6.8: Elastic Bonding in Practice

6.8.1 Crash-Resistant Direct Glazing Adhesives

One-component polyurethane adhesives for direct glazing are widely used in the automotive industry. Since about 5% of car's windshields every year are damaged, efficient and reliable replacement methods are of increasing importance. To achieve short safe-drive-away time after replacement of windshields, the adhesive must meet extremely strict requirements.

The definition of Safe- Drive- Away Time (SDAT) is the time required for curing of the windshield adhesive to achieve full passenger retention in the case of a defined crash (Fig. 69).

With short safe-drive-away times, costs are reduced and customers can put the car in service faster. To achieve windshield retention in the event of a frontal barrier impact, partly cured adhesives must have high initial tensile strength and fracture energy. Additionally, they must also fulfill the original equipment specifications such as good corrosion resistance, antenna suitability and mechanical performance.

Before conducting the expensive sledge test and full crash test with a car, extensive laboratory experiments are generally carried out at high speeds on various lab test machines, including small falling weight towers, impact pendulum and high- speed tensile testers.