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Bioplastics: Mirel Structure and Properties: Page 5 of 6

• Molecular Weight • Thermal Properties • Mechanical Properties • Surface Energy • Gas Barrier Properties • Biodegradability • Stability to hydrolysis • UV Stability

6. Biodegradability
Metabolix bioplastics offer a unique combination of biodegradability and hydrolytic stability under normal service conditions. When exposed to microbial organisms naturally present Metabolix bioplastics break down enzymatically in soil, composting, waste treatment processes, river water and marine environments, however, they rapidly decompose to carbon dioxide and water. They will also degrade in anaerobic environments unlike many current biodegradable materials. Since carbon dioxide and water are the raw materials used to make Metabolix bioplastics, the lifecycle is essentially a closed-loop process. This is different from the hydrolytic breakdown processes which can compromise performance.

Biodegradability is often associated with poor lifetime performance during service, and a number of the commercially available polymer systems that claim to be biodegradable are highly sensitive to liquid water or water vapor. In these cases, the "biodegradation" process involves both hydrolytic breakdown as well as bacterial decomposition. The presence of liquid water or high humidity can limit the serviceability of these products.

The following table compares the rate of film degradation (micrograms/sq mm) for a typical metabolix Mirel polymer, polycaprolactone and CellophaneTM film under marine and soil composting conditions.

All Metabolix bioplastics meet the ASTM and DIN biodegradability requirements.

• Molecular Weight • Thermal Properties • Mechanical Properties • Surface Energy • Gas Barrier Properties • Biodegradability • Stability to hydrolysis • UV Stability