Cold-Resistant Plasticizers for PVC: DOA vs. DOS Guide

Adipate and sebacate esters are the two standard routes to low-temperature flexibility in flexible PVC. Both are classified as non-phthalates, both are used in cold storage curtains, cable jackets, and food-service films, and both are often quoted interchangeably in inquiries. In practice, however, they are not interchangeable: DOA (CAS 123-79-5) offers low viscosity and low cost, while DOS (CAS 122-62-3) provides lower volatility and better retention of elongation after heat aging. The choice affects the formulation, processing window, and end-of-life profile.

Where the two esters actually differ

Values indicate direction only, not specifications. Purity, acid value, color, and volatile loss for the delivered batch are specified in the COA shipped with that batch.

Selection logic that stands up in court

1. Define the service temperature and the validation test. For most buyers, this means a low-temperature impact or cold bend test after 7 days at the service temperature—not relying solely on the plasticizer datasheet.
2. Define the heat history. A strip curtain stored in a warm warehouse but used at −25 °C has different volatility requirements than a freezer film that remains in the cold chain.
3. Adjust the plasticizer loading to meet the hardness target, not the supplier's initial value. Adipates and sebacates vary in efficiency; therefore, the phr that yields 65 Shore A with DOA will not produce the same hardness with DOS.
4. Run a single trial batch for each candidate at the same loading level, then compare hardness, tensile strength, elongation at break, and elongation retention after heat aging. Only the retention value reliably distinguishes between the two esters.

Formulation notes

• Both esters are compatible with Ca/Zn stabilizer systems and ESBO co-stabilizers; switching between them typically requires no changes to the stabilizer package.
• Due to its lower viscosity, DOA wets out resin faster and can reduce dry-blend time. DOS may require a slightly longer mixing cycle or a modest temperature increase during the hot-mix stage.
• In strip curtains and films, a small amount of higher-molecular-weight secondary plasticizer or chlorinated paraffin substitute may be added to reduce volatility. Before incorporating any chlorinated component, verify the target market's regulatory restrictions.
• For cable compounds, verify insulation resistance requirements before assuming any cold-flex plasticizer is acceptable. Adipates may lower volume resistivity compared to trimellitates.

Documentation typically requested by buyers

TDS for the grade, batch COA with purity, acid value, color, and volatile loss. For exports to the EU, include a REACH SVHC screening statement limited to the supplied substance. Cold-performance claims must be supported by a test report on the finished article, as the compound—not the ester—determines the result.

FAQ

Can DOA and DOS be combined?

Yes. Blending is common when a buyer seeks the cost advantage of DOA alongside part of the volatility benefit of DOS. The blend ratio should be determined through trials measuring elongation retention after aging, as the two esters do not age additively in every compound.

Does DOS always offer better cold flexibility than DOA?

No. Both perform well at low temperatures. The practical difference emerges after heat aging and in terms of volatility loss, where the longer sebacate chain typically retains its properties better. Cold impact on the finished product remains the deciding test.

Which one is used in food-contact films?

Both are technically viable, but the destination market's approved substance list and migration limits ultimately determine compliance. Verify the current regulatory text and conduct migration testing on the finished film instead of relying solely on the plasticizer datasheet.

How many samples are required for the trial?

One kilogram is typically sufficient for lab-scale dry blending and producing pressed or extruded sheets for mechanical and cold-bend testing. Request a free 1 kg sample along with the corresponding TDS and COA, and specify the target hardness and service temperature so we can confirm the appropriate grade first.