Plastic packaging is certainly very practical: tough and lightweight, it keeps food fresh and protects consumer articles like a new shirt or a book from dirt and damage. Plastic garbage sacks help make garbage disposal a clean process. But after use, plastic packaging also has to be disposed of, and this is a weakness. Because it is not biodegradable, however, it is unsuitable for one important disposal route, namely composting.

Attempting to develop alternative methods of use and disposal for plastic packaging, BASF researchers have come up with a class of fully compostable / biodegradable plastics: Ecoflex®. Under certain environmental influences of the kind present for example in compost, Ecoflex is degraded completely by microorganisms.

The scientists assembled an ambitious profile of properties for the desired biodegradable polymers:

• properties similar to polyethylene
  
• producible using conventional starting materials available on a large industrial scale, if possible with reverse integration into BASFs raw materials
  
• Utilization of existing BASF polymerization technologies / plants
  

Translating this idea into reality involved modifying/disrupting the crystalline structure of PBT by incorporating aliphatic monomer (such as adipic acid) in the polymer chain in such a way that the material properties of the polymer would remain acceptable (e.g. melting point of the crystalline range still around 100 °C), but the polymer would also be readily compostable / biodegradable. Pursuing this strategy it was possible to combine the degradability of aliphatic polyesters with the outstanding properties of aromatic polyesters.

This is how biodegradable plastics with properties similar to those of polyethylene are created. And this is also how the requirement to integrate the new polymers into BASFs value-adding chains was fulfilled: Ecoflex is a copolyester based on conventional monomers available on a large industrial scale and is produced in an existing plant using available polymerization technologies.

• determination of the degree of degradability using the newly established test method ("aerobic composting test")
  
• residual polymer analysis
  
• ecotoxicology

Based on the results of these tests, Ecoflex is certified as a compostable material according to DIN V 54900.

The result: the material is fully compostable and has no adverse ecotoxicological effects.

Studies on fundamental aspects such as

• mechanism of degradation / identification of intermediate degradation products
  
• correlation between mechanisms of degradation and morphology (amorphous / crystalline structure)
  
• isolation, characterization and cloning of the enzymes responsible for degradation

are performed in cooperative ventures with universities.

In a large number of applications, Ecoflex combines improved benefits with ecological advantages. For example, Ecoflex can be used to make plastic bags for biological refuse. Carrier bags made from Ecoflex or Ecoflex starch blend become bifunctional and thus especially consumer-friendly: first they can be used several times for shopping, and then can be composted as a garbage bag together with organic waste.

Interesting applications were also found for Ecoflex in packaging. A coating of Ecoflex makes paper, cardboard or starch-based foam tougher and protects against fat, moisture and temperature variations. These are ideal properties for hamburger boxes, coffee cups, packaging for meat, fish, poultry, fruit or vegetables, food dishes and fast-food boxes.

Film made from Ecoflex also has many uses in agriculture: after being used as cover sheeting, it can be ploughed into the field and is degraded in the soil. Not least, this results in cost savings since labor-intensive clearing of fields and expensive disposal are unnecessary.