Mineral-filled biopolyester coatings for paperboard packaging materials: Barrier, sealability, convertability and biodegradability properties

The authors wish to thank Arctic Biomaterials Oy for the compounding of the masterbatches. Metsä Board research laboratory technicians are also acknowledged for assistance in laboratory analyses along the research group of Paper Converting and Packaging Technology at Tampere University, for the extrusion coating trial, OTR analysis and hot air sealing tests. Finally, Kruunukartonki – Länsipahvi Oy is thanked for assistance with the cup forming trials, and Itene for the biodegradability tests.Changing trends in packaging materials has been driven by increasing environmental awareness as well as legislation. In this context, paperboard-based packaging have become increasingly popular due to its bio-based origin, potential biodegradability and physical properties. However, conventional systems lack behind in barrier performance and heat sealability. Hence, the addition of functional layers have been considered as alternative solutions to this challenge. Here we propose a biodegradable PLA-based polymer coating filled with minerals (0-10 wt% loading), namely, talc, kaolin and calcium carbonate, all of which were used in surface application on uncoated folding box board. For this purpose, we used a pilot-scale extrusion unit that produced materials that were tested for key properties. We found that the presence of filler in the PLA layer improved both water vapor (up to 16 %) and oxygen (up to 56 %) barrier properties. Moreover, the main effect of the fillers was observed in heat sealability, which was improved via adhesion at low temperatures, resulting in full fiber tear. Cup forming was less effected by filler loading in the PLA coating while repulping tests indicated the presence of large flakes of the polymer coating in 1 %-consistency slurries. Finally, biodegradability was slightly delayed in filler-containing samples (biodegradation within 10-60 days), most likely due to the nucleating effect of the fillers. Nevertheless, all the samples can be classified as biodegradable. Overall, our results represent a step forward in scale-up adoption of PLA-based coatings most useful in the development of packaging materials.Peer reviewe