Impulse-cyclone Drying Treatment of Poplar Wood Fibers and its Effect on Composite Material's Properties

The fiber quality after a conventional drying treatment used for wood-plastic composites (WPCs) cannot be ascertained prior to use. Through the application of scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, the effect of an impulse-cyclone drying (ICD) treatment on the quality of poplar wood fiber was first investigated. Subsequently, the effect of ICD conditions, such as inlet temperature, inlet wind velocity, and feed rate on the mechanical properties of WPCs and fiber dispersibility was considered. Also, the quality of fibers and WPCs was compared to those treated via an oven-drying method. Poplar wood fibers with a moisture content of 12.4% were pre-treated at different drying conditions by ICD. The obtained fibers were compounded with high-density polypropylene. The results showed that ICD could promote the hydration of poplar wood fibers and improve the mechanical properties of WPCs. The ICD-treated wood fibers were uniformly dispersed in the plastic matrix. With the increase of inlet temperature, the number of hydroxyl and carbonyl groups of poplar fibers decreased, whereas the degree of crystallinity increased as the inlet temperature and fiber meshes was increased. This study demonstrated the feasibility for the application of an ICD treatment in the WPCs production industry.