The SiO2/PU superhydrophobic coatings were prepared by using rapid expansion of supercritical CO2.Firstly
by modifying nano-silica with thirteen fluoride octyltriethoxysilane(F-silane)andγ-(methacryloyloxy-oxy)propyl trimethoxysilane (KH-570)
nano-silica particles containing double bonds were prepared and then were dispersed in supercritical CO2.At the same time
a polyurethane coating containing double bond and an initiator was prepared.Subsequently
the nano-silica particles were injected onto the polyurethane coating surface making use of rapid expansion of supercritical CO2
and then were dried by heating to form a stable rough structure because of the nano-silica particles being grafted on the polyurethane coating.This way
a SiO2/PU film with superhydrophobic surface was obtained.Moreover
the effect of nozzle temperature
reaction kettle temperature and pressure
ratio of coupling on coating hydrophobicity and surface roughness were studied.The results showed that the static water contact angle of the coating could be up to 169.1°±0.6°.When the temperature of the nozzle and the reaction kettle were all 90℃
the reaction kettle pressure was 16 MPa and ratio of F-silane to KH-570 was 1∶1
the surface roughness was 7.3 μm
the obtained film had good super-hydrophobicity
and had excellent scratch resistance.In addition
the superhydrophobic coating had good performance and was environmental
and also could be produced cost-effectively on a large scale.