Abstract
Abstract In this work, octamercapto polyhedral oligomeric silsesquioxane (POSS-8SH) and octaphenol polyhedral oligomeric silsesquioxane (POSS-8Phenol) were successfully synthetized. POSS-8Phenol was added into the synthesis process of liquid thermoset phenolic resin (PR) to obtain POSS-modified phenolic resin (POSS-PR). Chemical structures of POSS-8SH, POSS-8Phenol, and POSS-PR were confirmed by FTIR and 1H-NMR. TG and DTG analysis under different atmosphere showed that char yield of POSS-PR at 1,000°C increased from 58.6% to 65.2% in N2, which in air increased from 2.3% to 26.9% at 700°C. The maximum pyrolysis temperature in air increased from 543°C to 680°C, which meant better anti-oxidation properties. XRD results confirmed both POSS-8Phenol and POSS-PR-generated crystalline SiO2 in air, which could explain the improvement of anti-oxidation properties. SEM showed that the POSS-PR had phase separation during curing process. Finally, carbon fiber fabric-reinforced POSS-PR (C-POSS-PR) was prepared to verify the anti-oxidation properties of POSS-PR.
Highlights
As an indispensable member of the polymer family, phenolic resin (PR) has many excellent properties, such as thermal stability, Many studies reported that silicone was an effective ingredient to improve the antioxidant properties of PR
Li et al [8] synthesized silicone-modified PR through the esterification reaction between methyltrimethoxysilane and novolac resin; high-temperature oxidation experiments showed that the siloxane improved oxidation resistance of the phenolic resin; the improvement of oxidation resistance was related to the formation of SiO2 at high temperature in air
In order to improve the anti-oxidation properties of phenolic resins, Polyhedral oligomeric silsesquioxane (POSS)-modified phenolic resins (POSS-PR) were prepared, in which POSS was efficiently prepared by siloxane condensation reaction and Michael addition reaction
Summary
As an indispensable member of the polymer family, PR has many excellent properties, such as thermal stability,. Li et al [8] synthesized silicone-modified PR through the esterification reaction between methyltrimethoxysilane and novolac resin; high-temperature oxidation experiments showed that the siloxane improved oxidation resistance of the phenolic resin; the improvement of oxidation resistance was related to the formation of SiO2 at high temperature in air. That research showed that phenolic resin with silicone coatings had satisfactory anti-overheating property and ablation resistance and was the first choice for ablation-resistant materials. Yin et al [11] mixed novolac resin, methyltrimethoxysilane, and the curing agent, the porogen, to prepare a phenolic/silicone. Polyhedral oligomeric silsesquioxane (POSS)-modified phenolic resin 317 composite aerogel. Tests showed that the silicone resulted in a layered micro-mesoporous structure and higher thermal stability than the original PR aerogel. The anti-oxidation properties of POSS-PR were further confirmed by comparing the flexural strength of carbon fiber-reinforced POSS-PR after high-temperature oxidation test
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