[Dmeddings]

The biodegradable co-polymer PBAT (polybutylene adipate terephthalate) is widely used in the production of compostable bioplastic film. According to Wikipedia it is a co-polyester of adipic acid, 1,4-butanediol and terephthalic acid (from dimethyl terephthalate). PBAT is typically blended with thermoplastic starch to make compostable carrier bags and food waste caddy liners.

I believe (rightly or wrongly) that PBAT is partially bio-based and partially petroleum-based? I work with compostable packaging products but I do not have a science background, so I was hoping that someone here might be able to tell me what percentage of PBAT, if any, is oil based?


Thx


Dmeddings

[Enthalpy]

Welcome, Dmeddings!

Wiki's articles call and describe PBAT as "a copolyester of adipic acid, 1,4-butanediol and terephthalic acid"
https://en.wikipedia.org/wiki/Polybutylene_adipate_terephthalate
https://de.wikipedia.org/wiki/Polybutylenadipat-terephthalat
which shall be biodegradable, and whose reactants are produced from fossil materials, which could be coal too
https://en.wikipedia.org/wiki/1,4-Butanediol
https://en.wikipedia.org/wiki/Adipic_acid
https://en.wikipedia.org/wiki/Terephthalic_acid
https://en.wikipedia.org/wiki/P-Xylene

en.wiki states "fully biodegradable when composted due to the presence of butylene adipate groups". I don't know the fate of the butanediol terephthalate groups... Possibly a subtlety in some definition of "biodegradable". It doesn't imply neither that PBAT would degrade in the Ocean for instance.

Note that butylene adipate is of fossil origin, while PA11, made from biological sources, is not biodegradable. Not link between both.

de.wiki tells that "PBAT is used pure or blended with PLA or starch", without telling any proportion. PLA and starch are of biological origin (fossil materials too by the way, just longer ago)
https://en.wikipedia.org/wiki/Polylactic_acid
so if you find the proportion of PLA or starch in a blend, it's the fraction of biological origin.

[Dmeddings]

@enthalpy Many thanks for responding. 

Compostable bio plastic film normally contains around 30 - 50% bio-based material. This is typically starch or Polylactic Acid (PLA) depending on the manufacturer. The balance is PBAT.

I am just trying to find out if any percentage of the PBAT could be classed as being from a bio-renewable source, but if I understand your answer correctly, all the component polymers are fossil-based?

[Enthalpy]

All the feed for PBAT is obtained indirectly from fossil materials.
PBAT is compostable without any addition.
So "compostable" doesn't relate with a proportion of starch nor PLA blended with PBAT.
Starch or PLA in the blend would be the fraction obtained from biology.

[Dmeddings]

Thank you very much for clarifying that enthalpy.

Your help is much appreciated