Synthesis And Properties Of Polyvinylsilazane And Silicon-Containing Arylacetylene Hybrid Resins

Silicon-containing arylacetylene resin (PSA-V) possesses high temperature resistance and functional performance and which has considerable potential application in the fields of aerospace. It is intrest in modification of PSA to meet the demand for modern technology. Polysilazane is an attractive ceramic precursor and derives ceramics with excellent oxidation resistance at elevated temperatures. In this dissertation, PSA-V and polysilazane hybrid thermosets were devloped to improve the thermo-oxidative stability of PSA-V resin.Firstly, a serial of methylvinylcyclosliazane (MVSZ) and branched methylvinylcycloslia-zanes (MVSZ-T) were synthesized by ammonolysis reaction of chlorosilanes, and their structure was characterized by FT-IR, NMR, GC-MS, GPC, etc. The cure behavior of MVSZ and MVSZ-T was investigated by DSC, the results showed that, the weight loss of methylvinylcyclosliazane during cure process was63.0%under250℃, attributed to the escape of the cyclosliazanes, and catalyst aided crosslinking (DCP) under lower temperature was necessary to obtain cured polymers. But branched methylvinylcyclosliazanes could be cured by thermal polymerization.Secondly, the thermal ability of the cured polyvinylsilazanes (MVSZ, MVSZ-T) were determined by using TGA. Pyrolysis and ceramization of the cured MVSZ and MVSZ-T were investigated in tube furnace, and the structures of the derived ceramics were characterized by FT-IR, EDS, SEM, XRD, respectively. The results show that, with the branching degree of polyvinylsilazanes increased, the char yield increased and the β-Si3N4formed in lower tempratures.Finally, the PAS-V/MVSZ-T hybrid resins were prepared in different weight ratios and their effect on properties was researched. The curing behavior of PSA-V/MVSZ-T hybrid resins was investigated by using DSC and FTIR, and the thermal stability of the cured hybrid resins was determined by TGA in N2and air. The morphology and structures of pyrolysis residues of cured hybrid resins were examined by SEM and EDS. As the content of MVSZ-T increased, the thermal stability of the cured hybrid resins decreased slightly, but the oxidation resistance increased obviously. The antioxidant mechanism of PSA-V/MVSZ-T hybrid resins was suggested to the formation of ceramic layer on the surface of PSA-V/MVSZ-T hybrid resins after oxidation.