ABSTRACT
A polymeric system based on LDPE would be qualified as a “photo(biodegradable synthetic polymer” for use as films or thin systems in plasticulture and later in packaging where severe specific criteria should be respected. The evolution of such a system in environmental conditions should present three phases. In Phase I, corresponding to storage and use, in the presence of physicochemical and biological aggression, chemi cal evolution should be very limited and resistance to any microorganism should be observed. In Phase II a rapid abiotic degradation should occur until the complete destruction of physical (mechanical) properties and spontaneous fragmentation of the thin systems into more and more di-
vided parts. Phase III corresponds to bioassimilation of heavily trans formed (oxidized) solid particles. Phase I should be predicted and con trolled on the basis of artificial photoaging or thermoaging experiments. Depending on the desired lifetime of the system, nonaccelerated, acceler ated, or ultra-accelerated photoaging techniques could be used. The ear liest fragmentation, which should be observed in Phase II, should be predicted within the same experiment. The prediction of the long-term fate of the polymeric materials should be based not only on the varia tions of physical properties but on a full analysis of the chemical evolu tion, i.e., determination of the major final transformed groups of the macromolecular chains (and especially the acidic end groups) and the molar mass distribution. In a recent BRITE-EURAM European con tract, we developed an experimental protocol for the control of Phase III based on the use of pure cultures of strains from collections or selected adapted wild strains (from industrial polyethylene site dumpings) which had been examined. Abiotically oxidized LDPE was the only carbon source in a starving mineral medium. Bioerodibility caused by the car boxylic acid formed throughout abiotic degradation has been observed.
