Many polymers that are claimed to be ‘biodegradable’ are in fact ‘bioerodable’, ‘hydrobiodegradable’ or ‘photo-biodegradable’. These different polymer classes all come under the broader category of ‘environmentally degradable polymers’.
Various classes of biodegradable plastics, considered in terms of the degradation mechanism are:
3. Hydro- biodegradable
4. Photo- biodegradable
6. Degradable polymers
Biodegradation is degradation caused by biological activity, particularly by enzyme action leading to significant changes in the materials chemical structure. In essence, biodegradable plastics should break down cleanly, in a defined time period, to simple molecules found in the environment such as carbon dioxide and water.
Compostable biodegradable plastics must be demonstrated to biodegrade and disintegrate in a compost system during the composting process (typically around 12 weeks at temperatures over 50°C).
Hydro-biodegradable polymers are broken down in a two-step process - an initial hydrolysis followed by further biodegradation.
Photo-biodegradable polymers are broken down in a two-step process - an initial photo-degradation stage, followed by further biodegradation.
Many polymers are ‘bioerodable’. They degrade without the action of micro-organisms. This is also known as abiotic disintegration, and include processes such as dissolution in water, ‘oxidative embrittlement’ (heat ageing) or ‘photolytic embrittlement’
A material is called degradable if it undergoes degradation to a specific extent within a given time measured by specific Standard Test methods.
It is an irreversible process leading to a significant change of the structure of a material, typically characterized by a loss of properties (e.g. integrity, molecular weight, structure or mechanical strength) and/ or fragmentation.
Disintegration means the falling apart into very small fragments of packaging or packaging material caused by degradation mechanisms.
It is the excretion and metabolism of polymer and erosion product from mammals.
It is the mass loss of a polymer matrix which can be due to the loss of monomers, oligomers or even pieces of non degraded polymers. Erosion can be the result of biological, chemical or physical effect.