The mechanical properties and the cell distributions of rigid polyurethane foams were studied on the effects of the contents of gelling catalysts of amine(dimethylcyclohexyl amine(DMCHA)) and potassium type(potassium octoate (PO)) after the processing of foaming with polyester polyol and polymeric-methylene diphenyl diisocyanate (polymeric-MDI). The additives such as pentamethyl diethylene triamine(PMDETA), water, blowing agents and surfactant were used. The processing methods of foaming were the free rising test and the expanding method in the mold. Flexural strengths were measured by the universal testing machine (UTM). As the contents of catalyst DMCHA increased, flexural strengths decreased from 0.20 to 0.12MPa at the free rising test. However they increased from 1.10 to 1.35MPa at the expanding method in the mold. Effects of flexural strengths on the contents of catalyst PO were similar with catalyst DMCHA. Also it was verified that cell population densities (CPD) increased and the cell size distributions became narrow as the contents of gelling catalysts increased.

본 연구에서는 polyester계 polyol과 polymeric-methylene diphenyl diisocyanate(polymeric-MDI)를 사용하여 발포체를 형성할 때 아민계 젤화 촉매인 dimethylcyclohexyl amine(DMCHA)과 칼륨계 젤화 촉매인 potassium octoate(PO)가 발포체의 기계적 강도와 발포 셀의 분포에 미치는 영향에 대해 연구하였다. 첨가제로는 pentamethyl diethylene triamine(PMDETA) 촉매, 물, 발포제, 정포제를 사용하였다. 발포방식은 free rising test와 mold 공법을 사용하였다. Universal testing machine(UTM)을 통해 굴곡강도를 측정하였다. 굴곡강도는 free rising test의 경우 DMCHA 촉매의 함량에 따라 약 0.20에서 약 0.12 MPa로 감소하였으나 mold 공법의 경우 약 1.10에서 약 1.35 MPa로 증가하여 반대의 경향을 보였다. PO 촉매의 함량에 따른 영향도 DMCHA 촉매와 유사하였다. 또한 scanning electron microscope(SEM)으로 젤화 촉매의 함량에 따라 cell population density(CPD)가 증가하는 것을 확인하였고, 발포 셀의 크기 분포가 좁아지는 것을 확인하였다.

Keywords: rigid polyurethane foam; flexural strength; cell distribution; gelling catalyst