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The use of polyvinyl alcohol and its gelation process

Poly (vinyl alcohol) is a kind of water-soluble polymer obtained by hydrolysis of polyvinyl acetate instead of monomer polymerization. It is soluble in glycerin at 120-150 ℃, but becomes jelly at room temperature. In the dissolving step of polyvinyl alcohol, the material should be added into room temperature water under stirring, and then heated to accelerate the dissolution.

The viscosity of PVA 17-88 aqueous solution increases with time at room temperature. However, when the concentration is 8%, the viscosity is absolutely stable. Polyvinyl alcohol 17-92 is referred to as PVA17 92. PvA17 99 solution is more sensitive to PVA17-88 than the PVA17-88. The borax of 0.1% of the solution quality will gelatinization of 5%PVA17 99 solution, and the amount of borax caused by the same concentration of PVA17-88 aqueous solution is 1%. Polyvinyl alcohol 1799b is mainly used to make high viscosity polyvinyl butyral. It is widely used as dispersant of sizing agent.

In addition, polyvinyl alcohol has various typical reactions of secondary hydroxyl compounds, such as esterification. It can be degraded in strong acid, softened or dissolved in weak acid and base. High concentration PVA is not compatible with inorganic salt, especially sulfate and phosphate. Phosphate can precipitate 5% (w / V) PVA. Borax can form gel with polyvinyl alcohol solution.

Polyvinyl alcohol is a good glue, which can replace most of the industrial glue. How to boil polyvinyl alcohol glue? First of all, prepare several polyvinyl alcohol, 1000 ml beaker, glass plate, electric stove, and a stainless steel basin (the diameter is 30-40 cm). When ready, take 50-80 grams of polyvinyl alcohol into the beaker. Add 900-1000 ml of normal temperature water to the beaker and stir with a glass rod. The water should not be too full. It's better to be 2-3cm away from the beaker mouth. If it's too full, the heat will overflow. Put the beaker into the stainless steel basin, add normal temperature water to the stainless steel basin, and submerge 2 / 3 of the height of the beaker. Put the stainless steel basin on the electric furnace to heat and stir while heating. After the solid polyvinyl alcohol is completely dissolved, take out the beaker (be careful of scalding) and cool it to room temperature for standby. Be careful of electric leakage and avoid electric shock. Caution: Hot. Fully stir during heating to avoid pimples.