Engineering pulp foam with highly improved water stability and multifunctional properties by incorporation of natural rubber and montmorillonite

Considering the aim of carbon neutrality and reducing plastic pollution, lightweight porous materials with good thermal insulation and mechanical robustness derived from renewable resources are in high demand. Cellulose-based pulp foams (PFs) offer considerable potential applications in many fields; however, the cost-effective manufacturing of PFs with satisfactory properties remains challenging. Herein, we demonstrate a simple and low-cost strategy to prepare a novel pulp/natural rubber (PNR) foam by combining wood pulp fiber and natural rubber latex through wet foaming and oven drying, eliminating traditional freeze-drying and solvent exchange processes. The obtained PNR foam exhibited high porosity (98.4%-99.1%), low density (14.1–24.0 mg/cm³), and excellent water stability (without disintegration under magnetic stirring for 14 days). Moreover, montmorillonite (MMT) was easily incorporated into the PNR during the preparation process, improving the mechanical strength and heat insulation of the obtained PNR-MMT foam. The optimized PNR-MMT foam could be compressed more than ten times without losing its resilience, exhibiting a compressive strength of 2.7 MPa at 80% strain, five times higher than that of pristine PF. Moreover, the PNR-MMT foam exhibited excellent flame retardant, good “spill” oil absorption, and good antibacterial properties towards Escherichia coli and Bacillus subtilis. Overall, this study provides a facile, sustainable, and low-cost route for manufacturing PNR-MMT foams with high resilience, good thermal insulation, excellent flame retardancy, and strong antibacterial properties, thus highlighting their usage potential in a broad range of applications.