Tailoring the rheological behavior and mechanical properties of cellulose foams: The role of fiber length in foam-forming processes.

Conventional petroleum-based foams are used to protect objects during storage and transportation. Despite being lightweight and having excellent shock absorption, their petroleum origin and difficult recycling raise environmental concerns. This research investigates an alternative foam made from cellulosic fibers, a promising raw material due to its structure and bio-based nature. We studied the influence of cellulose fiber dimensions (0.344-1.322 mm) and concentration on the development of cushioning materials via the foam-forming method. Fiber size was correlated with the rheological behavior of the aqueous dispersions, wet foam stability, and solid foam mechanical performance. Oscillatory strain sweeps revealed a gel-like behavior governed by fiber size and concentration, with pronounced fiber-fiber interactions. Wet foam stability, evaluated by water drainage, increased with fiber length and concentration. Solid foam densities ranged from 10 to 120 g L-1. Compressive strength increased with density following a power-law relationship. The cushion factor remained nearly constant regardless of fiber length, indicating similar energy absorption efficiency. However, resilience tests revealed that recovery of the longer fibers did not appear to be affected by density variations, whereas the shortest fibers displayed a significant dependency. Findings demonstrate that longer fibers are well-suited for lightweight, resilient foams with tailored properties.