Generalized kinetics for thermal degradation and melt rheology for poly (lactic acid)/poly (butylene...

Systematic kinetics of melt-blended Poly(lactic acid) (PLA)/Poly(butylene succinate) (PBS) and PLA/PBS/functionalized chitosan (FCH) nanobiocomposites with dicumyl peroxide (DCP) and chemical changes thereof at degradation temperatures are evaluated using thermogravimetry (TGA) and thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA-FTIR). A comprehensive kinetic model is employed on above blended samples, including (i) Flynn-Wall-Ozawa, Kissinger, Kissinger-Akahira-Sunose methods to investigate the kinetic and thermodynamic variables, and (ii) Generalized master plots to propose the thermal-induced mechanism. The thermal stability of PLA/PBS reduced with increasing FCH loading up to 3 wt%, and improved for DCP treated PLA/PBS/1FCH at maximum degradation temperature (T_max) is noticed. The activation energy estimated from Flynn-Wall-Ozawa method are (129-139 kJmol^-1), (116-152 kJmol^-1), (109-146 kJmol^-1), (132-169 kJmol^-1) and (120-166 kJmol^-1) for PLA/PBS, PLA/PBS/1FCH, PLA/PBS/3FCH, PLA/PBS/1DFCH and PLA/PBS/3DFCH respectively. The generalized master plots depicts that the PLA/PBS blend exhibited L2-F1 mechanism whereas their nanobiocomposite with or without DCP followed L2-D_n and A2-L2-D_n mechanism respectively. Coupled TGA-FTIR highlights the similar kinds of products such as lactide, acetaldehyde, esters, CO₂ and CO liberated during the thermal degradation of PLA/PBS blend and their nanobiocomposites. These crosslinked/branched structures are postulated by the rheological behavior which confirmed increase in the complex viscosity (η*) and storage modulus (G') of PLA/PBS/D/1FCH.