A masterbatch data sheet cannot prove a geomembrane meets GRI-GM13
If a liner producer receives a supplier's masterbatch data sheet, can that document alone establish GRI-GM13 conformity for the finished liner? No. The specification applies to the finished sheet, while the data sheet describes the concentrate. They answer two different questions, and mixing them is how a trial gets approved on the wrong evidence.
By Zoe Lin, Export Manager, E-LUCK (Guangdong Yijuyuan Plastic Industry Technology Co., Ltd.)
The standard is written for the sheet, not the bag
GRI-GM13, published by the Geosynthetic Institute, is a specification for finished HDPE smooth and textured geomembranes. Tables 1 and 2 set carbon black content on the sheet at 2.0–3.0 percent, measured by ASTM D4218, across the thickness grades; note 3 permits ASTM D1603 or D6370 as alternates when correlated with D4218. Note 4 of those tables sets the dispersion rating as a ten-field count — nine fields in Category 1 or 2, one field may be in Category 3 — using the microscopic method cited in the note.
That is what the document says. What it does not say: the standard contains no masterbatch grade, no carbon black loading for a masterbatch and no let-down ratio. It does not describe how a compounder should make its pellets. It sets properties of the liner and how often the liner manufacturer has to test them.
Fact vs inference. The first paragraph is a reading of the published specification. The conclusion — that a figure printed on a masterbatch bag cannot, by itself, establish sheet conformity — follows from that scope, not from any test we ran on a particular product.
GSI also states that GM13 is a voluntary specification and does not warrant or indemnify material produced to it. It is a technical specification, not a certificate that a supplier is awarded. Whether a specific product holds a test result, a compliance statement or a third-party declaration is a separate question, and has to be checked against that supplier's own documents.
What a masterbatch data sheet can establish
A grade data sheet is still worth asking for. It describes the ingredient, which is exactly what you need in order to run a controlled trial. Typically it gives the carrier resin, the carbon black type and loading in the concentrate, a recommended let-down range, melt flow rate, ash or screen-pack behaviour, moisture, and the dispersion or filter-pressure data the supplier actually measures — provided the test method and conditions are written down alongside the number.
It cannot give you the carbon black content of your finished liner, the dispersion rating of your sheet, or oxidative induction time after your extrusion pass. Those are properties of a film that does not exist until you run it on your own line with your own resin.
| Document | Who issues it | What it establishes | What it does not establish |
|---|---|---|---|
| Grade technical data sheet | Masterbatch supplier | Composition and typical values of the concentrate; starting let-down; the methods behind its own measurements | Any property of the finished liner; conformity to a liner standard |
| Lot certificate of analysis | Masterbatch supplier | Measured values for one production lot, where the supplier holds them | What happens after the concentrate is diluted into a different resin |
| Trial film report | Liner producer (the buyer) | Carbon black content, dispersion, OIT / HP-OIT and mechanical results on the sheet actually extruded | Performance under a different resin, gauge or line setting |
| MQC / conformance records | Liner manufacturer, and the purchaser's QA where specified | Roll-level traceability and the testing frequency the standard calls for | Anything about the masterbatch supplier's internal process |
The four rows are a division of responsibility, not a claim that any one supplier issues all of them. Ask for the documents you need and confirm which of them can actually be supplied before you build a qualification plan around them.
Three evidence requests to put in the RFQ
1. To the masterbatch supplier. Ask for the current technical data sheet for the exact grade, with the test methods and conditions stated; a lot-specific certificate of analysis where one is available; and written confirmation that you will be told if the carbon black source, carrier resin or production site changes. If a dispersion or filter-pressure figure matters to you, ask which method produced it — a number without a method is not comparable between two suppliers.
2. In your own trial. Run the grade at your intended let-down in the resin, gauge and line you will actually produce on. Measure carbon black content and dispersion on that sheet, and the oxidative and aging properties your project specifies. Keep the roll numbers, the masterbatch lot and the test results together. This is the only place where sheet conformity can be established.
