In short. A plasticizer Technical Data Sheet (TDS) states the limits a lot must meet; a batch Certificate of Analysis (COA) states what one lot actually measured. Read plasticizing esters by GC first, then acidity, moisture and colour, then the physical constants (specific gravity and refractive index at 27 °C), and finally volatile loss and heat stability, where the test conditions matter as much as the number. The examples below use the SPC TDS for dibutyl phthalate (DBP), SPC-TDS-PLA-002, and for DOP, SPC-TDS-PLA-001.
A plasticizer arrives as a clear oily liquid, and two lots that look identical can behave very differently in a PVC compound, a nitrocellulose lacquer or an adhesive. The paperwork is how you tell them apart before the drum is opened. This guide explains each row of a typical phthalate plasticizer TDS and batch COA, using DBP and DOP as examples, and sets out a short routine for checking a certificate against the data sheet.
TDS and batch COA: what each one tells you
The TDS is the product-level document. It lists each test, its unit and the limit, for example “colour, HU (APHA): 20 max”. It is the yardstick. The batch COA is lot-level. It lists the measured result for each test on one production lot, with a batch number. A COA that only repeats the limits, with no measured values, is a restatement of the TDS and tells you nothing about your lot.
The SPC TDS values for both DBP and DOP come from the producer Certificate of Analysis for the grade, and the producer cites ASTM D-1045 as the test method. Note the wording: ASTM D-1045 is a method for testing plasticizers, not a grade or a quality level. A certificate that says “grade: ASTM D-1045” has misread its own document.
The tests side by side
| Test | What it tells you | DBP (TDS limit) | DOP (TDS limit) |
|---|---|---|---|
| Plasticizing esters by GC | How much of the liquid is the target ester, by peak area | 99.50 min, % by area | 99.50 min, % by area |
| Ester content | Ester content on a weight basis | Not a separate row on the DBP TDS | 99.50 min, wt. % |
| Colour, HU (APHA) | Visual cleanness; matters in light-coloured products | 20 max | 20 max |
| Acidity as phthalic acid | Residual free acid | 0.010 wt. % max | 0.01 wt. % max |
| Moisture | Water content | 0.10 wt. % max | 0.10 wt. % max |
| Specific gravity at 27 °C | Identity and consistency check | 1.035 - 1.041 | 0.980 - 0.986 |
| Refractive index at 27 °C | Identity and consistency check | 1.489 - 1.495 | 1.483 - 1.489 |
| Ester value, mg KOH/g | Saponification-based check on the ester | 377 - 393 | 284 - 290 |
| Volatile loss | Material lost on heating | 0.10 wt. % max (110 °C / 2 hrs) | 0.10 wt. % max (130 °C / 3 hrs) |
| Heat stability | Change after heating | No change (150 °C / 2 hrs) | No change (180 °C / 2 hrs) |
Source: SPC TDS SPC-TDS-PLA-002 (DBP, Kanatol-400 (M)) and SPC-TDS-PLA-001 (DOP, Kanatol-800), both from the producer Certificate of Analysis (scripts/tds-data/di-butyl-phthalate-dbp.json and scripts/tds-data/di-octyl-phthalate-dop.json, specs, docNo, grade). The DOP data sheet also lists residual alcohol, 0.10 % by area maximum.
Plasticizing esters by GC: read the basis
The headline purity figure on both data sheets is plasticizing esters by gas chromatography, expressed as 99.50 % by area, minimum. Area percent means the ester peak must make up at least 99.50 % of the total peak area. It is not weight percent. The DOP data sheet carries an additional row, ester content, 99.50 wt. % minimum, which is a weight-basis figure; the DBP data sheet does not list that row. A 99.50 on an area basis and a 99.50 on a weight basis are different measurements, so when you compare two documents, check the unit and the basis first.
If the esters figure on a batch COA falls below the TDS limit, the balance is something other than the target ester: residual alcohol, related esters or other impurities. In a PVC compound the usual symptoms are changes in fusion behaviour, colour or smell; in a lacquer, haze or poor compatibility. Do not accept the lot without asking why.
