Epoxy Modification by Polyurethane and Its Effects on Abrasion and Adhesion Properties

In this research, epoxy modification was successfully performed by polyurethane and its effect on abrasion and adhesion properties have been investigated. The most important concern in the blending of these polymers was the formation of gels upon exposure of epoxy resin and isocyanate in polyurethane.

One solution to overcome this problem is to control the chemical activity of Isocyanate. Therefore to reduce the chemical activity of isocyanate and prevent gel formation due to the combination of epoxy and polyurethane, first polyurethane prepolymer containing 3.58 wt.% NCO was prepared by mixing poly tetra methylene glycol 2000 (PTMG 2000) and toluene di isocyanate (2,4-TDI); and then by adding 20 wt.% of it to the epoxy resin, the curing process was completed by using dimethyl thio-toluene di amine (DMTDA) as a common curing agent and also specific heat treatment.

Fourier transformation infrared spectroscopy results showed that the modification process has been successful by elimination of the peaks related to epoxide and isocyanate groups in the prepared sample in addition to the formation of a broad peak related to secondary hydroxyl group (C-O) due to the opening of epoxide rings. Pull off tests also confirmed increasing adhesion to carbon steel substrate as a result of secondary hydroxyl generation through this blending. Although, the Persoz hardness of modified epoxy decreased by 5%, but with a 17-fold reduction of elastic modulus (as per tensile test result), abrasion resistance improved 6 times according to abrasion test. Finally, joining of the cavities to each other is introduced as the abrasion mechanism by considering the field emission- scanning electron microscope images.