Optimization of concentrations of natural antioxidants (curcumin) to enhance the thermal stability of ultra high molecular weight polyethylene (UHMWPE)

The impact of different concentrations of natural antioxidants (curcumin) on the thermal stability of UHMWPE (ultra-high molecular weight polyethylene) is examined via the thermogravimetric (TGA/DTA) technique, in the temperature region 50–600 °C at a 5 °C/min heating rate. This work employs the model fitting (Coats and Redfern) approach to determine the optimal curcumin concentration. UHMWPE samples at optimum concentration are further subjected to three other heating rates, viz., 10, 15 and 20 °C. A bi-Gaussian asymmetric function is utilized for deconvolution to elucidate the complexities of thermal decomposition. Through deconvolution, two peaks are obtained and the activation energy corresponding to each peak is determined through two iso-conversional kinetic (Friedman and Starink) models. By utilizing activation energy, the random nucleation reaction mechanism involved in thermal decomposition is recognized. Finally, changes in entropy \(\left(\Delta S\right)\) $\left(\mathrm{\Delta },S\right)$ , enthalpy \(\left(\Delta H\right)\) $\left(\mathrm{\Delta },H\right)$ and Gibbs free energy \(\left(\Delta G\right)\) $\left(\mathrm{\Delta },G\right)$ are determined.