Effects of wood fiber impulse-cyclone drying process on the UV-accelerated aging properties of wood-plastic composites

Abstract

The impulse-cyclone drying and the silane coupling agent (A187) modification are applied to treat wood fibers under the following conditions: 180°C, 180°C+A187, 200°C+A187, 220°C+A187 and 240°C+ A187. Then, HDPE/wood fiber composites are fabricated with a two-stage plastic extruder, and the effects of impulse-cyclone drying technique on the UV-accelerated aging properties of composites are investigated. Fourier-transform infrared spectroscopy (FTIR) reveals that the silane coupling agent chemically reacts with the hydroxyl groups on the wood fiber surfaces, the anti-UV aging properties of composites is enhanced. Mechanical test shows that during the 0–3000 h of UV aging process, the mechanical properties of samples tend to increase initially and then decrease within a period of time. After 3000 h of UV aging, the specimen 4 exhibits the least loss of mechanical properties, with flexural modulus, flexural modulus and impact strength of 65.40 Mpa, 2082.08 Mpa and 12.85 Mpa, respectively. The effects of impulse-cyclone drying technique on the UV-accelerated aging properties of composites are investigated through Spectrophotometry and Surface microstructure observation. indicates that the ΔL* and ΔE* values increase greatly at the stage of 0–1000 h aging, which though tend to stabilize after 1000 h. The degree of discoloration changes little for specimen 4,and the number of surface cracks is relatively small, which exhibits the optimal aging resistance. In conclusion, the addition of wood fibers treated by impulse-cyclone drying (220°C) and A187 modification is effective in enhancing the anti-UV aging properties of HDPE/wood fiber composites. Nevertheless, such enhancing effect turns to decline when the temperature of impulse-cyclone drying treatment is excessively high.