Toughness improvement of poly(lactic acid) by the addition of pre-crosslinked powdered nitrile rubber/CaCO3 for thermoforming molding

Abstract

Polylactide (PLA) is an eco-friendly biodegradable thermoplastic with excellent processability, demanding less energy to be produced compared to the petroleum-based polymers. However, PLA has drawbacks that impose some restrictions of uses use such as poor toughness property. Blending PLA with other polymers is a more practical and economic way to improve its toughness. The present study assessed the effect of the addition of the pre-crosslinked powdered nitrile rubber (NBR) containing calcium carbonate (CaCO3) and extruder screw rotation on the mechanical, rheological, morphological and thermal properties of polylactide (PLA) by using a Central Composite Rotatable Design (CCRD) analysis, which provides statistical support for the experimental data. The results showed that NBR/CaCO3 can be used as toughness modifier for PLA. This property improved due to the increase in energy expended to deform the material and generate cracks, as showed in the impact and morphological analyzes. Despite this improvement, the presence of CaCO3 caused a slight decline in the thermal resistance of the composites. The influence of rubber (NBR/CaCO3) content in PLA matrix on rheological properties, such as elongation viscosity, melt strength and drawability was also investigated. The results showed that the composition PLA/NBR/CaCO3 with higher NBR/CaCO3 content can be used in thermoforming applications.