Influence of SiO2 fillers on the irradiation ageing of silicone rubbers (original) (raw)
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Radiation Physics and Chemistry, 2019
The objective of this comparative study is to investigate the effects of electron-beam irradiation on the mechanical and stress relaxation properties of vinyl-methyl-polysiloxane (VMQ) and phenyl-vinylmethyl-polysiloxane (PVMQ), as well the variation of these properties with irradiation depending on the silicone and co-agent type. For this purpose, firstly a series of silicone mixtures was prepared using 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane as the peroxide and either a Type I (ZDA) or Type II co-agent (TAIC). The rheological properties and curing conditions of the prepared mixtures were investigated by rubber process analyzer. In the second step, cured elastomers were irradiated with electron beams at doses of 0-80 kGy. The percent gelation of elastomers before and after irradiation was determined by sol-gel analysis. In order to investigate the effects of irradiation on the mechanical properties and cross-link density, the stress-strain behavior was determined. The stress relaxation properties of samples were determined by temperature scanning stress relaxation technique. After the irradiation, it was found that the main effect of irradiation on the silicone elastomers is cross-linking. Irradiation increased the cross-link density for both the silicone and gel fraction up to 94.3% for PVMQ and 96.7% for VMQ. A higher cross-link density was achieved for all of the nonirradiated and irradiated PVMQ elastomers than for VMQ elastomers. The relaxation studies revealed that elastomer type and irradiation are two important parameters affecting the relaxation behaviors of silicone elastomers. Increasing the irradiation dose resulted in maintaining of mechanical properties owing to the isothermal relaxation of both VMQ and PVMQ elastomers. This improvement was higher in the VMQ elastomers. In non-isothermal or temperature scanning stress relaxation behavior, an increase in the irradiation dose resulted in an improvement in the properties of the VMQ elastomers and a decrease for the PVMQ elastomers. The reason for this reduction is thought to be some undesirable side reactions occurring with the free radicals stabilized by the phenyl groups during irradiation and that these groups accelerate the decomposition at high temperatures during the relaxation experiments. Highlights • Effect of electron beam irradiation on the VMQ and PVMQ elastomers • Variation of mechanical properties depend on the silicone and co-agent type. • Controlling of stress relaxation of VMQ and PVMQ by radiation and of co-agent type.
Polymer Degradation and Stability, 2003
RTV-5370 is a filled polydimethylsilxoane-polymethylphenylsiloxane copolymer system originally developed by Dow Corning and now supplied by Rhone Poulenc. There is a desire to develop lifetime assessments of this material for certification programs and as a model system for understanding other filled siloxane polymer systems. We have initiated aging studies on these materials by employing accelerated aging tests with exposure to Co-60 g-radiation. The effects of radiation exposure have been investigated by thermal (differential scanning calorimetry), mechanical (dynamic mechanical analysis), chemical (solvent swelling), and segmental dynamics (nuclear magnetic resonance) methods. The data show that RTV-5370 undergoes predominately radiation-induced crosslinking reactions over the dose range investigated. These reactions reduce the molecular weight between crosslinks, thereby hardening the composite and reducing the motional dynamics of segmental motion. DSC studies show dose dependent crystallization phenomena. Published by Elsevier Science Ltd.
Comprehensive characterization of silica-modified silicon rubbers
Journal of the Mechanical Behavior of Biomedical Materials, 2019
In this study a commercially liquid silicone rubber was filled with fumed silica particles in different concentrations and evaluated for medical applications. The thermal, morphological and mechanical properties of silicone/silica composite samples were studied before and after aging, flexural tests and immersion in saline environment. Understanding the effect of silica content, aging conditions and thickness (from 0.6 to 2 mm) of the samples on the behavior of these materials in different environments is crucial for applications as implantable devices. Before inducing any mechanical stress, tensile strength was found to increase for samples containing 3 or 5 wt% of fumed silica, depending on the thickness. A similar trend was observed after 10 6 flexes for tensile strength, storage modulus and hardness at room temperature, which increased with the concentration of fumed silica. Moreover, tensile strength decreased with increasing the thickness of the samples from 0.6 to 2 mm. The thermal degradation was found to start at higher temperature in the case of the composites as compared with neat silicone, however, the glass transition and melting temperatures were only slightly modified by the presence of the silica particles, regardless the mechanical aging. The MTT assay using L929 fibroblasts mouse cells showed a good short-time cytocompatibility for both silicone elastomer and the composite with 3 wt% fumed silica. Similarly, the measurement of the cytokine secretion revealed no inflammatory response.
