Evaluation of Thermomechanical Properties of Polymer Blends Intended for Additive Manufacturing Processing: Comparative Study of Poly(Lactic Acid) and Poly(Lactic Acid)/Polyhydroxyalkanoate Blends

The following article presents the results of research on the assessment of the effect of FDM printing process conditions on the properties of the obtained products. During the research, unmodified PLA and a PLA/PHA mixture were subjected to comparative analysis. Both materials exhibit excellent processability under standard FDM process conditions; however, the PLA/PHA blend is gaining attention due to its potential as a more thermally resistant and less brittle alternative to unmodified PLA. The printing procedure conducted at high bed platform temperature confirmed that for standard PLA varieties and the PLA/PHA blend, it is possible to obtain improved thermomechanical properties only by modifying the machine parameters of the printing process. The increase in the Vicat softening temperature value was about 80 °C, reaching above 130 °C. Interestingly, for materials based on pure PLA, most mechanical properties exhibit noticeable improvement, with the improvement in impact strength being particularly beneficial. For most materials, the measurements revealed significant anisotropy of properties within the tested samples, which was particularly due to the use of different bed platform temperatures. The apparent effect of this was the change in the thermal conditions of the PLA phase crystallization process, with crystallinity levels ranging from 17 to 33% for selected samples. The obtained results confirm that PLA/PHA blends are an interesting alternative for the PLA-based material; however, further research is needed to improve the application potential further.