Preparation of rigid polyurethane foams catalyzed by metal-alkanolamine complexes

Abstract

In this research, the catalysts for preparation of rigid polyurethane (RPUR) foams were developed in order to reduce odor as compared with commercial catalyst as dimethyl-cyclohexylamime (DMCHA). The investigated catalysts were metal-alkanolamine complexes in ethylene glycol solution, namely Cu(OAc)₂(EA)₂ and Zn(OAc)₂(EA)₂, where OAc = acetate and EA = ethanolamine. These complexes were further used as catalysts in the preparation of rigid polyurethane foams without purification. Characterization of metal-alkanolamine complexes were done using UV-visible spectroscopy, FTIR spectroscopy and mass spectrometry. Physical and mechanical properties of RPUR foams were studied. The reaction times of the foam formation were studied. The data were compared with those obtained from DMCHA. The experimental results showed that 43 wt% Cu(OAc)₂(EA)₂ (1:4) and 48 wt% Zn(OAc)₂ (EA)₂ (1:1) were obtained as homogeneous solutions. RPUR foams catalyzed by 43 wt% Cu(OAc)₂(EA)₂ (1:4) and 48 wt% Zn(OAc)₂(EA)₂ (1:1) gave longer gel time, tack free time and rise time as compare with DMCHA. Therefore, Cu(OAc)₂(EA)₂ and Zn(OAc)₂(EA)₂ are suitable for RPUR foam applications which require longer gel time.