Durable and recyclable biomimetic glycol lignin/polyolefin compounds for a circular economy

Polyolefins are some of the most widely used plastics in the world due to being lightweight, low cost, and resistant to water and most chemicals. However, they are highly susceptible to photo-oxidative degradation under ultraviolet radiation, leading to environmental problems such as microplastic pollution, and furthermore making it difficult to recycle. In this paper, glycol-modified lignin (GL) is blended with polypropylene to form a bio-mimetic structure similar to human skin, in which melanin absorbs UV light and sunburned tissue is removed to reveal fresh skin. We show that GL acts as a simultaneous UV absorbent, antioxidant, and reinforcement, resulting in high retention of mechanical properties even after severe UV exposure, and nearly full recovery of the original properties after mechanical recycling. This performance is attributed to the compatibility of GL with maleic anhydride-grafted PP, which is greater than other types of lignin/polyolefin blends reported in the literature. This improves the durability and in-service performance of polyolefin-based composites and makes their end-of-life recycling possible. These results demonstrate the potential for more sustainable usage of polyolefins and biomass in various applications such as automobiles, containers, household items, and building components. Glycol lignin acts as a simultaneous UV absorbent, antioxidant, and mechanical reinforcement in polyolefins, thereby reducing carbon emissions and facilitating effective mechanical recycling.