Improved Performance of Environmentally Friendly Blends of Biobased Polyethylene and Kraft Lignin Compatibilized by Reactive Extrusion with Dicumyl Peroxide

In this work, different contents (0.25, 0.50, 0.75, and 1 phr) of dicumyl peroxide (DCP) are incorporated into the bio‐based high‐density polyethylene (bioPE)/kraft lignin (KL) blends with a composition of 80 and 20 wt%, respectively with the aim of improving overall performance. The samples are obtained by reactive extrusion and injection‐molding process, and then their overall performance is assessed by tensile tests, thermal analysis, optical and surface appearance, and wettability studies. The obtained mechanical properties confirm the successful interaction between bioPE and KL due to the addition of organic peroxide, which plays a key role in compatibilization. In particular, bioPE/KL blends with 1 phr of DCP achieve an increase in elongation at break of about 300% together with a noticeable increase in the impact strength of about 29% higher than the uncompatibilized bioPE/KL blend, while the tensile modulus decreases 42%. In addition, images obtained by field emission scanning electron microscopy show that the presence of DCP in the blends enhances better dispersion of KL into the bioPE matrix. The wettability analysis indicates that KL and DCP affect the hydrophobicity of the neat bioPE. Therefore, the resultant blends can be considered as potential sustainable polymers with balanced properties. The use and revalorization of the lignin constitutes a very promising field to study because according to the results obtained reactive extrusion with dicumyl peroxide improves compatibilization of bio‐polyethylene and kraft lignin, in addition, it prevents the formation of kraft lignin aggregates, which also affect the mechanical and thermal properties of the samples.