Influences of poly(lactic acid)‐grafted carbon nanotube on thermal, mechanical, and electrical properties of poly(lactic acid)

Abstract

Abstract Poly(lactic acid)‐grafted multiwalled carbon nanotubes (MWNT‐ g ‐PLA) were prepared by the direct melt‐polycondensation of L ‐lactic acid with carboxylic acid‐functionalized MWNT (MWNT‐COOH) and then mixed with a commercially available neat PLA to prepare PLA/MWNT‐ g ‐PLA nanocomposites. Morphological, thermal, mechanical, and electrical characteristics of PLA/MWNT‐ g ‐PLA nanocomposites were investigated as a function of the MWNT content and compared with those of the neat PLA, PLA/MWNT, and PLA/MWNT‐COOH nanocomposites. It was identified from FE‐SEM images that PLA/MWNT‐ g ‐PLA nanocomposites exhibit good dispersion of MWNT‐ g ‐PLA in the PLA matrix, while PLA/MWNT and PLA/MWNT‐COOH nanocomposites display MWNT aggregates. As a result, initial moduli and tensile strengths of PLA/MWNT‐ g ‐PLA composites are much higher than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, which stems from the efficient reinforcing effect of MWNT‐ g ‐PLA in the PLA matrix. In addition, the crystallization rate of PLA/MWNT‐ g ‐PLA nanocomposites is faster than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, since MWNT‐ g ‐PLA dispersed in the PLA matrix serves efficiently as a nucleating agent. It is interesting that, unlike PLA/MWNT nanocomposites, surface resistivities of PLA/MWNT‐ g ‐PLA nanocomposites did not change noticeably depending on the MWNT content, demonstrating that MWNTs in PLA/MWNT‐ g ‐PLA are wrapped with the PLA chains of MWNT‐ g ‐PLA. Copyright © 2008 John Wiley & Sons, Ltd.