A New Use of Polysorbate-Type Nonionic Surfactants as Plasticizers for Highly Flexible Poly(lactide) Formulations

Abstract

Polysorbates are non-ionic amphiphilic organic compounds, widely used as surfactants. They have a molecular weight in the 1200–1400 g mol⁻¹ range, so they are on the borderline between monomeric and polymeric plasticizers. Therefore, they can potentially provide the benefits of both plasticizer types. In this work, polyethylene glycol sorbitan monolaurate (Tween^® 20), and polyethylene glycol monooleate (Tween^® 80) are proposed as environmentally friendly plasticizers for PLA with enhanced ductile properties. The addition of 20 wt% of polysorbates into a PLA matrix, leads to a noticeable increase in elongation at break, from 4.0% (neat PLA) up to values around 180%. The plasticization efficiency was assessed by the decrease in the glass transition temperature (T_g), from 61.0 ºC (neat PLA) down to such los values of 29.5 ºC, and 36.6 ºC, for plasticized PLA formulations with 30 wt% Tween^® 20, and 30 wt% Tween^® 80, respectively. Moreover, due to the high molecular weight of polysorbates, they are not highly volatile, which allows processing PLA by conventional extrusion and injection molding without plasticizer volatilization. This works widens the industrial applications of polysorbates, as cost-effective, highly efficient and environmentally friendly plasticizers for PLA with enhanced toughness.