Polyethylene degradation acceleration

The Course of Thermooxidative Degradation of LD- and HD- Polyethylene under Accelerated Testing Conditions... 

Polylactone and poly(vinyl alcohol) films are readily degraded by soil microorganisms, whereas the addition of iron or calcium accelerated the breakdown of polyethylene. Degradable mulches should break down into small brittle pieces which pass through harvesting machinery without difficulty, and do not interfere with subsequent planting. Effective funaigant mulches require reduced-porosity films which reduce the escape of volatile chemicals, i.e. nematocides, insecticides, herbicides, etc., and therefore allow for lower application rates. 

E. Chiellini, A. Corti, S. Dantone, R. Baciu, Oxo-biodegradable carbon backbone polymers— oxidative degradation of polyethylene under accelerated test conditions. Polym. Degrad. Stab. 91, 2739-2747 (2006)... 

Chiellini, E., Corti, A., D Antone, S., and Baciu, R. (2006) Oxo-biodegradation carbon backbone polymers - oxidative degradation of polyethylene under accelerated test conditions. Polymer Degradation and Stability, 91(11) 2739-2747. 

Valadez-Gonzalez, A., Cervantes-Uc, J.M., Veleva, L. Mineral influence on the photooxidation of high density polyethylene. I accelerated UV chamber exposure test. Polym. Degrad. Stab. 63, 253-260 (1999)... 

If degradation is due to sequential or synergistic mechanisms, then a simple extrapolation may not be reasonable. For example, in accelerating the rate of oxidation of polyethylene it may be necessary to identify the induction time and subsequent degradation time separately and to produce Arrhenius diagrams for each. The total time to failure is the sum of the two times. Figure 9.3 shows an instance of where unknowing extrapolation of the short-term results in tests on polyaramid fibres could have led to overestimates of lifetime and premature failure. 

Bulk dorzolamide drug substance was found to be stable under accelerated thermal and photolytic conditions. When kept in double polyethylene bags inside cardboard shipping containers, the substance showed no evidence of degradation after 51 months of storage at ambient temperature and relative humidity. 

There are many reports in the literature describing photodegradation sensitized by aromatic ketones and quinones. Beachell and Chang (24) showed that triplet excited benzophenone accelerates degradation of polyurethanes by hydrogen abstraction. Harper and McKellar (25) showed the same effect with benzophenone on opolypropylene, and Amin and Scott (26) on polyethylene. Rabek and Ranby (27) have demonstrated that triplet excited quinones enhance... 

The search for accelerated testing procedures to predict the useful service life for polyethylene (PE) compositions has been the main incentive for numerous studies on the thermo-oxidative degradation of PE in oxygen-rich atmospheres below 200 C (1 ). 

As mentioned previously, lifetimes of more than Uo years have been predicted for polyethylene used for electrical insulation where electrical, thermal, mechanical and environmental stresses exist. The fact that cables are failing in a much shorter time period than predicted seems to point to an acceleration in rate of degradation over that assumed. This is directly opposite the results for thermal degradation obtained in this work where the rate of thermal degradation was found to be much slower than that predicted from high temperature experiments. 

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