Phenylethynyl-terminated Imide Oligomers Modified by Reactive Diluent for Resin Transfer Molding Application

To meet the processing requirements of resin transfer moulding (RTM) technology, reactive diluent containing m-phenylene moiety was synthesized to physically mixed with phenylethynyl terminated cooligoimides with well-designed molecular weights of 1500-2500 g/mol derived from 4,4 '-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,4 '-oxydianiline (3,4 '-ODA) and m-phenylenediamine (m-PDA). This blend shows low minimum melting viscosity (<1 Pa center dot s) and enlarged processing temperature window (260-361 degrees C). FPI-R-1 stays below 1 Pa center dot s for 2 h at 270 degrees C. The relationship between the molecular weight of the blend and its melting stability was first explored. Blending oligoimides with lower molecular weights exhibit better melting stability. Upon curing at 380 degrees C for 2 h, the thermosetting polyimide resin demonstrates superior heat resistance (T-g=420-426 degrees C).