Thin Solid Films, Vol.570, 33-37, 2014
UV protective zinc oxide coating for biaxially oriented polypropylene packaging film by atomic layer deposition
Biaxially oriented polypropylene (BOPP) packaging film was coated with zinc oxide (ZnO) coatings by atomic layer deposition (ALD) in order to protect the film from UV degradation. The coatings were made at a process temperature of 100 degrees C using diethylzinc and water as zinc and oxygen precursors, respectively. The UVprotective properties of the coatings were tested by using UV-VIS and infrared spectrometry, differential scanning calorimetry (DSC) and amechanical strength tester, which characterised the tensile and elastic properties of the film. The results obtained with 36 and 67 nm ZnO coatings showed that the ZnO UV protective layer is able to provide a significant decrease in photodegradation of the BOPP film under UV exposure. While the uncoated BOPP film suffered a complete degradation after a 4-week UV exposure, the 67 nmZnO coated BOPP film was able to preserve half of its original tensile strength and 1/3 of its elongation at break after a 6-week exposure period. The infrared analysis and DSC measurements further proved the UV protection of the ZnO coatings. The results show that a nanometre scale ZnO coating deposited by ALD is a promising option when a transparent UV protection layer is sought for polymer substrates. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Atomic layer deposition;Zinc oxide;Polypropylene;Biaxially oriented polypropylene;UV degradation