The Effect of Concentration of Epoxy Group in Epoxy Primer on the Adhesion Strength and Adhesion Durability of Polyethylene-Coated Steel Pipe

The adhesion strength (90°peel strength) and adhesion durability of polyethylene-coated steel pipe was investigated. The steel pipe had three layers of coatings structure : polyethylene, adhesive polyethylene, and amine cured epoxy primer. The adhesion strength and adhesion durability of polyethylene coating was dependent on the concentration of epoxy group in amine-cured epoxy primer. The polyethylene coating on steel with epoxy primer that contained higher concentration of epoxy group showed better adhesion strength and adhesion durability when equivalent or less amounts of amine-curing agent were added to the epoxy primer in the concentration range of epoxy group 2.8 to 3.8 mol kg-1. The curing agent was able to reduced up to 20% from the equivalent amounts without affecting the adhesion strength and adhesion durability. For the best adhesion performance, epoxy primer with high concentration of epoxy group and reduced amounts (up to 20%) of curing agent were preferable.