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The Process Of Polyvinyl Alcohol PVA

ammonium | 09 February, 2017 10:25

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 (sometimesPVAc) which is insoluble in water. PVAc emulsions are also used for adhesives, paints and various coatings but processing is different. PVA is soluble in hot and cold water. A solution would typically be prepared as follows: 1.The powder is slowly added to 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. 2.Once the powder is fully dispersed the mix is heated to the temperature at which the polymer becomes solubilized (ranging from 194 - 208˚F [90˚C to 98˚C] - this depends on the grade of PVA used). 3.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.Using conventional mixers and agitators, a number of problems can be encountered during production: 1.Incorporation and dispersion of the powder becomes increasingly difficult as the viscosity starts to rise. 2.Lumps cannot readily be broken down by agitation and long mixing times are required to complete solubilization. 3.The vigorous agitation required to wet out the powder can lead to aeration problems. 4.Inefficient agitation takes longer to achieve full solubilization at temperature. A degree of shear is required to accelerate the process. 5.The heating stage of the process adds to costs and process time. Contact Us: BouLing Chemical Co., Limited Tel: 0086-25-52397806 Fax: 0086-25-51192304 E-mail: info@wanwei-pva.com Web: http://www.wanwei-pva.com
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