Abstract
The objective of this study is to improve the toughness and the thermo-oxidative resistance of the cured Novolac type phenolic resin modified with polysiloxane. In order to improve the miscibility between Novolac type phenolic resin and polysiloxane, poly-(dimethylsiloxane adipamide) ( PDMSA ) were synthsized. By the addition of amide group in the main chain, strong intermolecular hydrogen bonding interaction was formed, consequently, the miscibility between Novolac type phenolic resin and polysiloxane was improved. The subjects of this study include the synthesis of PDMSA, miscibility between Novolac type phenolic resin, the improvement of toughness of PDMSA modified Novolac type phenolic resin and the improvement of thermo-oxidative resistance and flame resistance properties.From the experimental results, the predicted structure can be synthesized by reacting 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyl-disiloxane with adipic acid to form amide (nylon) salt, then was polymerized by melting reaction at 160 oC. By the investigations of IR, H1-NMR and C13-NNR, the molecular structure can be identified.Differential scanning calorymetric (DSC) and Infrared spectroscopic results show that there are strong intermolecular hydrogen bonding interactions existed between Novolac type phenolic resin and PDMSA. In the low PDMSA content regions, Kwei equation is feasible to the experimental Tg data; however, in the region between 30 wt.%~70 wt.% of PDMSA contents, the experimental Tg data closed to the prediction by Gordon-Taylor and Fox equations. furthermore, DSC results show great miscibility between Novolac type phenolic resin and PDMSA.TGA results of uncured Novolac/PDMSA blends show that PDMSA improves the thermo-resistance property of Novolac type phenolic resin at low temperature region, while Novolac type phenolic resin improved thermo-resistance property of PDMSA at high temperature region.Novolac type phenolic resin blended with PDMSA was cured by DGEBA type epoxy resin and using DBU as promotor The mechanical properties (include flexural strength, flexural modulus and Notched Izad impact strength) of Novolac type phenolic resin modified by PDMSA show great improvement. The flexural strength of cured resin specimen contains 5 phr PDMSA is 66% higher than that of neat phenolic resin. Flexural modulus of cured resin specimen contains 5 phr PDMSA is 3.6 times that of neat phenolic resin. Notched Izod impact strength of cured resin specimen contains 5 phr PDMSA is 37% higher than that of neat phenolic resin.TGA results of PDMSA modified Novolac penolic resin cured specimen in air show two step degradation. The addition of aliphatic chain of PDMSA to phenolic resin will decrease the first step degradation temperature of the cured resin specimens; however the siloxane chain will increase the second step degradation temperature.The flame resistance of the PDMSA modified novolac type phenolic resin cured specimens of UL-94 shows V-1 and its L.O.I is 35, which exhibit good flame resistance properties.