Natural Terpenes Used as Plasticizers for Poly(3-hydroxybutyrate)

Abstract

Natural terpenes such as linalool (L), geraniol (G), and geranyl acetate (GA), from 10 to 20 wt %, were compounded with poly(3-hydroxybutyrate) (PHB) to assess the influence of the content of these biobased molecules on the structural and mechanical properties of PHB. Differential scanning calorimetry (DSC) measurements showed a decrease of Tg from 8.5 °C to −13 °C, showing the plasticization effect of the terpenes. This effect is correlated with the decrease of the crystallinity degree from 57 to 36%. Moreover, tensile tests were conducted on PHB-containing terpenic plasticizers. The increase of the elongation at the break of the plasticized PHB over 650% combined with a decrease of the Young’s modulus with regard to pure PHB were obtained in the presence of 20 wt % of geranyl acetate. Dynamical mechanical analysis also revealed that the use of terpenes as additives promoted the decrease of E′ and the glass transition temperature. The effect is more pronounced with geranyl acetate due to the presence of the segment bearing an ester group that increases free volume and molecular mobility. Among the different plasticizers used here, the addition of geranyl acetate is an attractive way to obtain soft PHB from renewable additives.