Morphology and Thermal Property of Poly(L-Lactide)/Layered Double Hydroxides Nanocomposites via Melt Intercalation

In this work, sodium dodecyl sulfate (SDS) was used to obtain organically-modified layered double hydroxide (OMgAl-LDH) by anion-exchange reaction. The PLLA/LDH nanocomposites were prepared via direct melt intercalation. The results from both XRD patterns and FTIR spectra showed that SDS entered into the layers of LDH successfully and the layer space was increased from 0.756 to 1.64 nm. For the PLLA/LDH nanocomposites, the increase of the layer space was verified by the good dispersion of LDH in the PLLA matrix from the SEM images. The rheological analysis showed that the typical Newtonian behaviour shifted to shear-thinning behaviour with the addition of LDH. In addition, DSC data illustrated that the glass transition temperature of the PLLA/LDH nanocomposites decreased and the crystallinity of PLLA increased due to the addition of LDH, which indicates that LDH acts as a heterogeneous nucleating agent and induces the crystallization of PLLA. The modified LDH provided a better nucleating effect than the unmodified LDH. TGA results showed that OMgAl-LDH in the PLLA matrix caused earlier initial decomposition, suggesting that the presence of LDH decreased the thermal stability of the PLLA matrix.