Rigid Macroporous Wood Microparticles Impart Universality and Scalability to Lightweight Foam Insulation

Abstract

Foam-formed nonwoven materials have recently experienced a surge in popularity, but research focuses on flexible fibres with scant information on rigid particles. This work showcases how rigid, minimally-processed, macroporous wood microparticles work synergistically with the foam-forming method to offer a robust manufacturing strategy that is insensitive to feedstock and water quality. Lightweight oven-dried foams suitable for rigid thermal insulation are produced using four types of wood residue and can be made using ocean water instead of ultrapure water. The bio-based content in the foam can be increased by partially/fully replacing the polymer binder with mechanical pulp or using a biosurfactant. For the 15 foams produced with slightly modulated compositions, the densities are low (90–130 kg m⁻³), the thermal conductivities are low (38–45 mW m⁻¹ K⁻¹), and many meet ASTM insulation standards for compressive strength. Pilot plant scaling produced large-scale (100×50×4 cm) foam boards. The structure-property relationships elucidated offer new guidelines to optimize foam performance by matching microparticle size to bubble size, having a distribution of microparticle lengths, and preserving wood's natural macroporous character. This work demonstrates how to harness the functionality that nature has already engineered for plants in the design of novel, sustainable and advanced bioproducts.