Closed cell backer rod is a round, flexible, closed cell polyethylene foam with an exterior "skin" used as a backing and thickness control device for elastomeric and other cold-applied sealants.
Backer Rod is an integral component of sealant joints, it provides three main functions that allow the sealant joint to perform.
*Acts as a bond breaker, preventing what is commonly referred to as three sided adhesion.
*The backer rod supports tooling. the sealant is pushed to the bond line with a spatula, ensuring wet-out of the sealant to the substrate.
*Promotes an hour glass shape, this maximizes the bond area but keeps the depth of sealant consistent in the middle allowing for movement.