液体硅氮烷前驱体的制备、热固化与陶瓷化

Preparation, Thermal Cure and Ceramization of Liquid Silazane Oligomeric Resins

通过甲基氢二氯硅烷、甲基三氯硅烷和三甲基氯硅烷的共氨解,制备了液体硅氮烷低聚物（LSZ）,并通过六亚甲基二异氰酸酯（HDI）对LSZ进行加成扩链反应,预聚制备了不同黏度的液体聚硅氮烷（PSZ）.在预聚反应中,随着HDI用量的增加,PSZ产物黏度增大;HDI用量小于10％（质量分数）时,PSZ为长期稳定的液体状态;HDI含量大于10％时,PSZ在反应的48h内能保持液体状态,最终变为固态.随着HDI用量的增大,PSZ热固化时的转胺基反应呈现明显的2段;60-135℃区间的固化峰偏向低温,170-250℃区间的固化峰也更为明显;预聚扩链反应消除了LSZ热固化时挥发形成的吸热峰.随着HDI用量的增加,PSZ陶瓷产率显著提高（HDI用量0、5％和20％时,陶瓷产率分别为22.6％、43.2％和58.7％）.

Liquid silazane oligomers （LSZ） were prepared via co-ammonolysis of methyldichlolrosilane, methyltrichlorosilane andtrimethylchlorosilane, and liquid polysilazanes were subsequently synthesized via the prepolymerized chain extention of LSZ withhexamethylenediisocyanate （HDI） in nucleophilic addition reaction. In the prepolymerization of LSZ and HDI, the viscosity of PSZgradually increases with the increase of HDI amount, becoming a gel-like solid product. The PSZ is stable as a liquid or the PSZ willbecome a solid after it is as a liquid for 48 h when HDI amount is 〈 10%. The thermal cure exhibits two-stage exotherm when the HDIincreases in PSZ, i.e., one exothermic peak at 60？135 ℃ shifted to lower temperature and another exothermic peak at 170？250 ℃.Also, the chain extention prepolymerization eliminates the volatiles in the thermal cure. The ceramic yield of PSZ increases with theincrease of HDI dosage in PSZ formulation （i.e., the ceramic yield is 22.6 for LSZ, 43.2% for LSZ？5%HDI, and 58.7% for LSZ-HDI）.