Combination of Esterified Kraft Lignin and MAPE as Coupling Agent for Bark/HDPE Composites

摘要

Refined black spruce bark fibers and high density polyethylene (HDPE) were used to produce wood plastic composites (WPC) while exploring for the first time the potential of using esterified Kraft lignin as a coupling agent. Two types of lignin esterification (succinic acid and maleic acid anhydrides) were examined alone or in combination with maleated polyethylene (MAPE), and compared with a commercial coupling agent: maleated polyethylene (MAPE). Three contents of coupling agents (2%; 5%; 10% by weight) were considered for esterified lignin and three combinations of lignin and MAPE (100:0; 50:50; 0:100), while bark fibers content was kept constant at 30%. Morphological (scanning electron microscopy - energy dispersive X-ray spectroscopy [SEM-EDS]), thermal (thermogravimetric analysis [TGA] and differential scanning calorimetry [DSC]) and mechanical properties (tensile and flexural) of the composites were measured. Two optimum formulations were determined based on the best bark-matrix interface leading to highest mechanical properties: an equal content of maleic acid anhydride esterified lignin and MAPE at 5%, or an equal content of succinic esterified lignin and MAPE at 2%.