Stereocomplex PLLA–PBAT copolymer and its composites with multi-walled carbon nanotubes for electrostatic dissipative application

Because of its low thermal stability and brittleness, both the drawbacks of poly(l-lactide) (PLLA) were solved by forming stereocomplex (ST) and its copolymer with poly(butylene adipate-co-terephthalate) (PLLA–PBAT). In this study, we synthesized PLLA and PLLA–PBAT copolymer by ring-opening polymerization. Both polymers were blended with poly(d-lactide) to form ST crystals. Multi-walled carbon nanotubes (MWCNTs) were added into the polymer matrix at 5 phr by the solvent casting method. The surface resistance of the composite was ≅106 Ω, which is appropriate for electrostatic dissipative purposes. The copolymer and its ST crystallites were confirmed by the peaks in infrared spectra at 922 and 908 cm−1, respectively. The PLLA–PBAT copolymer had 60% lower tensile strength than PLLA and its stereocomplex, but 10% higher elongation at break. The elongation at break of the PLLA–PBAT copolymer/MWCNT composite decreased by 17% while its thermal stability slightly increased when compared to the unfilled copolymer. The melting temperature for both ST PLLA–PBAT copolymers, with and without MWCNTs, was around 225°C, which is 50°C higher than that of the homocrystals. Moreover, the glass transition temperature and crystallinity of the ST PLLA–PBAT copolymer also increased by adding MWCNTs.