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Bioplastics: Mirel Structure and Properties: Page 1 of 6

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

Metabolix Mirel bioplastics are semicrystalline thermoplastics with the following generic structure:

Chain length and side chains can be varied to provide a broad range of physical and mechanical properties. R can be hydrogen or hydrocarbon chains of up to around C13 in length, and x can range from 1 to 3 or more. Varying x and R effect hydrophobicity, Tg, Tm, and level of crystallinity which can range from around 70% to very low, giving excellent stiffness or elasticity as needed.

When R is a methyl group and x=1, the polymer is poly-(3-hydroxybutyric acid) (PHB), the base homopolymer in the Mirel bioplastics family. [For comparison, when R is a methyl group and x=0, the product is polylactic acid (PLA) and when R is a hydrogen atom and x=4, the product is polycaprolactone.]

Metabolix Mirel bioplastics containing 3-hydroxy acids have a chiral center and are optically active. By the very nature of the manufacturing process at Metabolix, all 3-hydroxy units have an R configuration.

Metabolix has achieved the ability to produce a variety of homopolymers, copolymers, and terpolymers, using high-productivity microbial bio-factories. Copolymers vary in the type and proportion of monomers, and typically have random in sequence distributions. The range of structures that is now achievable has enabled access to a broad property space, from rigid thermoplastics to thermoplastic elastomers, and grades useful in waxes, adhesives, and binders. Metabolix can also convert its bioplastics into their building blocks, which have applications as solvents and chemical intermediates.

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