Pyrolysis of Phenolic Resin in SiC

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New York State College of Ceramics at Alfred University. Kazuo Inamori School of Engineering.
When phenolic resin is pyrolized, carbon is left behind. Maximizing the carbon yield from this pyrolysis was the goal. Standard pyrolysis loses a sizeable amount of carbon in the form of volatile organic compounds (VOC’s) due to polymer chain scission. It is proposed that by selectively stripping hydrogen from the polymer, carbon yield can be increased. Pressureless sintering of silicon carbide (SiC) requires excess carbon for densification. Carbon can be introduced either by adding carbon or a carbonaceous polymer that will be pyrolized. The SiC production granules that were used contained phenolic resin. There are two purposes for the resin: first, when cured, the strength of the phenolic resin allows for green machining and second, providing excess carbon from pyrolysis. To test if hydrogen can be preferentially removed to increase carbon yield, the pyrolysis conditions were changed. Thermogravimetric analysis (TGA) experiments were conducted to identify the heating rate and peak temperature along with the pyrolysis behavior in different gas chemistries and dwell temperatures. From industry, it was understood that flow rate has an impact on pyrolysis. A statistical experimental design was created to test flow rate (0, 7.5 and 15 ml/sec), gas chemistry (2%, 5% and 10% O2, balance nitrogen) and dwell temperature (150°C, 200°C and 250°C). The pyrolized samples were sintered (below the optimal sintering temperature) to understand the effect that pyrolysis has on the sinterability on SiC. TGA demonstrates that a higher carbon yield is seen with lower dwell temperatures and increased oxygen levels. All samples fully densified at 2100°C. Flow rate was found to be statistically significant in increasing carbon yield from pyrolysis. The measured carbon yields were not greater than those obtained from the standard pyrolysis used in industry. However, the standard pyrolysis stops at 600°C and the TGA data suggests that the pyrolysis is not complete. The TGA data suggests that the hydrogen stripping hypothesis has merit.
Advisory committee members: Matthew Hall, Andrew Eklund. Dissertation completed in partial fulfillment of the requirements for the degree of Masters of Science in Ceramic Engineering at the Kazuo Inamori School of Engineering, New York State College of Ceramics at Alfred University