Polyvinyl alcohol PVA Molecular composition and structure :(CH3CHCOOCH3) x (CH2CHOH) y Where, x + y represents the degree of polymerization, and y/ (x + y) represents the degree of alcoholysis Physical properties: Appearance is white flake, granular or powdery solid (low alkali alcoholysis process) or white flocculent solid (high alkali alcoholysis process). Specific gravity: 1.23-1.31g/cm3, flake PVA filling specific gravity: 0.42-0.52g/cm3, flocculated PVA filling specific gravity: 0.20-0.27g/cm3. Chemical properties: The structural formula of PVA is -[CH2CH(OH)] N -, where N represents the average degree of polymerization. The basic properties of PVA are determined by its average degree of polymerization and alcoholysis, but there are more than 10 irregular structures in PVA molecules, which greatly affect its properties. (1) Water solubility: PVA molecule is soluble in water because it contains a large number of hydroxyl groups. Its solubility increases with the increase of water temperature, only expansion in cold water (low alcoholysis products can slowly dissolve in normal water), in hot water can be completely dissolved, its aqueous solution has good film formation and cohesiveness. (2) Thermal stability: this series of products soften when heated, there is no significant change below 40ºC, over 160ºC for a long time heating will gradually color, above 220ºC decomposition, water, acetic acid, acetaldehyde and butenal. (3) Chemical resistance: this series of products are almost not affected by weak acid, weak alkali or organic solvent, high oil resistance. (4) Storage stability: this series of products have good stability, no mildew, no deterioration, no moisture absorption in the natural dry state storage for a long time. (5)PVA is a kind of polymer with secondary hydroxyl group. The secondary hydroxyl group in the molecular formula of PVA has high activity, and can carry out typical chemical reactions similar to low molecular alcohol, such as esterification, etherification, acetal, etc., and also react with many inorganic and organic compounds. Harmless to people and animals, can be naturally degradable, known as green products. Storage and transportation conditions and market application (1) Polyvinyl alcohol (PVA) is made from vinyl acetate by polymerization reaction, alcoholysis, is a kind of white, stable, harmless water-soluble polymer, can quickly dissolve in water, forming a stable colloid, water is a good solvent. (2) Polyvinyl alcohol resin (PVA) aqueous solution has good film formation and emulsification. The formed film has different adhesion force, solvent resistance, friction resistance, tensile strength and oxygen resistance. Polyvinyl alcohol resin (PVA) has both hydrophilic and hydrophobic functional groups, so it is a material with interfacial activity, so it can be used as a protective colloid in polymer emulsification and suspension polymerization reaction. (3) Polyvinyl alcohol resin (PVA) is mainly used in the production of synthetic fiber, plastics, adhesives, coatings, new building materials and other products, and is widely used in chemical industry, textile, printing and paper making, leather industry, construction and other industries and fields.
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