Multifunctional Lignin/Natural Rubber Composite Films for Sustainable Nitrogen Delivery in Agriculture

In this study, a bio-based slow-release nitrogen (N) fertilizer was developed using a novel composite material composed of natural rubber (NR) and lignin. To enhance its performance, the composite was further modified with epoxidized natural rubber (ENR), cassava starch (CS), and carboxymethyl cellulose (CMC). The chemical and mechanical properties of the resulting composites were thoroughly characterized using FT-IR spectroscopy and tensile strength measurements. FT-IR analysis revealed strong chemical interactions, particularly-COO stretching from CMC and-OH stretching from epoxide ring-opening and lignin, in the Lignin/NR/ENR/CMC composite. Among all formulations, the Lignin/NR/ENR/CMC film exhibited the highest tensile strength, indicating superior mechanical performance. The slow-release behavior of the composites was evaluated by monitoring cumulative nitrogen release in water. The Lignin/NR/ENR/CMC/Urea formulation demonstrated the most prolonged and controlled release profile, attributed to strong chemical interactions between CMC and the lignin matrix. SEM analysis further confirmed that CMC formed a uniform coating and potentially encapsulated lignin particles. This bio-based composite not only improves mechanical strength and chemical stability but also significantly enhances slow-release performance, making it a promising and sustainable alternative for agricultural fertilizer applications.