Study on Thermoplastic Polymer Modified Novolac Type Epoxy Resin Derived Carbon/Carbon Composite

• Main Authors: Chih-Yuan Chen, 陳致源
• Other Authors: Chen-Chi M. Ma
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/58681941866263544402

碩士 === 國立清華大學 === 化學工程學系 === 89 === In this study, modified novolac type epoxy resin has been used as a new matrix precursor to fabricate C/C composites. The polydimethylsiloxane polyurethane synthesized was used as a modification agent. Novolac type epoxy has almost the same chemical structure as phenolic resin, however, it possesses the epoxied functional group that is easy to react with the modification agent. The modification system utilized is polydimethylsiloxane polyurethane(PDMS-PU) which protects the fiber surface and improves the thermal stability of matrix. PDMS-PU was synthesized in this study and it structure was confirmed by IR and NMR. Results show that modified epoxy with low content(<10phr) of PDMS-PU is miscible, the PDMS-PU can completely disperse in the epoxy matrix and decrease the glass transition temperature and crystallinity of novolac type epoxy. In the study of curing kinetics, it was found that the content of PDMS-PU will affect the collision factor, total heat of reaction and the active energy of reaction. In order to achieve the modification purpose, the first step is utilizing novolac type epoxy resin to derive carbon/carbon composite instead of using phenolic resin. Different post curing times and temperatures, and different carbonization heat treatment temperatures were applied to the novolac type epoxy resin. Results show that the matrix cured at a higher post-curing time and temperature exhibits a significantly weight loss on the post curing process and limits the weight loss on carbonization processing. In the modified composite system, results show that the flexural strength of composite after post curing process will be reduced when the PDMS-PU content increase because of the flexible molecular structure. In the carbonization process, PDMS-PU will protect the fiber surface to prevent the intense shrinkage deriving from thermal degradation consequently, increase the flexural strength of C/C composite from 94.2Mpa to 106.9MPa after carbonization process. Oxidation testing result shows that PDMS-PU containing carbon/carbon composites exhibit better oxidation resistance and lower oxidation rate than those derived from pure epoxy resins. Increasing the post-cure time and temperature will improve the mechanical properties after carbonization. In the carbonization process, the mechanical properties and density decrease rapidly after 400℃. When heat treatment temperature rises up to 800℃ the mechanical properties and density will maintain constant and then increasing slightly. The mechanical property of the carbon/carbon composite made by epoxy resin was better than that of phenolic resin, and the flexural of composite strength was increased from 63.9MPa to 94.2Mpa.