Effect and investigating of graphene nanoparticles on mechanical, physical properties of polylactic acid polymer

Polylactic acid (PLA) is a linear aliphatic polyester thermoplastic made from renewable sources such as sugar beet and cornstarch. Methods of preparation of polylactic acid are biological and chemical. The advantages of polylactic acid are biocompatibility, easily processing, low energy loss, transparency, high strength, resistance to water and fat penetration and low consumption of carbon dioxide during production. However, polylactic acid has disadvantages such as hydrophobicity, fragility at room temperature, low thermal resistance, slow degradation rate, permeability to gases, lack of active groups and chemical neutrality. To overcome the limitations of polylactic acid, such as low thermal stability and inability to absorb gases, nanoparticles such as graphene are added to improve its properties. Samples were prepared by solution casting method using chloroform as solvent and in thin films. The mechanical, thermal, and structural properties of Polylactic acid pure and Polylactic acid/graphene nanocomposites were studied using tensile Test X-ray diffraction (XRD), Root mean square (RMS) and Differential Scanning Calorimetry (DSC). Also, by exposing the samples to Ultraviolet (UV) rays and then performing the tensile test, the resistance of the produced nanocomposites against Ultraviolet (UV) rays was investigated. With performing the above tests, it was found that by adding graphene nanoparticles to Polylactic acid, the crystallinity decreases and the strength and elongation of graphene particles (0.4% graphene) increase to a certain extent and then decrease. The loss modulus and storage modulus are also increased by the addition of graphene nanoparticles. By comparing the samples exposed to Ultraviolet (UV) rays with other samples, a significant decrease in elongation and a significant increase in modulus of elasticity were observed. In other words, Ultraviolet (UV) rays make Polylactic acid/graphene nanocomposites brittle.