Dimensional stability bulking treatments

Bulking Treatment with Water Insoluble Chemicals. The chief shortcomings of dimensional stabilization of wood with polyethylene glycol are that it can be leached from the wood and that the wood feels damp when held for prolonged periods of time at relative humidities of 80% and above. It thus appears desirable to deposit water insoluble materials within the cell walls of wood. This can be done by a replacement process with waxes (42). Water in green wood is replaced by Cellosolve (ethylene glycol monoethyl ether) by soaking the wood in this... 

Other bulking treatments have their special applications. Phenolic resin treatment, the first to be developed, gives high permanent dimensional stability, decay, heat, acid, and electrical resistance. When compressed prior to setting of the resin, it gives the hardest treated wood known, hardness increases up to... 

In those reactions where the isocyanate enters the cell wall and bulking takes place, the ASE values will be high. If, on the other hand, the isocyanate polymerizes in the lumen and no cell wall bulking takes place, there will be little, if any, ASE as a result of the treatment. Table III shows varying degrees of dimensional stability by reacting southern pine with ethyl, ri-propyl and ji-butyl isocyanate. Less dimensional stability is achieved with phenyl and p-tolyl isocyanates, and 1,6-diisocyanate hexane and none with tolylene-2,4-diisocyanate. 

Dimensionally Stabilized Wood. Wood that has been saturated by immersion in water for long periods of time and subjected to related biological deterioration will often require a dimensional stabilization treatment before drying can be permitted safely. This treatment is usually done with bulking compounds such as polyethylene glycol (PEG). 

Wood that has survived archaeological time and conditions will undoubtedly have gluing properties that are, in varying degrees, different from those of fresh unmodified wood. Bulk strength may have been reduced and fluid permeability and absorbency increased. Surfaces, in particular, may have strength and wettability that have been altered by aging. Treatment with consolidants and dimensional stabilizers may have been necessary, and this will often leave surface residues and reduce permeability and absorbency. 

The hydrophilic character of wood, intrinsically connected with the structure of its three main macromolecular components, has been a longstanding source of problems, mostly arising from its lack of dimensional stability in moist environments. An additional major drawback is its susceptibility to photolytic and biological degradation. The interest of both scientists and technologists in modifying wood in order to overcome these drawbacks has called upon specific treatments like chemical, thermal, enzymatic or purely physical modifications. This chapter examines recent contributions to these issues, based on approaches which only involve the chemical modification of wood, carried out in bulk or at its surface. The other treatments have been aptly covered in a recent book [1] and a thorough review [2]. 

Dimensional stability treatment Reduces or prevents swelling in the fibers Bulking the cell wall with polyethylene glycol, penetrating polymers, or bonded cell wall chemicals, or crosslinking cell wall polymers. Mostly used in wood fibers. 

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