THERMAL DEGRADATION STUDY OF SILOXANE-DGEBA EPOXY COPOLYMERS

Siloxane-modified DGEBA epoxy (ESDG) copolymers were prepared from Epikote 1001 and siloxane oligomers. Thermal stability studied by TGA of these ESDG copolymers indicates that thermal degradation is being effected by either structure or content of the siloxane moiety in the copolymers. The study reveals that siloxane-modified epoxy copolymer with phenyl-enriched siloxane oligomer (ESDG-7430) provides higher thermal stability than dimethyl siloxane modified copolymer (ESDG-8430). Delaying thermal degradation by the siloxane segment of ESDG copolymers is observed and the increase in thermal stability of copolymer is also observed consistently, with the increase of the siloxane content. These results indicate that the cause of the delaying degradation may be due to the siloxane segment being stable at the epoxy degradation temperature and the heat irradiated on the copolymer being absorbed by the siloxane segment which may dissipate that portion of thermal energy efficiently through its flexible siloxane structure. The delaying degradation behaviour is also confirmed by a direct pyrolysis/mass spectrometry (DP/MS) study, by the observation of the formation and contents (TIC and SIC) of the thermal degradative volatiles (TDVs). Nonflammability of ESDG copolymers as indicated by the LOI values is increased consistently with the increase in siloxane content in the copolymers. IR analysis and SEM/EDX observations on the char residue are also carried out.