Evaluation of the biopolymer Poly-hydroxi-alkanoates

Abstract: Biopolymers are interesting materials from a sustainable point of view. Especially since consumers increasingly demand environmental friendly packages as well as more convenient packages with easy open and close features on the packages. The demands for convenient packages lead to more and more plastics in the packaging industry. The purpose with this project is to find out typical properties of the biopolymer, polyhydroxyalkanoate (PHA) and to evaluate chemical, mechanical and barrier functions of the polymer PHA. The purpose is also to indicate if this polymer is useful in different Tetra Pak applications and define possibilities and restrictions leading to a final recommendation of what application the polymer is useful for. The main focus when it comes to Tetra Pak applications is on Tetra Brik Aseptic (TBA) and caps for the TBA. Tetra Recart (TRC) was also included in the project. The scientific attitude used in this thesis is a system theory, both qualitative and quantitative research approaches have been used. The thesis is based on literature studies, interviews, pilot study and laboratory evaluation. The material is then analysed with the SWOT (Strengths, Weaknesses, Opportunities and Threats) method. Poly-hydroxi-alkanoates is a family of bio-based polyesters that serve as a energy reserve and is produced by fermentation of carbon substrate within the micro-organisms. PHAs are fully biodegradable in both aerobic and anaerobic conditions. Three different suppliers, Metabolix, BioMatera and Nodax, of PHA were invited to take part in this evaluation of PHA by Tetra Pak. Nodax was not able to deliver any material and thereby were excluded from further investigation in this thesis, The pilot production including injection moulding and extrusion coating shows that the PHA requires changes in the process, in order to be used. A big difference between the PHA and the materials used today is the slow crystallization that is possible to speed up by using warm tools when injection moulding and a warm chilly rolls when extruding. The laboratory testing of the material properties indicates that most of the tested properties of the PHA both from Metabolix and from BioMatera are in need of improvement to match the materials used today and to measure up to the demands. In the laboratory testing of recycling properties the PHA extruded on carton did pulp readily and no flakes of fibres could visibly be noticed. The breakdown of the polymers into smaller pieces indicates that the polymers are more brittle than LDPE, which could be an issue in the recycling of paper. The conclusion of this thesis is that the Poly-hydroxi-alkanoates possess good and needed properties compared to other biopolymers. But there are still properties needed to be improved and they are not as easy to process as the materials used today. The tested PHAs are all in need of improvement to be able to use in the laminar packaging materials for TBA, TRC or in a cap. The recommended next step is to contact the potential suppliers in order to discuss the result of the laboratory testing and the possibilities to make improvements. If the discussion is successful and new and improved grades are processed , I suggest further testing of the material. If it does not result in a new modified PHA grade I suggest further research for potential suppliers.