THE EFFECT OF FORMULATED MOLECULAR-WEIGHT ON TEMPERATURE RESISTANCE AND MECHANICAL-PROPERTIES IN POLYIMIDE BASED COMPOSITES

This experimental study examines the role of formulated molecular weig ht between crosslink sites on the temperature resistance and mechanica l properties of composites based on a polyimide containing a diphenyl thioether unit (PTI). The composites are fabricated by in situ polymer ization of monomer reactants (PMR) using three monomeric ingredients: bis(3,4-dicarboxyphenyl) sulfide dianhydride (TDPA); 4,4'-methylene di aniline (MDA); and the monomethyl ester of norbornene anhydride (NE). By changing monomeric molar ratio, three formulations are prepared, in which formulated molecular weight between crosslink sites varies from 1487 to 3446 g mol(-1). Unidirectional composite laminates from each formulation and T300 carbon fibres are compression moulded and cut int o a series of test specimens. By measuring the glass transition temper ature (T-g), Mode I interlaminar fracture toughness (G(IC)) and other mechanical properties at room and elevated temperatures, the influence s of formulated molecular weight on the temperature resistance and mec hanical properties of PTI-based composites are investigated.