In a groundbreaking study published in the Journal of Bioresources and Bioproducts, researchers Eva Pasquier and Jost Ruwoldt from RISE PFI AS in Norway have demonstrated that Kraft lignin can significantly enhance the wet-strength and stiffness of molded pulp materials. This development paves the way for sustainable alternatives to traditional plastic packaging, addressing the growing need for environmentally friendly solutions.
The study investigates the use of Kraft lignin as a wet-strength agent in bleached kraft pulp, which is then thermopressed into materials with potential applications in packaging. The researchers found that adding Kraft lignin, along with retention aids such as cationic starch or flocculants, significantly improved the mechanical properties of the molded pulp. The results showed that pressing the materials at elevated moisture levels further enhanced their wet strength, achieving up to 9 MPa in tensile tests. Additionally, the wet stiffness of the substrates increased from 200 to 938 MPa, without compromising elongation or causing embrittlement.
The study also explored the impact of lignin particle size and the type of flocculant used. The results indicated that while lignin nanoparticles provided better dispersion and homogeneity, the overall strength was more influenced by the moisture content during pressing. The researchers concluded that the high moisture content facilitated the plasticization of lignin at high temperatures, leading to a stronger cellulose-lignin network after cooling.
This research highlights the potential of Kraft lignin as a sustainable and effective wet-strength agent for molded pulp materials. By optimizing parameters such as moisture content and lignin particle size, the study offers a foundation for developing new, eco-friendly packaging solutions that can replace plastics while maintaining recyclability and biodegradability.
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DOI
Original Source URL
https://www.sciencedirect.com/science/article/pii/S2369969825000337
Journal
Journal of Bioresources and Bioproducts
