Properties of blends of amorphous and semicrystalline PLAs containing multiwalled carbon nanotubes

Blend nanocomposites of amorphous polylactide (aPLA) and semicrystalline PLA (scPLA)-multiwalled carbon nanotubes (MWCNTs) were prepared by a twin-screw extruder below the melting temperature of the scPLA. The maximum weight percent of MWCNTs in the blends was 0.9 wt.%. The extrudates were either pelletized immediately or after drawing at a drawing ratio of about 10. According to small amplitude oscillatory shear rheological analysis, the rheological properties of the aPLA/scPLA (85/15 wt.%) drawn sample were significantly increased compared to the undrawn samples. With the presence of MWCNTs, more crystallites could develop in the scPLA, and the electrical conductivity of the aPLA/scPLA nanocomposites was reduced due to the encapsulation of MWCNTs within the crystallites of scPLA. Increasing the temperature during compression moulding to 190°C, which is above the melting temperature of the scPLA, effectively removed this obstacle and the electrical conductivity was increased by a factor of up to 10⁶ compared to the samples moulded at 150°C.