Comparative Study of Polyethylene Composites Containing Industrial Lignins
In this work, free-radical grafting was investigated in order to enhance the compatibility between lignins and polyolefins. High density polyethylene (HDPE) was used as the matrix and two types of industrial lignins were selected as eco-friendly fillers: Kraft lignin which represents most of the global lignin production, but lacks adequate applications; and organosolv lignin which has received increasing attention for its low molecular weight, homogeneity and sulfur-free characteristics. The compounds were produced by batch mixing, and were compression molded. From these samples, morphological, tensile and thermal properties were studied. The results show that incorporation of different lignins into HDPE yielded materials of different tensile behavior, but improvement in morphological and mechanical properties through free-radical grafting was obtained. Furthermore, free-radical grafting was found to decrease the thermal oxidation resistance and the crystallinity of the composites.