Polyethylene glycol bulking treatments

Constipation bulk-forming laxatives by increasing faecal mass tend to soften stools and relieve constipation, and have value in a range of symptomatic problems associated with anal fissure, haemorrhoids, and with ileostomy and colostomy dysfunction. Faecal softeners, lactulose and macrogols (polyethylene glycol) retain fluid in the bowel. Stimulant laxatives, such as the anthraquinone, senna, and bisacodyl, increase motility and can cause colic verdoses can cause diarrhea and electrolyte depletion. Chronic treatment for constipation is seldom needed, but may be in children with a tendency to faecal impaction, specialist advice should be sought. 

The strength properties of polyethylene glycol treated wood are virtually those of the swollen wood. This is not surprising as the polymer tends to maintain green wood dimensions. Unlike heat stabilized and formaldehyde cross-linked wood and wood bulked by resin forming polymers within the cell walls (to be considered later), the toughness of the wood is not adversely affected by polyethylene glycol treatment (35). 

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... 

Treatment of solid wood over the years for increased utility included many chemical systems that affected the cell wall and filled the void spaces in the wood. Some of these treatments found commercial applications, while some remain laboratory curiosities. A brief description of the earlier treatments is given for heat-stabilized wood, phenol-formaldehyde-treated veneers, bulking of the cell wall with polyethylene glycol, ozone gas-phase treatment, ammonia liquid- and gas-phase treatment, and p- and y-radiation. Many of these treatments led to commercial products, such as Staybwood, Staypak, Im-preg, and Compreg. This chapter is concerned primarily with wood-polymer composites using vinyl monomers. Generally, wood-polymers imply bulk polymerization of a vinyl-type monomer in the void spaces of solid wood. 

As an alternative to the conventional polyethylene glycol (PEG) treatment of waterlogged wood see Chapter 8), attempts were made in 1966-1967 to apply a radiation-curing process (i, 2). The aim was to reduce treatment time and achieve more stability for treated objects subjected to interior climatic changes. The impregnation of waterlogged wood by immersion involves a liquid-liquid exchange process. Dry wood was directly bulked by monomers by a vacuum-pressure process. 

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). 

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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