From spongy wood to strong material: tiny molecules build a better bioplastic composite

Fast-growing woods like balsa are abundant and lightweight, but their low strength and tendency to swell in humid conditions keep them out of structural applications. One common fix is to fill wood’s pores with plastic resin, but commercial PLA is too thick to penetrate deep into wood’s microscopic channels.

A team from Northeast Forestry University takes a different route. Instead of forcing large polymer chains into the wood, they use small L-lactide molecules as a precursor. After removing lignin from balsa wood to open up its porous cellulose skeleton, they soak the wood in molten L-lactide under vacuum and heat, triggering in-situ ring-opening polymerization inside the wood’s cells.

The resulting composite gains 1 333% in mass, far exceeding the 50%–215% achieved by conventional melt impregnation. Compressive strength jumps from 2.40 MPa to 35.40 MPa, achieving roughly 14-fold increase. The densely packed polymer physically blocks moisture pathways, limiting water uptake to just 20% after 168 h of immersion.

By using a fully biobased monomer and a low-temperature process that preserves the wood’s cellulose framework, this strategy offers a practical path to strong, dimensionally stable, and completely biodegradable wood-plastic composites for construction and engineered materials. The work titled “Preparation and properties of delignified wood skeleton structures reinforced by in-situ polymerization of polylactic acid”, was published on Journal of Forestry Engineering (published on July 25, 2026).