Polystyrene Ecolyte

R2 polystyrene (Ecolyte PS), polyethylene (Ecolyte PE) and polypropylene (Ecolyte PP) are the first to be developed. Controlled outdoor lifetimes over a very wide range of time periods (days to months) are possible with apparent long term stability indoors. 

Degradable Polystyrenes. The Ecolyte "Fast" polystyrene foam has a higher concentration of photosensitive vinyl ketone comonomer than the Ecolyte "Slow" foam and as a result has a shorter irradiation time to embrittlement as listed in Table I. The "Fast" foam was brittle after one month outdoor exposure or 275 hr xenon arc irradiation. The outdoor exposure was facilitated by wind and rain erosion. Turning the sample over after 35 hr xenon irradiation lowered the embrittlement time to a remarkably short period of 70 hr considering the thickness and opacity of the foam. Similarly the "Slow" foam had its xenon embrittlement time reduced from 21+00 hr to only 600 hr by turning the foam over after each 2l+ hr irradiation period. To obtain a better idea of the rate of... 

Figure 12.5 Biodegradability of photodegraded Ecolyte polystyrene and polyethylene in various soil environments.

Studies of the biodegradation of " C-labelled Ecolyte polystyrene [24] have confirmed the presence of the radiolabel in the growing hyphae of bacterial species as well as in proteins, nucleic acid derivatives, and the CO2 developed during the culture. In experiments in Guillet s laboratories with a closed terrarium, it was demonstrated that up to 5% of the carbon in a photodegraded " C-labelled Ecolyte polystyrene in the soil was converted into CO2 or directly into the growing plants during a five-month period. 

Table 12.6 Total " 0 derived from " C-tabelled Ecolyte polystyrene after five months in terrarium...

Preliminary results on plant and soil assays indicate that the plants contain nearly as much as the CO2 released. A similar result was observed in earlier studies with C-labelled Ecolyte polystyrene [24]. Taken together with the CO2 results, this suggests that PET is more than 30% biodegraded after burial for two years in an active soil environment, a result comparable to those reported for straw by Jansson [19]. 

Potential uses for photodegradable polymers, such as ethylene-carbon monoxide and Ecolyte polystyrene and poly(ethylene terephthalate), 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 [35]. Because E-CO and foamed plastics float and are photodegradable when in water, there should be commercial opportunities for them in marine packaging, fishing gear, and similar applications. 

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