The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na-MMT, the surface of Na-MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion-exchange and adsorption technique. Both Fourier transform infrared and X-ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt-blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co-modified MMT (C-MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C-MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C-MMT nanocomposites with 5.0wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C-MMT. Copyright (c) 2015 John Wiley & Sons, Ltd.