Preparation of epoxy hardeners from waste rigid polyurethane foam and their application

Aliphatic amines were used as decomposer to decompose waste rigid polyurethane and polyisocyanurate foams, and the obtained decomposed products were directly used as curing agent of epoxy resin. Effects of the decomposing condition including amine type, foam–decomposer ratio, and reaction temperature on the decomposition reaction and properties of the decomposed products were investigated. Using amines with low molecular weight could enhance decomposition reaction rate and total amine number and lessen viscosity of the obtained decomposed products. Viscosity of the decomposed products decreased with increase of reaction temperature, but increased with increment of foam–decomposer ratio. Shear strength of adhesives consisting of decomposed products and epoxy resin was measured, and their thermal properties were analyzed. The adhesives could be cured completely over 60°C and their shear strength enhances with adding coupling agent in the adhesive system. The adhesives have good thermal stability and show satisfactory shear strength with more than 15, 15, 7, and 3 MPa at 25, 60, 100, and 150°C, respectively. The results demonstrate that the obtained adhesive systems can be used as structural adhesive.