Thermal Analysis of Highly Filled Composites of Polystyrene with Lignin
This paper focuses on the thermal properties of polystyrene/lignin composites over a wide range of lignin content. Blending with and without a compatibilizer (styrene/ethylene/butylene copolymer) was performed in an internal batch mixer to prepare samples between 0 and 80%wt of lignin. From the compounds, an extensive thermal study was performed, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). TGA results indicated that the thermal stability of polystyrene increases with increasing lignin content. DMTA analysis showed higher storage modulus and lower loss factor with increasing lignin content for the range of temperature studied (30-150 °C). DSC results showed that the lignin/PS composites have a single Tg which is close to that of polystyrene. The addition of a compatibilizer up to 2%wt was found to improve the storage modulus of lignin/PS composite, especially at low temperature. Finally, scanning electron microscopy micrographs were used to show the state of interfacial adhesion or compatibility between lignin particles and the polystyrene matrix.