Polyvinyl alcohol biodegradable water-soluble polymer

Degradability of other polyesters There are two main water-soluble polymer types commercially available polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH). PVOH is a readily biodegradable, water-soluble polymer. The degradation of PVOH is influenced by its crystallinity and molecular weight PVOH does not biodegrade, but simply dissolves in water or can be biodegraded by activated sludge treatment. EVOH is another water-soluble synthetic plastic. 

Polyvinyl alcohol is a vinyl polymer with a carbon-carbon backbone similar to other polymers such as polyethylene and polystyrene and is widely used as a water-soluble biodegradable polymer in the manufacture of delivery systems for fertilizers, pesticides and herbicides and is also used to manufacture containers and films. To date, only bacteria have been described as causing biodegradation of polyvinyl alcohols with some causing complete degradation of the polymer (see Shimao, 2001 for review). 

Several water-soluble polymers are known which are stable in the solid state but will biodegrade once they are dissolved. These include both synthetic and natural polymers, such as polyvinyl alcohol, cellulose esters and ethers, acrylic acid polymers, polyacrylamides, and... 

Fibers bonded with water-soluble polymers such as starches, carboxymethyl cellulose, polyethylene oxides, polyvinyl alcohols, polyacrylates, etc. This may involve bonding of biodegradable fibers or films or other structures that will break down in the flush. 

Water soluble polymers are also now finding application in the area of packaging. For example polyvinyl alcohol pouches are used to dispense liquid detergent formulations. The pouch is placed in the washing machine and the polyvinyl alcohol slowly dissolves to release the liquid. The emphasis nowadays is to use natural polymers, both polysaccharides and proteins, as packing materials because of their ability to biodegrade and recent advances in this area are covered in Chapter 10. 

Industrial water soluble polymers (IWSPs) represent just a small fraction of polymers used in packaging (mainly as polyvinyl alcohol (PVOH), ethylene-vinyl alcohol copolymer (EVOH), and ethylene-vinyl acetate copolymer (EVA)), but depending on additional research, two factors may lead to a growth of their relative importance the need to ensure (1) renewability and (2) biodegradability. 

Polyvinyl alcohol (PVOH) is a water soluble polymer prepared by the hydrolysis of poljwinyl acetate. The degree of solubility and biodegradability as well as other physical attributes can be controlled by varying the MW and the degree of hydrolysis of the polymer [63]. Polyvinyl acetate, if hydrolysed to less than 70%, is claimed to be nonbiodegradable under conditions similar to those that biodegrade the fully hydrolysed polymer [64]. 

Most synthetic polymers are not biodegradable. However, there are a few synthetic polymers which are truly biodegradable. Some are water-soluble and become biodegradable once dissolved. Others are insoluble in water. The major families are lactic acid-based polymers, polycapro-lactone, other synthetic polyesters, and polyvinyl alcohol. 

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