Anti-shrink efficiency

Recent experiments to determine the dimension stabilizing efficiency of water soluble fire retardent chemicals (41) showed ammonium sulfamate to be superior to phosphate salts, giving anti shrink efficiencies of 51 to 66% compared to polyethylene glycol-1000 values of 63 to 77%. Sodium silicate, because of its alkalinity, caused collapse of the wood that resulted in negative anti shrink efficiencies. Strongly alkaline systems should hence be avoided. 

Hydroxyl groups reacted with acetic anhydride and pyridine catalyst to form esters. Capillaries empty. Anti-shrink Efficiency (ASE) about 70%. 

The dimensional stability of Impreg made in the aforegoing way increases with an increase in the resin content of the veneer up to about 10% anti shrink efficiency at a resin content of 30 to 35%. This ASE value is less than that obtainable with polyethylene glycol because of loss of water and subsequent contraction of the resin forming chemicals within the cell walls as polymerization occurs. 

Figure 13 shows that anti-shrink efficiency (ASE) for the PAN-WPC (irradiation) system and the PMMA-WPC (irradiation) system increases up to ca. 70% with increase of polymer. In order to prevent the formation of cracks by moisture adsorption, an improvement of ASE of the system by the combination of polymers with cellular parts of wood is necessary. 

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