Silicone Rubber Particles Research Articles

Influence of production method, silicone type and thickness on silicon rubber superhydrophobic coatings

This study evaluates the influence of production method, silicone fluid, rubber type and thickness on the hydrophobic properties of RTV silicone rubber coatings that are used for high voltage insulators. These coatings were fabricated from simple mixing of silicone rubber and nanofluoric particles and were cured at room temperature. The results determined that the production method could increase the contact angle and reduce the sliding angle of coatings. Also, silicone fluid reduced the hydrophobicity of coatings. Coatings prepared from silicone rubbers containing silica filler indicated lower contact angles and higher sliding angles. The increasing of coating thickness could reduce the hydrophobicity of coatings and decrease the surface roughness.

Experimental and theoretical studies of effective thermal conductivity of composites made of silicone rubber and Al2O3 particles

In this study, effective thermal conductivities of composite materials were investigated both experimentally and theoretically. The composites made of silicone rubber and spherical Al2O3 particles of four mean diameters were prepared with various volume fractions. Experimental results indicate that the effective thermal conductivity increases nonlinearly with increasing particle volume fraction and is higher for larger particles, indicating its dependence not only on conductivities and volume fraction, but also on the materials' interfacial geometry. The experimental results were used to evaluate the performance of theoretical models. It was found that the models by Deissler and Boegli and by Maxwell that contain no parameter for interfacial effects were unable to predict the experimental results. On the other hand, the models by Hsu et al. and by Agari and Uno that provide interfacial contact parameters fit very well with the data over the whole ranges of the present experiment.

Preparation and Thermal Stability of Micro/Nano Silicone Rubber Particles

The micro/nano particles of silicone rubber were prepared with α, ω-dihydroxy polyorganosiloxane, as basic polymer and crosslinking agent via emulsion polymerization method at room temperature. The structure and performance of the particles were characterized by transmission electron microscopy (TEM), FT-IR, thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results indicated that the particles had certain ordered structure and thermal stability.

Preparation and Mechanics Properties of MR Elastomers Based on Silicone Rubber

MR elastomers, which consisting of silicone rubber and carbonyl iron particles, are prepared under different magnet fields intensity. Their micro-structure and mechanics properties are investigated and compared. Results show that the bearing capacity and stiffness of both MR elastomers will increase when subjected to a magnet field. But the controllable range and comprehensive properties of the MR elastomers prepared with magnet fields are better than what of the MR elastomers prepared without magnet fields.

Influence of magnetic field upon the electric capacity of a flat capacitor having magnetorheological elastomer as a dielectric

The flat capacitor is built of two non-magnetic plates (with dimensions 0.065 m × 0.050 m) between which there is a layer of magnetorheological elastomer (MRE). The thickness of the layer is 0.0015 m ± 10%. MRE is based on silicone rubber and iron particles. The iron particles diameter ranges between 0.12 μm and 0.75 μm. The electric capacity, in absence of the magnetic field, is 377 ± 1 pF. In cross magnetic field with strengths up to 94 kA/m, the flat capacitor's capacity increases by up to 200%. For well chosen values of the intensity of the magnetic field, the capacity of the flat capacitor with MRE changes with time. The experimental results obtained in this manner are discussed.

Contact Resistance Characteristics of Improved Conductive Elastomer Contacts for Contaminated Printed Circuit Board in SO2 Environment

Characteristics of conductive elastomer that is composed of silicone rubber and dispersed carbon black particles show conductive and elastic properties in one simple material. This material has been widely applied to make-break contacts of panel switches and connectors of liquid crystal panels. However, since surface state of the contact is very soft, it is difficult to remove contaminant films of contaminated opposite side contact surface and to obtain low contact resistance owing to break the film. This is an important problem to be solved not only for the application of make-break switching contact but also static connector contacts. This study has been conducted to examine some complex structures of the elastomer which indicate removal characteristics for contaminant films and low contact resistance. As specimens, six different types of elastomer contacts composed of different type of dispersed materials as carbon and metal fibers, metal mesh, and plated surfaces were used. The contacts of opposite side were Au and Sn plated contact surface on a printed circuit board (PCB) which is usually used in the static connector and make-break contacts. In order to contaminate contact surfaces of PCB, the surfaces were subjected to exposure in an SO 2 gas environment. The elastomeric contacts contained hard materials showed lower contact resistance than only dispersed carbon particles in the elastomer matrix for both contaminated PCB contact surfaces.

