Airbags and Windshields
The recent recall of airbags by some automakers has brought to the forefront the relationship between the airbag and windshield. This week I thought I would give you my opinion on this subject.
Some vehicles utilize the bonding and the strength of the windshield to help position the airbag after deployment. In other vehicles, the airbag deploys out the front of the dashboard so the windshield does not play as important a role. However, the majority of vehicles on the road today do rely on the windshield during airbag deployment in some way.
Fact: Safe Drive Away Time (SDAT) is defined as being met when the vehicle can pass Federal Motor Vehicle Safety Standards (FMVSS) 208 and 212. No. 208 is the passive restraint standard and 212 addresses windshield retention.
Question: How can urethane be strong enough to deliver SDAT when I know that it is not fully cured?
We know that urethane gains strength the longer it is exposed to humidity. The more humidity the urethane is exposed to, the faster it will cure. Modern urethanes have tensile strengths that exceed 700 psi, with some exceeding 1000 psi when fully cured. Tensile is the strength necessary to meet the FMVSS 208 & 212 requirements. In addition, there are other factors built into the chemistry of urethane adhesives that contribute to the initial strength of the adhesive.
The first generation of airbags exerted approximately 300 psi of force to the inside surface of the glass upon deployment. The new generation is significantly less than that. These facts put together give you the answer. Even with partial cure, the urethane is strong enough to withstand the pressures put upon it during airbag deployment. The only negative result will occur when you couple a poor application of materials with improper installation, which will cause the adhesives to perform improperly.
Adhesive companies and their chemists spend significant time and money testing their products. They know what sticks and what doesn’t. By following their instructions on safe drive away time to the letter, you will assure that your customers are safe.