Influence of TiO2 in Absorbing Electron Beam Radiation on Silicone Rubber
International Journal of Polymer and Textile Engineering, 2016
The influence of electron beam radiation on silicone rubber compounded with TiO 2 was studied with variation in doses of the pigment. The rubber was mixed with TiO 2 and a proportionate quantity of silicone rubber cross linker which was then subjected to varying doses of electron beam. The physicomechanical and the ageing properties of the rubber was investigated with increasing incorporation of the TiO 2 pigment. It was observed that the tensile strength of the polymer rose marginally with a corresponding marginal reduction in the value of elongation at break. The tear strength also displayed a pattern similar to that of the changes in elongation with the highest value lying with the base rubber compound. The heat ageing behaviour indicated a profound positive effect on the retention of tensile properties with increasing content of TiO 2 at different doses of radiation. Considering all the results, the concentration level of TiO 2 and radiation dose has been optimized to achieve a modified silicone elastomer having the best possible physicomechanical properties.
Investigation on the Surface Condition of Gamma Irradiated Silicone Rubber Micro-Nanocomposites
IEEE Access
Silicone rubber (SR) micro nanocomposites formed with micro-ATH and nano-alumina particles have been subjected to different levels of gamma-ray irradiation to understand the characteristic variation in the surface condition of the material through contact angle measurement, Atomic Force Microscopy (AFM) studies, water droplet-initiated corona inception voltage (CIV) measurement and by laser-induced breakdown spectroscopy (LIBS) analysis. It is realized that the recovery rate of silicone rubber micro nanocomposites is less compared with the base SR material. It is observed that, irrespective of the level of irradiation, the contact angle and water droplet initiated CIV of the specimen have shown direct correlation. FTIR analysis clearly indicates variation in methyl group formation on irradiation is less with S2 specimen. It is also observed that fractal dimension calculated by three different techniques for the surface profile data obtained using AFM is in directly in proportion with average surface roughness. In addition, the lacunarity values of the irradiated samples followed the same pattern as that of the average surface roughness. The variation in thermal degradation temperature has been analyzed by adopting thermogravimetric analysis (TGA). The calculated plasma temperature values from laser-induced breakdown spectroscopy and the crater depth formed due to laser ablation have shown inverse relationship. Artificial neural network (ANN) has been employed successfully using LIBS data, to understand the level of irradiation of the SR samples. Overall, the silicone rubber micro-nanocomposite sample S2 filled with micro-ATH and nano Alumina has reflected relatively lesser degradation after being exposed to gamma irradiation, over other test specimens.
The High Energy Irradiation Ageing of Reinforced Elastomers Based on Rubber Blends
RAD Conference Proceedings, 2016
Elastomers are very often used in severe environments, for instance, in nuclear power plants, where they may be degraded by high-energy radiation and heat. The ageing behaviour of materials used in different equipments is very important. Elastomers based on chlorosulfonated polyethylene (CSM) are used for cable jacketing materials and have excellent radiation resistance needed in nuclear power stations. In the current work, the influence of γirradiation dose (100, 200 and 400 kGy) on the ageing of reinforced blends based on CSM, styrene butadiene rubber (SBR) and natural rubber (NR) has been evaluated. The content of silica in CSM/SBR and CSM/NR rubber blends was varied. The curing behavior of compounds was estimated using the oscillating disk reometer. The irradiation of nano composites has been performed in air in the Co 60 radiation sterilization unit with the dose rate of 10 kGy h-1. The thermal properties were studied by thermogravimetric test. The mechanical properties (hardness, modulus at 100% elongation, tensile strength and elongation at break) were determined before and after irradiation. A decrease in the elastic modulus and in the strain at break has been observed with increasing irradiation. At higher doses, the network chain scissions become the main degradation process, the cross-linked topology becomes irregular, and material contains more and more weak zones, which deteriorate the ultimate properties.
PLOS ONE, 2021
Degradation in the polymeric insulators is caused due to the environmental stresses. The main aim of this paper is to explore the improved aging characteristics of hybrid samples by adding nano/micro silica in High Temperature Vulcanized Silicone Rubber (HTV-SiR) under long term accelerated aging conditions for 9000 hours. As HTV-SiR is unable to sustain environmental stresses for a long time, thus a long term accelerated aging behavior is an important phenomenon to be considered for field application. The aging characteristics of nano/micro filled HTV-SiR are analyzed by using techniques such as Scanning Electron Microscopy (SEM), Leakage Current (LC), Fourier Transform Infrared Microscopy (FTIR), Hydrophobicity Classification (HC), and breakdown strength for the aging time of 9000 hours. FTIR and leakage currents are measured after every cycle. All the co-filled samples revealed escalated aging characteristics as compared to the neat sample except the SN8 sample (8% nano-silica+20...
Preparation of Ultraviolet Curing Type Silicone Rubbers Containing Mesoporous Silica Fillers
Here we have been focusing on mesoporous silica (MPS) as inorganic filler material to improve the mechanical strength of silicone rubbers. The MPS particles are more effective in reducing the coefficient of thermal expansion (CTE) and hardening silicone rubber composites when compared to commercially available nonporous silica particles. In this study, we utilize ultraviolet curing type silicone rubbers and prepare MPS composites according to a simple single-step method. From an industrial viewpoint, simplifying the fabrication processes is critical. The thermal stability and mechanical strength are examined in detail in order to showcase the effectiveness of MPS particles as filler materials.