Toughening of a Polysilsesquioxane Network by Simultaneous Incorporation of Short and Long PDMS Chain Segments

An effective toughening approach is described in this report. This approach uses a combination of both short and long PDMS segments, simultaneously incorporated into a polysilsesquioxane-based rigid network through chemical bonding at the terminals of these segments. Upon curing, the short chain PDMS remains molecularly dispersed (phase I PDMS) and the long chain PDMS segregates to form silicone rubber particles in situ (phase II PDMS). Proper combinations of phase I with phase II PDMS toughen the network 7−9 times more effectively than the phase I alone at the same total PDMS loading level, while the phase II PDMS alone deteriorates the mechanical properties. The effectiveness of the phase I/II combinations is dependent on the particle size. Submicron-sized particles are more effective than particles of a few microns in diameter. Particles larger than a few tens of microns become ineffective. The size of the particles can be controlled by changing these parameters: the precoupling reaction conditions, the amount of phase II PDMS, the phase II PDMS chain length, and the chain length ratio of phase I PDMS segment to phase II PDMS segments. With appropriate phase I/II combinations, the KIc is increased by up to 220% and the GIc by up to 900%, with less loss of elastic modulus as compared with toughening by the phase I alone. It is proposed that the effective engagement of high cross-link density domains into the deformation process by submicron-sized rubbery particles is responsible for the increased fracture toughness.

An investigation of the contact resistance of a commercial elastomer interconnect under thermal and mechanical stresses

The contact behavior of a commercial elastomer interconnect, composed of silicone rubber and silver particles, was evaluated under thermal and mechanical stresses. Its contact resistance demonstrated a linear relationship in a log-log plot with contact force at room temperature; however, a deviation of the trend occurred when temperature was changed. With the interconnect compressed under a constant force, a fluctuation in contact resistance was initiated by a change of temperature. This phenomenon may be attributed to the inherent conduction mechanisms of the elastomer interconnect. The multiple interfaces between metal particles make the contact sensitive to a variety of factors. This sensitivity may have a direct impact on its long-term reliability.

Influence of crosslinking degree of silicone rubber particles on properties of epoxy resin

Silicone rubber particles with different degrees of crosslinking were prepared. Silicone oils containing Si—H groups and vinyl groups were reacted at various mol ratios in their composite emulsions. Epoxy resin was modified using these particles and the results indicated that the content of the silicone rubber particles, the crosslinking degree of the rubber particles, and the addition of a coupling agent affected the properties of the modified epoxy resins. The influence of the coupling agent depends on the crosslinking degree of the silicone rubber particles. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 619–625, 1998

The use of polydimethylsiloxane in the treatment of incontinence after radical prostatectomy.

To report the results of transurethral submucosal injection therapy of polydimethylsiloxane (PDS) to treat incontinence after radical prostatectomy (RP). Since 1993, about 80 retropubic RPs have been carried out at our institution each year. Severe post-operative incontinence occurred in six patients, with a mean duration of incontinence after RP of 28 months. The pre-operative evaluation consisted of cysto-urethroscopy and urodynamics. Because we have no experience with artificial sphincter implantation, transurethral injection therapy was used to treat the post-operative incontinence, using PDS (vulcanized silicone rubber particles). This material has a mean particle size of 188 microns, providing stability of the material at the injection site. The six patients with severe post-operative incontinence were treated using injection therapy with PDS. After a mean follow up of 15.5 months, five patients, who suffered from day and night incontinence and required at least five pads per day, were dry after injection therapy. One patient improved significantly but still required two pads during the day, but was continent during the night; three patients required a second injection. A mean of 7.5 mL of PDS was used per patient and the side-effects of therapy (dysuria and urinary retention) were minimal. Because PDS has excellent biocompatibility, few side-effects or complications, transurethral injection therapy using silicone particles is a justifiable procedure for treating incontinence after RP.

