Translucent Biocomposites from Hot-Pressed Wood Fibers and Poly(limonene acrylate)

Translucent wood fiber composites offer new functions to stiff composites. Most "eco-friendly" thermoset resins are only partially biobased. Poly(limonene acrylate), PLIMA, can be fully biobased and is combined with hot-pressed softwood fibers (WF) by liquid resin impregnation and curing. Fibers are random-in-plane or strongly oriented and have different lignin characteristics. Microstructure-mechanical property relationships are compared for hot-pressed WF networks and WF/PLIMA biocomposites from the same fibers. Stress transfer in WF/PLIMA biocomposites is enhanced with a modulus of up to 16.7 GPa and a tensile strength of up to 139 MPa, compared to transparent plastics like poly(methyl methacrylate) (modulus ∼3 GPa, tensile strength ∼70 MPa). Optical transmittance is high, even at 35 vol % fiber content, suggesting translucent panels or lighting applications. Eco-indicators show that the PLIMA matrix accounts for ∼80% of biocomposite cumulative energy demand (CED, cradle to gate) of 60 MJ/kg, compared to ∼120 MJ/kg for glass fiber/thermoset composites.