Curing kinetics of a siloxane pre-ceramic prepreg resin

Abstract

Ceramic matrix composites are being investigated as new material of choice for aeronautic and aerospace applications, because of their higher thermal resistance. Among the different ways to manufacture these materials, the polymer infiltration pyrolysis (PIP) is the most versatile. This route uses preceramic resins that present the benefit to be processed like thermosets. However, there is a lack of information available regarding the curing kinetics of preceramic resins and their detailed chemical composition. This limits the possibility for the end user to freely operate the resin, with sufficient accuracy to manufacture components. Dynamic Differential Scanning Calorimetry (DSC) were carried out at 1, 3, 5, 10, 15 and 20°C/min, to plot a Time-Temperature-Transformation (TTT) diagram for a commercial polysiloxane resin, the SPR-688. The activation energy and kinetic parameters were estimated using Kinetics Neo. The glass transition temperature of SPR-688 was modelled using the Di Benedetto's equation. The gelation point was investigated by chemorheology using a Dynamic Mechanical Analysis (DMA) apparatus, by plotting tan δ vs time. The degree of cure was thereafter estimated. The curing mechanism was shown to be a single step reaction (A→B). The cure kinetic was successfully described by numerical optimization, which is based on the analytical Friedman method. The proposed model showed a good agreement between predicted and experimental data. This suggests that the curing kinetics of preceramic resins can be approximated using models that are well accepted for thermosetting polymers. This general strategy is key to manufacturing prepregs made of preceramic resins.