Curing conditions of polyarylacetylene prepolymers to obtain thermally resistant materials

Prepolymers of polyarylacetylene (PAA) were synthesized from 1,4-diethynylbenzene using nickel catalyst (C20, C25, and C30) or by direct thermal polymerization (T48). Their curing behaviors were investigated in detail to determine the proper curing conditions that lead to high char yields in cured PAA resins. Dynamic and isothermal differential scanning calorimetry (DSC) measurements were employed to investigate the curing conditions of the prepolymers. Dynamic DSC study reveals that exothermic heat starts at about 120 degrees C, reaches to a maximum at 210 degrees C, and ends around 300 degrees C. Moreover, step isothermal DSC investigation (at 120,160, 200, 250, and 300 degrees C 1 h for each temperature) shows that the major curing occurs at 160 degrees C, 200 degrees C and 250 degrees C, with more than 85% of the acetylene groups reacted. Using this step-curing conditions, very high thermal resistance is realized on C30, with thermal decomposition temperature (at 10% weight loss) and char yield (at 800 degrees C) being 686 degrees C and 86%, respectively. Current results indicate that highly thermal resistant PAA resins are obtainable using step curing of PAA prepolymers synthesized by Ni-catalyzed reaction. (C) 2009 Elsevier Ltd. All rights reserved.