Exposing industry shortcuts to SDAT recommendations

As introduced on the FMVSS 212/208 Standards page the specifications are not clear in all respects and leave room for interpretation.

Sika’s Mission is to ensure customer safety. Because of this stance we have historically applied the most severe interpretation to the FMVSS 212/208 standards. However, there are some specific areas of the FMVSS 212/208 Standards that can be manipulated to achieve shorter SDAT recommendations that may not be completely accurate for all vehicles or climates.

Vehicle Selection
Vehicle selection plays an integral part of an adhesive’s ability to meet SDAT. Angle and size of the windshield, crumple zones and airbag impact against the windshield all play a critical role when evaluating direct glazing adhesives during a crash test. Most vehicles offered in the U.S. are equipped with full-size airbags. As these airbags deploy and make contact with the windshield, an incredible amount of force is transferred to the bond line, making it more difficult to pass the FMVSS 212/208 Standards. Conversely, many European vehicles come equipped with smaller airbags, which puts less stress on the windshield and thereby makes it much easier to meet FMVSS windshield retention requirements.

  1. US Car with full size airbags, using the windshild as backboard
  2. European Car with smaller airbags, using mainly the dashboard as backboard

Using Belted or Unbelted Crash Test Dummies

Over the years, Sika has performed multiple crash tests to assess the variability between using belted and unbelted dummies when determining Safe Drive Away Time recommendations.

The two crash test videos below clearly depict the differences between tests performed with belted dummies vs. tests performed with unbelted dummies. For these tests, Sika used the same vehicle make and model, the same adhesive, nearly identical climatic conditions and 30 minutes waiting time for the crash test with belted dummies and 45 minutes for the crash test with unbelted dummies.

Crash Test with unbelted Dummies

  • The passenger airbag and even the head of
    the dummy had full contact with the wind-
    shield.
  • The windshield was fully smashed by the
    impact and popped out

The crash test has failed

 

Crash Test with belted Dummies

  • The passenger airbags had little contact to the windshield
  • The windshield itself remained intact and was not damaged by the crash (sign of little force on the screen)

The crash test has passed

 

  • What Safe Drive Away Time recommendation would you give to that product?
  • Demand to understand how your adhesive supplier tested their products against the FMVSS 212/208 Standards and how they used this information to develop SDAT charts.

Selecting Cure Conditions
Sika’s automotive direct glazing adhesives are specifically formulated to ensure that the necessary strength is achieved in order to pass the most stringent parameters of FMVSS 212/208. All one-component windshield adhesives require ambient moisture to cure. Increased heat will also play an important role by speeding the reaction time.

So if high heat and humidity are required for the adhesive to cure, then it could logically be assumed that performing a crash test at 0°F (-15°C) would be the most severe condition as there is almost no ambient moisture.  However, this conclusion would be incorrect.  Aside from the adhesive curing, another important component to consider when determining SDAT is the viscosity of the adhesive during the crash test.  At static pressure, as a liquid is cooled down and individual molecules become more sedentary, the viscosity (a liquids resistance to flow) of the material increases. With increased viscosity comes increased cohesive strength, better energy absorption and ultimately shorter SDAT recommendations. Sika’s extensive evaluation of adhesive performance during a crash undeniably proves that crashing a vehicle at 0°F (-15°C) is much less demanding on the adhesive than crashing a vehicle at moderately higher temperatures and humidity.

Therefore, crash test results and SDAT recommendations can vary greatly depending on the climate.

Several years ago Sika invented the MOVE Technology, which allows an adhesive to achieve optimum performance as it relates to SDAT. Sika’s MOVE Technology is the integration of an energy absorbing resin to the product composition. As a result the required strength level to pass FMVSS 212/208 can be achieved over a large climate range. For specific products, this improved performance allows Sika to provide a single, across the temperature range, recommendation when referring to SDAT.