Reaction injection molding of polyurethane foam for improved thermal insulation

A study on the apparent thermal conductivity of polyurethane foam was carri ed out. A HCFC (hydrochlorofluorocarbon) gas and carbon dioxide were used a s the physical blowing agent and ultrasonic excitation was applied to incre ase the rate of bubble nucleation. The thermal conductivity of the binary g as mixture was predicted theoretically to estimate the apparent thermal con ductivity of the polymer foam. Effects of conduction and radiation on the a pparent thermal conductivity of the cellular polyurethane were considered w ith respect to the cell size and the effect of convection was neglected bec ause of the small cell size. A laboratory RIM machine was designed and buil t for foaming experiments. The foaming experiments were performed at variou s processing conditions, and density, apparent thermal conductivity, number of cells, and cell sizes were measured. Best results such as low thermal c onductivity and small bubbles were obtained when the polyol was mixed with the HCFC gas and saturated with carbon dioxide at 0.3 MPa, and foamed with ultrasonic nucleation.