The objective of Task 3 is the development of new food packaging materials from the PHAs produced in Task 1 and extracted in Task 2, in relation to the needs of the McCain company which serves as a case study. To this end, Task 3 aims to deepen the understanding of the relationships between the structure of PHAs (composition, molecular weight, sequential distribution of monomer units, crystallinity), their processability and the final properties of the materials (thermal properties, mechanical properties, gas and water barrier properties). This issue has already been widely addressed for P(3HB) and P(3HB-co-3HV) with low 3HV content. However, the impact of the composition, sequential distribution of monomer units and molecular weight of polymers with high 3HV content and mcl-PHAs on the final properties of the materials remains poorly known. Task 3 of the LOOP4PACK project thus aims to study the influence of these structural parameters on the thermomechanical properties of PHAs, via the supply of samples of controlled and contrasted molecular mass (production in task 1 of PHAs from different strains and consortia and under different conditions, and use in task 2 of different extraction methods).
Finally, since PHAs are recovered in the form of fine powders, a pre-mixing step (i.e. compounding by melt extrusion) is necessary to allow the shaping of the packaging materials using conventional plastics processing equipment. The addition of nucleating agents is notably required to increase the crystallization kinetics of PHAs, which are naturally very slow. Furthermore, due to the thermal sensitivity of PHAs, it has already been shown for P(3HB) and P(3HB-co-3HV) with low 3HV content, that optimization of processing conditions is particularly important to control the final properties of the materials. Finally, in view of food packaging applications, a high degree of purity is considered necessary. However, the crystallization phenomena and the thermomechanical behavior of polymers with a high 3HV content and mcl-PHAs deserve further investigation. Task 3 of the LOOP4PACK project thus aims to provide new knowledge on the crystallization mechanisms of high 3-HV PHBVs and mcl-PHAs, with a focus on the impact of PHA purity.
Task 3 is thus divided into 3 subtasks:
- Task 3.1 – Characterization of PHA powders produced in task 1 and extracted in task 2 (molecular weight, thermal properties, crystallinity, thermal stability).
- Task 3.2 – Compounding of PHAs produced in task 1 and extracted in task 2 (formulation using conventional nucleating agents).
- Task 3.3 – Shaping and Study of Structure/Properties Relationships in PHA-based Materials