Development of high bio-content polypropylene composites with different industrial lignins

Sustainability, eco-efficiency, pollution prevention, industrial ecology, and green chemistry are considering platform-based approaches to the development of the next generation of products and processes. Recently, renewable alternatives to traditional petroleum-derived plastics have motivated recent interest in bio-based composite materials which can contribute to the reduction of the environmental footprint. Lignin is a complex and amorphous biopolymer with a high density of functional groups and high modulus, which makes it potentially promising for material applications. In this sense, lignin can potentially be employed to improve the performance of materials and an economical alternative to convert lignin into high value-added materials. Two different types of Kraft lignin were incorporated into polypropylene to fabricate composites with high bio-content. In this study, polypropylene, Kraft lignin, and coupling agent were subjected to reactive extrusion. The composites prepared by melt processing were compared in terms of morphological, mechanical, and thermal characterizations. The results revealed that the incorporation of lignin into polypropylene matrix resulted in composites with properties suitable for various industrial sectors, especially those in which mechanical and thermal properties are crucial, such as the replacement of engineering plastics and polypropylene mineral filled. As a result, this work provides an effective way of using lignin as a low-cost bio-renewable resource in the plastics industry.