Thermal degradation behaviour and crystallization kinetics of poly (lactic acid) and cellulose nanocrystals (CNC) based microcellular composite foams

The current investigation addresses the thermal degradation and non-isothermal crystallization behaviour of the fabricated poly (lactic acid) foam (nPLA) and poly (lactic acid) (PLA)/cellulose nanocrystal (CNC) based foams at three different loadings of CNC (i.e. 1%, 2% and 3%) as PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 having highly porous, interconnected and microcellular morphology. The formation of various gaseous products at two different conversions (α = 0.3 and α = 0.7) are investigated by using thermogravimetric analyser hyphenated Fourier transmission infrared spectroscopy (TGA-FTIR) analysis in isothermal condition. Effect of porosity and CNC reinforcement towards thermal degradation and crystallization of the PLA is thoroughly investigated by using mercury intrusion porosimetry (MIP). “Model-free” and “modelistic” approaches like Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sinouse (KAS), Kissinger and Augis & Bennet have been utilized for non-isothermal degradation kinetics of the fabricated foams. Non-isothermal melt crystallization kinetics of fabricated foams reveals that both primary and secondary crystallization process taking place. The apparent activation energy calculated from FWO are ~175.8 kJ/mol, ~198.6 kJ/mol, ~175.5 kJ/mol and ~174.7 kJ/mol for nPLA, PLA/CNC 1, PLA/CNC 2 and PLA/CNC 3 respectively. It is also observed that at higher conversions, complex three dimensional diffusion mechanism of degradation might be taking place in accordance with Criado plots.