ObjectiveThe main objective of this study is to figure out the effects of montmorillonite (MMT) on the photostability of wood-plastic composites as well as its mechanisms during accelerated UV weathering.

MethodIn this study, five groups of wood flour/polypropylene (WF/PP) composites were prepared using wood flour of poplar (Populus tomentosa) and PP as raw materials, combined with Na-MMT and OMMT as additives at different loading levels (0, 0.5%, 1.0%, and 1.5%). The total duration of accelerated UV weathering was set at 960 hours. During weathering, the surface color and flexural properties of the composites were tested, accompanied by characterizations using scanning electron microscope (SEM) and attenuated total reflection Flourier transformed infrared spectroscopy (ATR-FTIR).

ResultWeathering results in the surface discoloration and cracking of composites. After 960 hours weathering, for control group, the retention ratios of its flexural strength and modulus were only 76.4% and 61.7%, respectively. Both types of montmorillonite successfully alleviated the photodegradation of composites during weathering, exhibiting better flexural properties than control after weathering. Montmorillonite had both UV-shielding effect and photocatalytic effect, while its anti-weathering effect was only obvious at the early stage of exposure (before 480 hours). Compared with Na-MMT, the photodegradation of organic modifiers in OMMT accelerated the weathering process of composites.

ConclusionNa-MMT was more effective on alleviating the photodegradation of composites, especially at a lower loading level (0.5%).