Polylactid acid (PLA) is at the present time the most used biopolymer due to its high mechanical strength and easy processability (Arrieta et al., 2014). However, PLA shows disadvantages such as brittleness, sensitivity to high temperature and humidity, low impact strength and high cost. One alternative to modify PLA properties is by the addition of low amounts of nanoclays. Although thermal properties of PLA based nanocomposites have been studied extensively but there is still a lack of information about their mechanical properties. In this work, the effect of a modified nanomontmorillonite (NMN) added to PLA over its flexural and tensile properties was studied. The nanocomposites were prepared with PLA 3251D (Nature Works) and 1.34 NMN modified with methyl dihydroxyethyl hydrogenated tallow ammonium (25-30 wt. %) (Sigma Aldrich). The nanocomposites were obtained with NMN contents of 1, 3 and 5 % wt in a twin-screw extruder followed by an injection molding process. The nanocomposites were characterized by tensile and flexural tests as well as dynamic mechanical thermal analysis (DMTA) and X-ray diffraction (XRD) analysis. The results obtained showed increases in tensile and flexural modulus with NMN content, up to 26% in the case of flexural modulus and 19% for tensile modulus. The flexural strength results were increased independently of the NMN content (24%) indicating a good interaction between PLA and NMN. Also the tensile strength was increased by 10% with NMN addition. XRD tests indicated that the nanoclay was exfoliated with the extrusion process. DMTA results showed that storage modulus of nanocomposites increased with nanoclay addition; however the thermal stability was not modified displaying a significant drop in storage modulus around 60 °C (Tg of PLA) for all materials. Figure 1. Flexural and tensile properties of PLA nanocomposites References 1. M.P, Arrieta, F. Parres, J.López, A. Jiménez, Journal of Analytical and Applied Pyrolysis 101 (2013) 150–155.