How Does Oxo-biodegradable Plastic Work?
The chemical degradation process involves the reaction of very large polymer molecules of plastics, which contain only carbon and hydrogen, with oxygen in the air. This reaction occurs even without prodegradant additives but at a very slow rate. That is why conventional plastics, when discarded, persist for a long time in the environment. EPI’s TDPA® formulations catalyze or accelerate this reaction and increase the rate of the degradation by several orders of magnitude – i.e. 100’s to 1000’s of times faster, making TDPA® incorporated products degrade and physically disintegrate within a few weeks to 1-2 years, depending on the formulation and the disposal environment. To illustrate, a TDPA® incorporated plastic bag and a conventional plastic bag were hung on the fence and the difference in degradation rates was observed in the degradation test.
These lower molecular weight fragments are known to, and have been shown, in laboratory simulated composts, to biodegrade into carbon dioxide, water and biomass (cell structure of micro-organisms), which are materials found in nature and part of the biocycle. Commercially available LDPE films incorporating TDPA® have been shown to convert 60% of their carbon backbone into carbon dioxide in 1.5-2 years with most of the balance of the carbon remaining as micro-organism cells. Unmodified films would take much longer to achieve this.
The chemistry described above has been well known to polymer scientists for years. Indeed manufacturers of polymer resins routinely add antioxidant chemicals to their products to prevent any oxidation during thermal processing into products. EPI’s contribution lies in its ability to manage these processes in a predictable way – to balance the effect of its catalytic additives with the effect of contained antioxidants in order to make products that satisfy needs for adequate shelf and service lives while providing degradation/biodegradation rates suitable for the final disposal environment.
A useful feature of catalyzed oxo-degradation chemistry is that, as long as there is any residual antioxidant in the plastic, the catalytic additive has absolutely no effect. These antioxidants are slowly consumed as they do their job. This fact is important in designing shelf and service life of TDPA® incorporated products and allow these products to be safely recycled in existing recycle streams prior to them exhibiting visual signs of degradation – brittleness or disintegration. Other practical features of the technology are that it is applied to the most common commercially available and used polymers and does not affect the processability or the other properties of these polymers.
The overall process, from polymer to water, carbon dioxide and biomass is called oxo-biodegradation. EPI is the pioneer and world’s leading practitioner of oxo-biodegradable technology and has the experience and technical knowledge to design additive systems for polyethylene, polypropylene and polystyrene to meet widely varying needs for shelf and service life and degradation performance in a range of disposal medium and situations.