STRUCTURE-PROPERTY RELATIONS OF SILOXANE MODIFIED POLYIMIDE COMPOSITES

摘要

Imide oligomers were formulated using siloxane modified diamines with various concentrations of siloxane segments and phenyl/methyl ratios. 4-phenylethynyl phthalic anhydride was used as the end-cap and 6FDA as the backbone. The effects of diamine chemistry and siloxane concentration on aging durability and mechanical properties of modified polyimide composites were characterized. The location of phenyl substitution and concentration of molar substitution in modified diamines are critical for thermo-oxidative stability. The flexural property test and short-beam strength test of the aged (400°C, 100 hours) and un-aged siloxane modified polyimide composites show that the mechanical properties of modified composites are maintained or improved at siloxane concentrations of 10% to 35%. The extremely low melt viscosities observed for these oligomers make them excellent candidates for resin transfer molding (RTM).