Development of a Novel Epoxy Resin Having Cardo Structure

摘要

A novel epoxy resin (E-NP-BPDA) having the cardo structure derived from the phthalein dye was prepared from 3,4'-biphthalic anhydride (a-BPDA). a-BPDA was reacted with phenol in methanesulfonic acid, affording a cardo structure. Fixation of the cardo structure was achieved by reaction with methylamine in which cyclic ester was converted to cyclic amide. Further reaction with epichlorohydrin gave E-NP-BPDA. Thermal analysis revealed that E-NP-BPDA has both high thermal stability (Td5 = 301 ℃) and a low softening point (Tsp= 109 ℃) probably due to the low symmetry and the cardo structure. Curing E-NP-BPDA with slightly excess phenol novolac in the presence of tetraphenylphosphonium tetraphenylborate (TPP-MK) by heating up to 200 ℃ afforded a dark brown thermoset with almost no epoxy groups indicated by IR spectra. The glass transition temperature of the thermoset evaluated by DMA reached 192 ℃ and the value was higher than that of the conventional phenol-novolac-cured bisphenol-A-type epoxy resin.