Both Resin Quotes Say MFI 10. Are They Actually Comparable?

*By Daoyu Guan*

A buyer receives two resin quotations. Each spreadsheet contains the same entry: “MFI 10.” The purchasing team moves on to price, assuming the flow specification matches.

That comparison is unfinished. One supplier may be reporting a mass flow rate; the other may be reporting a volume flow rate. Their test temperatures or applied loads may differ. Even a correctly matched flow measurement would leave the finished part's other requirements to be assessed.

Before treating the numbers as comparable, identify the measured quantity, its unit, the test conditions and the material represented by the result. Then distinguish a published typical value from evidence about the lot being offered. Those checks give purchasing and engineering a shared starting point without turning a short datasheet entry into a material approval.

MFR and MVR describe different quantities

Melt mass-flow rate, or MFR, expresses mass extruded over a stated time, commonly g/10 min. Melt volume-flow rate, or MVR, expresses volume, commonly cm³/10 min. The number 10 therefore describes different quantities depending on the unit.

Toyo Seiki's explanation of melt flow testing distinguishes the mass measurement from the displacement measurement used to determine volume. It also explains the need for melt density at the test temperature when converting between them.

“MFI” remains a familiar label in commercial discussions. For a purchasing comparison, ask the supplier to expand it into the actual reported quantity and unit. A shared abbreviation cannot resolve an omitted unit. Nor can a spreadsheet column headed “melt index” establish which measurement a supplier entered.

Keep the unit beside the value wherever it appears: the English product page, downloadable datasheet, quotation and comparison table. A reader copying one row should retain enough information to understand the measurement.

The temperature and load belong to the result

ISO 1133-1:2022's public abstract describes MFR and MVR determination under specified temperature and load conditions. It identifies a mass-based procedure and a displacement-based procedure. The full standard contains requirements beyond that public description; this guide does not reproduce or verify the complete procedures.

For the buyer, the immediate consequence is practical: “10 g/10 min” is still an incomplete comparison when its temperature and load are missing. Do not insert conditions from another grade, an older brochure or a commonly used test setting simply to fill the spreadsheet.

The following quotation records are fictional. Their temperatures and loads illustrate missing comparability; they are not recommended test settings for any particular resin.

Quotation B cannot be made comparable to A by replacing “cm³” with “g.” It also cannot be moved from 230 °C to 190 °C through a unit conversion. Ask for a measurement under the agreed conditions, or a technically justified comparison supplied by the responsible specialist.

A density conversion changes the unit, not the approval status

When the relevant melt density is known, the relationship is:

MFR [g/10 min] = MVR [cm³/10 min] × melt density [g/cm³].

For a fictional calculation, suppose quotation C has a documented melt density of 0.75 g/cm³ at the relevant test temperature. Its 10 cm³/10 min corresponds to 7.5 g/10 min. It does not become the 10 g/10 min shown in A.

Using 0.90 g/cm³ instead would produce 9.0 g/10 min. That second calculation is a sensitivity illustration, not permission to select a convenient density. The conversion input needs its own provenance and applicability to the material and conditions. A room-temperature density field alone does not establish the required melt-density value.

Retain the original MVR result alongside any calculated MFR, together with the density input and its source. Label the MFR as calculated. Otherwise a later reader may believe the laboratory directly measured a mass result that never appeared in the report.

The conversion says nothing by itself about strength, shrinkage, impact performance, color, regulatory suitability or behavior in a particular mold. Those remain separate questions in the material qualification.

A flow result has a limited job

ASTM's public D1238 page, displaying D1238-26 when reviewed, describes a quality-control use for thermoplastic flow measurements. Its significance-and-use discussion cautions against extending flow uniformity to other properties without a valid correlation supported by other tests.

This matters when a quotation describes two grades as interchangeable because their flow numbers match. A flow comparison can be one part of an assessment. It does not establish every property needed for the buyer's application.

Likewise, ISO's public abstract notes that these measurements use shear rates below those normally encountered in processing, so results may not always correlate with processing behavior. A flow result alone cannot promise that an alternative resin will run identically in an existing production setup.

Keep the purchasing decision explicit. Is the team checking that a document contains the requested flow specification, screening a candidate for trials, accepting a delivered lot under an agreed requirement, or approving a substitution? Each decision requires a different evidence package. Recording which decision is pending prevents “the numbers match” from becoming an unrestricted release instruction.

