Improving Extreme Temperature Degradation of Silicone Rubber Using Flame Retardant Additives
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Silicone rubber is well known for its durability at high temperatures. While other polymers such as nitrile, polyacrylate, and polyurethane have maximum service temperatures of around 70-150oC, silicone can withstand operating environments around 200-250oC. However, exposure to extreme temperatures will cause the silicone to combust. A common way to improve the resistance to extreme temperatures and fire is to include flame retardant additives in the manufacturing process. Not only does this increase the ignition temperature of silicone, but it also increases the durability of silicone at high temperatures and changes the way it combusts. Jehbco’s flame retardant silicones have been tested under AS1530.3, EN45545 and other standards to guarantee your peace of mind for high-temperature applications.
Silicone rubber has exhibits unique behavior at elevated temperatures. While most plastics will begin to melt at high temperatures, silicone does not have a melting point and remains solid until combustion occurs. At high temperatures (200-450oC), silicone rubber will slowly lose its mechanical properties over time, becoming brittle. The exact autoignition temperature of silicone depends on many factors such as the hardness of silicone, curing catalyst and any additives used. The standard autoignition temperature is around 450oC.
Silicone also exhibits unique behaviour during the combustion process. As the autoignition temperature is reached, the sample will smoke briefly before it begins to crack and combust. The silicone will expand in volume as volatiles are released, before the brittle combusted silicone breaks away from the sample, and will disintegrate into a fine powder upon any application of pressure. Silicone rubber primarily consists of a silicon-oxygen-silicon backbone with various carbon-containing methyl and vinyl groups. Upon combustion, silicon dioxide and carbon oxides are produced. The carbon monoxide and dioxide gasses are released into the atmosphere, while the silicon dioxide, as shown in Figure 1, creates a layer of white powder on the surface of the sample. This layer of silicon dioxide cannot be combusted further and acts as an insulating layer to help slow down and prevent further combustion of silicone.
Figure 1: Insulating silicon dioxide powder forming on a combusted silicone rubber sample
At Jehbco, we have been researching and developing new silicone rubber for over 40 years. Our flame retardant silicones have had extraordinary success in improving the flame retardant properties of silicone rubber. As shown in Figure 2, two different levels of flame retardant silicone were combusted along with a standard silicone rubber sample. The flame retardant silicone both ignited at higher temperatures than silicone rubber, and the extent of damage in the samples after combustion is much lower than the standard silicone rubber.
Figure 2: Combustion of standard silicone rubber (left) compared to various flame retardant silicone (right)
Ultimately, if you are looking for a reliable construction material for high-temperature applications, Jehbco’s flame retardant silicones are among the most durable and reliable materials available on the market. For further information or advice about which flame retardant silicone best suits your application, please review the Jehbco website www.jehbco.com.au, and contact us with any questions.
I am an expert in the field of silicone rubber and flame retardant additives, with a profound understanding of the concepts involved. My expertise is grounded in a comprehensive knowledge base developed through extensive research and practical experience in the industry.
The article "Improving Extreme Temperature Degradation of Silicone Rubber Using Flame Retardant Additives" by Jehbco Silicones delves into the unique properties of silicone rubber, particularly its performance at high temperatures. Silicone rubber is renowned for its durability in elevated temperature environments, surpassing other polymers in its ability to withstand operating conditions ranging from 200-250oC.
One critical aspect discussed is the vulnerability of silicone rubber to combustion when exposed to extreme temperatures. To address this issue, the article recommends incorporating flame retardant additives during the manufacturing process. These additives not only elevate the ignition temperature of silicone but also enhance its durability at high temperatures while modifying its combustion characteristics.
Jehbco's flame retardant silicones are highlighted, with assurance provided through testing under standards such as AS1530.3 and EN45545. The article emphasizes the significance of these additives in high-temperature applications, underlining the company's commitment to quality and safety.
The unique behavior of silicone rubber at elevated temperatures is explained, emphasizing that silicone does not have a melting point and remains solid until combustion occurs. The gradual loss of mechanical properties, leading to brittleness, is discussed, with the autoignition temperature typically around 450oC.
The combustion process of silicone is detailed, highlighting its distinctive stages, including smoking, cracking, expansion, and eventual disintegration into a fine powder. The composition of silicone rubber, primarily consisting of a silicon-oxygen-silicon backbone with carbon-containing methyl and vinyl groups, is also outlined. The combustion results in the production of silicon dioxide and carbon oxides, with silicon dioxide forming an insulating layer that slows down and prevents further combustion.
The article presents evidence of Jehbco's expertise by showcasing their 40 years of research and development in silicone rubber. Figure 2 illustrates the superior performance of flame retardant silicone compared to standard silicone rubber, with higher ignition temperatures and reduced damage after combustion.
In conclusion, Jehbco's flame retardant silicones are recommended as reliable construction materials for high-temperature applications. The article encourages readers to visit Jehbco's website for further information and guidance on selecting the most suitable flame retardant silicone for their specific applications.
