Patent ID: 6036900
Filing Date: 2000-03-14
Classification: B29C,B29K

Abstract:
A method for resin transfer molding a fiber-reinforced article from a thermosetting polyimide resin system consisting essentially of, in weight percent, about 30 to 40% MDA, about 40 to 50% BTDE, and about 20 to 30% NE, the method comprising the steps of:positioning a dry fiber preform in a mold cavity, the fiber preform having a complex architecture;diluting the thermosetting polyimide resin system with a solvent to reduce the viscosity of the thermosetting polyimide resin system and thereby form a diluted thermosetting polyimide resin system, the diluted thermosetting polyimide resin system being in an uncured state and containing unreacted MDA;injecting the diluted thermosetting polyamide resin system into the mold cavity under a pressure of not greater than one atmosphere, such that the diluted thermosetting polyimide resin system permeates and wets the fiber preform without damaging the fiber preform;evaporating and removing at least a portion of the solvent from the diluted thermosetting polyimide resin system to yield an undiluted thermosetting polyimide resin system;heating the mold cavity and imidizing the undiluted thermosetting polyimide resin system to form an imidized thermosetting polyimide resin system and applying a vacuum to the mold cavity to remove condensation byproducts produced during the imidizing step; and thencuring the imidized thermosetting polyimide resin system to yield a cured thermosetting polyimide resin system by heating to a temperature sufficient to remelt the imidized thermosetting polyimide resin system, and then applying pressure and additional heat to cause the remelted imidized thermosetting polyimide resin system to cross-link and thereby form the fiber reinforced article.