NEW HIGH-PERFORMANCE POLYESTER-IMIDE FOR ELECTROTECHNICAL USE. 2 MECHANISM AND STAGES OF THERMAL CURING OF ESTER-IMIDE OLIGOMERS

摘要

Ester-imide oligomers obtained by melt copolycondensation of tris(2-hydroxy-ethyl)isocianurate, ethylene glycol or neopentylglycol, diaminodiphenylmethane, trimellitic anhydride and dimethylterephthalate were cured by heating. The curing conditions, mechanism, and steps were established by TG. Superposed TG curves of uncured and cured compounds, normalized to unity, show that curing produces an increase of the heat resistance within the 250-350℃ temperature range. This is assigned to the increase of the chain length, supposition supported by the DSC curves that show higher glass transition temperatures for the cured compounds. IR, DTA, DSC and gas chromatography emphasise the reactions responsible for chain length increase and reaction steps. Attenuation of the absorption bands of hydroxyl and methylene or hydroxyl and methyl groups suggests that curing occurs by elimination of water and glycols. In this way, molecular weights increase about 40 times and oligomers transform into polymers.