Evaluation of polyhydroxyalkanoates-based blends for sustainable drug delivery device component manufacturing

• Application of the Avrami model indicates an optimal balance between semi-crystalline and amorphous PHAs for improved crystallisation rates. • Mechanical testing showing enhanced strength and lower creep behaviour in blends with a near-equal ratio of PHBV and PHBH. • A notable reduction in carbon footprint by 4% with optimised composition, coupled with successful moulding of the identified best-performing blend into a high precision component. The suitability of different polyhydroxyalkanoate blends for the replacement of polypropylene in Novo Nordisk’s injection pen application was evaluated. Polyhydroxyalkanoate blends were analysed, each with varying ratios of PHAs, including poly-3-hydroxybutyrate -co- 3-hydroxyvalerate, poly-3-hydroxybutyrate- co- 3-hydroxyhexanoate, and poly-3-hydroxybutyrate -co- 4-hydroxybutyrate, with variable talc compositions. The crystallisation kinetics, secondary crystallisation and mechanical properties were examined through differential scanning calorimetry and tensile testing. Lastly, a life cycle analysis and an environmental risk assessment were performed, and the influence of different crystallisation rates on processing cycle time was studied. The Avrami model was applied to isothermal crystallisation of the blends, it revealed that an equilibrated balance between semi-crystalline and amorphous polyhydroxyalkanoate, with shorter hydrocarbon chains and a small talc addition, accelerated crystallisation. Tensile tests indicated a higher strength and lower creep behaviour for blends that have a ratio close to 1:1. In addition, blends containing poly-3-hydroxybutyrate- co- 3-hydroxyhexanoate exhibited lower tensile strains and toughness but a larger Young’s modulus. Life cycle assessment results demonstrated a carbon footprint reduction of 4% with optimised composition. The blend containing 55 wt% poly-3-hydroxybutyrate -co- 3-hydroxyvalerate and 45 wt% poly-3-hydroxybutyrate- co- 3-hydroxyhexanoate with a low amount of talc exhibited the best potential based on all measured parameters, which was confirmed by successful moulding into a high-precision component.