Abstract

A novel blend of polypropylene (PP) with Chlorella, a natural microalga, was synthesized successfully by a melt-mixing method with maleic anhydride-modified polypropylene (MPP) as a compatibilizer. The adhesion of hydrophobic PP to hydrophilic Chlorella is based on the formation of chemical bonds between the maleic anhydride groups of MPP and hydroxy groups of Chlorella through solid-phase esterification. The single maleic anhydride groups have the highest reactivity with Chlorella. From the comparison with PP–Chlorella blends without MPP, the ester bonds between MPP and Chlorella cause a decrease in crystallinity of the MPP matrix which is a primary origin of the decrease in melting and solidification enthalpies of the MPP–Chlorella blend, and induce intensive expansion of the MPP matrix around the Chlorella particles which decreases the glass transition temperature. Consequently, the PP–Chlorella blend with MPP exhibits a marked increase in tensile strength and Young's modulus compared with the blend without MPP because of the stronger interactions between MPP and Chlorella than those between Chlorella cells.