3. Where the project requires it. Independent, owner-witnessed or third-party conformance testing is a separate arrangement between the liner buyer and the testing party. A masterbatch supplier's own reports do not substitute for it, and a system certificate does not either.
If you want a worked example of how to read the concentrate side of this split, our note on reading a black masterbatch CoA goes field by field. For the other direction — what the carbon black figure on the sheet is there to protect — see carbon black loading for UV service life in pipe and geomembrane.
Where the boundary sits for us
Our geomembrane page asks for the standard and clause you audit, your carrier resin and your final film thickness before a grade is proposed. It also asks you to tell us your dispersion test method and acceptance criteria, so that the evidence available with a quotation can be reviewed against them. That is a request for your specification, not a promise about the finished film.
Our certifications page lists management-system certificates, and our SGS report library publishes product-level compliance reports covering RoHS, REACH and PAHs. Those are product and system documents. They are not geomembrane performance tests and they are not a GRI-GM13 conformity claim; please read them for what they cover. The distinction matters, because a compliance report on a concentrate says nothing about OIT retention or dispersion in a 1.5 mm sheet.
We make no claim of GRI-GM13 certification, no standing claim about lot release against a fixed set of checks, and no claim that a finished liner will pass. Which records can be supplied for a given grade is confirmed against your enquiry, before a quote.
A short checklist before you approve a trial
- Has the supplier identified the exact grade and issued its current data sheet with the test methods stated?
- Do you have the finished-sheet value your standard requires, and do you know which method will measure it?
- Is the let-down stated as a starting point to be verified on your line, rather than as a guaranteed outcome?
- Have you asked which lot records can be supplied, and are they tied to lot numbers?
- Is the person who signs off sheet conformity the liner manufacturer, not the concentrate supplier?
- Where a third-party declaration is required, has it been checked against the issuing body rather than a marketing page?
Sources and related pages
- Geosynthetic Institute, GRI-GM13 specification (PDF) — finished-sheet properties, carbon black range, dispersion note and testing frequency
- Black masterbatch for geomembrane and pond liner — the application page and its enquiry form
- Certifications and SGS test reports — what our own documents cover
- Technical data — grade data sheets and what is published
- How to read a black masterbatch CoA — the concentrate-side document
- Let-down calculator — converting a concentrate loading into a dose
Send us your liner specification
Questions buyers ask
Does GRI-GM13 certify a black masterbatch?
No. GRI-GM13 is a technical specification published by the Geosynthetic Institute for finished HDPE smooth and textured geomembranes. It sets test methods, properties and testing frequency for the sheet. It does not grant a certification, does not name a masterbatch grade and does not define a let-down ratio. GSI also states that the standard is optional and does not warrant material produced to it. Whether a particular product holds any test result, compliance statement or third-party declaration is a separate question to check against that supplier's own documents.
What carbon black content does GRI-GM13 require?
Tables 1 and 2 of GRI-GM13 set carbon black content on the finished HDPE geomembrane at 2.0–3.0 percent, measured by ASTM D4218, for both smooth and textured sheet across the thickness grades. Note 3 allows ASTM D1603 or D6370 as alternates when correlated with D4218. The figure applies to the sheet, not to the masterbatch bag.
Can a masterbatch supplier guarantee the carbon black content of the liner?
Not from a data sheet alone. A supplier can state the carbon black loading of its grade, the carrier resin and a starting let-down, and can supply whatever lot records it actually holds. The finished-sheet figure depends on the buyer's resin, let-down, sheet thickness, extrusion conditions and the test method used. Conformity is established by testing the buyer's own film.
Which documents should I request before a geomembrane masterbatch trial?
From the masterbatch supplier: the grade technical data sheet with the test methods stated, a lot-specific certificate of analysis where available, and written notice of any change in carbon black source, carrier resin or production site. From your own trial: results for carbon black content, dispersion and oxidative induction time on the sheet you actually extruded, tied to roll numbers and the masterbatch lot used. Any project-required third-party or owner-witnessed testing is arranged separately.