Cell wall polymers, chemical modification

Because these types of degradation are chemical in nature, it should be possible to eliminate them or decrease their rate by modifying the basic chemistry of the wood cell wall polymers. Chemical modification of wood is any chemical reaction between some reactive... 

Most of the chemical modification methods investigated to date have involved the chemical reaction of a reagent with the cell wall polymer hydroxyl groups. This can result in the formation of a single chemical bond with one OH group (Figure 2. Id), or cross-linking between two... 

With chemical modification of wood, it is necessary to prove that a chemical bond has been formed with the wood cell wall polymers. One simple test involves determining the... 

The mechanism of adhesion is also an important factor in failure analysis in composites [31]. Some adhesives work due to a physical entanglement of the resin into the wood structure whereas others require a free hydroxyl group on one of the cell wall polymers to participate in a chemical reaction with the resin. Substitution of hydroxyl groups was shown to decrease adhesion between chemically modified veneers due to the loss of hydroxyl functionality [32]. Resins that are water-soluble and depend on a hydrophilic substrate for penetration will be less efficient in chemically modified wood due to the decreased hydrophilic nature of the celt wall resulting from modification [33]. 

These techniques demonstrate that it is possible to change the basic chemistry and, therefore, the properties of wood cell wall polymers through chemical reactions. These chemical modifications can greatly enhance the properties of wood products. 

Chemical modification of wood to impart decay resistance and to provide dimensional stability depends on adequate distribution of reacted chemicals in water-accessible regions of the cell wall. It is important, therefore, to determine the distribution of bonded chemicals. This information may also lead to a better understanding of how chemical modification of wood changes the chemical properties of cell wall polymers. 

Chemical Modification of Cell Wall Polymers as Potential Treatments of Archaeological Wood... 

Chemical modification is generally taken to mean a process involving the creation of a chemical bond (usually covalent) between a surface cell wall polymer and an introduced reagent to form a novel adduct. This can be done through several approaches, including plasma activation and graft polymerization with vinyl monomers, which are very well described in literature. The primary... 

Chemical modification will be defined for this chapter as any chemical reaction between some reactive part of a wood cell wall component and a simple single chemical reagent, with or without catalyst, that forms a covalent bond between the two components. This excludes in situ polymerizations of monomers in the lumen structure of the wood and those reactions that result in cell wall-penetrating polymer systems that do not result in any cell wall attachment. It is well known that lumen-filling polymer treatment results in large improvements in mechanical properties, but these are mainly a result of the properties of the new polymer introduced [ 1 ]. 

On the other hand, native cellulose is an abundant and inexpensive macromolecular compound that reinforces most plant cell walls. During recent years, attention has been devoted to the use of cellulose (nanocellulose or nanofibrillated cellulose), and important studies have been published [13-22]. The outstanding mechanical properties of nanocellulose or nanofibrillated cellulose, linked to its wide availability, biodegradability, and extensive number of alternatives for chemical modification, have been the driving force for its utilization as reinforcement in polymers. These cellulosic materials are composed of nanosized cellulose fibrils with a high aspect ratio (length-to-width... 

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