Synthesis And Porous Ceramic Of Si-acetylene High Temperature Resistant Polymer With Si-H Bonds

As a kind of important high temperature resistant polymer,silicone polymer has been widely used in ceramic precursors,resin matrix composites and high temperature resistant materials because of its excellent comprehensive properties,which favored by aerospace and emerging industries and other areas.Therefore,a polydihydrodiphenyl acetylene silane with containing Si-H was synthesized by organic lithium reaction,and the porous SiC ceramics were prepared by sacrificial template method.The main research contents are as follows:1.Poly(phenylacetylene silane)was synthesized by organic lithium reaction from diphenyl dichlorosilane,trichloroethylene,and n-Butyllithium,and then reacted with trifluoromethylene sulfonic acid and LiAlH4 to form polydihydrodiphenylacetylene silane(DPHES)resin with containing Si-H bonds.The structure of DPHES was characterized.2.The curing properties of cured DPHES were studied by DSC and FT-IR and other characterization methods.The results showed that the initial curing temperature,peak temperature and termination temperature were 250 ?,285 ? and 350 ?,respectively.On the basis of this,the curing conditions of the resin were determined,and the cured DPHES were prepared.Py-GC-MS and fluorescence analysis indicated that the structure of cured DPHES contained a large number of organic groups,such as benzene ring,olefin and aromatic fused ring,etc.The curing process was mainly composed of the following three reactions:(a)Cyclic trimer:ization and addition reaction between C-=C and C?C;(b)hydrosilyl addition reaction between Si-H and C?C.The thermal properties and thermal decomposition kinetics of cured DPHES were studied by TG The results showed that the Td5(temperature of 5%weight loss)of cured DPHES was 572 ? and the weight loss at 800 ? was only 13%in nitrogen atmosphere,and it had excellent heat resistance.The activation energy of thermal decomposition kinetics of cured DPHES by Fly-Wall-Ozawa method and Master Curves method was 131.31 kJ·-mol-1.The kinetic mechanism follows the principle of Mample method.3.The ceramic transition process of cured DPHES were studied.The result indicated that the ceramic product of DPHES mainly consisted of ?-SiC,containing a small amount of SiO2and graphite carbon,when the pyrolysis temperature was 1600 ?,the chemical composition of the ceramic product was SiC1.18O0.22,which indicated that the near chemical composition ratio of SiC ceramics was obtained.On this basis,porous SiC ceramics were prepared by sacrificial template method using DPHES as ceramic precursor and polyurethane foam as template.The density of F/DPHES was 0.29 g-cm3,the specific surface area was 532.79 cm·g-1,and the mean pore size was about 4 nm.This indicated that F/DPHES was a light mesoporous material with excellent properties.