Mixing Applications

Preparation of Polyvinyl Alcohol (PVA) Solutions

Polyvinyl Alcohol (PVA, sometimes referred to as PVOH) is a water soluble polymer used widely in adhesives, paints, sealants, coatings, textiles, plastics, etc. The polymer is normally supplied in powder form and several grades are available with varying viscosity and solubility characteristics. 

This should not be confused with Polyvinyl Acetate, also known as PVA (sometimes PVAc) which is insoluble in water. PVAc emulsions are also used for adhesives, paints and various coatings but processing is somewhat different. 

The Process

PVA is soluble in hot and cold water. A solution would typically be prepared as follows: 

• The powder is slowly added to the cold water to avoid formation of lumps, as it becomes sticky and the tendency to form lumps increases as temperature rises. In some cases water at lower than ambient temperature may be used to reduce this risk.
• Once the powder is fully dispersed the mix is heated to the temperature at which the polymer becomes solubilized (ranging from 194ºF to 208ºF - this depends on the grade of PVA used).
• Mixing continues at this temperature until the PVA is fully solubilized. Depending on the grade of material and efficiency of the agitation system this can take some time to achieve.