Assessing effects of ultraviolet ageing on the thermal properties and thermal degradation kinetics of long glass fiber‐reinforced polyamide 6 composites filled with zinc oxide

Abstract In this work, the effects of ultraviolet (UV) ageing on the thermal stability, mechanical properties, and thermal degradation kinetics of long glass fiber‐reinforced polyamide 6 (PA6/LGF) composites filled with zinc oxide (ZnO) are analyzed. The composites with different contents of ZnO expose in the UV radiation of the wavelength of 340 nm for 0 to 800 h. An increase in tensile strength and a decrease in impact strength are observed with longer ageing time while samples filled with ZnO have a higher retention rate of tensile and impact strength after long time ageing. The morphology of the impact fractures of aged and unaged samples obtained by scanning electronic microscopy shows nearly no difference. Then the thermal stability and degradation kinetics of the samples with different filler fraction and different ageing time are investigated by thermal gravimetric analysis with the methods of Kissinger, Friedman, and Flynn‐Wall‐Ozawa in the dynamic measurements (10‐40°C/min). Calculated apparent activation energy (E) values by the three methods show that the samples filled with 6 wt% ZnO have a slightly lower value of E than PA6/LGF composites and nearly no change after longtime UV irradiation.