Polyvinyl alcohol is also called PVA, polyviol, alvyl, ethanol homopolymer and vinol. Its molecular formula is [–CH2CHOH-] n and CAS No 9002-89-5. Its melting point temperature is approximately 200°C. Its degree of hydrolysis is between 86.5% and 89%. When swallowed, this chemical is very harmful and causes serious side effect, if not death. It also causes irritation if it comes into contact with the skin and eyes. If it spills on your clothes, wash them with plenty of running water. When working with it, or are in a room where it is stored, avoid as much as possible breathing its fumes or getting into contact with its dust.
Polyvinyl Alcohol – Description, Properties and Uses
PVA is odorless, translucent, tasteless cream or white in appearance and comes in a granular powder form. This chemical is used as a moisture barrier film for food supplement tablets and for foods that contain inclusions that need to be protected from absorbing moistures from the air. Polyvinyl alcohol does not occur naturally, rather is all factory manufactured. Furthermore, PVA is soluble in water and slightly soluble in ethanol. It is insoluble in all other organic solvents. Basically, a five percent solution of PVA exhibits a pH in the range of 5 to 6.5.
Production of Polyvinyl Alcohol
Typically, vinyl acetate is main material that is used in the production of PVA. Typically, it is produced by vinyl acetate polymerization which is then followed by subsequent partial hydrolysis. Hydrolysis process is centered on partial substitution of ester cluster in vinyl acetate with hydroxyl cluster. It is concluded by the addition of aqueous sodium hydroxide on these two (ester and hydroxyl group), then is followed by the slow addition of a saponification agent. Note that the degree of hydrolysis is determined by the time at which saponification reaction is stopped. The finished product (the polyvinyl alcohol) is then precipitated, cleaned up and then dehydrated ready for whichever storage method settled upon.
Polyvinyl Alcohol Process Byproducts
There are numerous by-products; for instance, methyl acetate, methanol and sodium acetate that results from the production process of PVA. The level of such by-products as sodium acetate is monitored using the residue on ignition test. The other two (methyl acetate and methanol) are monitored during the production process.
Technical uses of PVA
PVA has several applications in the food production industry; for example, as a coating and binding agent. This is a film coating agent that is applied where moisture is to be prevented. What does this mean? As a component of tablet coating formulation intended for products, for instance food supplement tablets, PVA is used to protect the active ingredients from all environmental components, especially moisture and oxygen. It also masks their odor and taste. Additionally, it facilitates swallowing and ingestions at the same time allowing easy handling of the finished coated product. Its viscosity allows for ease of application on such items as capsules, tablets and other forms where coating is required.
Food Categories and Usage Levels
PVA is used in high moisture foods so as to retain the overall quality, texture and taste. Mostly, confectionery items contain polyvinyl alcohol so as to preserve the integrity of the moisture sensitive constituents. The food items in which polyvinyl alcohol is intended to be used should have a natural pH and stored either at room temperatures or low temperatures that wouldn’t result into the breakdown of polyvinyl alcohol. Similarly, food items which PVA has been used should have a neutral pH so as not to impact on its stability.
All in all, the physical characteristics and specific functions of PVA depend on the degree of polymerization and the degree of hydrolysis. Polyvinyl alcohol is categorized into two classes; partial hydrolyzed and complete hydrolyzed. Mostly, partial hydrolyzed polyvinyl alcohol is used in the foods.