Method for Simultaneously improving the thermal stability and mechanical properties of poly(lactic acid): effect of high-energy electrons on the morphological, mechanical, and thermal properties of PLA/MMT nanocomposites.

Nanocomposites derived from poly(lactic acid) (PLA) and organically modified montmorillonite (oMMT) have been cross-linked by high-energy electrons in the presence of triallyl cyanurate (TAC). The morphology of untreated and cross-linked PLA/MMT nanocomposites was characterized by wide-angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). This treatment can improve both the thermal stability and the glass-transition temperatures of the PLA nanocomposites (e.g., PLA-MMT-TAC 30kGy, 50kGy, and 70kGy) because of the formation of cross-linking structures in the nanocomposites that will considerably reduce the mobility of polymers. Interestingly, at relatively low irradiation doses (e.g., 30 and 50 kGy) a good balance between tensile strength and elongation at break for the PLA nanocomposites could be achieved. These mechanical properties are superior to those of pure PLA. Therefore, combining nanotechnology and electron beam cross-linking is a promising new method of simultaneously improving the mechanical properties (toughness and tensile strength) and thermal stability of PLA.

A new approach to reducing the flammability of layered double hydroxide (LDH)-based polymer composites: preparation and characterization of dye structure-intercalated LDH and its effect on the flammability of polypropylene-grafted maleic anhydride/d-LDH composites.

Dye structure-intercalated layered double hydroxide (d-LDH) was synthesized using a one-step method, and its intercalated behaviors have been characterized by Fourier transform infrared spectroscopy (FTIR), wide angle X-ray scattering (WAXS), scanning electron microscopy, thermogravimetric analysis (TGA), etc. As a novel functional potential fire-retarding nanofiller, it was used to prepare a polypropylene-grafted maleic anhydride (PP-g-MA)/d-LDH composite by refluxing the mixture of d-LDH and PP-g-MA in xylene, aiming to investigate its effect on the flammability of the PP-g-MA composite. The morphological properties, thermal stability, and flame retardant properties of the PP-g-MA/d-LDH composite were determined by FTIR, WAXS, transmission electron microscopy, TGA, and microscale combustion calorimetry. Compared with NO3-LDH (unmodified LDH) and LDH intercalated by sodium dodecylbenzenesulfonate (conventional organo-modified LDH), d-LDH can significantly decrease the heat release rate and the total heat release of the PP-g-MA composite, offering a new approach to imparting low flammability to LDH-based polymer composites.