•Polysiloxane elastomer-based composites can be converted into a high-strength residue by sintering.•The residue structure was converted from two phases to a uniform matrix as the sintering temperature increased.•Amorphous silica was transformed into quartz crystals by liquid phase sintering up to 800 °C.•MgSiO3 crystals were produced via a eutectic reaction to 1000 °C.•The ceramic mechanism and the related mechanical properties of the residue were discussed.Polysiloxane elastomer-based ceramizable composites can be used as insulation materials in wires and cables. These composites are transformed into hard ceramics in high-temperature environments to protect the inner copper. The sintering temperature is one of the key factors to determine the formation of ceramic protecting layers. The effect of sintering temperature on the weight loss, linear shrinkage and ceramic strength of the ceramic residue was investigated. The appearance of the ceramic residue was observed using a digital camera. The morphology of the impact fracture surface was observed by SEM. The element composition of the ceramic residue and their concentrations were revealed by EDS analysis, and the ceramic mechanism was revealed by XRD analysis. The results showed that the weight loss and linear shrinkage, as well as the flexural strength and impact strength of the ceramic residue, increased as the sintering temperature increased from 700 to 1100 °C. SEM analysis showed that the structure of the ceramic residue was converted from two phases to a uniform matrix with the increased sintering temperature. XRD analysis showed that quartz and MgSiO3 crystals were produced in the ceramic residue at 800 °C and 1000 °C, respectively. Quartz and MgSiO3 crystals are beneficial to the mechanical strength of the ceramic residue.