Fluorosilicone Rubber Research Articles

Extending the application of fluorosilicone elastomers

An investigation sponsored by Dow Corning as part of its regular ongoing research has recently included work carried out by Rapra Technologies to compare the overall properties of fluorosilicone rubber (FSR) with other high performance elastomers. The results demonstrate the capability of FSR to operate over a wide temperature range, and the retention of mechanical properties at high temperature compared to alternative materials. Applications where these materials can compete effectively with other high performance elastomers are also discussed here.

Plasma surface modification of poly(m-aramide) fabric for adhesion improvement to fluorosilicone rubber

Poly(m-phenylene isophthalamide) fabric is important as a reinforcement for highperformance rubber diaphragms, such as fluorosilicone diaphragms. Because of their low affinities for each other, it is difficult to develop a good adhesion bond between poly(m-aramide) fiber and fluorosilicone rubber. The present study demonstrates that the bond strength between a poly(maramide) fabric and fluorosilicone rubber can be improved through N2 plasma treatment of the fabric in combination with a silane coupling agent. The effectiveness of the treatment is dependent on the gas species, the plasma input power, and the time of exposure. The chemical changes in the fabric surface were studied by X-ray photoelectron spectroscopy (XPS). It turned out that free radicals were formed on the surface after the N2 plasma treatment, which enabled the bonding of the coupling agent to the fabric surface.

Effect of dose rate and oxygen on radiation crosslinking of silica filled fluorosilicone rubber

Abstract Fluorosilicone (polymethyltrifluoropropylsiloxane) rubber containing silica filler was irradiated with γ-rays and accelerated electrons in air, argon and vacuum. Doses up to 0.5 MGy and dose rates of 1.4 and 103 Gy/s were used. The absorbed dose distribution across the rubber thickness during electron irradiation was determined. Oxidation, swelling in ethyl acetate and mechanical properties of this rubber depended on the conditions of irradiation that testified to different effectiveness of the rubber radiation crosslinking under these conditions. Effects of dose rate, diffusion of oxygen into rubber during irradiation, local heating and the oxygen desorption from the filler particles during the electron irradiation are considered for explanation of these differences.

Viscous Displacement In Fractured Porous Media

Abstract In some fractured reservoirs, a gas pressure gradient of the order of 3–5 kPa/m may be established in the- fractures due to flow. Such a pressure gradient could result in recovery enhancement of the matrix oil. Several tests, are conducted to study viscous displacement in fractured porous media, with artificial fractures. These tests are analysed by using a fully-implicit finite difference simulator with appropriate fracture capillary pressure. The results show that there is considerable recovery improvement due to viscous displacement. For a gas pressure gradient of 3 kPa/m, the matrix oil recovery increases by 10% of PV in one of the tests. Introduction In fractured porous media comprised of matrix blocks and a fracture network, gravity and capillary forces affect the two-phase flow in the matrix blocks and the fractures. Capillary forces play a major role in the interaction between the matrix blocks via the capillary continuity mechanism(1). Gravity forces affect the drainage performance of the matrix blocks and the reinfiltration process (2). In addition to capillary and gravity forces, in certain cases, viscous forces are expected to affect the production performance of fractured reservoirs. Gas injection in some fractured reservoirs with low oil viscosity (say 0.2 mPa.s and an effective permeability to matrix permeability ratio of less than say 30) may result in a small pressure gradient in the fractures between an injection and production well. The gas pressure gradient in the fractures away from the well could be of the order of 3–5 kPa/m. Such a pressure gradient in the fractures improves matrix oil recovery by reducing the matrix capillary threshold height for gravity drainage and the capillary end effect in the horizontal displacement. There is no published data in the literature on viscous displacement in fractured porous media. The purpose of this work is to:provide experimental data on viscous displacement in fractured porous media for gas-oil displacement processes, andanalyse the data to examine the nature of displacement improvement from viscous forces. In the following, we first discuss the experimental set up and present the data, and then analyse the data using a finite difference simulator. FIGURE 1: Viscous displacement experimental setup.(Available in full paper) FIGURE 2: Matrix-fracture configurations used in the experiments (drawn not to scale). (Available in full paper) Experimental The apparatus schematic is depicted in Figure 1. It consists of a glass-walled case with metal top and bottom plates supported by metal framing. The metal framing allows the 0.95 cm thick glass plates to be forced against the rock faces. Design allows the setup to be tilted through 240 ° about a central horizontal axis. The glass case was sealed using fuel resistant room temperature vulcanizing fluorosilicone rubber. The bottom and the top end plates were made of 2.54 cm and 0.64 cm thick aluminum plates, respectively. Both plates provided connections for vacuum, ventilation, gas injection, fluid loading and drainage (see Figure 1). A valve mounted 6 cm above the bottom face of the coreholder allows gas to flow out freely without interfering with liquid flow.

