الفهرس 
Preparation and characterization of unradiated and radiated poly(lactic acid) bio-based nanocomposites
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Abstract
Poly(lactic acid) (PLA) loaded with various levels of chitosan nanoparticles (CsNP) (0{u2013}5.0%) were prepared by twin{u2013}screw extrusion. The nanocomposites were investigated based on their morphology, thermal, mechanical and dielectric properties. The SEM morphology showed that CsNP was dispersed uniformly in the PLA matrix. Mechanical properties of nanocomposites were investigated. Incorporation of the CsNP in the PLA matrix improved the elongation and the impact strength, but decreased the tensile strength. A reduction in the creep strain of the composites was observed compared with neat PLA, indicating an enhancement performance of the nanocomposites. Thermal analysis through DSC revealed that the cold crystallization temperature of PLA in the case of nanocomposites slightly decreased with increasing content of CsNP; indicating a limit nucleating effect of CsNP. TGA analysis revealed that the incorporation CsNP slightly decreased the thermal stability of the PLA matrix. The dielectric properties of these materials have been investigated for the Ü- relaxation process as a function of the temperature and frequency. The Ü- relaxation process was analyzed with Vogel-Fulcher-Tamman and Havriliak{u2013} Negami models and fitting parameters and their evolution were obtained. The effect of Þ-irradiation on the properties of poly(lactic acid), PLA, and PLA composite containing 3.0% chitosan nanoparticles, PLA-3CsNP, was also investigated due to sterilization required in medical and packaging applications. The tested materials were exposed to Þ-irradiation at different doses (5-40 kGy). The irradiated samples both in solid state or chloroform solution were characterized with respect to physicochemical properties. The tested materials showed a reduction in the molecular weight with the increase in irradiation dose, indicating that random chain scissions of the main chains, as dominant effect of Þ-irradiation, was occurred