Thermophysical properties and rheology of PHB/lignin blends

The thermal and rheological properties of poly(hydroxybutyrate) (PHB) and lignin blends were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and rheological analysis over the entire range of composition. The drop in the apparent energy of activation of decomposition, Ea from 112 kJ mol−1 for pure PHB to half that value with PHB/lignin blends, suggests that the addition lignin reduces the thermal stability of PHB. The rheology results show that for ≤30 wt% lignin, lignin behaved like a plasticizer forming a single phase with PHB (as shown by glass transition data and scanning electron micrographs), and reduced the elasticity and viscosity relative to pure PHB. Further additions of lignin (e.g., 60 wt% lignin) result in phase separation and thus decreased the ability of the blends to dissipate energy and increased the viscosities of the blends.