Polyvinyl alcohol

Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula n. It is used in papermaking, textiles, and a variety of coatings. It is white (colourless) and odorless. It is sometimes supplied as beads or as solutions in water. Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula n. It is used in papermaking, textiles, and a variety of coatings. It is white (colourless) and odorless. It is sometimes supplied as beads or as solutions in water. Polyvinyl alcohol is used as an suspension polymerization aid, as protective colloid, to make polyvinyl acetate dispersions. This is the largest market application in China. In Japan its major use is vinylon fiber production. Other uses of polyvinyl alcohol include injection moulding of soluble containers for active release of detergents and agrichemicals, paper adhesive with boric acid in spiral tube winding and solid board production, thickener, modifier, in polyvinyl acetate glues, textile sizing agent, Paper coatings, release liner, as a water-soluble film useful for packaging (an example is the envelope containing laundry detergent in 'liqui-tabs'), feminine hygiene and adult incontinence products as a biodegradable plastic backing sheet, carbon dioxide barrier in polyethylene terephthalate (PET) bottles, as a film used in the water transfer printing process, as a form release because materials such as epoxy do not stick to it, movie practical effect and children's play putty or slime when combined with borax, used in eye drops (such as artificial tears to treat dry eyes) and hard contact lens solution as a lubricant, PVA fiber as reinforcement in concrete, raw material to polyvinyl nitrate (PVN) an ester of nitric acid and polyvinyl alcohol, as a surfactant for the formation of polymer encapsulated nanobeads, used in protective chemical-resistant gloves, used as a fixative for specimen collection, especially stool samples, when doped with iodine, PVA can be used to polarize light, as an embolization agent in medical procedures, carotid phantoms for use as synthetic vessels in Doppler flow testing, and used in 3D printing as support structure that can then be dissolved away (cire perdue). Polyvinyl acetals are prepared by reacting aldehydes with polyvinyl alcohol. Polyvinyl butyral (PVB) and polyvinyl formal (PVF) are examples of this family of polymers. They are prepared from polyvinyl alcohol by reaction with butyraldehyde and formaldehyde, respectively. Preparation of polyvinyl butyral is the largest use for polyvinyl alcohol in the U.S. and Western Europe. PVA is widely used in freshwater sport fishing. PVA moulded capsules and 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 dissolves in water, leaving the hook bait surrounded by ground bait, pellets etc. Anglers also use string made of PVA for the purpose of making temporary attachments. For example, holding a length of line in a coil, that might otherwise tangle while the cast is made. Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer as the monomer, vinyl alcohol, is less thermodynamically stable with respect to its tautomer acetaldehyde. PVA instead is prepared by first polymerizing vinyl acetate, and the resulting polyvinylacetate is converted to the PVA. Other precursor polymers are sometimes used, with formate, chloroacetate groups instead of acetate. The conversion of the polyesters is usually conducted by base-catalysed transesterification with ethanol: