Preparation of rigid polyurethane foam catalyzed by nickel and cobalt complexes

Abstract

Transition metal complexes, namely M(en)₂, M(en)₂(sal)₂, M(trien) and M(trien)(sal)₂ (M = Ni and Co), were synthesized and used as catalysts for the preparation of rigid polyurethane foams (PURFs). The reaction times, physical and mechanical properties of PURFs were investigated and compared to those prepared by commercial catalyst, N,N-dimethylcyclohexylamine (DMCHA). UV-vis spectroscopy, IR spectroscopy, elemental analysis and atomic absorption were used to characterize the transition metal complexes catalysts. ATR-IR technique was used to study isocyanate (NCO) conversion and polyisocyanurate/polyurethane (PIR/PUR) ratio in the PURFs. The polymerization reaction of foaming preparation is exothermic reaction. The maximum reaction temperature is in the range of 114-125 ℃. During the foam preparation, cream time, gel time, tack-free time and rise time were investigated. The results showed that the apparent density of PURFs was in the range 42.3-73.9 kg/m³. Co complexes showed better catalytic activity than Ni complexes. Compressive strength of PURF prepared from Ni(trien)(sal)₂ was better than that prepared from DMCHA. PURFs obtained from Ni(en)₂ and Co(en)₂ showed similar thermal decomposition with that obtained from DMCHA catalyst. Thermal conductivity of PURFs showed that PURFs catalyzed by Co(trien) and Co(en)₂ gave thermal conductivity similar to that catalyzed by DMCHA