Identification of Butyl, Silicone and Polyurethane

When installing a replacement windshield, it is essential that the residual material on the pinchweld is polyurethane.

SikaTack® and Sikaflex® polyurethane direct glazing adhesives develop strong adhesion to multiple brands of polyurethanes and to some recent MS Polymer direct glazing adhesives.However, if the residual material on the pinchweld is butyl or silicone it must be completely removed, as SikaTack® or Sikaflex® adhesives do not adhere to butyls or silicones.  

• Press very firmly with the fingernail into the existing material.
  
• If it is a polyurethane or a direct glazing MS Polymer, it should barely be possible to make an indentation into the material.
  
• If it is a butyl or silicone, it should be possible to press halfway or even all the way through to the pinchweld.
  
• If it is a butyl, it should retain an indentation and not regain its original shape.

• Cut out a long piece of the material and pull it apart.
  
• If it is polyurethane, a great amount of force is needed to pull apart the material and break it.
  
• If it is a silicone, it will stretch a great distance without exerting too much force. It will also stretch back and forth rather easily.
  
• If it is a butyl, it should pull apart very easily.

• Completely remove the old adhesive and follow the procedures as indicated in the Complete Removal Method Section.