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 (Tg) 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.
