PLA vs Polyethylene terephthalate
PLA and Polyethylene terephthalate are commonly confused, and 1 measured property separates them — density most clearly.
PLA vs Polyethylene terephthalate
PLA
Made from sugar rather than oil, and compostable in an industrial composter and almost nowhere else.
Polyethylene terephthalate
The polyester in every drinks bottle and most clothing — and the only plastic with a genuinely working recycling stream.
| Property | PLA | Polyethylene terephthalate |
|---|---|---|
| Density | 1.24–1.27 g/cm³ | 1.38–1.4 g/cm³ higher |
| Melting point Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 250–260 °C |
| Tensile strength Only one of the two has a figure we can stand behind, so there is nothing to compare. | 50–70 MPa | Not known |
| Young's modulus Only one of the two has a figure we can stand behind, so there is nothing to compare. | 3–3.8 GPa | Not known |
Choosing between them
PLA is recorded as a substitute for Polyethylene terephthalate — lower environmental impact.
What it gives up: A worse barrier, a far lower service temperature, and compostable only in an industrial composter — in a home heap, in landfill or at sea it persists.
Partial substitute, on the evidence cited above.
Why these get confused
similar enough in appearance and in near-infrared sorting to be mis-sorted, and PLA in a PET recycling batch degrades the whole lot
The confusion is a real and documented one, not a resemblance we have invented.