Compostable polymers: Biodegradable polymers that undergo controlled degradation under industrial or commercial composting conditions and that also meet certain quality criteria.The European standard EN 13432 (≈ ASTM D-6400 and ISO 17088):
• Must biodegrade by at least 90%, yielding only water and CO2.
• Under standardized temperature conditions (preferably at 580C).
• Within a period not exceeding six months.
• No more than 10% of the particles may be larger than 2 mm.
• Heavy metal concentrations in the material must not exceed the limits established by environmental agencies such as the U.S. EPA.
Oxo-degradable: It breaks down through a multi-step process using chemical additives to initiate degradation (UV radiation, heat, etc.); the polymer’s molecular weight is reduced, leaving a residue that is susceptible to biodegradation.
Photodegradable: It degrades under the influence of solar UV radiation, breaking down into smaller particles.
Biodegradable: A plastic made from a blend of organic material and polyolefins (a mixture of starch and PP, PE). Microorganisms degrade the organic component without affecting the polymeric fraction.
• PHAs (polyhydroxyalkanoates) are reserve polyesters produced by bacteria under stress conditions; these bacteria synthesize them in various chemical forms (variability in the position of their functional groups, variety of monomers, degrees of polymerization) with different properties:
– Different melting and crystallization points.
– Flexibility and tensile strength.
– Rate of biodegradation.
• General properties similar to those of polyethylene.
• Resistant to fats and solvents.
• They are UV-stable, unlike other bioplastics such as PLA, and have low permeability to water and medium permeability to gases and odors.
• They are highly susceptible to thermal degradation.
• In general, PHAs are thermoplastics and can be processed using conventional techniques such as film forming, injection molding, and extrusion.
• The main challenges in processing them stem from moisture absorption.
• More than 150 PHAs have been developed. Polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) are the most widely used commercially.
Source: Paula Fajardo Bernárdez, ANFACO-CECOPESCA, New Preservation Technologies.