S−1) shear rates, in order to determine their feasibility for dip‐coating applications. The effect of a surface‐active additive, bentonite, and the solid content (15 and 20 wt percent) on solution viscosity was of main interest. At low zero‐shear viscosity (<50 Pa·S) an excessive sagging of the wet film was experienced; at high zeroshear viscosity (>100 Pa‐·S) the coating showed poor leveling. Zeroshear viscosity was found to be less affected by bentonite than oligomer‐based solutions, at the same time, the solid content and the molecular weight of the polymer had more pronounced effects. With a proper balance of the parameters, seamless coating films were achieved, with excellent tensile and tear properties, and good permeation resistance against benzene.

High elasticity and strength of the structure of butyl rubber vulcanizates at different temperatures

The limiting values of high elastic strain γ e max and the strength of the structure of vulcanized solutions of butyl rubber in transformer oil at 20–80°C have been studied. With fall in the density of the network γ e max rises, it too depending on the rate of strain. With rise in temperature γ e max falls, especially with increase in the density of the network. The dependences of log P r on 1/ T are expressed by straight lines meeting at the glass transition point. The dependence of the largest values of γ e max ∗ on the logarithm of the rate of strain is expressed by broken lines and passes through a maximum which falls linearly depending on the concentration of the vulcanizing agent. The size of the statistical segment which in all cases, apart from the densest network, proved equal to two was calculated.