Polyvinyl Alcohol (PVA, sometimes referred to as PVOH) is a water soluble polymer provided extensively in adhesives, paints, sealants, coatings, textiles, plastics, and so on The polymer is normally provided in powder form and also numerous qualities are accessible via differing viscosity and solubility qualities.
You are watching: When dissolving pva in water, why is it important that the temperature not exceed 80 °c?
This have to not be confused through Polyvinyl Acetate, also well-known as PVA (periodically PVAc) which is insoluble in water. PVAc emulsions are also used for adhesives, paints and miscellaneous coatings yet processing is somewhat different.
PVA is soluble in hot and cold water. A solution would frequently be prepared as follows:The powder is gradually added to the cold water to protect against development of lumps, as it becomes sticky and also the tendency to develop lumps rises as temperature rises. In some instances water at reduced than ambient temperature might be supplied to alleviate this threat.Once the powder is totally spread 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 till the PVA is fully solubilized. Depending on the grade of product and efficiency of the agitation system this deserve to take some time to achieve.
Using standard mixers and also agitators, a number of troubles deserve to be encountered during production:Incorporation and also dispersion of the powder becomes progressively tough as the viscosity starts to climb.Lumps cannot be conveniently damaged down by agitation and also lengthy mixing times are compelled to finish solubilization.The vigorous agitation forced to wet out the powder deserve to cause aeration troubles.Ineffective agitation takes longer to accomplish solubilization at temperature. A level of shear is required to accelerate the procedure.The heating stage of the procedure adds to expenses and process time.
A Silverboy high shear mixer deserve to disperse and also solubilize PVA powder in warm water, reducing mixing times to a fraction of that taken by traditional approaches. A typical operating procedure would certainly be as follows:
The vessel is charged via hot water and the mixer is began. The PVA is added to the water and is quickly wetted out and also included right into the liquid. The high speed rotation of the rotor creates a powerful suction which draws ingredients right into the mixer's workhead.
Centrifugal pressure drives the materials to the perimeter of the workhead wright here they are subjected to intense high shear in the gap in between the rotor and stator prior to being required out via the holes in the stator and projected ago into the mix. Any agglomerates are promptly distributed.
Fresh products are simultaneously attracted right into the workhead, establishing up a circulatory pattern of mixing. The entire contents of the vessel passes many kind of times with the workhead, progressively breaking down any type of agglomeprices and also increasing the solubilization procedure.
The AdvanterasDispersing the PVA into hot water eliminates the heating stage, drastically reducing process time.Rapid dispersion of powder eliminates operator error.Powder is completely spread before viscosity buildup commences.Any agglomeprices are damaged down by intense high shear mixing, leading to increased solubilization and much better batch consistency.
Typically PVA solutions are ready in mass. In-Line mixers are commonly offered for extremely big quantities. In-tank mixers are likewise offered relying on batch size, viscosity of finish product, and so on.
High Shear In-Line MixersIdeal for bigger batchesAeration freeMust be offered in conjunction through an effective in-tank agitator to wet out powderEasily retrofitted to existing plantSelf-pumpingHigh Viscosity models availableMultiphase units easily accessible for greater level of shearUnits easily accessible for Explosion Proof or Hazardous duties More around this Mixer
High Shear Batch MixersIdeal for tiny batchesUnits obtainable for Explosion Proof or Hazardous dutiesSpecial devices for abrasive products obtainable More around this Mixer
Silverchild UltramixIdeal for larger batchesCapable of promptly incorporating big volumes of powdersIdeal for high viscosity mixesExcellent in-tank movementUltra Sanitary CIP designLow maintenance More about this Mixer
High Shear Bottom Entry MixersIdeal for bigger batchesIdeal for mass powder incorporationMinimized aerationMinimized cleaning requirementsProper for greater viscosity mixesSuitable for operation at better temperatureMinimum operator input required More around this Mixer
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