Abstract:

Objective: A furfuryl alcohol (FA)- epoxidized vegetable oils (EVO) composite modification method was used to improve the problem of FA modification reducing the toughness of wood and to promote its application in the field of building structures. Method: Two kinds of EVO, epoxidized soybean oil (ESO) and epoxidized linseed oil (ELO), were compounded with FA solution in different additive amounts to prepare impregnation solution, and the FA-EVO composite modified wood with different EVO additives was obtained by treating the wood of poplar (Populus tomentosa) with the full-cell method. Scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) were utilized to investigate the distribution pattern of FA and EVO in the cell structure of the wood and to reveal their chemical reaction relationship. The mechanical property changes of composite modified wood were analyzed, and the appropriate toughening agent addition amount was optimized. Result: The observation of SEM of the composite modified wood, combined with the results of its weight gain rate and density test (significant increase), proved that the FA resin and EVO impregnated into the cellular structure of the wood. The ring opening reaction of FA with EVO was revealed by FTIR analysis. Compared with the FA modified wood, the tangential swelling and volumetric swelling of air-dry, tangential swelling and volumetric swelling of water-saturated of FA-ESO composite modified wood with addition of 20% (additions are mass fractions, same below) ESO decreased most by 36.9%, 20.0%, 35.9%, and 30.7%, respectively, and the greatest coefficient of the anti-swelling efficiency (ASE). When the addition of ELO was 40%, these indicators decreased most by 52.5%, 65.6%, 41.5%, and 46.0%, respectively, and the greatest coefficient of the ASE. The incorporation of EVO significantly improved the dimensional stability of FA modified wood. Compared with the FA modified wood, the modulus of rupture (MOR) of the composite modified wood increased most by 17.9% and 25.3%, respectively, and the static hardness increased by 30.0% and 25.1%, respectively, when the addition of ESO and ELO was 20%. When the addition of ESO and ELO was 40%, the modulus of elasticity (MOE) of the composite modified wood increased most by 22.7% and 21.1%, respectively. Compared with other mechanical properties, EVO improved the toughness of FA modified material the most. When ESO and ELO were added at 40%, the impact bending strength of the composite modified wood was increased by 88.7% and 59.8%, respectively. The addition of EVO can significantly increase the MOE, MOR and static hardness of FA-modified wood, and improve their toughness degradation. Conclusion: By analyzing the significant differences in the properties of dimensional stability, MOE, MOR, static hardness and impact bending strength of FA-EVO composite modified wood with different addition amount of EVO, the physical-mechanical properties of the composite modified wood were optimal when the addition amount of EVO was 20%. EVO and FA have a ring-opening reaction, and its long aliphatic chain is introduced into the FA resin chain to make up for the defects of the reduced toughness of the FA modified wood, and further improve its physical and mechanical properties, which promotes its application in the field of building structure.

Key words: poplar (Populus tomentosa) wood, furfuryl alcohol-epoxidized vegetable oil, composite modified wood, toughness, physical mechanical properties