The preparation of multi-walled carbon nanotube/poly(lactic acid) composites with excellent conductivity

Multi-walled carbon nanotube (MWCNT)/poly(lactic acid) (PLA) composites were prepared by meltblending and hot-press processing. First, stearyl alcohol was added to the acid-treated MWCNTs (MWCNT-COOH); it reacted with the carboxylic group to form modified MWCNT with long alkyl chain of 18 carbons (MWCNT-C18). Furthermore, the MWCNT-C18 and PLA were then mixed and a small amount of transesterification agent (TA) was added, so that the MWCNT-C18 was grafted onto PLA chains by transesterification. The results show that an excellent dispersion of modified MWCNT in the PLA matrices was achieved. Moreover, two Tms and re-crystallization peak are found for the TA-modified MWCNT/PLA composites, but they do not appear for the non-TA-modified ones. SEM analysis shows that an excellent dispersion of modified MWCNT in the PLA matrices was achieved. Composites with the addition of 3 wt.% MWCNT-C18 and 3 wt.% TA-modified MWCNTs showed increases in the storage modulus at 40 °C of 77.4% and 88.0%, respectively. The increases of loss modulus at the glass transition temperature were 43.8% and 75.6%, respectively. The surface resistivity of the PLA decreased from 5.30 × 1012 to 8.58 × 10−2 Ω/sq after the addition of 3 wt.% TA-modified MWCNTs.

► The MWCNT was chemically modified with long alkyl chain of 18 carbons.
► This modified MWCNT was grafted onto PLA chains by transesterification.
► The maximum increment of the storage modulus of PLA at 40 °C was 88.0%.
► The surface resistivity of the PLA can decrease from 5.30 × 1012 to 8.58 × 10−2 Ω/sq.