Study of Mechanical and Thermal Behavior of PLA Modified with Nucleating Additive and Impact Modifier

Poly(lactic acid) (PLA) is the biodegradable polymer with greatest potential to replace petroleum-based polymers for the packaging industry. However one of its major limitations is the poor thermal dimensional stability. This paper presents a study of the influence of two additives: thermal modifier (nucleating) and impact modifier on the Heat Distortion Temperature (HDT), Vicat Softening Temperature (Vicat) and mechanical properties of PLA. The mechanism of these additives was evaluated by analyzing the glass transition temperature (Tg) and degree of crystallinity by Differential Scanning Calorimetry (DSC) in the samples with and without annealing treatment. An experimental design was applied for the statistical treatment of the data. The values of HDT and Vicat were slightly altered by the presence of additives, although the tensile elastic modulus increased. Annealing was responsible for the increase in HDT as well as in Vicat due to an increased degree of crystallinity. DSC curves showed a great complexity in the thermal behavior of PLA, being strongly influenced by the conditions of heat treatment.