Formation mechanism of silicone rubber particles with core-shell structure by seeded emulsion polymerization

Silicone rubber particles with core–shell structure were prepared by polymerization of vinyl monomers in the presence of crosslinked and linear poly(dimethyl siloxane-methyl vinyl siloxane) latex. The monomers were added with either continuous or swelled-continuous addition mode. The core–shell morphology of silicone rubber/polystyrene [PST] and silicone rubber/poly(methyl methacrylate-divinyl benzene) [P(MMA-DVB)] composite particles were obtained. The effects of monomer addition mode, the compatibilities of the monomers or their homopolymer with silicone rubber, and the reactivity of polysiloxane with vinyl monomers on the formation of the core–shell structure were discussed. © 1996 John Wiley & Sons, Inc.

Study of the Preparation of Silicone Rubber Particles with Core-Shell Structure by Seeded Emulsion Polymerization

Silicone rubber particles with core–shell structure were prepared by polymerization of vinyl monomers in the presence of linear or cross-linked poly(dimethyl siloxane–methyl vinyl siloxane) latexes. The monomers were added in either continuous or swelled-continuous modes. Core–shell particles with poly(butyl methacrylate), or poly(methyl methacrylate), as the shell were obtained by using either addition mode. The core–shell structure was not observed for polysiloxane–polystyrene particles. The influence of monomer addition mode, the compatibilities of the monomers and their homopolymers with silicone rubber, and the reactivity ratios of the vinyl monomers with the vinyl group of linear polysiloxane particles, on the formation of the core-shell structure is discussed.

Volume fraction and temperature dependence of mechanical properties of silicone rubber particulate/epoxy blends

At all temperatures, both the Young's modulus and tensile strength of silicone rubber particle/epoxy resin blends decreased as the volume fraction of the silicone rubber particles was increased, and this decrease became greater with falling temperature. A volume fraction-temperature superposition held for both the Young's modulus and tensile strength of the blends. The shifted volume fraction of silicone rubber particles needed to obtain master curves increased with increasing temperature and the shift was almost the same for both properties. An optimum suitable volume fraction of rubber particles existed in terms of improving impact fracture energy. A volume fraction of silicone rubber particles of 5–10% appears to be the most suitable for obtaining a blend in which the decrease in Young's modulus and the tensile strength is relatively low and the increase in impact fracture energy is relatively high.

Volume fraction and temperature dependence of mechanical properties of silicone rubber particulate/epoxy blends

At all temperatures, both the Young's modulus and tensile strength of silicone rubber particle/epoxy resin blends decreased as the volume fraction of the silicone rubber particles was increased, and this decrease became greater with falling temperature. A volume fraction-temperature superposition held for both the Young's modulus and tensile strength of the blends. The shifted volume fraction of silicone rubber particles needed to obtain master curves increased with increasing temperature and the shift was almost the same for both properties. An optimum suitable volume fraction of rubber particles existed in terms of improving impact fracture energy. A volume fraction of silicone rubber particles of 5–10% appears to be the most suitable for obtaining a blend in which the decrease in Young's modulus and the tensile strength is relatively low and the increase in impact fracture energy is relatively high.

Malignant lymphoma with intranodal silicone rubber particles following metacarpophalangeal joint replacements

A case of malignant lymphoma developing in a regional lymph node nine years after insertion of silastic finger prostheses is reported. A striking feature of the histology was the presence of multinucleated giant cells containing silastic particles, situated between the tumour cells. The significance of this is discussed.