Study On Preparation Of Composite Nanoparticles Containing Hals And Their Application In UV-Curable Coatings

UV-curable coatings are widely used in many areas because of its high-efficiency curing process and environment friendly characteristics.But the UV-aging degradation problem limits the advanced technology applied in outdoor coatings,which include the car coatings,outdoor billboards protected coatings,building exteriors coatings.Light stabilization of UV-curable coatings has become an important engineering of base materials protection.Main measure of light stabilization of UV-curable coatings is to add various light stabilizers into the formulations of coatings.However,most of the commercially light stabilizers are single function,low molecular weight HALS vaporizes easily and have poor extraction resistance,decreasing their photostabilization effect.Therefore,it is of great significance to develop a durable and high-efficiency multifunctional light stabilizer.This work prepared a multifunctional light stabilizer（composite nanoparticles include polymeric HALS）,which combined reactive HALS with inorganic UV absorber Ti O₂-Si O₂（low photocatalytic activity,silic coated rutile titanium dioxide）.The obtained filler posses light stability of HALS and ultraviolet absorbance.The migration loss of HALS in UV-curable coatings has been reduced a lot,and the dispersion of Ti O₂-Si O₂nanoparticles modified by polymeric HALS in the coatings has also been promoted,which related to the achievement of macromolecule of HALS,and anchoring of HALS onto the surface of Ti O₂-Si O₂nanoparticles.The design of composite nanoparticles presented the synergistic effect of HALS and Ti O₂-Si O₂nanoparticles.The main research contents and results are as follows:（1）The organic surface modification of Ti O₂-Si O₂nanoparticles was carried out by using silane coupling agent MPS,and Ti O₂-Si O₂/MPS nanoparticles were obtained.The structure and modified effects of nano Ti O₂-Si O₂were characterized by FTIR,TG,CA and SEM.The results showed that MPS has successfully grafted onto the surface of nano Ti O₂-Si O₂particles,and the SEM measurement showed that the Ti O₂-Si O₂/MPS nanoparticles have good dispersivity in organic media.（2）Polymeric hindered amine light stabilizers（HALS）-functionalized silica coated rutile titanium dioxide（Ti O₂-Si O₂）nanoparticles were prepared by encapsulating Ti O₂-Si O₂/MPS with methyl methacrylate（MMA）and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate（PMPM）copolymers via miniemulsion polymerization.When the polymerization reaction temperature is 80℃,the surfactant concentration is 24 m M,Ti O₂-Si O₂/MPS content is 4 wt%,costabilizer content is 4 wt%,the miniemulsion polymerization system is very stable,monomer polymerization reaction rate is fast,and the final monomer conversion is rather high.The structure of the composite nanoparticles was characterized by FTIR,NMR,XPS,and the results showed that MMA-co-PMPM copolymer has been successfully grafted and coated onto the surface of the nano Ti O₂-Si O₂.TG result showed that grafting ratio is about 40.9 wt%.TEM images clearly showed that the composite nanoparticles are spherical particles with core-shell structure,and with an average particle size of about 90 nm.UV-vis absorption spectrometry showed that Ti O₂-Si O₂/P（MMA-co-PMPM）composite nanoparticles have superior UV absorption and shielding performance.Rhodamine B（Rh.B）photocatalytic degradation study revealed UV-shielding characteristics for Ti O₂–Si O₂/P（MMA-co-PMPM）composite nanoparticles and showed a remarkable decrease in photocatalytic activity of Ti O₂–Si O₂nanoparticles.（3）The Ti O₂-Si O₂/P（MMA-co-PMPM）composite nanoparticles have been added to polyurethane acrylate（PUA）oligomers to get UV-curable nanocomposite coatings,which were coated polycarbonate sheets.The effects of composite nanoparticles on optical properties,hardness,adhesion and abrasion resistance of nanocomposite coatings were studied.The results showed that when the composite nanoparticles were 2 wt%,the surface pencil hardness and abrasion resistance of UV-curable coatings were the best,and the optical properties and adhesion could be guaranteed.Rh.B photodegradation measurement confirmed the excellent UV-shielding performance of PUA nanocomposite coatings containing Ti O₂-Si O₂/P（MMA-co-PMPM）.After 240 h UV-aging,nanocomposite coatings with 2 wt%Ti O₂-Si O₂/P（MMA-co-PMPM）were found a little change in color difference,transmittance and haze.The surface morphology of the nanocomposite coatings observed by optical microscope showed less micro-holes and micro-cavities.There was no significant change in the infrared spectra of nanocomposite coatings before and after the UV-aging test.All in all,the UV-curable coatings containing Ti O₂-Si O₂/P（MMA-co-PMPM）have excellent light stability,compared with the unmodified UV-curable coatings,the polycarbonate sheets,which were coated UV-curable nanocomposite coatings,can be better protected.