New strategy for reinforcing polylactic acid composites: Towards the insight into the effect of biochar microspheres

Having even particle size and regular morphology of biochar microspheres (BM) provides the possibility for preparing polylactic acid (PLA) films. Hence, the novelty is proposing a strategy for reinforcing PLA by BM. It was found that BM exhibited regular morphology, higher thermal stability, even particle size, and better pore characteristics. Although adding BM decreased the toughness of PLA due to the poor compatibility between BM and PLA, the nucleation effect of BM facilitated the crystallization in the PLA system. The tensile strength and modulus of BM/PLA composite films increased first and then decreased with increasing BM content. The stress concentration formed by BM particle agglomeration was responsible for the tensile strength and modulus decreases of BM/PLA composite films under higher BM addition. 2% BM added and 3% added composite films exhibited the best tensile strength and modulus with 64.99 MPa and 1.59 GPa, which was mainly attributed to the proper proportion of BM to PLA and the uniform distribution of BM in PLA. The results of this study confirmed the positive reinforcing effect of BM in PLA and are expected to be available in the composite film field.