Sodium hypophosphite (SHP) has been recognized as the most efficient catalyst in the esterification reaction of cellulosic fabrics with citric acid (CA), but both the high cost and the environmentally harmful property of SHP call for optimization of its application. In this study poplar wood (Populus adenopoda Maxim.) was treated with CA to various weight percent gains (WPGs) and the effect of SHP on the resulting properties of treated wood was investigated. Esterification with CA can occur also in the absence of SHP, as evidenced by the resistance to water leaching of CA. Wood treated with CA alone to 36% WPG exhibited 7% bulking, 50% anti-swelling efficiency, 30% reductions of the modulus of rupture, and 50% lower impact strength. Treatments with CA in the presence of SHP provided wood properties comparable to wood treated with CA alone. Thus the application of SHP can be questioned from the point of view of an economic production and environmental protection.

To improve the interfacial adhesion and dispersion of a poplar fiber in a polylactic acid (PLA) matrix, maleic anhydride (MA) and a silane coupling agent (KH550) were used to modify the poplar fiber. The poplar fiber/PLA composites were produced with different modifier contents. The mechanical, thermal, rheological, and physical properties of composites were investigated. A comparison of different natural fiber modifications on the properties of composites was also analyzed. The results showed that both MA and KH550 could improve the interfacial adhesion between the poplar fiber and PLA, resulting in the enhanced mechanical properties of the composite, with 17% and 23% increases of tensile strength for 0.5% MA and 2% KH550, respectively. The thermal properties of the composites were improved at 6% KH550 (a 9% enhancement of T_90%) and decreased at 0.5% MA (a 6% decrement of T_90%). The wettability of the composites obtained a 11.3% improvement at 4% KH550 and a 5% reduction at 4% MA. Therefore, factors such as mechanical properties, economic efficiency, and durability should be carefully considered when choosing the modifier to improve the property of the composite.

Poplar wood (Populus adenopoda Maxim) has been modified by glucose (GLC) in the presence of citric acid (CA) or 1,3-dimethylol-4,5-dihydroxy ethyleneurea (DM) as crosslinker agents. GLC can penetrate easily the wood cell walls, and after crosslinking, the cell wall is bulked. At 20% GLC concentration level, the leaching ratio of GLC incorporated into wood decreased from 73% to 15% in the presence of 10% CA or DM. The crosslinking efficiency of DM was higher than that of CA. The fixed chemicals in the cell walls caused ca. 6% permanent bulking, namely, a 43% reduction in volumetric swelling after water saturation. FTIR spectroscopy shows that GLC can be activated in the presence of a catalyst; however, the reaction of GLC with a wood polymer is very limited. Scanning electronic microscopy (SEM) reveals that some of the chemicals remained located in the cell lumens. The findings demonstrate that GLC alone is not efficient, but joint treatment of GLC with crosslinkers is a feasible way of wood modification.