Enhancing water resistance and flame retardancy of wood through phytic acid catalyzed in-situ polyesterification

The treatment of wood using in-situ polyesterification with citric acid and D-sorbitol (SCA) is a novel method for enhancing wood properties. This method can effectively improve the dimensional stability and biological durability of wood. However, achieving effective fixation of polyester in wood at lower curing temperatures has not been achieved. In this study, phytic acid was used to catalyze in-situ polyesterification of SCA. The autocatalytic reaction pattern of SCA polyesterification was elucidated through an investigation of the kinetics of the curing reaction. It was also confirmed that phytic acid reduces the curing temperature and activation energy of SCA. The investigation of polyesters revealed that phytic acid catalysis enhances the esterification degree and thermal stability of the polyester. Wood treated with SCA and 2%wt phytic acid exhibited a 44% reduction in polyester leaching. Moreover, it demonstrated high water resistance and dimensional stability, with water repellency efficiency of up to 33.8% and anti-swelling efficiency of up to 46.2%. Remarkably, it exhibited excellent flame retardancy, with an oxygen index of 33.1% and a 47.5% reduction in total heat release. The outstanding flame retardancy is attributed to the dual action of phytic acid in both the solid phase and gas phase.