Modeling of the Kinetics Degradation of Unstabilized and HALS-Stabilized LDPE Films Under Thermo-Oxidation and Natural Weathering Conditions

Abstract

Mathematical models are proposed to predict degradation of unstabilized low-density polyethylene (LDPE) and LDPE stabilized with hindered amine light stabilizers (HALS) under both thermo-oxidations at 70, 80 and 90 °C and natural weathering conditions (NWC). The degradation was measured by change in percent elongation at break \({(\varepsilon_{r})}\) with time. The mathematical approach developed was multiple linear regression analysis (MLRA). The reliability of the selected models was analyzed using four statistical criteria: residual variance, coefficient of determination (r2), Student test and Fisher–Snedecor test. The linear systems that resulted from the MLRA were solved using the GAUSS method. The results obtained indicated that the polynomial models developed to predict elongation at break were reliable for both unstabilized and HALS-stabilized samples under thermo-oxidation at 70, 80 and 90 °C and NWC This was also confirmed by the comparison of the half-life time values predicted from the models with those observed experimentally.