| abstract |
Safety glass windshields consisting essentially of polyurethane sheets laminated between moisture impervious sheets, such as glass, tend to separate. This separation has been discovered to be related to absorption of moisture in the polyurethane sheets along the exposed portion over an increasingly wider margin extending inward from the exposed surface during the time that the laminated glass-polyurethane window has its peripheral portion exposed until such time that its marginal portion is protected from exposure to atmospheric moisture when the windshield is installed with its marginal portion in a moisture impervious frame when assembled within an automobile or other vehicle. Bilayer windshields consisting essentially of a single glass sheet laminated to a polyurethane sheet also tend to delaminate on exposure to moisture. The present invention provides an adhesion promoting composition, such as a coupling agent, to a selected portion of the interface between glass and polyurethane to prevent separation of the windshield components. Care is taken to limit the proportion of the area of the interface treated with the adhesion promoting compositioin to control the overall adhesion of polyurethane to glass to a range in which the laminated windshield has an acceptable resistance to penetration, an acceptable lacerative injury rating and an acceptable Severity Index rating. |