Mechanical properties of poly(lactic acid)/multiwalled carbon nanotubes nanocomposites

Abstract

In this study, the mechanical properties of polylactic acid reinforced with carboxylic functionalized multiwalled carbon nanotubes were investigated. The polylactic acid/multiwalled carbon nanotubes nanocomposites were prepared using direct melt-blending method in a counter-rotating twin screw extruder with various loadings of nanotube. The extruded nanocomposites were then pelletized and injection moulded into test specimens for mechanical testing. The effects of the increased content of nanotube on the mechanical properties of polylactic acid nanocomposites were investigated through tensile, flexural and impact tests. The analysis showed that the tensile strength and modulus increase with increasing amount of multiwalled carbon nanotubes, indicating the ability of multiwalled carbon nanotubes to improve the stiffness of polylactic acid. The optimum loading of 5 phr gave the best tensile and flexural strength of 40·949 and 54·132 Mpa, respectively. However, both flexural and the tensile strength experienced rapid decrease after the optimum loading owing to agglomeration of nanotubes. The highest modulus was observed at 7 phr with 3·483 GPa, while the highest flexural modulus was observed at 7 phr with 4·244 GPa. On the other hand, the impact strength decreases with increasing amount of multiwalled carbon nanotubes.