Dispersion of unfractionated microalgae in various polymers and its influence on rheological and mechanical properties

Abstract

This study investigates unfractionated microalgae (Chlorella sp. HS2 (HS2)) as a new resource of biomass to develop microalgae-based bioplastic materials. For the fabrication of microalgae-based bioplastics, HS2 is melt-compounded with various polymers with different solubility. In addition, lipid-extracted HS2 (HS2-LE) is tested to compare the dispersion of unfractionated microalgae. Dispersion of HS2 in the polymer is assessed with morphological observations and image analysis, further evaluated based on mechanical, thermal, FT-IR spectroscopic, and rheological measurements. HS2 disperses in polymer with broad size distribution and forms large millimeter-sized agglomerates throughout the composite regardless of type of polymers. Meanwhile, size distribution of HS2 aggregates is shifting to smaller region at mixing condition realizing strong stress transfer. For poly(ethylene–vinyl acetate) (EVA)/HS2 showing smaller size distribution, the addition of 10% HS2 increases elongation at break of EVA. Moreover, lipid-extracted HS2 (HS2-LE) increases further ductility and strength of EVA composite due to better dispersion of HS2-LE. This preliminary study to screen out of several polymers to develop microalgae-based bioplastics has brought out a potential of HS2 for bioplastic application.