Study On Preparation Of UV Curable Nanosilica Hybrid Materials And Their Properties

The UV curable coatings have developed quickly because of fast curing speed, little pollution, energy saving advantages. However, the organic cured films have some drawbacks such as low hardness, bad abrasive resistance and low thermal stability and so on. The properties can be improved by introducing inorganic filler.Nanosilica is the inorganic filler which has the excellent property of high hardness and temperature resistance. Because of the serious aggregation and hydrophilic property of nanosilica, they can not disperse evenly in organic material, leading to the increase of viscosity of coatings and the decrease of photopolymerization rate of coatings. Therefore, the properties of cured films such as hardness and resistance abrasion can not be improved greatly if it was directly added into the organic coatings. In order to resolve the problem in above, the different structure polymerizable nanosilica hybrid materials were prepared by a series of experiments, which used the hydroxyl of nanosilica. The main experiments were as follows:(1) Nanosilica grafted hydoxyethyl acrylate was prepared by reaction of nanosilica with isophorone diisocyanate, then the nanosilica bearing isocyanate group reacted with the hydoxyethyl acrylate.(2) Nanosilica grafted hydoxyethyl acrylate was also prepared by esterificatoin of nanosilica and hydoxyethyl acrylate, in which p-toluenesulfionic acid was used as catalyst.(3) The macromolecular nanosilica hybrid materials were synthesized by the reaction of the hydoxyethyl acrylate and nanosilica which was modified with isophorone disocyanate and polypropylene glycol.(4) Nanosilica hybrid particles with tertiary amine structure were prepared by reaction of nanosilica with isophorone diisocyanate, then the nanosilica bearing isocyanate group reacted with the acrylic compound containing tertiary amine structure synthesized from tripropylene glycol diacrylate and ethanolamine.(5) Nanosilica/polyurethane acrylate prepolymer was prepared by in-suit reaction of nanosilica with isophorone disocyanate, polypropylene glycol and hydoxyethyl acrylate.The preparations were characterized by Fourier transform infrared spectrometry (FT-IR), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM) and so on. Nanosilica hybrid materials were applied into the UV curable coatings, the effects of nanosilica hybrid materials on the viscosity of coatings and photopolymerization rate were analysed and the effects of nanosilica hybrid materials on properties of cured films were also discussed. The results were as follows:(1) Different organic prepolymer containing C=C double bonds were grafted on the surface of nanosilica, which give them polymerizable characters and aggregation improved obviously. Nanosilica has good dispersion and combination ability in organic coatings.(2) The grafting percentage based on nanosilica which was modified with isophorone disocyanate and hydoxyethyl acrylate was 64.4% and prepared by esterificatoin was 14.2%. The grafting percentage based on nanosilica with tertiary amine structure was 105% and the macromolecular nanosilica hybrid materials grafting percentage was 92.2%.(3)The curable coatings with the nanosilica hybrid material had lower viscosity and higher UV curing rate compared with the coatings added unmodified nanosilica. Nanosilica hybrid materials with tertiary amine structure can increase the curing rate of coatings because of the oxygen inhibition resistance when the addition was below 5w%. The properties of cured films with nanosilica hybrid material can be improved obviously when the addition was below 6w%, but more than 6w%, the properties of cured films reduced again result from aggregation in coatings.