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The Specialty Polymers Age (1980-1999)

1992

Polybutylene Adipate Terephthalate (PBAT)

Against Pollution

“The Story of a Polymer That Learned to Disappear”·thermoplastic·biodegradable-polyester · polyester·BASF

In June 1992, delegates from more than 170 countries gathered in Rio de Janeiro for the Earth Summit, the largest environmental conference the world had yet held, to try to agree on how industrial economies could keep growing without the planet paying the whole bill. Greenpeace’s verdict on how that negotiation was going hung, literally, over the city: activists scaled Sugarloaf Mountain and unfurled a banner reading “SOLD — VENDIDO” across its granite face, accusing the summit of trading real commitments for diplomatic language everyone could sign.

Plate I

An aerial photograph of Sugarloaf Mountain in Rio de Janeiro, with a cable car passing in the foreground and a large white banner reading 'SOLD / VENDIDO' with a Greenpeace logo hung across the rock face.
A Greenpeace banner on Sugarloaf Mountain during the June 1992 Earth Summit, protesting what activists saw as a conference trading firm commitments for compromise.Wikimedia Commons

Whatever the summit itself delivered, “compromise” is not always a dirty word, and in materials chemistry that same year it was producing something genuinely useful. Every biodegradable polyester before it had come with a trade-off attached: flexible aliphatic polyesters broke down readily but were mechanically too weak to replace an everyday film, while aromatic polyesters like PET were tough enough to use but essentially permanent. Chemists at BASF’s Ludwigshafen site, working through the early 1990s, set out to build a single chain that carried both halves of that trade-off at once (flexible, microbially vulnerable segments alternating with rigid, load-bearing ones) rather than picking a side. The result, refined through the decade and launched commercially in 1998 as ecoflex, was the first PBAT to reach the market, and it remains the benchmark the rest of the category is measured against.

Plate II

A wide view across farmland toward a large chemical plant on the horizon, its skyline dense with distillation towers, storage tanks and a tall red-and-white striped chimney.
Part of BASF's Ludwigshafen site, where PBAT was developed through the early 1990s and first sold, as ecoflex, in 1998.Wikimedia Commons

Two Molecules, Stitched Together

PBAT is not one repeating unit but two, joined into a single random chain. One stretch of the polymer is built from adipic acid and 1,4-butanediol: an entirely aliphatic sequence, flexible and, crucially, exactly the kind of ester linkage that soil bacteria already know how to attack. Threaded between those stretches are units built from terephthalic acid instead, the same rigid, ring-bearing acid that gives PET its strength and heat resistance. Neither segment alone would make a useful film: the aliphatic portion is too soft and the aromatic portion, used alone, is the barely-degrading plastic PBAT exists to avoid. Blended randomly into one chain, the aromatic segments hold the material together with real mechanical strength while the aliphatic segments give microorganisms a foothold to start taking it apart.

Properties: A Deliberate Middle Ground

PBAT is not a stiff, glassy plastic like PLA or PGA; it behaves, mechanically, much closer to ordinary polyethylene film, low in stiffness but genuinely tough, able to stretch and flex without tearing, which is exactly the profile a bag or a mulch film needs and the profile a more rigid bioplastic cannot offer on its own. That resemblance to conventional film is not an accident; it is the entire design goal, since a compostable film that behaved like brittle packaging tape would never survive being made into anything.

From Laboratory to Landfill Alternative

PBAT rarely appears alone. Because pure PBAT is soft rather than sturdy, it is typically blended with a stiffer, more brittle biodegradable partner, most often PLA, so that each covers the other’s weakness: PLA supplies rigidity and heat resistance, PBAT supplies the flexibility and tear resistance PLA lacks on its own. That combination, along with straight PBAT film and PBAT blended with starch, has become the material behind most compostable shopping bags, produce bags and mulch films sold today, alongside coatings that make paper cups resist a hot drink without a plastic lining that outlives the cup by centuries.

Plate III

A folded compostable plastic bag printed with green leaf logos and multilingual 'bio and compostable' text, laid beside a wrapped set of disposable cutlery marked with the same certification symbols and the brand name Mater-Bi.
Compostable bags and cutlery made with Mater-Bi, Novamont's brand for starch blended with an aliphatic-aromatic copolyester in the same family as PBAT.Wikimedia Commons

Under industrial composting conditions, testing on BASF’s own ecoflex has shown it breaking down almost completely within about three months, fast enough to qualify under the standards that let a product carry a genuine compostability certification. What it will not do is disappear in the ocean or a river: left in fresh or salt water, PBAT does not meaningfully biodegrade, an important limit on the “disappears harmlessly” story and one PBAT shares with PLA. It is a material built to solve composting, not littering, and the difference between those two problems is exactly the gap its critics (not unlike the ones hanging banners in Rio in 1992) are right to keep pointing at.

