Preparation And Properties Of Organic-inorganic Hybrid Materials Of Pu/fillers With Hydroxyl Group

Organic-inorganic hybrid materials are a kind of multiphase materials with uniform dispersion at nanometer level. They have excellent properties over organic polymers and inorganic materials. The hybrid materials can be ranged from organic polymers modified by inorganic substance to inorganic materials modified by organic substance, and the properties of the materials are able to be tailored and constructed by adjusting the composision and ratio of organic and inorganic phase. In this dissertation, according to rapid reaction principle of NCO group with OH group, a new type of organic-inorganic hybrid materials consisting of polyurethane (PU) and hydroxyl group-containing fillers were prepared through the mechanical blending and in situ reacting method. It is found that PU/precipitated silica (PU/P-Silica) organic-inorganic hybrid material have the best overall properties. In the basis of the results, PU/P-Silica hybrid materials were investigated systematically and thoroughly, including the hybrid mechanism, the best hybrid process conditions and the properties of hybrid materials, etc.Comparing PU and three kinds of hybrid materials, PU/Halloysite Nanotubes(PU/HNTs), PU/Fumed Silica(PU/F-Silica) and PU/Precipitated Silica(PU/P-Silica), which were prepared by mechanical blending and in-situ reacting method, the mechanical properties of three hybrid materials has improved significantly. It is found by XRD and DSC testings that the increase of the contents of inorganic fillers in the hybrid systems alters the hard segment structure and increases the relative content of hard segment of hybrid materials in PU. The thermal stability results showed that the hybrid materials had the better thermal stability than PU. The surface contact angle tests show that three kinds of hybrid materials had different hydrophilic and hydrophobic property.PU/P-Silica hybrid material has the best comprehensive properties in three kinds of hybrid materials. The deep investigation on PU/P-Silica hybrid materials shows that the second mixing of PU prepolymer with P-Silica by three-roll mixing machine can improve the dispersion effect of silica in PU prepolymer, and hence enhance the mechanical properties of PU/P-Silica hybrid materials. The tensile strength achieves to 51 MPa and the tear strength was improved to nearly 100 MPa. As the NCO and OH in the ratio of 2:1, the hybrid material is provided with the best mechanical properties. It is because that under certain conditions, the NCO groups at both ends of molecular chains can make direct chemical reaction with OH groups at the silica surface and form the hybrid materials with organic-inorganic hybrid crosslinked network structure. In addition, the right curing time and curing temperature of PU/Silica hybrid materials were determined by rubber vulcanization instrument and curing activation energy by DSC test. It is found that PU/P-Silica hybrid materials and metal aluminium also have certain bond strength and the tensile cutting strength arrived to 9 MPa.