화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.106, No.2, 1014-1023, 2007
Reactivity of the raw materials and their effects on the structure and properties of rigid polyurethane foams
Formulations for rigid polyurethane foams (RPUFs) based on crude 4,4'-diphenylmethane diisocyanate, polyether polyol, triethylenediamine, 1,4-butane diol, poly(siloxane ether), methylene chloride, and water were studied. The stoichiometric ratios of various foam ingredients and their effects on physical properties such as the cream time, gel time, tack-free time, and density of the RPUF samples were studied. The results indicated that the rate of RPUF formation increased with the catalyst (triethylenediamine and tin) and water content. The density of the RPUF samples blown with water, methylene chloride, and a mixture of water and methylene chloride decreased from 240.1 to 33.4 kg/m(3) with an increase in the blowing agent contents. However, the RPUF density increased with increasing contents of 1,4-butane diol. The cell morphology and thermal properties of the RPUF samples were investigated with scanning electron microscopy, thermogravimetric analysis, derivative thermogravimetry, and differential thermal analysis. Scanning electron microscopy results revealed an average increase in the cell size of the RPUF samples from 162 to 278 pin with increased water content. A thermal behavior study indicated that the RPUF samples decomposed in nitrogen and degraded in air through two and three weight-loss stages, respectively. Foam pyrolysis in nitrogen and combustion in air led to 15 and 0% char residue, respectively. The results indicated that the thermal stability of the RPUFs was better in nitrogen than in an air atmosphere. (C) 2007 Wiley Periodicals, Inc.