Study On Preparation And Properties Of PU/OMMT Nanocomposites

Polymer/layered silicate nanocomposite(PLSN) depends inorganic layered silicate as the dispersed phase and polymer as the matrix for forming an intercalation compound-based composite material. Polyurethane(PU) has many products and they have excellent performance, but there are some flaws such as poor thermal, flammable; Shandong has rich resources of bentonite, but the utilization rate is low. The bentonite can be finely processed to be OMMT to modify PU. It improves the economic value of bentonite while also improves the overall performance of the PU.The research maked the bentonite mine from Shandong Weifang as raw material. The material is purified, removed of iron and made to be Na-bentonite. At last we got OMMT of excellent performance and determined the corresponding optimal process parameters. The research systematically studied the effect of the reactive, non-reactive and type of composite which are modified on interlayer spacing of montmorillonite and analysed the mechanism of intercalation. Experimental results shows that the OMMT made by Dimethyl dioctadecy lammonium Bromide(D1817) in interlayer with arrangement of double tilt and has good lipophilicity with interlayer spacing in 3.30 nm.Using two methods of prepolymer and in situ polymerization of monomer insertion, the OMMT with PU are intercalated to be PU/OMMT nanocomposites. The tests of SEM, XRD, TG show that two ways are both formed to be intercalated nanocomposites. The last method is better.The method of in situ polymerization of monomer insertion can let polyether polyol(PPG) entered into OMMT layer and it reacted with MDI to be polymer chain. XRD test shows d(001) of OMMT expanded from 3.30 nm to 4.20 nm to form the intercalated PU/OMMT nanocomposites. This method defined the optimum amount of OMMT is 3%, the thermal decomposition temperature of PU/OMMT reached 398.21 ℃, higher than the pure PU about 8.40 ℃; Oxygen index increased to 25.50 and horizontal burning speeded down to 15.03 mm/min and the flame retardanc is improved. Tensile strength and tear strength increased to 2.62 MPa and 13.00 N/ mm.The elongation at break improved about 90.60%, PU can be improved both enhancement and toughening of OMMT.The prepolymer method depended the use of strong shearing force to force the polymer chains of PU to intercalate into OMMT layer. The d(001) of OMMT expanded from 2.50 nm to 3.47 nm, It is the intercalated nanocomposites materials. This method has an optimum amount of OMMT is 3%. The thermal decomposition temperature of PU/OMMT reached 397.10 ℃, which is lower than the in situ polymerization of monomer insertion about 1.10 ℃. Oxygen index increased to 24.50 and horizontal burning speeded down to 16.67mm/min. The tensile strength and tear strength increased to 2.26 MPa and 10.80N/mm and the elongation at break increasd about 40.10%. PU can be enhanced and toughened by adding OMMT, But the overall performance of this methord is lower than the situ polymerization of monomer insertion.The two kinds of prepared PU/OMMT nanocomposites are applied in sealant. They both maintain properties of mechanical and conventional of sealants. They can significantly improve the thermal stability and flame retardancy. Overall, performance of situ polymerization of monomer insertion of PU/OMMT nanocomposites is better.