Polyvinyl+alcohol

First produced in the early 20th century, polyvinyl alcohol has been used to produce fibers for medical sutures. To produce polyvinyl alcohol (PVA), polyvinyl acetate (PVAc) is first produced from vinyl acetate through free-radical polymerization. Then, the resulting rubbery polymer is hydrolyzed to a desired extent to produce polyvinyl alcohol. Since only the pendant group is modified, the of the polymers does not change after hydrolysis. The reaction usually results in 87-99% conversion of PVAc to PVA. Products with conversion above 98% are considered to have undergone full conversion. Unlike most linear polymers, PVA is crystalline. Higher levels of hydrolysis were shown to decrease water solubility, while increasing its tensile strength and adhesion to hydrophobic surfaces. Although biodegradable, PVA is not a biopolymer as it is derived from petroleum.

  Blends of PVA and other polymers, such as starch, are possible. For PVA-starch blends, sorbitol and glycerol are added as plasticizers. The resulting material can be used to produce films, which cannot be produced with thermoplastic starch alone. Its water solubility also allows applications in dissolvable packaging. Another example of PVA blend is produced by mixing PVA with gelatin, which is obtained from animal by-products such as bone and skin. This blend has potential applications as soil additives, since PVA can be used as a soil conditioner and gelatin can act as a nitrogen source. [1]

Figure 1. Core structure of polyvinyl alcohol