Effect of mineral filler additives on flammability, processing and use of silicone-based ceramifiable composites

Abstract

The aim of this work is to describe the changes in the properties of ceramifiable silicone rubber-based composites caused by the incorporation of novel alternative minerals in comparison to other popular, widely utilized fillers. TiO 2 , calcined kaolin and calcium-based minerals mix (CbMix) consisting of CaO (6.26 wt%), CaCO 3 (26.18 wt%) and Ca(OH) 2 (67.56 wt%) have not been considered as a dispersed phase of ceramifiable silicone composites destined for wire covers yet. Mineral fillers: TiO 2 (anatase), mica (phlogopite), CbMix, CaCO 3 , Al(OH) 3 , kaolin and calcined kaolin affect the processing and the various properties of silicone rubber-based composites destined for wire covers differently. The propertiesflammability, smoke intensity, micromorphology and mechanical durability after ceramification-are assessed by measuring: the kinetics of vulcanization, stress at different levels of elongation, tensile strength and the elongation at break of the materials. Although the curing process of the composites is disturbed by the addition of CbMix, it benefits from an increase in oxygen index value, which reaches 31.4%. What is more, also its flammability parameters measured by cone calorimetry improve, such as the total heat released (THR) reaching 9.3 MJ/m 2 . Samples containing kaolin and calcined kaolin exhibit the best mechanical properties before ceramification, whereas composites filled with calcium-based powders (CbMix, CaCO 3 ) mechanically display the strongest mineral char after heat treatment, possibly due to a more homogenous micromorphology and the creation of calcium silicates at elevated temperature. Significant amounts of wollastonite, parawollastonite and pseudowollastonite are visible in their structure after ceramification.

Effect of benzotriazole‐protected platinum catalyst on flame retardancy and ceramic‐forming property of ceramifiable silicone rubber

“…It is reported that in fireaccidents, the ceramics formed at high temperatures can resist propagation of flame, further combustion and strong water mist in fire extinguishing 9,10 . The ceramifiable silicone rubber is now commonly prepared by adding skeleton‐fillers like silicates, melting agents, dispersant agents and other additives to silicone rubber 4,9,11,12 . In 1978, Yajima et al synthesized SiC fiber with high tensile strength through polysiloxane precursor, which was widely used and industrialized in 1983 13,14 .…”

Ceramization Mechanism of Ceramizable Silicone Rubber Composites with Nano Silica at Low Temperature

“…There are many achievements in the research on the formulation and processing of ceramizable silicone rubber composites [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 ], but research on the ceramization process and mechanism is not enough. Hanu et al [ 1 , 2 , 3 ] researched the ceramization mechanism of mica/silicone rubber composites, and put forward that ceramization was a process where the edge of mica melted and reacted with silica, which was the residue of silicone rubber, and the liquid phase connected the fillers and improved the residual strength.…”

Impact of Basalt Filler and Ceramizable Additives on the Toxicity of Gaseous Products Emitted from Thermal Decomposition of Silicone Rubber Composites

“…Basalt fibres were proven to be an environmentally friendly and promising additive to polymer, metallic, and concrete composites [19], however its impact on the toxicity has not been presented yet. The problem of the emission of toxic gases during their decomposition is of key importance from the point of view of fire safety [20,21,22,23,24,25,26] if we take into consideration that ceramizable composites are at present more and more commonly used as an insulation material for wires that are intended for supplying power to electrical devices in huge malls, on the boards of planes, or in lifts. An earlier article presents the effect of basalt fillers on the thermal properties and flammability of silicone rubber composites, including ceramizable composites [27].…”