Abstract
Lignocellulose nanofibers were prepared by the wet disk milling of wood flour. First, an ethylene-butene copolymer was pre-compounded with wood flour or lignocellulose nanofibers to prepare master batches. This process involved evaporating the water of the lignocellulose nanofiber suspension during compounding with ethylene-butene copolymer by heating at 105 °C. These master batches were compounded again with polypropylene to obtain the final composites. Since ethylene-butene copolymer is an elastomer, its addition increased the impact strength of polypropylene but decreased the stiffness. In contrast, the wood flour- and lignocellulose nanofiber-reinforced composites showed significantly higher flexural moduli and slightly higher flexural yield stresses than did the ethylene-butene/polypropylene blends. Further, the wood flour composites exhibited brittle fractures during tensile tests and had lower impact strengths than those of the ethylene-butene/polypropylene blends. On the other hand, the addition of the lignocellulose nanofibers did not decrease the impact strength of the ethylene-butene/polypropylene blends. Finally, the addition of wood flour and the lignocellulose nanofibers increased the crystallization temperature and crystallization rate of polypropylene. The increases were more remarkable in the case of the lignocellulose nanofibers than for wood flour.
Highlights
Wood is the most abundant biomass resource and has attracted considerable attention as a reinforcement filler for plastics
Wood flour has been previously fibrillated into lignocellulose nanofibers (LCNFs) by mechanical disintegration using wet-state disk mill [3] and twin-screw extruder [4,5]
We investigated the mechanical and thermal properties of PP composites reinforced with heat-dried LCNFs
Summary
Wood is the most abundant biomass resource and has attracted considerable attention as a reinforcement filler for plastics. There have been significant advances in the development of wood-plastic composites [1,2]. Wood flour has been previously fibrillated into lignocellulose nanofibers (LCNFs) by mechanical disintegration using wet-state disk mill [3] and twin-screw extruder [4,5]. The obtained LCNFs exhibited a large specific surface area and were 20 nm in width in the most disintegrated area. LCNFs can be used as a nanoscale wood filler in PP composites. The dispersion of the hydrophilic LCNFs in PP composites is difficult, since LCNFs have a large specific surface area and readily form aggregations
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