Compostable polymers: Biodegradable polymers that undergo controlled degradation under industrial or commercial composting conditions and also meet quality criteria.European standard EN 13432 (≈ ASTM D-6400 and ISO 17088):
- Biodegrade at least 90%, yielding only water and CO2,
- Under standardized temperature conditions (preferably at 580C) .
- In a time not exceeding six months.
- There should be no more than 10% of particles larger than 2 mm in size.
- Concentrations of heavy metals in the material should not exceed the limits established by environmental agencies such as the US EPA.
Oxodegradable: Decomposed by a multi-step process using chemical additives to initiate degradation (UV radiation, heat...), the molecular weight of the polymer is reduced leaving a remnant susceptible to biodegradation.
Photodegradable: It degrades under the action of solar UV radiation, fragmenting into smaller particles.
Biodesintegrable: Plastic mixture of organic part with polyolefins (mixture of starch with PP, PE). Microorganisms degrade the organic part without attacking the polymeric fraction.
- PHA (Polyhydroxyalkanoates) are reserve polyesters produced by bacteria under stress conditions, which synthesize them in various chemical forms (variability of the position of their functional groups, variety of monomers, degrees of polymerization) with different properties:
- Different melting points, crystallization.
- Flexibility, tensile strength.
- Speed of biodegradation.
- General properties similar to polyethylene.
- Resistant to fats and solvents.
- They are UV stable, in contrast to other bioplastics such as PLA, and have low permeability to water and medium permeability to gases and aromas.
- They are very sensitive to thermal degradation.
- In general, PHA's are thermoplastics and can be processed with conventional techniques in the form of film, injection and extrusion.
- The main difficulties for their processing come from moisture absorption.
- More than 150 PHA's have been developed. Polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) are the most commercially used.
Source: Paula Fajardo Bernárdez ANFACO-CECOPESCA New Conservation Technologies.