Preparation and properties of nano-SiO₂/organosilicon modified waterborne polyurethane composites

In order to improve the water resistance and poor surface property of waterborne polyurethane (WPU), organosilicone and nano-SiO₂ were introduced into the WPU. First, WPU and organosilicon modified waterborne polyurethane (SWPU) were synthesized by self-emulsified method. Then, nano-SiO₂/SWPU composites were prepared by adding SiO₂ particles into SWPU using ultrasonic blending method. Finally, the structures of WPU, SWPU and nano-SiO₂/SWPU were characterized by FTIR and SEM, and their hydrophobicity and mechanical properties were analyzed by water contact angle measurement, water absorption and elongation mechanic test. Results show that nano-SiO₂ is successfully introduced into SWPU. Nano-SiO₂ could disperse uniformly in the film of nano-SiO₂/SWPU when nano-SiO₂ content is low (≤3wt%). When the content of nano-SiO₂ increases from 0 to 5wt%, the water absorption of nano-SiO₂/SWPU film decreases by 69%, the tensile strength increases from 16.72 MPa to 24.22 MPa, while the break elongation increases from 545% to 731%, which show that the introduction of nano-SiO₂ significantly improves the water resistance and mechanical properties of SWPU.