| Property | Typical value | Notes |
|---|---|---|
| Melting point (Tm) | 110–120 °C | Low, easy to process into film |
| Glass transition (Tg) | −30 to −20 °C | Soft and flexible at room temperature |
| Tensile strength | 15–35 MPa | Moderate |
| Elongation at break | 500–800 % | Very high, this is the key trait |
| Density | ~1.25–1.27 g/cm³ |
Look at elongation at break: 500–800%versus 3–10% for PLA. PBAT can stretch to many times its length before snapping, behaving like the low-density polyethylene in a shopping bag. That single property is why brittle PLA and weak starch are blended with PBAT: it contributes the stretch and toughness they lack, turning a rigid or crumbly material into a usable film.
Here's the twist that trips people up: PBAT is made from petroleumjust like conventional polyethylene. The difference is in its chemistry, its molecular backbone is built to be broken down by microbes, where polyethylene's is not. It's the cleanest illustration of why "bio-based" (what it's made from) and "biodegradable" (how it ends) are two completely separate questions. More on that distinction →
PBAT is produced by polycondensation, chemically joining three monomers (adipic acid, terephthalic acid, and 1,4-butanediol) into a long, flexible co-polyester. The aromatic part gives it strength; the aliphatic part gives it the flexibility and the biodegradability. Increasingly, producers are substituting bio-based versions of these monomers, which would make future PBAT both bio-based and biodegradable.
Flexibility and toughness. Most biodegradable polymers, PLA, PHB, starch, are stiff or brittle. PBAT is soft, stretchy, and tough, behaving much like the low-density polyethylene used in plastic bags. That makes it the ideal blend partner: mix it with brittle PLA or weak starch and you get a compostable film that can actually survive being a shopping bag or a mulch sheet. A large share of the world's compostable film is a PBAT blend.
It's still fossil-based today. PBAT solves end-of-life, not feedstock, most current PBAT does not reduce reliance on petroleum at the source, even though it composts. It's also less stiff than PLA, so it's rarely used alone for rigid items. The honest framing: PBAT is a brilliant enabler that makes other compostable materials work, rather than a standalone hero, and its sustainability case improves a lot once bio-based monomers scale up.
PBAT is engineered to biodegrade, primarily in industrial composting conditions. As with any compostable, check the specific certification, home-composting performance varies. In a blend, the compostability of the whole product depends on every component, which is why certified products test the finished item, not just the resin.
Related: Starch blends · PLA · Coatings
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