Photodegradable polymers, applications

Recently it has been shown that photodegradable polymers suitable for use in packaging applications can be prepared by copolymerization of ethylene or styrene with vinyl ketone monomers (1). Since PVC is the third important plastic used for packaging, we have investigated the possibility of using the same method to develop photodegradable PVC compositions. 

The synthesis, properties and applications of ethylene-carbon monoxide (E/CO) copolymers are described. These photodegradable polymers are now used to control plastic litter caused by polyethylene loop carriers for beverage cans which have been reported to entangle and endanger wildlife. 

Potential uses for photodegradable polymers, such as E/CO, will exist wherever plastics littering occurs. It has been estimated that almost a billion pounds of plastics find their way into the world s waterways annually [23]. Because E/CO floats and maintains much of its photodegradability when in water, there should be commercial opportunities for E/CO in marine packaging, fishing gear, and similar applications. 

Photodegradable polymers (plastics) are especially designed in order to control their degradability when exposed to sunlight in the environment. Their main applications are in the solution of the following problems ... 

Proposed aquaculture applications of degradable polymers include seaweed culture nets, fishing nets and lines, and temporary structures used for restoration of wet lands, beaches or other marsh areas [11-14], Weathering and hydrolysis are the most common degradation mechanisms encountered in aquatic applications. Continually submerged articles pose special challenges since temperatures are low and photodegradation and oxidation effects are limited. 

As in aquatic applications, weathering and hydrolysis are the dominant degradation mechanisms for terrestrial applications. Polymer articles covered with dirt can be problematic since photodegradation is not available however, the higher humidity levels and microbial activity in the soil when compared to the atmosphere are advantageous for degradation. 

Olefin-carbon monoxide co-polymers of the type (-RCH-CH2-CO-)n, known as polyketones, have a wide variety of interesting properties, such as thermoplasticity, flexibility, durability and high impact strength. The ketone function in the polymer makes them sensitive to UV radiation and as a consequence they are photodegradable and hence environmentally acceptable plastics. However their light sensitivity has limited their applications. They can be made by the copolymerisation of an alkene with carbon monoxide (Equation 27 see also Chapter 7, Section 7.7) ... 

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