Reconfiguring Rubberwood Starch from a Weak Link to a Protective Shield against Decay and Mold

Abstract Starch has long been regarded as a critical weakness limiting rubberwood’s construction applications due to its hygroscopicity and mold susceptibility. Instead of removing or chemically modifying this component, we develop a green hydrothermal and controlled drying strategy that reconfigures starch granules into a thin film (SF RW) firmly adhered to the inner cell walls. This film seals cell wall pits, reducing specific surface area to 3.52 m2/g, and acts as a physical barrier against moisture and fungi. SF RW exhibits water contact angles of 71° (radial) and 73° (tangential), 85.3% water absorption, and 21.5% lower volumetric swelling than raw wood. It also shows the slowest mold growth and best decay resistance, with mass losses reduced by 23.4% (field) and 38.7% (white-rot). This work successfully achieves the transformation of rubberwood starch from a traditional defect component into a functional driver, providing new insights for the development of high-performance rubberwood products.