Preparation of rigid polyurethane foams using mixed metal complexes and pentaethylenehexamine as catalysts

Abstract

The development of catalysts for rigid polyurethane (RPUR) foam is the main objective of this research. The catalysts employed were metal-amine complexes [M1(pentaen)] (M1= Cu, Zn, Co, Ni and Mn) and mixed metal-amine complexes [M1(pentaen):M2(pentaen)] (M1= Cu; M2= Zn, Co, Ni and Mn), which were prepared from metal acetates and pentaethylenehexamine (pentaen). FTIR, UV-vis spectroscopy and elemental analysis were used to characterize the catalysts. The metal complexes were used as the catalysts in the preparation of RPUR foams. The reaction times, physical and mechanical properties of the prepared foams were compared with that prepared using commercial catalyst, N,N-dimethylcyclohexylamine (DMCHA). ATR-IR technique was used to determine polyisocyanurate:polyurethane (PIR:PUR) ratio and isocyanate (NCO) conversion in the RPUR foam. RPUR foams catalyzed by Cu(pentaen):Zn(pentaen) had a similar catalytic activity when compared with foams catalyzed by commercial catalyst (DMCHA). Furthermore, the compressive strengths of RPUR foams catalyzed by Cu(pentaen):Zn(pentaen) were better than that catalyzed by DMCHA. The compressive strength of RPUR foam catalyzed by Cu(pentaen):Zn(pentaen) increased from 228.0 to 321.5 kPa with an increasing density from 40.8 to 47.5 kg/m3. SEM micrographs of foam prepared from Cu(pentaen):Zn(pentaen) had smaller cell size than that prepared from DMCHA. Therefore, the thermal insulation properties of RPUR foam prepared from Cu(pentaen):Zn(pentaen) was better than that prepared from DMCHA.