What to put in a geomembrane masterbatch trial request
“Please send a sample of your geomembrane grade” is a reasonable first email, but it is not a specification. The concentrate is an ingredient, and the same bag behaves differently in a different resin, at a different gauge, on a different line. Six inputs turn a sample request into something a supplier can answer and you can actually evaluate.
By Zoe Lin, Export Manager, E-LUCK (Guangdong Yijuyuan Plastic Industry Technology Co., Ltd.)
Why the trial conditions come from you
GRI-GM13 sets carbon black content at 2.0–3.0 percent on the finished HDPE geomembrane, measured by ASTM D4218, and sets a dispersion rating as a ten-field microscopic count. It does not set a masterbatch loading or a let-down ratio. That is a reading of the published specification; the practical consequence is that the dose is derived from your target, not from a grade code.
So a proposed grade and a starting let-down are hypotheses. Whether they produce the sheet you need depends on your base resin, your gauge, your screw and screen pack, your line speed and the stabiliser package you run alongside the concentrate. None of that is visible to the masterbatch supplier unless you send it.
Fact vs inference. The standard's scope is a published fact. The statement that trial conditions must come from the buyer is an inference from that scope and from how a concentrate is diluted — not a claim that any particular trial will succeed or fail.
Six inputs to send
| # | Input | What to state | Why it changes the answer |
|---|---|---|---|
| 1 | Liner standard and clause | GRI-GM13, or the project specification, and the property clauses you audit | Defines which finished-sheet values the trial has to reach and how often they are tested |
| 2 | Base resin / carrier | HDPE grade or blend; density and melt flow if you have them | Carrier compatibility and melt-flow match decide whether the concentrate disperses in your polymer |
| 3 | Final sheet thickness and surface | Gauge in mm; smooth or textured | Opacity and carbon black per unit area change with gauge; textured sheet has its own property table |
| 4 | Extrusion line | Flat-die or blown; screen pack; approximate output or line speed | Shear history and filtration decide dispersion and whether a filter-pressure figure is meaningful |
| 5 | Target in the finished sheet | Target carbon black content, or the let-down you intend to run | Determines the dose a starting grade proposal is calculated from |
| 6 | Records you need | Grade data sheet; lot certificate of analysis where available; dispersion test method and acceptance criteria; any trial or change-notification records | Lets the supplier say which documents can actually be supplied, instead of leaving it implicit |
On the sixth point, be as specific as you can about the method. A dispersion rating or filter-pressure value is only comparable when the method, mesh and test polymer are stated. Our note on reading a black masterbatch CoA explains why two correct numbers can disagree, and which documents can and cannot prove GRI-GM13 conformity separates the supplier's paperwork from your own sheet results.
What you should get back — and what not to ask for
A useful reply identifies the grade proposed and the reason for it, states a starting let-down as a starting point rather than a guarantee, and confirms which of the records you listed can actually be supplied for that grade. Sample quantity, carrier, any charge, trial feasibility and the time needed to prepare and ship a sample depend on the specification and destination; they are confirmed against the enquiry. Keep the quotation and the sample conditions as separate items so neither is assumed.
Do not build the request around a standing promise of samples at no charge, a fixed lead time, a certification in place of a test, or an assurance that the finished liner will pass. Those are either commercial terms to be agreed or claims that belong on the buyer's own trial film. If a project requires independent or owner-witnessed conformance testing, arrange that separately; a concentrate supplier's own reports do not replace it.
This guide is about one trial request. If you are changing suppliers rather than qualifying a single grade, our five-stage switching plan covers the line trial, parallel run and changeover, and the twelve-check RFQ guide covers verifying that the supplier is a compounding plant in the first place.
A request you can copy
Subject: Trial request — black masterbatch for HDPE geomembrane
We produce [smooth / textured] HDPE geomembrane at [gauge] mm to [standard and clause]. Base resin is [grade / density / MFR] on a [flat-die / blown] line with [screen pack]. Our target is [carbon black content in the sheet] / we intend to run [let-down]%.
Please propose a grade and a starting let-down, and confirm: (a) the current technical data sheet with test methods stated, (b) whether a lot-specific certificate of analysis can be supplied, (c) which dispersion method and acceptance criteria you can work to, (d) any notice you give for changes in carbon black source, carrier resin or production site, and (e) sample quantity, carrier, any charge, feasibility and the time to prepare and ship, based on the specification and destination above.
We will run the trial on our own line and report the finished-sheet results with roll and lot numbers. Please keep the quotation and the sample conditions as separate items.
The last sentence matters. It puts sheet conformity where it belongs — on the film you extrude — and stops the email turning into a request for a guarantee nobody can give from a bag of pellets.
Who this applies to
This request is written for liner producers, compounders and film plants that buy black masterbatch as an ingredient. Engineering contractors and geomembrane traders buying finished rolls are not buying concentrate, so a masterbatch trial request is the wrong document for them.
Sources and related pages
- Geosynthetic Institute, GRI-GM13 specification (PDF) — finished-sheet carbon black range and dispersion requirement
- Black masterbatch for geomembrane and pond liner — the application page and its enquiry form
- Let-down calculator — converting a target sheet loading into a dose
- Technical data and SGS test reports — what our published documents cover
- Can a masterbatch data sheet prove GRI-GM13 compliance? — the evidence split
Questions buyers ask
What information does a supplier need before a geomembrane masterbatch trial?
The liner standard and the clause you audit; the base resin or carrier system; final sheet thickness and whether the surface is smooth or textured; the extrusion line type; the target carbon black content in the finished sheet or the let-down you intend to run; and the records you need, such as a grade data sheet, a lot certificate of analysis, or a dispersion method and acceptance criteria.
Should a trial request assume samples at no charge or a fixed delivery date?
Sample quantity, carrier, any charge, trial feasibility and the time to prepare and ship a sample depend on the specification and the destination, and are confirmed against the enquiry rather than stated as a standing promise. Keep the quote and the sample conditions as separate items in the request so neither is assumed.
Can a supplier confirm that a grade meets GRI-GM13 before the trial?
Not for the finished liner. GRI-GM13 sets carbon black content and dispersion requirements on the finished HDPE sheet; the masterbatch is only one input. A supplier can propose a grade and a starting let-down. Conformity is established by testing the film the buyer extrudes, with the results tied to roll numbers and the masterbatch lot.
Who is this trial request for?
Liner producers, compounders and film plants that buy black masterbatch as an ingredient. Engineering contractors and geomembrane traders who buy finished rolls are not buying masterbatch, so a concentrate trial request is not the right document for them.