Process for preparing a carbon fiber reinforced composite article which utilizes a polyimide matrix

Claim 1

A process for preparing a carbon fiber reinforced composite article wherein a polyimide constitutes the continuous phase which comprises: (1) providing a polyimide forming catalyst-monomer mixture comprising: (a) at least one ester of the formula: ##STR16## wherein R 3 is a tetravalent aryl radical, and R 4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen, with two R 4 groups being alkyl and two R 4 groups being hydrogen; (b) at least one amine of the formula: H.sub.2 N--R.sub.5 --NH.sub.2 wherein R 5 is a divalent aryl radical; and (c) at least one ester of the formula: ##STR17## wherein R 4 is selected from the group consisting of a lower alkyl radical having 1 to 4 carbon atoms, and hydrogen with one R 4 group being alkyl and one R 4 group being hydrogen, and R 6 is a divalent radical of the formula: ##STR18## wherein Y, which is the same or different, is selected from the group consisting of hydrogen, and methyl and X is an alkylidene radical of from 1 to 6 carbon atoms; wherein monomers (a), (b) and (c) are present in said mixture at a molar ratio of n:(n+x):y respectively, wherein n is an integer of from about 1 to about 20, x is an integer of from about 0.5 to about 1, and y is an integer of from about 1.5 to about 2, and from about 0.5 to about 15%, by weight, based on the weight of the monomer mixture, of at least one peroxide catalyst represented by the structural formula: ##STR19## wherein R, which is the same or different, is a lower alkyl group having from 1 to about 3 carbon atoms, and R 1 is an alkyl acetate group of the formula: ##STR20## wherein R 2 is an alkyl group having from 1 to about 4 carbon atoms; (2) impregnating at least one carbon fiber lamina with said polyimide forming catalyst-monomer mixture of step (1); (3) reacting said polyimide forming catalyst-monomer mixture in the presence of the at least one carbon fiber lamina at a temperature of from about 250° to about 350° F. for a period of from about 0.5 to about 3 hours and at a pressure of from about 2 to about 30 in.Hg to form a prepolymer; and (4) curing the prepolymer to form a carbon fiber reinforced composite article while employing a short cure procedure which comprises the steps of heating the prepolymer to a temperature of from about 375° to about 425° F. at a continuous or intermittent pressure of from about 175 to about 225 psi; raising the temperature of the prepolymer to a temperature of from about 450° to about 625° F. while under a continuous or intermittent pressure of from about 175 to about 225 psi; and maintaining the temperature of the prepolymer thereat for a period of about 10 to about 120 minutes.