Gencorp, Inc.

H William Cocain

Earl G Melby

Gerd M Lenke

Chia L Wang

James F Beecher

A two component type polyurethane adhesive is provided for fiberglass reinforced plastics which requires no cleaning, preparation or treatment of the surface, and the like. The curative component is a nitrogen-free liquid polyether or polyester in an amount such that in association with a urethane prepolymer component containing free NCO groups, the ratio of the free NCO groups in the prepolymer component to the OH groups in said curative component is at least 1.2 and desirably at least 1.35. Such high NCO/OH ratios have unexpectedly been found to provide good adhesion and especially good humidity adhesion and peel strength adhesion to fiberglass reinforced plastics or metal surfaces which are free from any surface treatment.

Polyurethane adhesive for a surface treatment-free fiber reinforced plastic

A one-part, solvent free in-mold coating composition exhibiting good hardness, good crack resistance, and good adhesion to fiber reinforced plastic substrates includes a blend of a urethane polyacrylate compound having three or more (meth)acrylate groups, a urethane diacrylate or urethane divinyl compound, one or more adhesion promoters, and one or more ethylenically unsaturated copolymerizable monomers.

In-mold coating composition

A one-package primerless structural adhesive is disclosed that is particularly well suited for adhering one or more substrates of fiber-reinforced plastics. This adhesive uses dicyandiamide, its substituted derivatives, or melamine as the principal curative. A polyisocyanate prepolymer is made from various polyols reacted with polyisocyanates. In the absence of moisture, the curative and polyisocyanate can coexist in a single package without reacting for periods of time in excess of four months. Upon heating the adhesive to 150.degree. C., it cures in about five minutes or less, forming an initial structural bond that after heat aging is often stronger than the cohesive strength of the fiber reinforced substrate.

One-package structural adhesive

A two-component polyurethane composition has good shelf stability and the adhesive made by curing the same has good high temperature stability and no adhesion loss after high temperture bake. The base or prepolymer component containing a primary hydroxyl intermediate also has a sufficiently large excess of free isocyanate so that the ratio of free NCO groups in the prepolymer component to OH curative groups plus any amine groups in the curative component is generally from about 1.2 to about 2.0. The curative component contains a trimerization catalyst so that upon cure, isocyanurate units are produced. The system also contains molecular sieves, as well as phosphorous-type adhesion promoters.

Two-component primerless urethane-isocyanurate adhesive compositions

Cleaning of thermoset FRP part surfaces to be bonded together is accomplished by the application of low intensity, i.e., 0.05 to 10 watts per cm.sup.2, short wavelength ultraviolet radiation in the range of 170 to 300 nm, for a period of time of usually less than 10 seconds which results in removing an effective amount of material, e.g., from about 1 to about 200 angstroms. The cleaning increases the adhesive potential of FRPs to polyurethane adhesives. Furthermore, FRP polymer surfaces treated by this process retain more adhesive strength after aging at elevated temperature in the presence of moisture than untreated surfaces or surfaces washed with isocyanate in MeCl.sub.2. Epoxy adhesives, also, can be used.

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Cuyahoga Falls, OH, United States of America

H William Cocain