Descritption
Polyvinyl alcohol is a synthetic resin that is prepared by polymerization of vinyl acetate, followed by partial hydrolysis of the resulting ester in the presence of an alkaline catalyst. The number of acetate groups in polyvinyl alcohol is determined by the degree of hydrolysis (86.5–89.0% hydrolysis for this food additive specification). Polyvinyl alcohol is used as a coating, binder, sealing and surface finishing agent in food products such as dairy-based desserts, confectionery and cereal products and dietary supplement tablets, in the range of 0.2–1.8% by weight.
Preparation
Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer. The monomer, vinyl alcohol, almost exclusively exists as the tautomeric form, acetaldehyde. PVA instead is prepared by partial or complete hydrolysis of polyvinyl acetate to remove acetate groups.
Uses
Some uses of polyvinyl alcohol include:
- Adhesive and thickener material in latex paints, paper coatings, hairsprays, shampoos and glues.
- Carbon dioxide barrier in polyethylene terephthalate (PET) bottles.
- Carotid phantoms for use as synthetic vessels in doppler flow testing.
- Children's play putty or slime when combined with borax.
- Feminine hygiene and adult incontinence products as a biodegradable plastic backing sheet.
- As a mold release because materials such as epoxy do not stick to it.
- As a water-soluble film useful for packaging.
- As fiber reinforcement in concrete
- As a surfactant for the formation of polymer encapsulated nanobeads
- Used with polyvinyl acetate to make Elmer's glue
- Used in eye drops and hard contact lens solution as a lubricant.
- Used in protective chemical-resistant gloves
Fishing
PVA is widely used in freshwater sport fishing. Small bags made from PVA are filled with dry- or oil-based bait and attached to the hook, or the baited hook is placed inside the bag and cast into the water. When the bag lands on the lake or river bottom it breaks down, leaving the hook bait surrounded by ground bait, pellets etc. This method helps attract fish to the hook bait, though it does result in dissolved plastic in the water.