Acidity, moisture and colour
Acidity as phthalic acid
In general terms, free acid in a plasticizer can interact with stabilisers and metal soaps in a PVC compound and affect the colour and stability of the product. The TDS limit for both DBP and DOP is about 0.01 wt. % as phthalic acid. A result above the limit is a real deviation, because the limit is already small.
Moisture
Water causes bubbles and haze in plastisols and can affect lacquers and adhesives. The limit is 0.10 wt. % maximum. A drum that has been opened and reclosed in humid conditions can pick up water, so keep containers tightly closed.
Colour in HU (APHA)
The Hazen or APHA colour scale measures how yellow a clear liquid is. The limit is 20 HU maximum for both examples. It rarely affects a black cable compound but it shows in clear films and light-coloured products. As a general rule, a result well above the limit points to heat or contamination during production or storage.
Ester value, specific gravity and refractive index
The ester value (mg KOH/g) is a saponification-based result. In general terms it checks that the liquid is the expected ester and that the ester content is consistent. Specific gravity and refractive index are physical constants. They are not purity tests on their own, but they are quick consistency checks: a lot whose specific gravity or refractive index falls outside the band is not the expected material, or is contaminated.
Check the temperature basis. The SPC TDS states both at 27 °C. A figure quoted at 20 °C will differ slightly even for the same liquid. For example, the SPC DBP safety data sheet gives an approximate relative density of 1.05 at 20 °C, while the TDS limit is 1.035 to 1.041 at 27 °C. The two are not in conflict; they use different temperatures and different bases. Use the TDS band to judge a batch.
Volatile loss and heat stability: read the conditions
Volatile loss is the percentage of mass lost under a stated heating condition. The condition is part of the specification. The DBP TDS uses 110 °C for 2 hours; the DOP TDS uses 130 °C for 3 hours. A 0.10 % result at one set of conditions cannot be compared with a 0.10 % result at another. Heat stability conditions differ in the same way: the DBP TDS lists “no change” after 150 °C for 2 hours, while the DOP TDS lists “no change” after 180 °C for 2 hours. If a COA quotes a different condition from the TDS, ask for the TDS conditions or a clear statement of the method used.
How to compare a batch COA with the TDS
- Confirm the document identity. The grade name, batch number and date should be on the COA, and the product should be the one you ordered.
- Compare unit and basis row by row. Area percent against weight percent, 27 °C against 20 °C, and the heating conditions for volatile loss and heat stability.
- Check every result against the limit. Do esters, colour, acidity, moisture, specific gravity, refractive index, ester value and volatile loss all sit inside the TDS limits?
- Look at the spread. Real lots vary a little inside the limits. A COA that shows exactly the same figures lot after lot deserves a question.
- Keep a retained sample. If you accept the lot, keep a sealed sample and the COA together, so a later problem can be traced to a lot.
Signs a certificate may be copied or altered
- The certificate is identical to an earlier one except for the date or year.
- Values sit exactly at the limits, or all rows are round numbers.
- The test method, units or conditions do not match the producer data sheet.
- The batch number format, layout or fonts differ from other certificates of the same producer.
- The document cannot be traced to a named producer or an accredited laboratory.
When in doubt, compare the certificate with a producer original for the same grade, not just with another certificate from the same seller. Internal consistency is not proof: a copied certificate is usually consistent with itself.
Grade limits: technical is not food or pharma
A TDS limit tells you the quality of a technical product. It does not make the product suitable for food contact, medicines or cosmetics. The SPC safety data sheet for DBP restricts use to industrial and professional applications, and classifies the substance as Repr. 1B (H360). If your end use is regulated, check the rules for that use before you specify a phthalate at all; DOTP is the non-phthalate plasticizer in the SPC catalogue.
Getting the documents from SPC
Supreme Petro Chemicals is a Chennai importer and bulk distributor, not a manufacturer. The TDS and SDS for each plasticizer are linked on its product page, and a batch Certificate of Analysis is supplied with every delivery. For the full DBP specification, packing and quote path, see the DBP product page; for the general-purpose option, see DOP. To choose between plasticizers, read the plasticizer selection guide. We aim to quote within 4 working hours.