Epoxy-lignin polyblends. Part II. Adhesive behavior and weathering

Abstract

A bisphenol-A based epoxy polymer adhesive was modified by polyblending with Kraft lignin. Lignin, with amounts between 10 and 20% by weight, improved the adhesive tensile strength of the epoxy polymer system. However, polyblending with 5-20% lignin had little effect on the adhesive shear strength (by tension loading) or the weatherability of the epoxy system. A significant improvement of the adhesive strength in shear of both the epoxy systems and the epoxy-lignin polyblends was produced after a post-curing process (4 h at 75°C). The temperature dependence of the polyblends' adhesive joint strength is typical of epoxy polymer adhesives.