Sustained antioxidant properties of epigallocatechin gallate loaded halloysite for PLA as potentially durable materials

Halloysite nanotube (HNT) was etched by hydrochloric acid, and epigallocatechin gallate (EGCG) was loaded into the etched HNT (HH) to prepare loaded antioxidant (HH-E) for polylactic acid (PLA) with improved thermal-oxidative stability. The loading process was confirmed by TGA and FT-IR, and the loading capacity was 16.15%. The presence of EGCG on the surface of etched HNT was further confirmed by nitrogen adsorption and TEM. The effect of loaded EGCG on thermal-oxidative stability of PLA was characterized by the change in OOT values of PLA after the aging process under 140 degrees C. The results showed that HH-E increased OOT values of PLA from 231.2 degrees C to 293.6 degrees C at first, indicating that HH-E provided PLA with excellent thermal-oxidative stability. Furthermore, as can be seen from the trend of OOT changing over aging time, during the 14 days aging process, OOT values of PLA composites with HH-E decreased more slowly than that of PLA composites with EGCG alone, endowing PLA with sustainable thermal-oxidative stability. Further kinetic analysis showed that the apparent activation energy of the degradation process (Ea) of PLA composites with HH-E changed less than that of PLA composites with EGCG alone, which showed that the loading system provided PLA better sustainable stability. Moreover, the isothermal crystallization process of modified PLA was characterized by DSC and POM. The results showed that HH-E provided heterogeneous crystal nucleus for PLA, reducing the half crystallization time (t0.5) and improvement of crystallization rate for PLA. These results prove that HH-E exhibited excellent performance in improving the thermal stability and crystallization property of PLA, showing multifunctional characterization.