Preparation And Thermal Property Studies Of The Zirconium Hybrid Silicone Resin

Polysiloxanes have outstanding heat-resistant property due to the high bonding energy of Si-O chemical bond. Therefore silicone resin has good thermal stability. This article is based on normal silicone resin, modifying it in order to achieve better heat-resistant property with the method of chemical doping high melting point metal atom Zr in the main chain.Property of silicone resin ultimately depends on its structure, and the structure is mainly determined by the hydrolysis and condensation process of different silane monomer. So the study of hydrolysis and condensation process is very important. This article adopts the method of quantitative analysis of Near Infrared spectroscopy via establishing PLS model. Kinetic study of hydrolysis process of methyltrimethoxysilane, methyl triethoxysilane, phenyltrimethoxy-silane and triethoxyphenylsilane under different pH value and temperature was investigated. According to the silane hydrolysis influencing factors, alkoxy silane and zirconium acid ester were selected as the experimental reagents to prepare Zirconium hybrid silicone resin(ZrSR). The key factor to control the hydrosysis rate of the cohydrosysis system of alkoxylsilane and Zr(OBu)4 is to use the appropriate hydrolysis acidity to make sure each component hydrolyze with similar rate, which would influence the uniformity of the resin structure. The experimental results illustrated that the best hydrolysis pH is 3.Silicone resin with different content of phenyl group and zirconium was prepared in this experiment. The samples were characterized by method of IR, XPS, TGA, SEM, etc. Through the apparent of cured resin and its SEM morphology, it can be found that the texture of hybrid resin is homogeneous. XPS results demonstrate that the actual Zr/Si mole ratio accords with the theory. IR results show that the absorption of Si-O-Zr and Zr-O-Zr existed at the same time. The above analysis can prove that ZrSR synthesized successfully. The pattern of structure cleavage in hybrid silicone resin was obtained by rising-temperature Infrared Spectroscopy combined with TG Analysis. There are three phases in mass loss process of silicone resin:First, hydroxyl condensation and removal of micromolecule range from 200-400℃; Second, cleavage of pendant group and the backbone range from 400-650℃; Third, removal of free hydroxyl group range from 650-800℃. Relation between structure and heat-resistant property of silicone resin was studied. The mass loss rate reduced and the residue rate increased with the increasing of Zr content. The char yield increased with the increasing of phenyl group content and the best proportion concerning heat-resistant property is 15%. By comparing the same structure of ZrSR and normal silicon resin can be found that the introduction of Zr atom, improves the heat resistance of silicone resin.Especially with the introduction of phenyl group, resin char yield rate increase greatly. It is a great advantage for ablation material. So this article also studies the sintering performance of the hybrid zirconium silicon resin and influence on the crosslink density after joining into silicone rubber based material. By comparing the SEM morphology after high temperature pyrolysis of normal silicon resin and ZrSR, it can be found, ZrSR internal structure still maintain uniform and compact. EDS results found that, zirconium content on surface is greater than the internal after pyrolysis in high temperature, which suggesting that surface element enrichment protect the internal structure. So its internal cleavage degree is lower than normal silicone resin. XRD results show that the Zr atom bonding in the main chain gradually become zirconia crystal phase at high temperature at about 1000 ℃. Under the same conditions, the normal silicon resin do not generate SiC crystal phase. So ZrSR has good application prospect of being filler blended in ablation material. After joining the silicone resin into silicone rubber based material, through the curing time analysis and the crosslinking density analysis, it can be found that the addition of liquid resin into the silicone rubber will bring bad impact on vulcanization process and crosslink density, it will reduce the ablation property of silicone rubber. Therefore silicone resin containing lots of hydroxyl is not suitable for directly joining into silicone rubber based ablation material. Then silazane compound can be used for end-capping regent to modify silicone resin.