| Fluorosilicone resins have been widely applied in many important fields due to their excellent comprehensive,such as low surface energy,medium resistance,good mechanical properties and compatibility.Moreover,the UV curing technology has the advantages of high efficiency,energy savings,environmentally friendliness,enhanced quality and economics.However,few studies have been done on the combination of UV curing technology and fluorosilicone resin.In this paper,two series of UV curable fluorosilicone resins,grafted and graft copolymerization,were synthesized,which were blended with commercially UV curable polyurethane(DR-U356)in different ratios to prepare UV curable low surface energy coatings.The surface enrichment behavior of fluorinated side groups was studied,and then the mechanism of the influence of fluorosilicone resin on the surface properties of the UV cured films was further discussed,especially the influence of low fluorosilicone resin content.The medium resistance was further investigated.The specific research contents are as follows:Three kinds of hydroxyl monomers with different fluorine structures were prepared based on click chemistry,which was then reacted with isophorone diisocyanate and hydroxyl polydimethylsiloxane to prepare grafted UV curable fluorosilicone resin with polydimethylsiloxane as main chain,fluorine group and acrylic double bond as side group(SG0X,X for different fluorine structure,X was 1,5,6B).Moreover,two fluoropolymers with caroxylic acid end group were synthesized via Reversible Addition-Fragmentation Chain Transfer Polymerization which further reacted with the epoxy group of polydimethylsiloxane.The obtained fluorosilicone was modified by isophorone diisocyanate and hydroxypropyl acrylate to prepare UV curable fluorosilicone grafted copolymer(corresponding to SPG01,SP(G01-G05)).All synthesized resins were characterized by Fourier transform infrared spectrometer(FTIR)and 1H Nuclear Magnetic Resonance(1H-NMR).The UV curing process was monitored by FTIR,which indicated both these resins could be rapidly cured under UV irradiation.Then,the UV curable low surface energy coatings were prepared by combination of fluorosilicone resin and commercially polyurethane.The interface segregation behavior of the grafted foluorosilicone was investigated by X-ray photoelectron spectroscopy(XPS)and the surface properties of the cured films were measured by contact anlgle measurement.The water contact angle sharply increased with increasing content of fluorosilicone resin under 10 wt.%.For example,it increased from 59.41° for cured DR-U356 film to 109.92° for cured DR-U356 film with 10 wt.% SG06 B addition.And the surface enery decreased from 66.55 mN/m to 37.56 mN/m.The synthesized resin showed perfect efficiency to changing the coating surface properties and the water contact angle obviously increased from 59.41° without SG06 B to 109.92° with 1 wt.% SG06 B.The water contact angle also increased with increasing chain length of fluoroalkyl groups,which increased from 93.67° when the chain length was three to 109.92° when the chain length was six.The XPS analysis showed that the fluorosilicone resin possessed potential interface enrichment property.The fluorine contents were 2.21% and 1.54% for surface layer and bottom layer of the cured SG05 film,which were obviously higher than theoretical value 0.148%.Annealing showed no obviously effect on the surface enrichment process for fluorosilicone resin.The durability of fluorosilicone layer were monitored by "Friction-Annealing" cycle experiment.All samples showed good self-healing properties,which water contact angle obviously decreased after being abrased and could recover quickly after being annealed 1 h under 120℃.As a result,addition of the synthesized fluorosilicone resin could greatly improve the chemical resistance.The surface properties of the cured films with graft copolymerized fluorosilicone resin addition were also measured by contact angle measurement.The results indicated that the graft copolymerized fluorosilicone resin showed better efficiency to decreasing surface energy than the grated fluorosilicone resin and the equilibrious content decreased to 1 ~ 2 wt.%.Moreover,annealing could further decrease the surface energy.Compared with the grated fluorosilicone resin,the graft copolymerized fluorosilicone resin showed perfect anti-abrasion property and the water contact angle showed no obviously decreasing tendency after being abrased.The chemical resistance of coatings was greatly by the addition of graft copolymer fluorosilicone resin. |
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