Biocomposites based on renewable resource: Acetylated and non acetylated cellulose cardboard coated with polyhydroxybutyrate

Abstract

Renewable resource based bilayer films were prepared from polyhydroxybutyrate film (PHB) and cellulose cardboard via compression molding, containing 5, 10, 15 and 20 wt% of PHB. The effects of PHB contents on moisture absorption, water absorption and water vapor permeation of films were investigated. All biocomposites showed improved permeation properties. As of 15% of PHB, water permeation, equilibrium moisture content and polarity showed a marked drop. It is therefore assumed that the hydrophobic PHB covered up the cellulose cardboard and formed a continuous layer. The water–polymer interactions in materials are critical to the prediction of their behavior in applications where they are exposed to water or humid environment. The elastic modulus (E), tensile strength (σ) and strain at break (ɛ) of two-layer biocomposites depend on the PHB content. Improved uniaxial tensile behaviour was obtained in composites with more than 15% of PHB. In order to improve the adhesion between the cellulose and the PHB, the cellulose cardboard was acetylated. The percentage of moisture absorbed is less than the composites without treatment, due to the better adhesion between the PHB and the cellulose cardboard. This work showed the studies carried out to obtain and study a new biodegradable bilayer material with the needed amount of PHB to improve the barrier and the mechanical properties of cellulose cardboard. It was demonstrated that two-layer PHB-cellulose films exhibited suitable barrier and mechanical performance for packaging applications, taking advantage of the good properties of both materials. Use PHB coatings should provide an outlet for replace Tetra Pak packaging.