Modeling of the Kinetic Degradation of Unstabilized and HALS-Stabilized LDPE Films in Natural Aging

In this work, we propose new mathematical models describing the kinetic degradation of unstabilized low-density polyethylene (LDPE) and LDPE stabilized with hindered amine light stabilizers (HALS). The samples were exposed to natural weathering conditions, and the degradation was measured by a change in elongation at break with time. The mathematical approach developed was based on multiple linear regression analysis (MLRA). We tested the reliability of the selected models using four statistical criteria: residual variance, coefficient of determination, Student test and Fisher–Snedecor test. The linear systems resulting from the MLRA were solved using the Cholesky method. The results showed that the polynomial models developed to predict elongation at break were reliable for both types of samples under natural weathering conditions. The experimental half-life times are close to those predicted by the models.