Investigation of the thermal degradation kinetics of ceramifiable silicone rubber-based composite

A kind of ceramifiable rubber-based composite with high-temperature resistance and flame retardancy was prepared by adding silicate glass frits (SGFs) and ammonium polyphosphate (APP) to silicone rubber matrix. The ceramifiable performance was further improved by enhancing thermal stability of the composite through incorporating organo-modified montmorillonite (OMMT). The high-temperature resistance and ceramifiable performance of the ceramifiable silicone rubber-based composite under various pyrolysis conditions were tested. For the fired specimen of silicone rubber/SGF/APP/OMMT, its flexural strength decreased from 4.80 to 3.23 MPa as the heating rate increased from 5 to 20 K min^–1, which means that lower heating rate is more favorable to form a compact and dense ceramic body. The influence of thermal stability on the ceramization effects of the ceramifiable silicone rubber-based composite was quantitatively analyzed from the perspective of thermal degradation kinetics based on the Kissinger, Kissinger--Akahira--Sunose, and Flynn--Wall--Ozawa methods. The results show that the pyrolysis activation energy E_a of the composite has a certain relationship with the ceramifiable performance. The better the thermal stability of the composite is, the higher the E_a is and the better the ceramifiable performance is. The E_a increased with the process of ceramization reaction of the composite. The reliability of the regular relation between combustion intensity of material itself, external ablation conditions, and ceramization effect was also verified through cone calorimetry and scanning electron microscope analysis. These results are helpful in preparing ceramifiable polymer composite, which possesses high-temperature resistance.