Solvent free low-melt viscosity imide oligomers and thermosetting polyimide composites

Abstract

This invention relates to the composition and a solvent-free process for preparing novel imide oligomers and polymers specifically formulated with effective amounts of a dianhydride such as 2,3,3',4-biphenyltetra carboxylic dianydride (a-BPDA), at least one aromatic diamine and an endcapped of 4-phenylethynylphthalic anhydride (PEPA) or nadic anhydride to produce imide oligomers that possess a low-melt viscosity of 1–60 poise at 260–280° C. When the imide oligomer melt is cured at about 371° C. in a press or autoclave under 100–500 psi, the melt resulted in a thermoset polyimide having a glass transition temperature (T) equal to and above 310° C. A novel feature of this process is that the monomers; namely the dianhydrides, diamines and the endcaps, are melt processable to form imide oligomers at temperatures ranging between 232–280° C. (450–535° F.) without any solvent. These low-melt imide oligomers can be easily processed by resin transfer molding (RTM), vacuum-assisted resin transfer molding (VARTM) or the resin infusion process with fiber preforms e.g. carbon, glass or quartz preforms to produce polyimide matrix composites with 288–343° C. (550–650° F.) high temperature performance capability.