Fabrication of biodegradable poly (lactic acid)/carbon nanotube nanocomposite foams: Significant improvement on rheological property and foamability

Recently, biodegradable macromolecules have been highly desired as a promising alternative for traditional oil-based plastics to work out the eco crisis and biological health problems triggered by microplastics. Herein, we presented a simple, effective, environmentally friendly and CO-based foaming methodology for fabricating ultra-low-density poly (lactic acid)/carbon nanotube (PLA/CNTs) nanocomposite foam. By the gradual incorporation of CNTs, three kinds of networks generated in PLA/CNTs nanocomposites and had a distinct reinforcement influence on their melt viscoelasticity, which testified by transmission electron microscope, electrical conductivity and rheological property measurements, severally. Specifically, the storage modulus of PLA/CNTs nanocomposites were 3 orders of magnitude higher in contrast to pure PLA. Interestingly, relative to that under regular differential scanning calorimetry (DSC), a double melting peak phenomenon appeared in the high-pressure DSC curves of diverse PLA specimens. Biodegradable PLA/CNTs nanocomposite foam was successfully fabricated with a super-high volume expansion ratio (VER) of 49.6 times, which could offer a promising strategy for developing other thermoplastic polyester foams with ultra-high VER to obtain some unique functional attributes.