Sorption behavior and swelling of citric acid and sorbitol (SorCA) treated wood

Citric acid together with sorbitol (SorCA) have been used to modify wood and improve its properties, such as dimensional stability and biological durability, which partly result from its swelling and sorption behavior. However, the underlying mechanism of water interaction with SorCA-treated wood is very complex and not fully understood. Previous research confirmed cell wall bulking and suggested cross-linking, however the extent of their contribution to moisture-induced changes has not been researched. This study investigated the effect of SorCA treatment on sorption properties of wood in the hygroscopic range (0–95% RH). Scots pine sapwood (Pinus sylvestris L.) was chemically modified with an aqueous SorCA solution at different treatment levels and measured by dynamic vapor sorption (DVS). The observed permanent increase in oven-dry dimensions did not result in a decreased swelling compared to untreated specimens. It was ascribed to the excessive expansion of cell wall matrix caused by a degradation of cell wall constituents by the acidic impregnation solution. However, a reduction in moisture content in comparison to untreated reference was detected. Present findings suggest that the SorCA polyester structure is altered after impregnation inside the wood and affects its sorption behavior by covalent bonding and, presumably, cross-linking with wood polymer constituents.

Effect of different coupling agents on the thermal, mechanical and biological behavior of vinyl acetate-wood polymer composite

Poplar wood (Populus deltoidesBartr.) was modified by a combined two-step treatment with different chemicals to improve its properties. Maleic anhydride (MAN), 3-(trimethoxysilyl) propyl methacrylate (TMPS) and glycidyl methacrylate (GMA) were first employed to modify wood cell wall resulting in WMAN, WTMPSand WGMA. Then, in a second step, the vinyl acetate (VA) monomer was let to polymerize within the cell lumina resulting in WPCMAN/VA, WPCTMPS/VAand WPCGMA/VA(WPCs). Field emission scanning electron microscopy (FESEM) observations confirmed the bulking of modified cell walls. The thermal stability, mechanical properties and decay resistance of WPCs were remarkably improved compared to unmodified wood in the order WPCGMA/VA > WPCTMPS/VA > WPCMAN/VA. WPCMAN/VAdisplayed a significant decay resistance increment, despite lower retention and reactivity than the WPCTMPS/VA, which is probably due to a better penetration into the cell wall and the higher degree of chemical modification of the wood components.

An innovative method for the chemical modification of Carpinus betulus wood: a methodology and approach study

The objective of this research was to evaluate the influence of acetyl and methyl bonds on the physical, mechanical, photochemical and biological resistance properties of hornbeam wood.Carpinus betulus(hornbeam) wood is considered to be a less valuable species due to poor durability. In order to improve its properties, a novel and simple method was applied to modify wood samples. Hence, wood samples were modified by either acetylation or methylation at four treatment levels. Reactions between hornbeam wood and the formalin and acetic acid treatment system were successful as exemplified by increased mass [weight percent gain (WPG)], slightly better compression strength and considerably improved impact bending strength. Furthermore, the biological decay resistance of the treated wood samples increased for all of the treatments.

Mathematical Simulation of Temperature Profiles within Microwave Heated Wood Made for Wood-Based Nanocomposites

High intensive microwave pretreatment is a new method to modify wood for the fabrication of wood-based nanocomposites. Based on the physical law on heat transfer, a mathematical model to describe the temperature profiles within wood heated by high intensive microwave was established and simulated in this research. The results showed that the temperature profiles within wood were related to microwave heating methods; The temperature inside wood firstly increased and then gradually decreased along the direction of microwave transmission when the unilateral microwave heating was applied, and the temperature difference along the thickness direction of wood was very significant; The temperature with wood firstly increased and then gradually decreased from the wood surface to interior when the bilateral microwave heating was applied. Compared with the unilateral microwave heating, bilateral microwave heating is a better microwave heating method for the more uniform wood microwave pretreatment.

Transient gene expression in differentiating pine wood using microprojectile bombardment

We have used microprojectile bombardment to obtain transient expression of the reporter gene β-glucuronidase in differentiating wood (secondary xylem) of loblolly pine (Pinustaeda L.), thereby providing a method for studying expression of introduced DNA in this important tissue. β-Glucuronidase activity can be observed in different cell types, including tracheids, ray parenchyma, and axial parenchyma associated with resin canals. Microprojectile bombardment can be used to identify active promoters and to compare the relative activities of different promoters in specific cell types. We have studied the expression of three promoter gene fusions by bombardment of loblolly pine stem sections. Wood samples bombarded with an abscisic acid inducible (Em) promoter–β-glucuronidase fusion contained nearly 10 times the number of stained cells as those bombarded with two more commonly used promoter fusions (nopaline synthase or cauliflower mosaic virus 35S). Microprojectile bombardment of differentiating wood should be useful for studying promoters and gene constructs in future attempts to modify wood properties by genetic engineering.