UV-shielding, flexible and enhanced thermal-conductive polylactide composites modified with single-layered, large-sized MXene nano-sheets

An updated organic solvation-assisted intercalation and collection (OAIC) strategy was developed to prepare high-quality 2D transition metal carbon/nitride (MXene) and evaluate its effects on the structure and properties of polylactide (PLA). Then, PLA composites with different MXene contents were prepared by solution casting method. Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, UV–visible spectrometry, x-ray diffraction, differential scanning calorimetry, polarized optical microscopy and mechanical tests were used to characterize the MXene/PLA composites. Also, physical models were established to describe the modification mechanism of MXene on PLA. The results show that our updated OAIC strategy successfully prepared single-layered, large-sized MXene nanosheets, which can disperse in both aqueous phase and organic solvent uniformly and stably. MXene and PLA are physically blended in the resultant composites, since PLA shows the typical spherulite morphology. Crystallite size of PLA was refined by the as-synthesized MXene nanosheets. The MXene/PLA composites illustrated prominent UV shielding effect: its UV shielding performance is very close to 100% when the MXene reaches up to 4.0 parts per hundreds of resins (phr). Elongation at break increases to 95.85% with 3.5 phr of MXene, which is 4.32 times that of pure PLA. Thermal conduction of the resultant PLA composites was greatly improved with small amount of MXene: its thermal conductivity was increased up to 0.59 W·m⁻¹·K⁻¹ with 1.0 phr of MXene, which is 2.2 times that of pure PLA.