Phenolic resin silica hybrid

TGA curves of phenolic resin/silica hybrid eeramer with various TEOS contents. 

J. M. Lin, C. C. M. Ma and W. C. Chang, Carbon/carbon composites derived from phenolic resin/silica hybrid creamers. Part I. Oxidation resistance and morphological properties , J. Mater. Sci., 36, 2001, 17, 4259. 

Chiang and co-workers [50] studied the flame retardance of phenolic resin-silica nanocomposites. The char yields of the polymer were observed to increase when the tetraethoxysilane content of the polymer was increased. LOI and UL-94 [13] tests revealed that the hybrid possessed excellent flame resistance. 

The sol-gel process has been examined as a cost-effective alternate for expensive and somewhat complicated polycarbosilane route, and to reduce the carbothermal reaction temperature. Tanaka and Karachi used the silica-organic resin hybrid, which was made by the toluenesulfonic acid-catalyzed hydrolysis ofTEOS in the presence of proper amount of phenolic resin, as the precursor for SiC powders (Tanaka, 1988). They obtained finely divided and highly sinterable /S-SiC powders almost free from Si02 and excess carbon. The two-step hydrolysis of TEOS/novolac resin mixture (catalyzed by oxalic acid in the first step and hexamethyltetramine in the second step) provided gels, which also transformed to nearly pure greenish 6-SiC powders (O 0.5 wt%, N 0.4 wt%) (Li, 2000). 

Such Si02-phenolic resin hybrids have been found to be easily formed to fibers if the hydrolysis condihons (the amount of water and/or catalyst) were properly adjusted (Hasegawa, 1995), and spun fibers with C/Si ratios of 2.6-4.3 were converted to SiC fibers containing excess free carbon only by 2 wt% and no silica at 1500°C in the inert... 

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