Printability in flexographic printing of compostable plastics

Abstract

This study was focused on printability compostable of plastic compounds which are PLA/PBAT and PBAT/Starch. Those two kinds of compostable plastic compounds were printed with water-based flexography printing ink. The print quality was observed in various variable parameter; density, print contrast, tone value increase (TVI), rub resistance, ink adhesion, surface roughness, and wettability (contact angle). The printing conditions were varied with three anilox line resolutions 400, 600 and 700 lpi and four levels of corona-discharge treatment 0, 500, 1,000 and 1,500 watt. Also, the water-based flexography printing ink was developed for this study with some additive in order to make the ink compatible for compostable plastic compounds. The results showed that two kinds of compostable plastic compounds could be printed with good high details but they were not suitable for printing without surface treatment because of its low adhesion, rub resistance and print uniformity. It was because the surfaces of those plastics compound films had hydrophobicity and low surface energy. However, the surface treatment increased the surface energy and roughness which made those plastics could be printed with better print result. The best printing condition was 700 lpi anilox line resolution and 500 watt corona treatment at 30m/min constant speed. Thorough this condition suitable ink density was gotten achieved in range of 1.38-1.40, and TVI was the lowest. The print contrast for PBAT/Starch and PLA/PBAT was about 21 and 18, respectively. It also was found that was no difference of tone rendering in high-light and mid-tone areas. While the ink adhesion property was in the lowest level in all condition.