Ecolyte

The persistence of outdoor mechanical integrity depends on the concentration of the ketone comonomer and its specific structure, e.g., the nature of Ri and R2. The time-to-embrittlement of Ecolyte PS and PE in our Weather-Ometer exposures are listed in Tables I and II. 

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... 

The Ecolyte LDPE films are numbered in relation to the concentration of photosensitive vinyl ketone comonomer present in the polymer ie. 1>>2>3. The Ecolyte 1 LDPE containing the most vinyl ketone comonomer was brittle in 820 hr in the Weather-Ometer and 2.5 months outdoors. The Ecolyte 2 was brittle in Il80 hr and the Ecolyte 3 required ll+65 hr while the EcoPlastics Ltd. LDPE control required 2075 hr xenon arc irradiation to reach embrittlement. This series of Ecolytes demonstrates the varied and controlled lifetimes that can be designed into Degradable Plastics by controlling concentration of the photosensitizer. 

Figure 3. Elongation at break of Ecolyte LDPE degradable plastics as a function of xenon arc lamp irradiation time...

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. 

SCHEME 16.2 Photolysis and further oxidation of Ecolyte copolymers. 

The rate of photodegradation of Ecolyte polymers was found generally not to be affected by the presence of antioxidants in the polymer, as the process is photolytic and not photoxidative (unless if they absorb in wavelength range that initiate degradation), but was shown to be directly proportional to the concentration of the... 

FIGURE 16.3 Effect of ketone concentration and film thickness of Ecolyte S on the rate of photodegradation (Reproduced with permission from Ref. 21 Published by Plenum Press, 1995.)... 

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