Preparation And Properties Of Waterborne Polyurethane/modified Inorganic Nanoparticle Composites

Waterborne polyurethane(WPU)is environmentally friendly and has excellent elasticity,flexibility,adhesion,abrasion resistance,fire resistance,etc.WPU is often used as an efficient alternative of solvent-based polyurethane(PU)and has begun to used in various fields,such as coatings,adhesives,elastomers,flexible and rigid foams,printing inks,and so forth.However,pristine WPU also exhibits some demerits of inferior mechanical properties,thermal stability,water resistance,and lower curing rate.Therefore,it is necessary to modify the pristine WPU for the enhancement of its prpperties and the expansion of its applications.In this thesis multiwalled carbon nanotube(MWCNT)and antimony doped tin oxide ATO)were applied as inorganic fillers to reinforce the WPU and waterborne polyurethane/multiwalled carbon nanotube(WPU/MWCNT)and waterborne polyurethane/antimony doped tin oxide(WPU/ATO)nanocomposites with the good dispersity and the high performance were prepared.In the first section,a series of novel covalently linked WPU/MWCNT nanocomposites were synthesized through an optimized condensation of hydroxyls.Multiwalled carbon nanotubes(MWCNT)as the inorganic filler were pretreated with a successive two-step modification route for its surface function with hydroxyl groups.3-Aminopropyltriethoxysilane(APTES)was embedded into the backbone of WPU,hydrolysis of which generates silanol groups in the polyurethane(PU)matrix at the emulsification stage.Meanwhile,the silanol groups could condensate with the hydroxyl groups on the surface of modified MWCNT,generating the hydrogen bond between the modified MWCNT and APTES embedded PU matrix.These results revealed that compared to pristine WPU,the WPU/Si/MWCNT system with APTES and MWCNT possesses outstanding water resistance,high thermal stability and excellent mechanical properties.In the second section,ATO nanoparticles were modified with 3-methacryloxypropyltrimethoxysilane(MPS)to make its surface loaded with unsaturated carbon carbon double bonds(C=C).2-hydroxyethyl acrylate(HEA)was grafted on the PU chains to incoporate C=C in the backbone of the PU molecules.Thus,free radical polymerization of C=C from ATO and PU could be carried out in the persence of UV irradiation to form chemical bond between PU and ATO during the curing process.The result of TGA revealed that about 12.6wt.%was absorbed on the surface of modified ATO nanoparticles.It can be infered that the crosslink density and the performance of WPU and WPU/ATO films could be improved by adjusting the mole ratio of HEA to trimethylolpropane(TMP)and the content of ATO.When the mole ratio of HEA was 0.8,the gel content of WPU film reached to 83.33%;which illustrated that the WPU film had a high crosslink density.With ATO content increased from 1%to 8%,the degradation temperature of hard segments and soft segments of WPU/ATO films increased from 315? to 339 ? and from 400? to 411 ?,respectively,the swelling degree of WPU/ATO films decreased from 5.06%to 3.36%,the surface free energy decreased from 39.0mN/m to 30.8mN/m and the tensile strength increased from 14.4MPa to 21.9MPa.In addition,WPU/ATO hybrid films also exhibited excellent thermal inslution and preservation performance and good transparency in the visible light region due to the IR-shielding and VIS-transmission effects of the ATO nanoparticles.