Plate IV

Two long windrows of dark, decomposing organic material piled beside a paved yard, with an open-sided barn and trees in the background.
A central composting site in Germany, the kind of industrial-scale facility where a certified compostable film has to prove it breaks down on schedule.Wikimedia Commons

values with [n] cite the numbered references·estimates are flagged·“not yet available” and “N/A” are honest states, not gaps

polybutylene adipate terephthalate repeat unit O O O O O O O O ran ran

Polybutylene Adipate Terephthalate repeat unit

Abbreviation
PBAT
Type
polymer family (hub)
CAS number
130479-65-1
Resin ID code
none assigned
Formula
(C10H16O4)x·(C12H12O4)yA random copolyester. The flexible aliphatic adipate segments are what bacteria can attack; the rigid aromatic terephthalate segments are what make it strong enough to use.
Repeat unit (BigSMILES)
{[][>]OCCCCOC(=O)CCCCC(=O)[<],[>]OCCCCOC(=O)c1ccc(cc1)C(=O)[<][]}
IUPAC name
—
Synonyms
ecoflex; Origo-Bi; Eastar Bio
Also known as
ecoflex

Chemical family
biodegradable-polyesterpolyester
Backbone class
heterochain
Polymerization mechanism
step-growth-condensation
Constitutional monomer
Adipic acid1,4-ButanediolTerephthalic acid
Polymer class
thermoplastic

Year of origin
1992
Era
The Specialty Polymers Age (1980-1999)
Key figures
BASF
Events referenced
United Nations Earth Summit, Rio de Janeiro, June 1992

Polymerization type
step-growth condensation
Common monomers (feedstocks)
adipic acid, 1,4-butanediol, terephthalic acid
Catalysts
not yet available

Developed to address environmental concerns about PET plastic persistence: roughly 30% of global PET production becomes bottles, of which only 15–35% is recycled. Major manufacturers: BASF (ecoflex), Novamont (Origo-Bi), Eastman Chemical (Eastar Bio), and numerous Chinese suppliers.

Tacticity
not yet available
Crystal structure
not yet available
Typical crystallinity
not yet availableRandom copolymer structure prevents significant crystallization, giving a wide melting range rather than a sharp Tm.

Molecular weight

Number average (Mn)
not yet available
Mass average (Mw)
not yet available
Dispersity (Mw/Mn)
not yet available

Mark-Houwink constants

not yet available

Low elastic modulus and stiffness, but high flexibility and toughness, properties comparable to LDPE, which is what makes it a practical drop-in replacement for LDPE film in compostable applications.

Density
not yet available
Melt flow index
not yet available
Refractive index
not yet available
Transmittance
not yet available
Haze
not yet available
Gloss
not yet available
Water absorption
not yet available
Dielectric constant
not yet available
Dielectric strength
not yet available
Electrical conductivity
not yet available

Glass transition (Tg)
not yet available
Melting temperature (Tm)
not yet availableRandom copolymer gives a wide melting range rather than a single sharp value; no specific range sourced.
Crystallization (Tc)
not yet available
Heat deflection (HDT)
not yet available
Decomposition onset
not yet available
Thermal conductivity
not yet available

Tensile modulus
not yet availableQualitatively 'low elastic modulus'; no specific number sourced.
Yield strength
not yet available
Tensile strength at break
not yet available
Elongation at break
not yet available
Impact strength (Izod)
not yet available
Impact strength (Charpy)
not yet available
Hardness
not yet available
Flexural modulus
not yet available
Poisson's ratio
not yet available
Coefficient of friction
not yet available

Weathering / UV
not yet available
Hydrolysis resistance
Fully biodegradable when composted; ~90% degradation after 80 days (BASF ecoflex test)[1]
Flammability (UL94)
not yet available
Limiting oxygen index
not yet available
Solubility parameter (δ)
not yet available

Gas permeability

not yet available

Polymer-solvent interaction parameter (χ)

not yet available

Processing methods
film blowing/extrusioncompostable bag manufacturingextrusion coating (paper cups)
Drying required
not yet determined
Processing temperature
not yet available
Shrinkage rate
not yet available

  • Packagingcling wrap for food packaging · compostable plastic bags
  • Agricultureagricultural mulch film
  • Food servicewater-resistant coatings for paper cups
  • Emergingantimicrobial films

Recyclable
No
Biodegradable
Yes
Degradation pathway
Butylene adipate groups enable biodegradation under composting conditions (~90% degradation after 80 days per BASF ecoflex testing).

Does not degrade in marine and fresh water. This is an important caveat similar to PLA's marine-litter limitation.

LD50 (oral, rat)
not yet available
NFPA health
not yet available
NFPA flammability
not yet available
NFPA reactivity
not yet available
Carcinogenic classification
not yet available

  1. [1]Polybutylene adipate terephthalateWikipediaAccessed 2026-07-14https://en.wikipedia.org/wiki/Polybutylene_adipate_terephthalate[wiki-pbat]

Illustrations

  1. Plate IA Greenpeace banner on Sugarloaf Mountain during the June 1992 Earth Summit, protesting what activists saw as a conference trading firm commitments for compromise.Celso Meira · Public domainWikimedia Commons
  2. Plate IIPart of BASF's Ludwigshafen site, where PBAT was developed through the early 1990s and first sold, as ecoflex, in 1998.Felix König · CC BY 3.0Wikimedia Commons
  3. Plate IIICompostable bags and cutlery made with Mater-Bi, Novamont's brand for starch blended with an aliphatic-aromatic copolyester in the same family as PBAT.JKey128 · CC BY-SA 4.0Wikimedia Commons
  4. Plate IVA central composting site in Germany, the kind of industrial-scale facility where a certified compostable film has to prove it breaks down on schedule.Crystalclear · CC BY-SA 3.0Wikimedia Commons