Abstract
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%.
Highlights
It is a common consent among research scholars, scientific institutions, industries, research and development centers, as well as governments, that there is a real need for intensification of activities enabling the development of materials containing polymers derived from renewable resources
The results obtained in this study are similar to those published in the literature for black spruce bark (Ngueho-Yemele et al, 2010), with somewhat lower cellulose and hemicellulose contents, which could be explained by the fact that bark was refined prior to chemical analyses, while the literature results reported untreated bark
Fiber sizes determined by the fiber quality analyzer (FQA) are presented in Table 2 and aspect ratios (L/D) were found to be comparable to the findings of Ngueho-Yemele et al (2010, 2013), while the main difference found in the average fiber length between both studies could be again attributed to the use of the disk refiner which separated longer fibers
Summary
It is a common consent among research scholars, scientific institutions, industries, research and development centers, as well as governments, that there is a real need for intensification of activities enabling the development of materials containing polymers derived from renewable resources. The simple introduction of renewable resources into synthetic polymer matrices offers a myriad of combinations due to the variety of structures available from nature. As noted by Gandini (2008), one should not base a naive optimism merely on multiple possibilities of combination between different polymers available and high diversity of exploitable natural fibers. The main difficulty in developing good properties resides in the different chemical properties between hydrophobic polyolefin matrices and hydrophilic wood fibers, resulting in poor compatibility.
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