Poly(L ‐lactide) (PLLA) composites incorporating various inorganic fillers (ifR‐PLA) were prepared by the melt blending technique, and their mechanical and thermal properties were evaluated. The filler types influenced the mechanical properties of ifR‐PLA; for those incorporating particle‐ and whisker‐type fillers the tensile moduli were 3.1–3.7 and 3.7–4.5 GPa, respectively, and the flexural moduli were 4.1–4.8 and 4.8–6.1 GPa. It was found that the tensile strength and modulus, as well as the flexural modulus, of ifR‐PLA incorporating whisker‐type fillers increased in proportion to the volume percent of the fillers (Vf). The flexural strength of ifR‐PLA incorporating 9Al2O3 · 2B2O3 whiskers showed a similar increase, while that of ifR‐PLA incorporating CaCO3 whiskers showed a decrease with increasing Vf. This difference may be because the 9Al2O3 · 2B2O3 with its large aspect ratio kept its original fibrous shape, while the CaCO3 lost its fibrous shape during the blending process. However, the reinforcing effect of these fillers was relatively low compared with that known for the corresponding composites of the conventional polymeric materials, probably because of the poor surface adhesion of PLLA to the fillers.
Comparison of effect on storage moduli of different fillers.
