Application of different bark fractions in polypropylene composites: UV and thermal stability

For the comprehensive and value-added utilization of bark, different fractions such as bark extractives (BE), bark fibers (BF), micron-sized unbleached cellulose particles (UBCP), and bleached cellulose particles (BCP) were produced from western red cedar (Thuja plicata) bark. These fractions were melt compounded with polypropylene (PP) to make composites. The presence of lignin in UBCP significantly increased composite thermal stability. The addition of UBCP and BE alleviated the photodegradation of composites, increasing the UV stability. However, the addition of BCP accelerated the UV weathering process. The antioxidation and heat-insulating properties of lignin in UBCP were confirmed in this study.