Polyvinyl alcohol (PVA) is made from vinyl acetate through polymerization and alcoholysis. It is a white, stable, non-toxic water-soluble polymer, powdered, flake or flocculent solid.
Polyvinyl alcohol contains many alcohol groups, is polar, and can form hydrogen bonds with water, so it can be soluble in polar water, but also soluble in hot hydroxyl solvents such as glycerol, phenol, etc. It is insoluble in general organic solvents such as methanol, benzene, acetone, gasoline, etc.
A. Solubility: Polyvinyl alcohol powder can be dissolved in water. Polyvinyl alcohol (PVA) with an alcoholysis degree of less than 95% can be dissolved in room temperature water, and polyvinyl alcohol with an alcoholysis degree greater than 99.5% can only be dissolved in hot water above 95 ° C.
Thermal stability: polyvinyl alcohol softens when heated, does not change significantly below 40 ° C, glass transition temperature 75~ 85 ° C, heating to above 100 ° C slowly discoloration, brittle; above 160 ° C, long-term heating will gradually color, dehydration etherification, loss of solubility; above 220 ° C, decomposition occurs, generating water, acetic acid, acetaldehyde and butenaldehyde; over 250 ° C into a polymer containing conjugated double bonds.C, chemical resistance: PVA is hardly affected by weak acids, weak bases or organic solvents, and has high oil resistance.
D, Storage stability: PVA is a low viscosity polymer, its aqueous solution is very stable at room temperature, and the aqueous solution will not deteriorate during storage.
E, film-forming: Due to the high adhesion between PVA molecules, PVA is easy to form a film, and the formed film is colorless and transparent, with good mechanical strength, smooth surface without stickiness, and good solubility. Molecular membranes have good light transmittance, high moisture permeability, no charge, no vacuuming, and good printability.
PVA can be regarded as a linear polymer with secondary hydroxyl groups. The hydroxyl groups in the molecule have high activity and can perform typical chemical reactions of low alcohols, such as esterification, etherification, acetal, etc., and can also react with many inorganic or organic compounds.
Polyvinyl alcohol (PVA) aqueous solution has good film-forming and emulsifying properties. It can be used as a protective colloid during polymer emulsification and suspension polymerization.
Polyvinyl alcohol can be used in textile pulp, Winnie fiber, papermaking coating agent, construction material, adhesive, PVA film, PVB raw materials, food and medicine, etc. PVA can also be used as soil conditioner, polymeric suspension agent and emulsifier, quenching agent, etc. In addition, with the continuous development and improvement of PVA properties, its uses are constantly expanding.
