Novel PHB/Olive mill wastewater residue composite based film: Thermal, mechanical and degradation properties

In the last few years there has been a growing interest in the use of bio-based and biodegradable plastics, made of renewable resources. A common biodegradable polymer, microbial-derived, is Poly-3-hydroxybutiric acid (PHB). However, PHB homopolymer exhibits a high crystalline structure, which leads to mechanical properties that are not fully compatible with a number of production processes. An interesting approach is blending PHB with other compounds in order to improve its physical properties and reducing the production costs of the finished products. The olive mill wastewater (OMW) is an organic-rich residual that arises from the production and refinery of olive oil, mainly composed by aromatic and aliphatic compounds, proteins, sugars and lipids. In addition, some of these compounds exhibit a higher biotoxicity, which makes OMW not suitable for those applications in which biodegradability is required. Nevertheless, OMW is an inexpensive and abundant source of fine chemicals such as polyphenols, leading, after their extraction, to OMW matrix residuals (OMWR) rich in lignin-cellulose. In this work, OMWR was used as a natural filler for the production of PHB based films. PHB/OMWR composite samples were characterized by chemical, thermal, morphological and mechanical analyses. Furthermore, the degradation profiles, in different environments, were evaluated with the aim to develop materials suitable for agriculture and food packaging applications.