Process for preparing thermoplastic composites

Claim 1

A process of preparing a thermoplastic-resin composite having a low volatile content from a plurality of thermoplastic-resin prepregs under a vacuum ranging up to about 32 inches of H g below atmospheric and at temperatures ranging up to about 800° F. which comprises: (a) heating at least two plies of the thermoplastic resin prepreg in a flexible inner chamber under a vacuum to temperatures above the melting point of the resin while maintaining a vacuum in the rigid outer chamber; the vacuum in said outer chamber ranging from about zero to 2 inches of H g more or less than the vacuum in said inner chamber; (b) holding the inner chamber under said vacuum and at said temperatures until substantially all the volatiles are removed from the composite without pinching-off the diffusion paths within the composites needed for removal of said volatiles; (c) lowering the vacuum in the outer chamber causing an increase of pressure on said flexible inner chamber while maintaining the inner chamber under said vacuum and at said temperatures for a period sufficient to consolidate the prepregs; and (d) subsequently lowering the temperature below the melting point of the resin in the prepreg and releasing the vacuum in the inner and outer chambers to atmospheric pressures to obtain a substantially void-free consolidated thermoplastic composite having a volatile content of less than about 1.0 percent by weight.