In this work, the changes caused by a chemical modification of the properties and chemical structures of lignin are studied. Lignin from a mixture of Eucalyptus globulus and Eucalyptus nitens obtained through the kraft pulping process was used. The lignin was isolated by acid precipitation and modified by a reaction with maleic anhydride. Maleated lignin (ML) was incorporated to recycled polystyrene (rPS) at 2, 5, and 10 wt-% by a melt-blending process. Fourier transformed infrared spectroscopy (FT-IR) was used to determine the ML structure, and the morphology of rPS/ ML composites was studied by scanning electron microscopy (SEM).Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the glass-transition temperature (T g ) and the thermal stability of rPS and rPS/ ML composites and were compared with virgin PS. The T g values of rPS and their composites were higher than those of the virgin PS. TGA revealed that the thermal stability of rPS with 2 and 5% of ML was slightly greater than that of the virgin PS. These results suggest that postconsumer PS can be used to obtain composite materials with good thermal properties.

The morphology and thermo-mechanical properties of recycled polystyrene-based materials (rPS) reinforced with 5 and 15% lignin from kraft pulping of Eucalyptus nitens were studied. The lignin was modified through two esterification processes using either acetic or maleic anhydride, and changes in the structure of the esterified lignin functional groups were analyzed by Fourier transform infrared spectroscopy. The lignin was then incorporated into rPS by melt mixing. Torque variation in the process was evaluated, and the values were compared to those of neat rPS and virgin PS. The results show a plasticizing effect of lignin with a reduction in the torque values. The morphology, studied through scanning electron microscopy, shows a particle size reduction of acetylated and maleated lignin and a more homogeneous dispersion at 5%. The thermal behavior of the composites, studied through differential scanning calorimetry, does not show significant changes in the glasstransition temperature of rPS with the presence of lignin. The dynamic mechanical analysis shows an increasing storage modulus with increasing lignin content. Thermal stability, studied through thermogravimetric analysis, improved for composites containing 5% esterified lignin. The flexural modulus also increased with lignin addition. These results suggest that the thermal and mechanical properties of post-consumer recycled polystyrene can be significantly improved with only 5% esterified lignin.

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