Ask what material and record the number represents

A supplier's product datasheet and a lot-specific report serve different purposes. A typical value may help identify a candidate grade. The buyer still needs to establish whether the offered delivery has the agreed evidence and whether the stated acceptance requirement applies to that delivery.

Ask the supplier to identify the producer, grade, relevant formulation or variant, and the document revision. Where a reported measurement concerns a particular sample or lot, keep that identifier linked to the result. Avoid quietly merging a producer's typical value with a distributor's lot number in one row.

For a proposed replacement, use the wider material-substitution review process. Flow comparability resolves one technical question within that process; it does not authorize the substitution.

Sample preparation and timing also deserve attention when reports disagree. Toyo Seiki discusses variation associated with filling, degassing and preheating. ISO's abstract identifies limits for materials whose behavior changes significantly during measurement. The laboratory should determine the applicable method and controls. An export salesperson should request those details rather than invent a drying temperature or preheating time for a marketing table.

Build a comparison record engineering can review

Use one row per supported result. If a report contains multiple conditions, preserve separate rows and their identifiers. Avoid picking the row that happens to resemble the buyer's target while omitting the condition that produced it.

This is an editorial comparison template, not a replacement laboratory report or a list of every requirement in a test standard. The technical reviewer should add fields required by the actual specification and method.

When a field is absent, write “not supplied.” That status gives the sales team a concrete follow-up task. An invented default makes the comparison look complete while hiding the very question the buyer needs answered.

Put the same conditions on the English page

A public page often shortens a detailed datasheet into a few product bullets. Preserve the measurement context during that edit. If the source supports it, a sentence can identify the reported quantity, unit, temperature, load and whether the number is typical. Do not replace them with an unqualified “excellent flow.”

Keep the source revision accessible and define how a buyer can request the appropriate delivery evidence. If there is no authorized value for public use, explain what the supplier will confirm during quotation. A blank product template should not pressure a writer into inventing a technical specification.

Xindar's manufacturing GEO service can organize this English explanation and the website inquiry path. The manufacturer and its authorized technical reviewers supply and approve the material facts. That division of responsibility should remain visible in the working brief.

For AI search, the useful unit of content is the complete claim. “MVR 10 cm³/10 min at the stated temperature and load” carries more meaning than a loose number under a distant heading. Clear wording gives readers and summarization systems a better source to inspect; it does not guarantee a citation, recommendation or correct interpretation.

Review the comparison before discussing price

Give the draft comparison to a colleague who did not prepare it. Ask them to identify the measured quantity, conditions, material, evidence type and unresolved approval from the record alone. Then ask them to reproduce any conversion from the stated input values.

In the fictional table, an acceptable review recognizes that A and B are not established as comparable; C converts to 7.5 g/10 min only under the stated fictional density assumption; and D lacks essential information. None of the four records establishes that a resin is approved for a finished part.

Keep that review with the quotation version. If the producer, grade, report or requirement changes, revisit the affected comparison rather than carrying forward an old “matched” label. The next commercial discussion can then focus on the remaining evidence and the actual offer.

Questions from purchasing and export teams

Can we compare two “MFI 10” entries directly?

First establish what each entry measures, its unit and its test conditions. The numeral alone cannot distinguish MFR from MVR or show whether temperature and load match.

Can we convert MVR using density from a general datasheet?

Check that the density represents the melt at the relevant test temperature and applies to the material being compared. Preserve the input source and label the converted result as calculated. A density value with an unspecified state is an unresolved input.

Does higher MFR mean a better resin?

“Better” depends on the application and its requirements. A larger mass-flow result under stated conditions does not rank every other material property or establish finished-part suitability.

What if the two reports use different standards?

Ask the technical reviewer or laboratory to evaluate the reported procedures and conditions against the agreed requirement. Listing ASTM D1238 and ISO 1133 together does not establish that two particular reports are interchangeable.

Must the full report be public for GEO?

Publish only material the business is permitted to disclose. A clear public specification, its scope and a usable evidence-request route can support buyer review while confidential reports remain in the authorized commercial process.

Sources and scope

Sources were reviewed on November 10, 2026. ISO's public abstract supports the specified-condition and method-scope discussion; ASTM's public page supports the quality-control interpretation and limits; Toyo Seiki explains the measured quantities, conversion and selected sources of variation. The complete paid standards were not reviewed. The quotation records, density values, comparison template and editorial acceptance exercise are original fictional examples, with no claim of laboratory validation, customer approval or measured GEO effect.