Preparation of rigid polyurethane foam using mixed metal complexes and ethylenediamine as catalysts

Abstract

In this research, the catalysts for rigid polyurethane foams were developed by using mixed metal complexes [M1(OAc)2(en)2:M2(OAc)2(en)2] synthesized from metal acetates [M(OAc)2, where M = Ca, Ba, Mn, Co, Ni, Cu and Zn] and ethylenediamine (en). The mixed metal complexes were characterized by infrared spectroscopy, UV-visible spectroscopy, and elemental analysis. Rigid polyurethane foams were prepared from the reaction between polymeric 4,4 methane diphenyl diisocyanate and polyether polyol at the NCO indexes of 100 and 150. Mixed metal complexes were used as catalysts and their catalytic activities were compared with that of N,N-dimethylcyclohexylamine (DMCHA), which is a commercial catalyst, by investigation of reaction times, physical and mechanical properties of rigid polyurethane foams. ATR-IR spectroscopy was used to determine isocyanate (NCO) conversion of polyurethane foams. Among all mixed metal complexes, Cu(OAc)2(en)2:Zn(OAc)2(en)2 showed the best catalytic activity and was comparable to that of DMCHA. Density and the compressive strength of the foam prepared by Cu(OAc)2(en)2:Zn(OAc)2(en)2 at NCO index of 150 were 44.1 kg/m3 and 258.5 kPa, respectively.