Patent ID: 6017484
Filing Date: 2000-01-25
Classification: B29C

Abstract:
A process of making a substantially void-free and wrinkle-free consolidated thermoplastic-resin composite having a low void content from a plurality of prepregs impregnated with a thermoplastic resin placed on a flat or contour shaped base or mold contained in a flexible inner chamber having an absolute pressure, said inner chamber surrounded by an outer chamber having an absolute pressure, the process comprising the steps of:(a) reducing the absolute pressure in the flexible inner chamber and the absolute pressure in the outer chamber in increments in alternating unison to about 2 mm Hg while maintaining essentially equal pressures in both the flexible inner chamber and the outer chamber; then(b) heating the plurality of prepregs to a first temperature sufficient to lower the viscosity of the thermoplastic resin; then(c) increasing the absolute pressure in the outer chamber by about 20 mm Hg to 50 mm Hg; then(d) maintaining the absolute pressure in the flexible inner chamber at said about 2 mm Hg and the plurality of prepregs at said first temperature until removal of substantially all gases, water vapor, and volatiles from the plurality of prepregs; then(e) heating said plurality of prepregs to temperatures above the melting point of the thermoplastic resin while maintaining the absolute pressure in the inner chamber at said about 2 mm Hg and said absolute pressure in said outer chamber at said about 20 mm Hg to 50 mm Hg; then(f) increasing the absolute pressure in said outer chamber to at least atmospheric pressure at a controlled rate causing an increase of pressure on said flexible inner chamber thereby causing an increased pressure on the plurality of prepregs by the flexible inner chamber while maintaining said absolute pressure of said inner chamber at said about 2 mm Hg and at said temperatures above the melting point of the thermoplastic resin for a time sufficient to consolidate the plurality of prepregs together due to the increased pressure of the flexible inner chamber on the plurality of prepregs, and then(g) lowering the temperature of said plurality of prepregs to ambient temperature and venting said flexible inner chamber and said outer chamber to atmospheric pressure to obtain said substantially void-free and wrinkle-fee consolidated thermoplastic-resin composite.