Plasticization of poly(3-hydroxybutyrate) with biobased terpenoid esters of geraniol

Abstract

Poly(3-hydroxybutyrate) (P3HB) is, by far, one of the most promising bacterial polyesters at the commercial scale, but it is a brittle polymer due to physical aging occurring at room temperature, which promotes secondary crystallization. Plasticization is a cost-effective and technical approach to overcome or minimize, this drawback. In this work, the use of terpenoid-based organic compounds as plasticizers for P3HB is proposed. Geranyl esters with different chain length carboxylic acids, namely acetic (C2), propionic (C3), butyric (C4), and isovaleric (C5) acids, are used at a constant proportion with the main aim of improving the ductility of P3HB. In addition, thermal properties, morphology, and disintegration are also addressed. All geraniol-based plasticizers provided increased ductility. The elongation at break of neat P3HB (7.4%) increased up to 9.7%, which represents a percentage increase of 31.1%. A remarkable increase in toughness is also obtained by a change in the impact strength from 2.2 kJ·m–2 (neat P3HB) up to 3.4 kJ·m–2 with geranyl acetate. Thus, the proposed P3HB formulations widen the potential uses of P3HB since its ductile properties are improved. Other relevant results are related to the glass transition temperature reduction and an increase in the disintegration rate in controlled compost soil.

Keywords

• biodegradable polymers
• poly(3-hydroxybutyrate)
• geraniol
• terpenoids
• plasticizer