Microstructure of ceramized silicone composites
Zbigniew Pędzich, Dariusz Bieliński
Quarterly No. 3, 2010 pages 249-254
DOI:
keywords: cables, flammability, silicone composites, ceramization, mechanical strength
abstract The paper describes microstructural differences created during ceramization of commercially manufactured silicone composites used for fire resistant shields of electrical cables. From application point of view is crucial that degradation of polymer component has to result in the creation of ceramic layer, which could prevent adequate strength and integrity of cable shield. Microstructures of the composites subjected to ceramization in the temperature range 600÷1050°C were determined, as well as strength of the ceramized materials estimated. It was recognized that the way of polymer decomposition, determined the porosity of ceramized structure. The lowest porosity after ceramization at 600 and 800°C showed polymer with the higher temperature of decomposition temperature. Microstructural observations confirmed differences came from the different mineral composition of investigated materials. Porosity in all investigated samples evolved in different way with the increase of ceramization temperature. Analyses showed that in samples A and B porosity has changed significantly after firing at 1050°C. The total porosity was reduced about 50% when compared with porosity after firing at 600°C. Porosity in sample E was much more stable with temperature, and contrary to A and B, at the highest firing temperature the total volume of open porosity was increased. Results of performed investigations indicate that the suitable ceramized layer could be achieving by a few methods (different composition of the material). Performed experiments suggest that the range of temperature of 600÷800°C is decisive for the integrity of ceramized material. At this range the ultimate degradation of polymer component takes place and ceramic phases present in the composite are not bounded so fast. In composites with increased polymer matrix degradation temperature, the microstructure of ceramized structure shows the lowest porosity and the highest strength what is profitable for application of such materials.