Softwood impregnation by MMA monomer using supercritical CO2

Abstract

Supercritical carbon dioxide (scCO2) was employed to impregnate MMA monomer into five different types of softwood, i.e., spruce, cedar, western pine, eastern pine and costal hemlock, followed by in-situ polymerization initiated by azobisisobutyronitrile (AIBN) in scCO2. The operational conditions were investigated at scCO2 temperatures of 50 and 55 °C, pressures of 14, 21 and 28 MPa and equilibrium time from 12 to 72 h. 55 °C, 28 MPa, and 48 h were considered as the optimal experimental conditions. Microscopy analysis showed that the formed PMMA was distributed within the porous wood matrix thoroughly and evenly. Material properties including water resistance, dimensional stability, hardness, and thermal stability were significantly improved after the impregnation of PMMA into the wood structure. The supercritical CO2 process shows great promise as a novel and green technique for polymer impregnation of wood to achieve improved properties for next generation construction and architectural products.