Abstract:
UV-curable process is widely used for paints, inks and adhesives due to its rapid curing, low energy consumption, high efficiency and low volatile organic compounds (VOCs). Acrylate oligomers, reactive diluent, photoinitiator and additive are important components in UV-curable coating formulation. Most acrylate oligomers used in UV-curable coating are petroleum-based chemicals, which are obtained from a non-renewable source. The objective of this research is to prepare poly(lactic acid) (PLA) based UV-curable coating. Glycolyzed PLA was obtained by glycolysis of PLA with ethylene glycol (EG) at GPLA:EG weight ratio of 1:2. The lowest molecular weight of glycolyzed PLA was obtained at the reaction time of 90 minutes. The obtained glycolyzed PLA was reacted with two types of acrylate derivatives to provide PLA acrylate oligomers. The UV-curable coating formulations were prepared using obtained PLA acrylate oligomer with various types of reactive diluents; HDDA, TMPTA and TPGDA and amounts of a photoinitiator. The coatings were coated on substrate and cured using ultraviolet (UV) radiation. The curing time and the energy consumption in drying process decreased as a function of the amounts of photoinitiator and number of acrylate functional group of reactive diluent in coating formulation increased. The thermal stability, gloss, haze, hardness, adhesion and chemical resistance of UV-curable coating were investigated. It was found that their physical properties depended on types of reactive diluents and amounts of photoinitiator. Furthermore, biodegradable behavior of the UV-curable coating was studied by soil burial test. The UV-curable coatings were slowly degradability in soil burial within 15 weeks.