Rosin natural terpenes as processing aid for polyhydroxyalkanoate: Thermal, mechanical, and viscoelastic properties

Rosin natural terpene (Dertoline) is compounded with a bacterial thermoplastic polyesters polyhydroxyalkanoate (PHA), specifically here poly(3-hydroxybutyrate) (PHB), a biodegradable and biocompatible polymer. The compatibility of the blend is examined with differential scanning calorimetry and thermal gravimetry analysis. In the range of concentration of Dertoline, from 5 to 15 wt%, a cold crystallization peak first shifts to slightly higher then lower temperature. Dynamical mechanical analysis and tensile tests confirm that the addition of Dertoline slightly decreases the elastic modulus. The degree of crystallinity again increases then decreases with the content of Dertoline. Polarized light microscopy reveals smaller diameter spherulites for PHB/Dertoline blends and their presence is discussed in relation to tensile tests. Overall, the addition of Dertoline has limited effects on mechanical properties of the blends: the stress at break and the strain at break. In addition, oscillatory rheology at different temperatures provides the activation energies and the parameters of a generalized Maxwell model. The temperature dependence of the rheological properties follows an Arrhenius form. Finally, transient step viscosity measurements are used in order to quantify the PHB thermal degradation.