To read a melamine certificate of analysis, find the column that holds the lot’s own results, check that the batch number matches the bags, and read each result against the limit and the test method printed beside it. For melamine made in China, the limits behind the COA come from GB/T 9567-2016, the national standard for industrial melamine made from urea, and several figures common on offer sheets do not match it.
Check first that the document is for industrial melamine at all: certificates for MF moulding powder or for laboratory-reagent melamine carry different lines and are not read against this standard.
Specification Limits Versus Lot Results
The lot’s own result is the column of measured values, usually printed beside a column of limits marked ≥ or ≤.
GB/T 9567-2016 does not require that result column. Its certificate clause lets the quality certificate for each batch carry either the inspection results or only an inspection conclusion, so a certificate that says nothing but “qualified” still meets the standard. If you need the numbers for every lot, write that into the contract.
A producer’s specification sheet is a different document: it lists the minimum or maximum for each line with a method code and reports no lot. An SDS covers hazards and handling and says nothing about a lot’s quality.
What Ties the COA to the Lot
The batch number, or the production date where the producer uses that instead, ties a COA to the delivered lot, and GB/T 9567-2016 requires it on both the certificate and the bags. Match four fields between the COA and the bag marks: producer name, product name, batch number or production date, and the standard number.
The grade is printed on the bag under the standard but is not a required field on the certificate. A COA without a grade is therefore not defective; take the grade from the bag and check the results against that grade’s limits.
Under GB/T 9567-2016 each batch leaving the plant carries its own certificate, so a delivery spanning several batch numbers should come with one COA per batch.
GB/T 9567-2016 sets no expiry, shelf-life or retest date, so an expiry date on a COA is the producer’s own term.
What Each Line on a Melamine COA Means
A melamine COA made to GB/T 9567-2016 carries appearance plus six results: melamine content, moisture, pH, colour and turbidity from the formaldehyde dissolution test, and ash. Lines outside that set, such as iron, ammeline and ammelide, particle size or bulk density, have no national limit, so read each against the producer sheet or contract that set it.
Check the method column before comparing two COAs, because results by different methods are not directly comparable. GB/T 9567-2016 names picric acid as the referee method for melamine content and Karl Fischer for moisture, and a producer sheet can still cite the 1997 edition’s clause numbers, which the 2016 edition renumbered.
Melamine Content
The melamine content figure is the mass fraction of melamine in the lot. GB/T 9567-2016 requires at least 99.5 % melamine for superior grade and at least 99.0 % for qualified grade.
A 99.8 % minimum on a COA or offer sheet is a producer or contract limit. A lot that meets the 99.5 % superior-grade minimum can still fail a 99.8 % contract.
Read small gaps between lots with the method’s precision in mind. Under GB/T 9567-2016, two duplicate melamine-content determinations on the same sample may differ by up to 0.2 %, so two COAs reading 99.86 % and 99.80 % melamine do not show a meaningful difference between the lots.
Moisture
The moisture line tells a resin maker how much water came with the melamine. GB/T 9567-2016 limits moisture to 0.1 % for superior grade and 0.2 % for qualified grade; a 1.0 % moisture limit on an offer sheet matches neither grade.
Ash
The ash line is the residue left after the melamine is burnt off at high temperature, which tells a resin maker how much inorganic matter came with the lot. GB/T 9567-2016 limits ash to 0.03 % for superior grade and 0.05 % for qualified grade. An ash limit of 0.5 % on an offer sheet is not a GB/T 9567-2016 limit at either grade.
Colour
The Hazen colour figure measures the colour of the melamine dissolved in neutralised formaldehyde solution, not of the powder. GB/T 9567-2016 limits colour to 20 Hazen units for superior grade and 30 Hazen units for qualified grade.
Producer sheets may print colour in APHA or Hazen units without saying what solution was measured. Check the method code before treating a producer’s colour figure as the GB/T figure.
Turbidity
The turbidity figure measures the haze of the same formaldehyde solution used for colour, reported in degrees (kaolin). GB/T 9567-2016 limits turbidity to 20 degrees for superior grade and 30 degrees for qualified grade, so an offer sheet that claims the standard but prints 20 for both grades is misquoting it.
Some producers print no turbidity line and report clarity or water-insoluble matter instead. Their sheets do not say these are the same test as GB/T turbidity, so do not read one as the other.
Formaldehyde Solubility
The formaldehyde dissolution test shows how cleanly the melamine dissolves in formaldehyde, and its results are the colour and turbidity figures; GB/T 9567-2016 gives it no pass or fail limit of its own.
In the GB/T 9567-2016 test the melamine must dissolve within 10 minutes of reaching 80 °C before the solution is read, so a COA line reading “clear within 10 min” reports a step of the procedure in a producer’s or trader’s layout.
pH
The pH line measures the alkalinity of a water extract of the melamine, and GB/T 9567-2016 sets one range, 7.5 to 9.5, for both grades.
Some producers measure a 2 % melamine solution instead and print the same 7.5 to 9.5 range, so compare pH across COAs only when the preparation matches.
Iron
An iron figure on a melamine COA is read against the producer’s or the contract’s limit, because GB/T 9567-2016 has no iron line.
GB/T 9567 Grades on a Melamine COA
A grade on a melamine COA or bag names the column of GB/T 9567-2016 that the lot meets: 优等品, superior grade, or 合格品, qualified grade. A lot holds a grade only if every line passes that grade’s limit.
| Line | Superior grade (优等品) | Qualified grade (合格品) |
|---|---|---|
| Melamine, % by mass | ≥ 99.5 | ≥ 99.0 |
| Moisture, % by mass | ≤ 0.1 | ≤ 0.2 |
| pH | 7.5–9.5 | 7.5–9.5 |
| Colour, formaldehyde dissolution test, Hazen units | ≤ 20 | ≤ 30 |
| Turbidity, formaldehyde dissolution test, degrees (kaolin) | ≤ 20 | ≤ 30 |
| Ash, % by mass | ≤ 0.03 | ≤ 0.05 |
Both grades also require a white or light-yellow powder with no visible impurities.
The 2016 edition lowered the superior-grade melamine minimum from 99.8 % to 99.5 % and renamed the second grade from first grade (一等品) to qualified grade, keeping its limits. A COA that prints “first grade”, or 99.8 % as the superior-grade limit, is quoting the 1997 edition.
What the Production Process Changes on the COA
None of the GB/T 9567-2016 limits on a melamine COA depend on the production process: GB/T 9567-2016 sets one set of limits per grade for all melamine made from urea. The process can show only in the lot’s results and in lines outside the standard, such as bulk density.
For the industrial melamine powder we supply, the specified purity and bulk density differ by route:
| Process route | Purity, % (min.) | Bulk density, g/cm³ |
|---|---|---|
| Gas phase | ≥ 99.9 | 0.8–0.9 |
| Low pressure | ≥ 99.7 | 0.7–0.8 |
| Normal pressure | ≥ 99.6 | not specified |
| High pressure | ≥ 99.5 | 0.6–0.7 |
These are specification values by route with no test method attached, so the lot COA’s result column is still the figure to check.