Catalytic Thermocuring and Synergistic Photothermocuring of Single-Component Acrylate-Grafted Liquid Oligosilazanes.

Abstract

A novel thermosetting preceramic resin called acrylate-grafted liquid polysilazane (ALSZ) was readily synthesized. The curing behaviors of ALSZ were investigated by the techniques of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and rheological tests. The catalytic thermocuring process was controlled by the addition of a polymerization accelerator composed of a radical initiator (cumene hydroperoxide) and a transition metal catalyst (nickel naphthenate or cobalt naphthenate). Photocuring at room temperature can proceed readily by the addition of photosensitizer 819 (phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide). By combining a radical initiator, a transition metal catalyst, and a photosensitizer, synergistic photothermocuring was achieved, demonstrating advantages such as material shaping at room temperature and low weight loss during curing. The ceramization of the solidified ceramic precursors in an Ar atmosphere was studied using TGA and tube furnace pyrolysis. ALSZs exhibited comparatively high ceramic transformation yields (71-75% at 800 °C). The resulting pyrolytic ceramics maintained their original shape without deformation or foaming expansion. Polysilazanes containing acrylate groups can directly form casting bodies, showing a high static glass transition temperature (>380 °C) by thermomechanical analysis (TMA). FT-IR analyses revealed that multiple reactions are involved in the curing of ALSZ. The results in this paper showed that ALSZ might find prospective applications in material processing, such as additive manufacturing and ceramic-matrix composites.