Improving fast-growing poplar wood with furfuryl alcohol and a hyperbranched polymer

Abstract

To address drawbacks of significant toughness decrease of furfurylated wood and comprehensively improve properties of low-quality wood, this study synthesized hyperbranched poly(ester-amide) (HBP) as toughening agent and used synergies of furfuryl alcohol (FA) and HBP for poplar wood modification. The SEM–EDX and FTIR analysis showed that FA and HBP penetrated into wood and in situ polymerized in cell walls and cell lumina, leading to about 25% mass gain and 7% volumetric changes. After compound modification, wood exhibited enhanced hydrophobicity and dimensional stability, suggested by the maximum decrease of over 30% moisture content and volumetric change. This was mainly because polymers blocked water exchanging paths, reduced water accommodation, covered sorption sites and bulked cell walls. The flexural strength and surface hardness of modified wood were notably improved. The impact toughness increased by about 50% compared with that of furfurylated wood, which was mainly ascribed to (1) HBP with a three-dimensional globular structure had micro-phase separation with FA resin during polymerization. The HBP with high flexibility and mobility, acting as the second phase particles, increased the free volume for macromolecular movement. (2) The flexible group-ester group and tertiary amide group of HBP contributed to more absorption of energy and interruption of crack development under impact. Besides, the cracks would be blunted and dissipate impact energy by producing extensive shear deformation. (3) The HBP interrupted the cross-linking of furfural resin and reduced brittle furfural resin network dense. This study provided new references for improving toughness of resin-modified wood and upgrading low-quality wood products for wide application.

Graphical abstract