Biodegradable plastic

Biodegradable materials (BAW ) or plastics are defined differently depending on the application and intention. Materials are referred to as biodegradable, as they are decomposed by microorganisms or enzymes, for example in the soil. The degradation occurs mainly by oxidation and hydrolysis processes of the fission products of water, carbon dioxide and biomass.

Biodegradable and compostable plastics

This definition in addition to various plastics made ​​from renewable raw materials ( bioplastics ) and petroleum-based materials such as polyvinyl alcohols, polycaprolactone or certain copolyesters (eg Ecoflex from BASF). However, not all based on renewable raw bioplastics necessarily biodegradable ( eg vulcanized rubber).

To test the biodegradability, compostability, respectively, of plastic products made ​​to European Standard EN 13432 / EN 14995 was introduced, in which scientific methods are defined for the detection of biodegradability in 2000. According to this standard approved materials and products can be certified and are then entitled to use the compostable.

Many BAWs are already established in the international market. Increasingly, they are used for packaging materials of all kinds, shopping bags, garbage bags, mulch films and catering products. This article may be marked with the logo " compostable". Examples of biodegradable materials are the organic Rohkunststoffe CA (cellulose acetate), PLA (polylactide, polylactic acid ), PHA ( polyhydroxyalkanoates ), PCL ( polycaprolactone ), starch derivatives and special copolyesters such as PBAT ( polybutylene terephthalate) and PBS ( polybutylene succinate ).

Oxo - degradable and oxo- biodegradable

The term "biodegradable" is clearly distinguished from used in the packaging industry polyolefin films (especially PE), which are declared as " oxo- biodegradable" or " oxo- degradable". " Oxo - degradable " additives generally consist of metal ions ( cobalt, manganese, iron, zinc) which accelerate the oxidation and chain degradation in plastics, especially under heat, air and oxygen. Results of this decomposition chain are very small, barely visible chain fragments not biodegrade ( none of the additive manufacturer has been able to provide data ), but wander through our food chain which. Manufacturers of these additives sometimes refer to an ASTM test guideline, but which includes no limits, yet allows the achievement of a certificate.

In the body degradable materials

In a narrower sense (especially in the biomedical field ) as biodegradable materials are referred to, which are degraded in the body by macrophages, enzymes or hydrolysis within days to a few years. Among va fall biogenic polymers such as collagen, fibrin or hyaluronic acid, but also polylactic acid ( polylactide ), polyglycolide and polycaprolactone.

Test method

General recognized the OECD test methods that are used as part of the authorization of chemical substances. For classification as bioplastic also the compostability is investigated.

Ready biodegradability (OECD 301)

The tests of the OECD-test 301 Series (AF) demonstrate a rapid and complete biodegradation.

Ready biodegradability a fast and reasonably complete degradation of a substance in an aquatic environment under aerobic conditions. Different test methods are well or poorly soluble and volatile substances are available.

  • Carbon dioxide - Development Test (OECD 301 B): The resulting by the biodegradation of the test substance carbon dioxide is analyzed regularly over 28 days and is an indicator of biodegradation. This so-called Sturm test is used for the study of poorly water soluble chemicals.
  • Closed Bottle test (OECD 301 D): The biodegradability of the test substance is determined by a period of 28 days of consumption is determined by dissolved oxygen at regular intervals. This test is used for volatile chemicals.
  • Modified OECD screening test (OECD 301 E): The biodegradability of the test substance is determined by measuring the dissolved organic carbon ( = dissolved organic carbon ) over a period of 28 days. This test is used with a sufficiently water-soluble chemicals.

Inherent biodegradability (OECD 302)

The tests of the OECD test series 302 ( AC) demonstrate a limited indeed, but in principle possible biodegradability of the tested chemical. Substances composed such tests are considered to be fundamentally or inherently biodegradable.

  • The Zahn-Wellens EMPA Test (OECD 302 B) investigated the aerobic biodegradability of the substance and returns the result of the decrease of chemical oxygen demand or dissolved organic carbon on. It is the most commonly used test for the study of inherent biodegradability. It provides additional information about the adsorption of the substance tested.

Compostability

Bioplastics are subjected to the test of compostability of plastics. This was described 54900-1 ... 3 in Germany under the 2004 replacement retracted DIN standard DIN V; the American ASTM D -6400 calls for a degradability of plastics by 60 % within 180 days, to identify products as " compostable". Recognition as a biodegradable material and compostable material occurs only when the substances are degraded within 12 weeks in an industrial composting according to European Standard EN 13432 of at least 90 %. " 100 percent compostable " bio- plastic bags of Rewe and Aldi are still not degraded during composting and sorted in industrial composting facilities.

Plastic mulch Biomedicine
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