Preparation of hyperbranched polyurethane acrylates and their properties in UV curable nano-SiO₂ composite coatings for PET optical film

Polyethylene terephthalate (PET) films have been widely applied in the display industry. However, there is a problem in effectively protecting and extending the service life. To address this issue, a hyperbranched polyurethane acrylate (HPUA) has been synthesized with poly (hexylene glycol) neopentyl glycol ester (PNA), isophorone diisocyanate (IPDI), hyperbranched polyol Boltorn^™H2004 and pentaerythritol triacrylate (PETA). Further, a series of high-performance UV curable coatings have been prepared with HPUA, hollow nano-SiO₂ and silane coupling agents, along with other reagents. The structure of HPUA has been characterized by infrared spectroscopy (FT-IR), and the curing process has been monitored kinetically by real-time infrared spectroscopy to study its double-bond conversion ratio. The properties of the cured films have been investigated by thermogravimetric analysis (TGA). The water contact angle, aging and yellowing resistance, hardness, flexibility, abrasion resistance, light transmittance, and adhesion of the cured coatings on PET film have been tested. The results have shown that the addition of hollow nano-SiO₂ and silane coupling agents has not only not affect the light transmittance of the coatings but also improved the surface properties and heat resistance. When the silane coupling agent has been γ-Methacryloxypropyltrimethoxysilane (KH-570), the water contact angle of the coating has been 101.8°, excellent resistance to aging and yellowing, and the hardness, flexibility, and abrasion resistance have reached 89.4 HD, 3 mm, and 500 g/350 times, respectively. It was worth mentioning that the cured coating has shown excellent adhesion to PET film with the best overall performance. This work has offered important guidance for the protection of PET films.