Determining the curing parameters of furfuryl alcohol for wood modification by nanoindentation

Wood furfurylation is a very promising modification process, which can greatly improve several important properties of wood simultaneously. The polymerization degree of furfuryl alcohol (FA) in wood significantly influences the performances of modified wood. However, it is normally time-consuming and expensive to determine the curing parameters of a new FA solution formula for a target wood species, as the process requires lots of lab-scale experiments. To address this challenge, nanoindentation was used to determine the hardness and elastic modulus of FA resin which are cured with different catalyst content, curing time and curing temperature, assuming that these mechanical properties should closely relate to the polymerization degree of cured FA (resin). Single-factor experiments were designed to obtain preliminary curing parameters. Three key curing parameters were selected, namely the catalyst content of maleic anhydride (1.5, 3, 5 %), curing time (2, 3, 4, 5, 6 h) and curing temperature (95, 105, 115, 125 °C). The proposed set of curing parameters based on the nanoindentation results are 3 % maleic anhydride, 3 h curing time and 105 °C curing temperature. This set of parameters was slightly modified and then used as the starting process parameters for Masson pine modification, which resulted in greatly improved wood properties. Therefore, the method proposed in this study offers an effective and time-saving means of developing new processes of wood furfurylation.