A new class of catalyst for the preparation of rigid polyurethane (RPUR) foams was developed. Metal(II)-amine complexes [M(en) 2 and M(trien), where M ¼ Cu or Ni, en ¼ ethylenediamine, and trien ¼ triethylenetetramine] were synthesized and used as catalysts in the preparation of RPUR foams. The catalytic activity of the metal(II)-amine complexes and properties of the RPUR foams were investigated and compared to those prepared by N,N-dimethylcyclohexylamine (DMCHA), which is a common commercial tertiary amine catalyst used in the preparation of RPUR foams. The use of M(en) 2 and M(trien) can improve the working environment in RPUR foam processing because DMCHA and other commercial tertiary amine catalysts have a strong odor, whereas M(en) 2 and M(trien) do not have any odor. The reaction times in RPUR foam preparation, namely, cream time, gel time, tack-free time, and rise time, were investigated. These data indicated that the copper-ethylenediamine complex [Cu(en) 2 ] and copper-triethylenetetramine complex [Cu(trien)] had comparable catalytic activity to DMCHA, whereas the catalytic activity of the nickel complexes was not good. Attenuated total reflection-IR spectroscopy of the RPUR foams prepared with Cu(en) 2 and Cu(trien) showed quantitative isocyanate (NCO) conversion. The density and compressive strength of the RPUR foams prepared from Cu(en) 2 and Cu(trien) were comparable to those prepared from DMCHA.
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