Preparation Of Glazed Hollow Bead/Poly Urethane Foam Composite Materials

The rigid polyurethane foams are considered to be the best thermal insulation materials because their extreme low thermal conductivity. But they are not widely used in our country due to the poor flame resistance and higher cost. Glazed hollow bead is a new energy-saving material for building insulation with advantages such as low prices, excellent heat resistant, inflammability and lower water uptake. The composites prepared from PU foam and glazed hollow bead has both advantages of organic PU insulator, the good thermal retardation, and inorganic insulator, the inflammability.The formulations of PU foam for the composites were investigated in this thesis. A PU foam with good dimensional stability was prepared by using3-11phr water levels and polyol combinations The morphologies and mechanical properties of the water-blown PU foams were characterized by SEM, FTIR and physi-mechanical evaluations. The results indicated that water level had various effects on the chemical compositions and microstructures of water-blown PU foams and therefore affected the physi-mechanical properties, because water acted not only as a gas supply for foaming but also a chain extender of poly urea-ure thane resin. The formula of polyol combination had slight effects on the microstructures, while the key polyether polyol was less than75phr, the compression strength sharply decreased due to the lack of crosslinking density. The foam density had great influences on the mechanical properties of foam when the key polyether polyol was more than75phr.Based on the optimized PU foam, the formulations of glazed hollow bead/polyurethane foam composites were also investigated in terms of various reaction index, polyether polyol species and the bead meshes. Test results indicated that the mechanical properties and the oxygen index of composites showed certain dependence upon the density of composite. With the increase of reaction index, the mechanical properties of composites were improved due to the more polyurea formed. Polyether polyol species showed slight effect on mechanical properties but more polyol with higher molecular weight introduced led to the decrease of flame resistance due to the more flammable-CH2CH2O-introduced. The finer glazed hollow bead resulted in better mechanical properties for less effect on foam structure and compression resistance. The composite had an improved oxygen index up to33%,83%more than that of the pure PU foam, while its heat conductivity was around0.023w/(m.k), showing the potential for the commercial applications.