Exploring Tannins from wood biomass as bioadditives for bioplastics

Synthetic plastics are considered as the most important materials in the world. However, recent studies have demonstrated how their diffusion has raised also environmental issues, especially due to their low biodegradability and poor recycling process. In order to overcome these limitations, the scientific community has analysed the use of biopolymers. In particular, the polyhydroxyalkanoates (PHAs) have attracted a lot of interest, since they are produced by microorganisms and they are easily available. Biopolymers used at the industrial scale need to be formulated with additives to be fully responding in terms of physical-mechanical properties, processability, durability and more. However, the selection of additives for bioplastics is made complex by the restrictions to be followed and their impact on the environment is not always negligible. Several kinds of natural molecules have been recently proposed as functional additives for bioplastics, as the hydrolysable and condensed tannins which are waste-biomass derivatives having a functionality as aromatic antioxidants units, potential antibacterial activity and thermal stabilizers. The purpose of this thesis is to develop novel bio-based plastics by including tannins in their formulation, and to assess their overall effect on the bioplastic's properties. Hydrolizable tannins from chestnut wood coming from a research laboratory at the University of Padova, have been used. As bioplastic matrix, we selected polyhydroxyalkanoates (PHAs) for the emerging potential as feasible sustainable substitutes for both standard and technical plastic grades. In order to assess the best strategies for including tannin molecules in PHA matrices, three different approaches have been developed: 1- SOLUTION MIXING 2- MELT MIXING 3- EMULSION MIXING The amount of tannin in the formulation has been varied from 0 to 5% and the samples have been fully characterised in terms of thermal properties and UV absorption.