Polybutyrate

Polybutyrate (short for polybutyrate adipate terephthalate, or PBAT) is a biodegradable random copolymer, specifically a copolyester of adipic acid, 1,4-butanediol and dimethyl terephthalate. PBAT is produced by many different manufacturers and may be known by the brand names ecoflex®, Wango, Ecoworld, Eastar Bio, and Origo-Bi. It is generally marketed as a fully biodegradable alternative to low-density polyethylene, having many similar properties including flexibility and resilience, allowing it to be used for many similar uses such as plastic bags and wraps. The structure of the PBAT polymer is shown to the right. It is depicted as a block co-polymer here due to the common synthetic method of first synthesizing two copolymer blocks and then combining them. However, it is important to note that the actual structure of the polymer is a random co-polymer of the blocks shown.

Production of plastics for use in the industrial sector around the world makes up a very large market. PET (polyethylene terephthalate) is one of the dominant plastics within this market. It is most commonly used for bottle production because of being a rigid container that is very lightweight. However, because of the stability of this polymer, it is also highly resistant to biodegradation, posing a significant environmental threat when it is taken into account the amount of PET produced, sold, used and thrown away on a daily basis. An estimated 30% of the worlds PET goes into making these plastic bottles and anywhere from 15 to 35% end up being recycled; the rest usually end up in a landfill. This has inevitably stimulated research into polymers that can function comparably to PET, but be biodegradable.

Like all developments in the materials world, there are always several requirements for an 'ideal' material. For biodegradable plastics, they would be: cheap, renewable, easy to produce and eco-friendly. In addition to these, the polymer would have to be resistant enough to be functional, such as handling the strain from being pressurized or flexible so that it is easy to mold. There are no polymers that can perfectly contain every one of these features. Therefore, researchers have turned their attention to copolymers: combinations of polymers that have chemical and mechanical properties that compliment each other. This led to identifying Poly(butylene adipate-co-terephthalate) (PBAT) as a potential copolymer for blending.

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