Acoustic Properties of Lens Materials for Ultrasonic Probes

The acoustic velocities and densities of 20 types of commercial rubber have been measured at a frequency of 2 MHz at room temperature, and they are evaluated in terms of their application to an acoustic lens or an acoustic window of probes of an ultrasonic diagnostic instrument. Fluorosilicone rubber and phoshazene rubber have lower acoustic velocities than the human body, and they have excellent impedance matching with the human body. Both the acoustic velocities and densities of butadiene rubber, polybutadiene rubber, acrylic rubber and polyurethane match those of the human body. It is also described that rubber having good impedance matching with the human body can be fabricated by adjusting the volume fraction of the added filler.

特集 シリコーンポリマー 最近のフルオロシリコーンゴム

特集 シリコーンポリマー 最近のフルオロシリコーンゴム

Accelerated Heat-Aging Studies on Fluororubber in Various Media

Abstract The nature, extent and, rate of chemical changes that take place in certain elastomers at long times is being studied. The chemical degradation of styrene-butadiene rubber (SBR) and fluorosilicone rubber (FVMQ) were reported previously. Investigations carried out with fluororubber (FKM) are discussed in this paper. Like fluorosilicone, this fluorocarbon elastomer is regarded as a high-temperature- and hydrocarbon-fuel-resistant rubber. The designation FKM is given to the copolymers of vinylidene fluoride (VF) and perfluoropropylene (PFP). The one discussed here is reported to contain also small quantities of a third component, tetrafluoroethylene. The detailed structure, assigned to the FKM polymer as a result of nuclear magnetic resonance studies, shows that it consists of blocks of VF homopolymer, 95% of which is head-to-tail, and blocks of VF-PFP copolymer, 93% of which is head-to-tail. The ratio of the copolymer to the VF homopolymer is dependent on the mole fraction of VF used. Vulcanization of FKM with derivatives of diamines is the commercially preferred method, although peroxides and high-energy radiation can be used for the same purpose. In the present study, N, N-dicinnamylidene-1,6-hexanediamine a Schiff 's base of 1,6-hexanediamine, was used with magnesium oxide as the acid acceptor. Chemical stress relaxation was the method most extensively used to determine the network changes taking place in the heat-aged fluororubber. Swelling, gel permeation chromatography (gpc), and infrared (ir) spectroscopy were also used to obtain additional information.

A method of moments for measuring diffusivities of gases in polymers

AbstractA method of moments has been formulated for the determination of the diffusivity of a gas in a polymer from a step response in a continuous permeation chamber. Contributions of system components other than the polymer are easily factored out to determine the contribution of the polymer alone, and this contribution is then analyzed to calculate the diffusivity. The method has been applied to the measurement of the diffusivities of sulfur dioxide in PTFE (Teflon) and fluorosilicone rubber tubes over a wide temperature range.

Accelerated Heat-Aging Studies on Fluorosilicone Rubber

Abstract The accelerated aging of a vulcanizate of fluorosilicone rubber was studied by four methods: infrared spectroscopy, GPC, weight loss, and stress relaxation, with the object of gathering information pertinent to understanding the basic mechanism of its aging. No changes were observed in infrared spectra of the rubber aged in air up to 315°C although severe degradation took place, as evidenced by high weight loss and drastic change in the physical condition of the test samples. It was concluded that although the polymer degrades, there is no change detectable within the precision of the analytical methods in the structure of the repeat unit of the elastomer. The gel-permeation chromatogram of unheated rubber showed peaks at MW 450 000 (95%) and 630 (5%). The low-molecular-weight component is very likely the cyclic tetramer of λ,λ′,λ″-trifluoropropylmethylsiloxane, the principal monomer of the FVMQ used. Heat aging increased the concentration of the 630 MW component, but rate studies were prevented by complications resulting from solvent-induced rubber degradation. Rapid decrease in the MW of FVMQ, as found by GPC, indicated random scission in the polymer backbone, as opposed to ordered unzipping of the repeat unit. The same conclusion was reached from the effects of crosslink density on stress relaxation. Activation energies obtained from weight-loss measurements (104 kJ/mol) were lower than those obtained from stress-relaxation measurements, (150–155 kJ/mol), suggesting that the processes being measured in each case may not be the same. Chemical stress relaxation takes place more rapidly in the presence of air than in an inert atmosphere, and intermittent stress-relaxation measurements indicate that crosslinks form during thermal aging in air, their rate first increasing and then decreasing.