Mechanical properties

Polylactide (PLA) is a glossy, high modulus, and high strength thermoplastic biopolymer with properties comparable to those of polystyrene and poly (ethylene terephthalate). This chapter introduces the mechanical properties of PLA materials as a general framework. Along with that, it explores the dependency of mechanical performance of PLA on temperature, relaxation and aging, annealing, orientation, stereoregularity of PLA molecules, and the use of reinforcements. The chapter then discusses the effect of copolymerization, plasticization, and blending on the final mechanical properties of PLA. The dependence of PLA mechanical properties on its molecular weight has been investigated by many authors. According to the work of Engelberg and Kohn, the increase of molecular weight from 107,000 to 550,000 g/mol resulted in a 20% increase in tensile strength. Mechanical orientation is another method for improving the mechanical properties of PLA due to its morphological change from α-crystallites into β-crystallites upon drawing.