Development of polyurethane nanocomposites with low thermal conductivity by addition of modified vermiculite

Polyurethane is one of the most miscellaneous material that has many usage area in the world, today. Rigid polyurethane foams that are an interesting family of polymers, with excellent thermal insulation, chemical resistance and toughness. They are extensively used as thermal insulation in refrigerator industry. Rigid polyurethane foam makes a major contribution to sustainability and eco-design by reducing the energy required to keep refrigerators cold. To reduce the energy required, the thermal conductivity of rigid polyurethane foam must be decreased and to decrease thermal conductivity, the cell size must be smaller. Various kinds of additives are used to decrease cell size of rigid polyurethane foam such as clay. It is important that the compatibility of clay particles and polymer matrix is crucial to achieve nanodispersion of clay. In this study, nanosize vermiculite was used as the clay to decrease thermal conductivity of rigid polyurethane foam. To provide compatibility, 1 CEC, 2 CEC and 3 CEC ratios of quaternary ammonium salt CTAB was used to achieve modification of vermiculite and effect of modified nanosize vermiculite which added 1%, 3%, 5%, 7% and 10% by weight on thermal and mechanical properties of rigid polyurethane foam was investigated. To determine whether vermiculite was modified or not, interlayer distance was measured and hydrophobicity with different modifier agent ratios was examined. The amount of modifier agent that gave highest contact angle was 2 CEC. The smallest cell size was obtained with addition of 2 CEC modified, 5% by weight vermiculite. Decreasing in mean cell size was 59% and thanks to that, decreasing in thermal conductivity was 8%.