Comparison on properties of lignocellulosic flour/polymer composites by using wood, cellulose, and lignin flours as fillers

In this study, cellulose flour (CF) and lignin flour (LF) were separated from wood flour (WF) by nitric acid-ethanol method and ball-milling coupled with dioxane extraction method, respectively. The separated CF, LF, and the original WF were blend with two types of polymers, namely, polypropylene (PP) and poly (lactic acid) (PLA) to make composites. The physical, mechanical, and thermal properties of the thus-filled composites were tested. The results showed that: (1) both CF and LF had significant influence on physical, mechanical, and thermal properties of PP or PLA composites; (2) CF benefited to most mechanical properties of the composites, while LF reduced water uptake and improved thermal stability. WF was more hydrophilic and was easier to thermal degrade than CF and LF. However, the flexural modulus was high in WF groups; (3) for different polymer matrix, the interface bonding between WF components and polymer was different. The interaction between LF and PP was stronger, while it was more compatible for CF and PLA, which showed totally contrary influence on the crystallization behavior of PP and PLA.