Bionanocomposites based on PLA and halloysite nanotubes: From key properties to photooxidative degradation

摘要

Halloysite nanotubes (HNT) and polylactide (PLA) were dry-mixed and melt-compounded to produce PLA nanocomposites with up to 12 wt-% nanofiller. The key characteristics of PLA-HNT nanocomposites were evidenced as follows: good nanofiller distribution and dispersion assessed by transmission electron microscopy (TEM), high tensile strength (values above 60 MPa) and mechanical rigidity, with Young's modulus increasing with HNT loading. The impact resistance of PLA is not decreased, whereas as it was revealed under dynamic solicitation (DMA), addition of HNT led to the notable enhancement of storage modulus. The degradation by photooxidation of PLA-HNT nanocomposites was compared to pristine PLA. The chemical modifications were evidenced by infrared (IR) and UV-visible spectroscopy, whereas from 1R absorbance at 1845 cm"1 was determined the rate of degradation. Like in the case of other natural clays, HNT had a dramatic pro-degradant effect on the photooxidation of PLA, ascribed to the presence of chromophoric groups and/or iron impurities. Indeed, by comparing nanofillers of different purity, the photooxidation of PLA was found significantly reduced using HNT having about four times lower traces of iron. The choice of HNT of adequate purity or/and its purification is looked as powerful method to reduce the photooxidative degradation of PLA nanocomposites.