Study On The Thermal Stable Insulating Varnishes

Polyarylethers are well known high performance thermoplastics which generally exhibit high thermal and excellent impact resistance. They can also be used in insulating varnish and adhesive applications. But as varnishes, they have poor adhesion. In this dissertation, the copolymer PPESK was modified by adding active groups, such as hydroxy, amino and epoxy groups, to terminus or sides of macromolecules. The insulating varnishes were prepared by crosslinking PPESKs functionalized with other resins. The adhesion of varnishes was improved remarkably.l.Epoxy-terminated poly(aryl ether sulfone ketone) (E-PPESK) was synthesized by the reaction of epichlorohydrin with PPESK oligomer prepared by nucleophilic substitution of 4,4'-dichloro-benzosulfone and 4,4'-difluorobenzophenone with 4-(4-hydroxypheny)-2,3-phthalazin-l-one. 2.Amino-terminated poly(aryl ether sulfone ketone) was prepared by two steps. (1) PPESK oligomer reacted with /?-Chloronitrobenzene in the presence of potassium carbonate. (2)The copolymer made in former step was reduced by hydrazine in the presence of Pd-C. S.Hydroxylized PPESK (PPESK-OH) was prepared by reaction ofNatriumborhydrid, a high choice reduction agent, with PPESK. 4.The crosslinking reactions took place when modified PPESKs containing active group were cured with low molecular weight polyamide, polyurethane or epoxy resin. Insulating varnishes with excellent thermal, mechanical and electrical properties were made by this method.