Polyvinyl alcohol was first prepared by Hermann and Haehnel in 1924 by hydrolyzing polyvinyl acetate in ethanol with potassium hydroxide. Polyvinyl alcohol is produced commercially from polyvinyl acetate, usually by a continuous process.
PVA is used in sizing agents that give greater strength to textile yarns and make paper more resistant to oils and greases. It is also employed as a component of adhesives and emulsifiers, as a water-soluble protective film, and as a starting material for the preparation of other resins.

Preparation of Polyvinyl Alcohol

Polyvinyl alcohol (PVA) is a water-soluble polymer that is used in a wide range of applications such as adhesives, coatings, films, and textiles. It can be prepared by alkaline hydrolysis of polyvinyl acetate (PVAc), which is a synthetic polymer produced by the polymerization of vinyl acetate monomer.

Alkaline Hydrolysis of Polyvinyl Acetate

The process of alkaline hydrolysis of PVAc involves the reaction of PVAc with a strong base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) in the presence of water. The reaction leads to the cleavage of the ester bond in PVAc and formation of PVA as shown below:

PVAc + NaOH → PVA + NaOAc

The reaction is carried out at elevated temperature and pressure to facilitate the reaction and obtain high yield of PVA. The degree of hydrolysis of PVAc can be controlled by adjusting the concentration of the base and reaction time.

Properties of Polyvinyl Alcohol

PVA is a white or cream-colored powder that is soluble in water but insoluble in organic solvents. It has a high tensile strength, good adhesion properties, and excellent film-forming ability. It is also resistant to oils, greases, and many organic solvents.

Applications of Polyvinyl Alcohol

PVA is used in a wide range of applications due to its unique properties. Some of the common applications of PVA include:

- Adhesives: PVA is used as a binder in adhesives for paper, wood, and other materials.
- Coatings: PVA is used as a coating material for paper, textiles, and other surfaces to improve their strength and durability.
- Films: PVA is used to produce films for packaging, food wrapping, and other applications.
- Textiles: PVA is used to produce fibers and fabrics with improved tensile strength and dimensional stability.

Conclusion

Polyvinyl alcohol can be prepared by alkaline hydrolysis of polyvinyl acetate. The process involves the reaction of PVAc with a strong base such as NaOH or KOH in the presence of water. PVA has unique properties that make it suitable for a wide range of applications such as adhesives, coatings, films, and textiles.