Biodegradable Coating on Packaging Paper Made from Fibres of Invasive Plant Spieces<em> Fallopia japonica</em>

Abstract

Fallopia japonica is a plant, native to East Asia, Japan, China and Korea, but in North America and Europe it is classified as invasive species. The root system and strong growth of these plants can damage buildings, streets, paving, retaining walls etc. It forms thick colonies, which crowd out other herbaceous species. In our project it was found out that the stem biomass of Fallopia japonica contains 40 percent of cellulose, which is comparable to the raw materials from which paper fibers are typically produced. With chemical and mechanical procedures and treatments, the fibers from Fallopia japonica were prepared and successfully the packaging paper has been produced. Generally, paper is widely used in packaging applications and it is considered as environmentally friendly substrate. It consists of a porous cellulose structure, composed of long-chain molecules in a crystalline state with amorphous regions in-between. Due to hydrophilic nature of cellulose and fiber network porosity, water barrier properties are limited. Conventional coatings that are used to improve water resistance, involve synthetic polymers such as polyethylene, rubber latex, polyvinyl alcohol etc. Natural renewable polymers have been the focus of many researches in recent years. Paper coatings are also commonly used with wax, but the recyclability of laminated and waxed papers is limited due to the separation from the paper, which is connected to the environmental issues. In this study biodegradable coating such as polysaccharide chitosan, was applied to paper made from Fallopia japonica. Namely, non coated paper from Fallopia japonica has high hydrophilic character and therefore it is not suitable for all packaging products. The aim of the research was to investigate the influence of different concentrations of chitosan in coating solution (5 and 10% w/w) on the physical and mechanical properties of the mentioned paper substrate. The water and moisture resistance of the coated paper substrates were determined via Cobb60 value tests, water vapor permeability and moisture. Scanning electron microscopy (SEM) was used to evaluate the effect of coating on the microstructures and the porosity of the paper. The results showed the compatibility of chitosan and paper substrate. Tensile properties of the coated paper has given promising results already at lower concentration (5%) of chitosan. Tensile strength and elongation at break increased, mainly by connectedness of chitosan matrix and polymer chain interactions. With thermogravimetric analysis (TGA) thermal stability and weight changes were detected at coated paper. A high weight loss of 20%, between 300°C and 400°C was detected at 5% and 10% chitosan coated paper, due to the degradation of chitosan main chains. The coated papers possessed better thermal, mechanical and water resistant properties. Considering the biobased nature of the coating and used paper substrate, the procedure can offer environmentally friendly and sustainable solution toward new packaging material. Using a Fallopia japonica as a source for the paper fibers, the need for the wood fibers could decrease and at the same time, the negative impact on the environment could reduce.