**5. Conclusions**

Blends of PLLA, PHBV and PCL were produced using twin screw extrusion and characterised using FTIR, DSC, tensile testing (including tensile creep) and rheometry. FTIR and DSC showed that all three materials were effectively processed and incorporated

into the blends. The tensile, creep and viscosity data show that in small concentrations, PHBV alone (up to 25%) and PCL/PHBV together (up to 10% of each polymer) can modify the behaviour of PLLA in a positive way, offering improved modulus, strength and elongation at break depending on the concentrations of each polymer used. Within the constraints of the range of concentrations of the three polymers used here, the influence of PHBV outweighs that of PCL in terms of the effect on modulus and strength, whereas for creep behaviour and viscosity, the influence of the PCL outweighs that of PHBV. At a concentration of 5% PCL in the ternary blends, the creep rate exhibited by the polymer blend was identical to that of PLLA alone. Overall, we consider that blending PCL and PHBV through melt processing with PLLA offers an effective approach to the development of new polyester-based biomaterials with combinations of properties which cannot be provided by any of the materials individually, and which have not been demonstrated through previous approaches to blending.

**Author Contributions:** Conceptualisation, K.D., A.M.F., P.G. and G.M.; methodology, R.N., G.M., M.J.G., A.M.F., P.G. and K.D.; investigation, R.N. and G.M.; resources, K.D., A.M.F., P.G. and M.J.G.; data curation, G.M. and R.N.; writing—original draft preparation, R.N. and G.M.; writing—review and editing, K.D., A.M.F., P.G. and M.J.G.; supervision, K.D., A.M.F., P.G. and M.J.G.; project administration, K.D.; funding acquisition, K.D., A.M.F., P.G. and M.J.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This project received funding from the European Union's Horizon 2020 research and innovation programme under gran<sup>t</sup> agreemen<sup>t</sup> no. 814410.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data supporting this publication are openly available at the following dois:10.5281/zenodo.7235496; 10.5281/zenodo.7235502; 10.5281/zenodo.7235530; 10.5281/zenodo.7235574.

**Conflicts of Interest:** The authors declare no conflict of interest.
