Gm Global Technolgoy Operations, Inc.

Harry A Mitchell

Hamid Ghavami Kia

Terrence Wathen

Mark A Buffa

Edward M Hagerman

Composite articles are prepared by a spray up operation. In a first step, a gel coat is applied onto a mold surface which has been optionally pretreated with a mold release coating. Next, a barrier coat is applied over the gel coat in the mold and thereafter a laminate formula is applied over the barrier coat. The laminate contains from 40-80% by weight paste and from 20-60% by weight reinforcing fibers. In a preferred embodiment, the paste comprises 90% or more by weight resin, up to 5% filler, and an initiator composition capable of initiating cure at a temperature of 50&#xb0; C. or lower. In a preferred embodiment, the multilayer composite has a thickness of about 15 mm or less, and is useful as an automobile body panel. The laminate preferably comprises a low shrink, low density glass fiber filled polyester resin. In a preferred embodiment, the paste of the laminate contains a dicyclopentadiene unsaturated polyester resin, polymeric hollow microspheres, and an initiator capable of initiating curing at room temperature or at temperature of 50&#xb0; C. or less.

Low shrink low density laminate formulation

A multilayer composite contains a gel coat layer, a laminate layer, and a barrier layer disposed between the gel coat and the laminate layer. The laminate contains from 40&#x2013;80% by weight paste and from 20&#x2013;60% by weight reinforcing fibers. The barrier coat also comprises a cured polyester resin, and contains reinforcing fibers shorter than those in the laminate layer. The barrier layer has sufficient flexibility to avoid cracking during demolding and handling. Preferably, the barrier layer exhibits an elongation at break of more than 1%, and more preferably about 2% or more. The resin of the barrier layer can contain up to about 25% by weight of the resin of an isophthalic acid based polyester resin. The composites can be made using an open tool molding process.

Barrier coat for open tool molding

A method is provided for compacting viscous polymeric molding compositions preparatory to compression molding to substantially improve the physical properties of articles molded therefrom. Suitable compositions include those filled with a geometric reinforcing particulate filler that are flowable and thermosettable when compression molded. The method comprises forming a slab of a said filler composition and thereafter reducing its thickness by passing it between spaced-apart pairs of compression means. The pair members of the means are spaced apart to ultimately substantially reduce its thickness. The method yields unexpected improvements in the tensile strength, isotropy and surface characteristics of articles compression molded from the compounds.

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Sterling Heights, MI, United States of America

Harry A Mitchell