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 T g 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.

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

“…For these reasons, many efforts have focused on the industrial formulation of PHB with external plasticizers able to improve their thermal and mechanical properties (Mangeon et al, 2018 ). The relevant literature is rich in number and type of plasticizers for PHB.…”

“…Among these, the oxygenated monoterpenes that contain alcohol have been described as having greater biological activity. Mangeon et al ( 2018 ) studied linalool (L), geraniol (G), and geraniol acetate (GA) as PHB plasticizers. In this study, the use of terpenes led to a decrease in Tg and an increase in elongation at break over 650% combined with a decrease in Young's modulus compared to pure PHB.…”

Plasticization of poly(3‐hydroxybutyrate) with triethyl citrate: Thermal and mechanical properties, morphology, and kinetics of crystallization

“…39 Several efforts have been made to improve PHB properties using different types of plasticizers, such as vegetable oils, 30 alcohols, 21 fatty acids, 40 citrates, 41,42 polyethylene glycols, 34 and others. 24,43 Mangeon et al 44 evaluated natural monoterpenes as plasticizers for PHB, observing a reduction of around 75% in the elastic modulus for the formulation containing 20% geranyl acetate. Kurusu et al 41 evaluated the efficiency of triethyl citrate (TEC) and tributyl citrate (TBC) as plasticizers for PHB, observing an increase in the impact strength of the plasticized formulations.…”

Low Molecular Weight and Polymeric Modifiers as Toughening Agents in Poly(3-Hydroxybutyrate) Films

“…Poly(3-hydroxybutyrate) (PHB) belongs to the large family of polyhydroxyalkanoates (PHAs), which are fully biodegradable biopolyesters of hydroxycarbonic acids produced by either chemical or bacterial synthesis from biorenewable and biowaste resources [2,3]. Due to its biodegradability, biocompatibility, and competitive physical properties, PHB is the most well studied PHA for biomedical and food packaging materials [4][5][6]. However, its high production cost and advanced brittleness narrow its application as a substitute for common synthetic polymers [4][5][6][7].…”

“…Due to its biodegradability, biocompatibility, and competitive physical properties, PHB is the most well studied PHA for biomedical and food packaging materials [4][5][6]. However, its high production cost and advanced brittleness narrow its application as a substitute for common synthetic polymers [4][5][6][7]. Plasticizers may increase PHB flexibility and toughness, thus solving the problem related to its high brittleness [4,[7][8][9][10][11][12][13][14][15].…”