Clay-based polyurethane foam nanocomposites for thermal insulation

Abstract

Polyurethane foams are classes of cellular plastics that exhibit mechanical robustness and lightness; they are widely applied as thermal insulators in the building and automotive fields. Nanocomposites play an important role in improving the energy efficiency of thermal insulation materials. In this study, a layered clay mineral (montmorillonite) was used as a nanosheet-type gas-barrier filler in a foam-type urethane/urea/isocyanurate copolymer to delay exchanges of thermal insulation gases (carbon dioxide and 1,3,3,3-tetrafluoropropene) in the polyurethane foam with air. This gas barrier is expected to prevent the deterioration of its long-term thermal insulation performance. Synchrotron radiation small-angle X-ray scattering was used to analyze the dispersion of the clay nanosheets modified with organic cations in the polyurethane matrix. The cations include benzyldimethylhexadecylammonium (C₁₆2MeB), dimethyldioleylammonium (2C₁₈₌2Me), and bis(2-hydroxyethyl)dimethylammonium (2EtOH2Me). The 2EtOH2Me-clay adduct was highly dispersed in the polymeric matrix, possibly because of its good compatibility with a polyurea domain. The dense ordering of C₁₆2MeB-clay in the polymeric matrix influenced the degradation of its thermal insulation performance. The degree of ordering in the polymeric matrix was reduced by decreasing the layer charge density of the negative charge in the montmorillonite, thereby improving the insulation performance for 4 months empirically. The reduction of the effects on power consumption during heating was simulated using a detached house over 30 years. This study designed a gas barrier agent for the macropore wall of PU foam.