THERMOLYSIS OF ACETYLENE-TERMINATED SULFONE RESINS .3. MECHANISMS OF DEGRADATION

Mechanistic pathways are developed to explain the cure chemistry, oxid ation, and thermal degradation of resin based on acetylene terminated sulfone (ATS) precursors. The cure reaction is proposed as a copolymer ization of primary acetylenes with oxygen to form a defect ridden poly ene oligomer. Peroxide chain segments are thermally unstable and decom pose to augment the radical population and continue the chain reaction through re-initiation of the polymerization reaction. The oxidation r eaction is initiated by thermal decomposition of the polyene to produc e methylated phenyl ethers which are successively oxidized to the alde hyde, and the carboxylic acid which finally couple to form benzoate an d benzoic anhydride derivatives. The thermal degradation of ATS resin under programmed conditions has been shown to proceed through four rea ctions which produce volatiles. At low temperatures (process 1) we see a concerted decomposition of the resin backbone to produce sulfur dio xide, phenol, and other sulfone containing products. At higher tempera tures (process 2), the residue from process 1 decomposes through more random scissions to produce (for example) benzene, water, etc. Finally , the residue of the degradation condenses around polyene nuclei (proc esses 3 and 4) and expels heteroatoms to form a residue of glassy carb on.