Influence of ultrasonic treatment on properties of bio-based coated paper

In the research, kraft paper was coated with a blend of chitosan and rice starch ultrasonic-treated coating solution. The novelty in this paper is the use of bio-based coating solution which was treated with ultrasound, which led to a positive effect on the mechanical, optical and water barrier properties. The goal of the research was to improve the coating solution with ultrasound and to make the coated kraft paper with chitosan and rice starch suitable for a packaging material. To evaluate the influence of the ultrasonic treatment on coating solutions, the moisture content, water vapour permeability, absorptiveness, tensile strength, elongation at break, tear and bursting strength, colour values, gloss and surface properties of coated paper were determined. The research showed that the moisture content in all coated papers decreased by less than 0.5%, the water vapour permeability reduction being around 20%. Tensile strength, elongation at break and tear strength improved at coated paper, even more at the one pretreated with ultrasound. Bursting strength, which is important at paper bags, increased by 9% at coated, and by 12% at coated and ultrasound -treated paper. Furthermore, gloss improved at both coated papers. As expected, the coating affected the surface, with fewer and smaller pores. At paper the coating of which was treated with ultrasound the surface was smoother and fewer pores were detected. The results showed that the ultrasonic treatment is not only an inexpensive and environmentally friendly process, but is also very effective in the preparation of solutions for bio-based coatings. Such coatings have better moisture resistance and are more flexible, which is important for packaging paper. Therefore, preparihg solutions using ultrasound as pretreatment is an improved and convenient procedure to enhance many properties of bio-based coatings. (C) 2016 Elsevier B.V. All rights reserved.