Layer-by-layer assembly of nanoclays for improved barrier properties of biobased polymers

Abstract

Today, 26 % of the total plastic volume in the world is used for packaging, and over 90 % of this plastic is fossil-based (MacArthur et al., 2016). A growing consumer awareness has led to a demand for alternatives to fossil-based plastic. Polymers made of biobased resources, called biobased polymers, are therefore of interest. Biopolymers are a promising replacement to fossil-based packaging. The industrial application of biopolymers for packaging has been limited because most biopolymers have poor mechanical- and barrier properties compared to fossil-based plastic. To improve these properties nanoclay can be used. The purpose of this thesis was to find the best combination of liquids and substrates which was able to create an even coating and improve the barrier properties of the substrates. The study was performed step by step, and only one nanoclay-suspension was combined with PEI at the time. Changes and adjustments of the experimental design were done to improve the method. The biobased polymers PLA and three carton qualities were used as substrates. The substrates were coated with a polyethyleneimine (PEI)-solution and three different nanoclays by using the layer-by-layer (LBL) method through dip-coating. The three nanoclays were montmorillonite K10, halloysite and hydrophilic bentonite. Dip-coating includes using liquids to coat a solid substrate by immersing it and then withdraw and dry it. After drying the substrate were immersed in liquid again. The dip-cycle was repeated for as many times as necessary based on the experimental design.