Fractionation systems formaldehyde resins

Diffusion and Penetration. Thermosetting condensation polymers such as phenol-formaldehyde and urea-formaldehyde resin systems generate water as a byproduct of cure. If water also is the solvent, it is a requirement that the solvent water diffuse into the wood to lower the concentration of water at the interface which might otherwise inhibit cure. Water, or other solvent(s) if present, will cany mobile lower molecular weight polymer fractions into the cell interstices and cell walls. This chromatographic effect is the initiation of penetration. 

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