In Situ Polymerization of Phenolic Methylolurea in Cell Wall and Induction of Pulse–Pressure Impregnation on Green Wood

Abstract

Impregnation of the cell wall with various chemicals continues to attract interest. For most studies, the method of impregnation is the vacuum-pressure process which is limited by the specimens' size in thickness and the requirement for low moisture content. In the present study, we impregnated fast-growing poplar (Populus euramericana) green wood by pulse− pressure at 0.7−0.8 MPa for 50 min with phenolic methylolurea, and then the modifier in situ polymerized within the wood cell wall by kiln drying. The microscopy analysis showed that the pulse−pressure impregnation method could be feasible because of the presence of a wide-bore capillary column system in the poplar xylem. As a result, the chemical treatment reduced the hygroscopicity and increased the dimensional stability of wood. Reactions mainly happened within the interfibrillar amorphous region of the cell wall. Among the reactions were etherification and esterification since the covalent bonds formed between modifier methylol groups, wood hydroxyl, and acetic acid derived from hemicelluloses.

In Situ Construction of Thermotropic Shape Memory Polymer in Wood for Enhancing Its Dimensional Stability

“…Subsequently, the blocks were dried via the programmed procedures (60 • C for 2 h, 80 • C for 2 h and 105 • C for 4 h) to an absolute dry state, with the moisture content (MC) being designated as MC 0 . After cooling, the weight and volume were determined based on the volume percent gain (VPG, %) and weight percent gain (WPG, %), which were calculated according to Equations ( 5) and (6), respectively. The blocks without any treatment were also subjected to the same drying and cooling steps as controls.…”

“…However, as a hygroscopic material, wood is sensitive to water, fungi, insects, etc., which restrains its wider applications [4,5]. The variation in moisture content causes wood to swell and shrink in various degrees, resulting in deformation and cracking [6,7]. Among the effects of these various defects, cracking is the most notable, as it is related to the mechanical performance and decay resistance of wood, raising safety concerns.…”

In-Situ Cross-Linking of Waterborne Epoxy Resin Inside Wood for Enhancing Its Dimensional Stability, Thermal Stability, and Decay Resistance

“…17−21 When impregnating the cell wall with phenolic methylolurea, covalent bonds between the methyl groups of the modifier and the wood hydroxyl groups can be formed, which can reduce the moisture absorption of poplar wood, thereby enhancing the dimensional stability of wood. 22 However, emission of formaldehyde during use limits their indoor applications. Furfuryl alcohol has also attracted much attention in wood modification.…”

Highly Stable Wood Material with Low Resin Consumption via Vapor Phase Furfurylation in Cell Walls

“…However, the hygroscopic nature of wood causes a deformation in response to changes in ambient humidity, which is normally unfavorable for wood utilization . To improve the dimensional stability of wood, various chemical modification methods have been explored, such as esterification, etherification, acetylation, , resin impregnation, , and in situ grafting polymerization reactions, etc. , Only a few methods, such as acetylation and furfurylation, have been introduced to the market whereas most of them are limited at the laboratory stage due to the difficulty in up-scaling and high production cost …”

“…4 To improve the dimensional stability of wood, various chemical modification methods have been explored, such as esterification, 5 etherification, 6 acetylation, 7,8 resin impregnation, 9,10 and in situ grafting polymerization reactions, etc. 11,12 Only a few methods, such as acetylation and furfurylation, have been introduced to the market whereas most of them are limited at the laboratory stage due to the difficulty in up-scaling and high production cost. 13 Traditional liquid phase vacuum-pressure impregnation (VPI) has resin deposited in both cell lumina and the cell wall.…”