Preparation And Properties Of UV-cured Functional Coatings For PET Film

Polyethylene terephthalate（PET）film has been widely used for packaging,screen and optical grade mirror protection due to its excellent light transmission,heat resistance and insulation properties.But its low surface hardness and poor wear-resistance limit application.It is an effective method to improve the PET film surface properties with coating,and the photocuring technology has advantages including fast curing speed,energy saving and environmental protection.In this paper,UV-curable PET film hardening and toughening transparent coating and anti-fouling and super-hydrophobic coating were prepared by organic-inorganic hybrid technology.Combined inorganic nanoparticles and UV curing system to prepare PET film UV-curable hardening,toughening and transparent coatings.The effect of structure and ratio of photocurable resins,the catergories and dosages of inorganic nanoparticles on the coatings properties of hardness,flexibility and impact resistance were studied.It was found that nanoparticles could improve the hardness of coatings without reducing transparency when adding less than 0.5%.Among them,0.3%octavinyl POSS was the best inorganic nano-hardening material,its coating displayed excellent properties,including 4 H of the pencil hardness,100 kg cm of impact resistance,0 grade of adhesion,2 mm of flexibility,and≥90%of light transmittance.Infrared spectra indicated that C=C bond in octavinyl POSS participated in photocuring reaction,resulting in Si-O-Si network structure polymer.Thermogravimetric and dynamic thermomechanical analysis revealed that the composite coating modified by 0.3%OVPOSS had good thermal stability with 5%weight loss temperature up to 335.2°C and storage modulus（E’）increases from 167.7 MPa to 258.9 Mpa.SEM and AFM images showed that OVPOSS particles were uniformly dispersed in the coating and had good compatibility with organic paints.In order to improve PET film’s contamination,flammability,poor mechanical strength,KH-5 70-m odi fi ed n an o Si O₂ A（abb reviat ed as KH-5 70/S iO₂ NPs A）and（Heptadecafluoro-1,1,2,2-tetrahydrodecyl）trimethoxysilane（FAS-17）-modified nano SiO₂ B（abbreviated as F17-SiO₂ NPs B）were synthesised to blend with UV paints to prepare PET film superhydrophobic coatings.The wettability and surface morphology of the coating were characterized by contact angle measuring instrument and scanning electron microscope.The effect laws of every component on coating properties were investgated.It was found that the water contact angle of the coatings increased with the increase of the addition of F17-SiO₂NPs B with 15%UV paints.When addition amount was more than 45%,it had super hydrophobic properties with the increased contact more than 160°.The film hardness,adhesion,abrasion resistance and chemical resistance increased with the increase of the amount of UV paints.However,It was difficult to obtain superhydrophobic coating when UV paints exceeded 25%,a large amount of nanoparticles were embedded in the coating.When w（KH-570/SiO₂ NPs A）:w（F17-SiO₂ NPs B）（mass fraction）=1,with 15%UV paints added,PET film coating had 160.3°of water contact angle,2°of rolling angle,2 H of pencil hardness,1 grade of adhesion,0.052 mg·100r^-1 of abrasion loss,and V-0 grade of flame retardancy.The SEM and AFM images demonstrated that the surface of coating showed the micro-nano roughness structure contaning papillary nanoparticles and pit-like concave surfaces.