What is Melt Volume Rate (MVR) and how does it differ from MFI?

Melt Volume Rate (MVR) is measured per ASTM D1238 Method B or ISO 1133 and expresses the volume of polymer that flows through the standard die in 10 minutes, in cubic centimetres per 10 minutes (cm³/10 min). Unlike MFI (which weighs the extrudate), MVR directly measures volume using a piston position encoder. MVR is more accurate for filled compounds (where density varies), for comparing polymers of very different densities, and when density data is needed for conversion. The two are related by: MFI = MVR × melt density.

What test conditions (temperature and load) are used for HDPE, PP and PVC?

Standard test conditions per ASTM D1238 / ISO 1133: HDPE — 190°C / 2.16 kg (general) or 190°C / 5 kg (pipe grade IS 4984); PP — 230°C / 2.16 kg; LDPE / LLDPE — 190°C / 2.16 kg; PVC — 180°C / 10 kg or 200°C / 5 kg; ABS — 220°C / 10 kg; Nylon (PA 6) — 235°C / 1 kg; PC (Polycarbonate) — 300°C / 1.2 kg. The temperature and load must always be reported alongside the MFI value as they completely define the test condition.

What is the die and piston specification for MFI testing?

The standardised die for ASTM D1238 / ISO 1133 MFI testing has: bore diameter 2.095 mm ± 0.005 mm, bore length 8.000 mm ± 0.025 mm, material — hardened steel. The piston has a diameter of 9.474 mm ± 0.007 mm, length 6.35 mm at the tip. The piston and die must be cleaned after every test using the cleaning rod to prevent polymer degradation buildup that would affect results. The die bore must be inspected and replaced when wear causes the bore to exceed 2.105 mm diameter.

MFI vs MVR: What's the Difference and When to Use Each

Q: What is Melt Flow Index (MFI) and how is it measured?

Melt Flow Index (MFI), also called Melt Flow Rate (MFR), is a measure of the ease of flow of a molten polymer through a standardised die. It is measured per ASTM D1238 Method A or ISO 1133 by extruding molten polymer through a standard die (2.095 mm diameter, 8.000 mm long) under a defined load at a defined temperature for 10 minutes, then cutting and weighing the extrudate. MFI is expressed in grams per 10 minutes (g/10 min). Higher MFI means the polymer flows more easily — indicating lower molecular weight or lower viscosity.

Q: What is the standard test method for MFI and MVR?

The internationally recognised standards are ASTM D1238 (Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer) and ISO 1133 (Plastics — Determination of the Melt Mass-Flow Rate and Melt Volume-Flow Rate of Thermoplastics). Both define Method A (mass-based MFI) and Method B (volume-based MVR), standardised die dimensions (2.095 mm diameter × 8.000 mm long), piston and load specifications, test temperatures and loads for different polymers, and the calculation procedures.

Q: When should I use Method A (MFI) vs Method B (MVR)?

Use Method A (MFI, mass-based) for: unfilled or lightly filled polymers, routine production quality control, materials with consistent density, IS 4984 HDPE pipe grade testing. Use Method B (MVR, volume-based) for: highly filled or reinforced compounds (glass-filled, carbon-filled) where density varies; comparing polymers of very different densities (e.g., HDPE vs PA 6); when melt density data is needed; when calculating MFI from MVR is required; when the computerised MFI tester output includes both values simultaneously.

Q: What does a high MFI value mean for polymer quality?

Higher MFI (more flow) indicates: lower molecular weight polymer, more chain scission degradation, or higher proportion of processing aids / lubricants. For pipe grade HDPE, IS 4984 specifies a maximum MFI — a higher-than-specified MFI indicates thermal degradation during extrusion that reduces pressure resistance and ESCR. For film grade LDPE, lower MFI (higher molecular weight) gives better mechanical properties but requires higher extrusion temperatures. MFI must always be interpreted in context of the specific polymer and application.

Q: How do you convert between MFI and MVR?

The conversion formula is: MFI (g/10 min) = MVR (cm³/10 min) × melt density (g/cm³). Melt density is the density of the polymer in the molten state at the test temperature — typically 0.74–0.78 g/cm³ for PE at 190°C, 0.73 g/cm³ for PP at 230°C. The computerised Method A&B MFI tester from International Equipments calculates both MFI and MVR simultaneously and outputs the conversion automatically, eliminating manual calculation errors.

📋 Table of Contents

What is MFI (Melt Flow Index)?
What is MVR (Melt Volume Rate)?
MFI vs MVR: Key Differences Side by Side
Test Principle: What the MFI Apparatus Actually Measures
ASTM D1238 and ISO 1133 — The Governing Standards
Test Conditions: Temperature and Load for Every Major Polymer
Method A vs Method B — When to Use Each
Converting Between MFI and MVR
How to Interpret MFI Values
MFI as a Quality Control Tool
The Four MFI Tester Models from International Equipments
Tips for Accurate and Reproducible MFI Results
Frequently Asked Questions

MFI and MVR are both outputs of the same instrument — the Melt Flow Index Tester — but they measure different things, use different calculations, and are suited to different materials and applications. Understanding the difference is essential for choosing the right test condition, the right tester model, and interpreting your results correctly.

The Melt Flow Index test is arguably the single most widely performed quality control test in the plastics industry. It is run on virtually every polymer — HDPE, PP, LDPE, LLDPE, PVC, ABS, Nylon, PC — at every stage of the supply chain: raw material acceptance, compounding quality control, production monitoring, and incoming inspection of finished products. Yet despite its ubiquity, confusion about MFI vs MVR, Method A vs Method B, and test condition selection is extremely common.

What is Melt Flow Index (MFI)?

Melt Flow Index (MFI) — also officially called Melt Flow Rate (MFR) or Melt Mass-Flow Rate (MFR) in ISO 1133 — is a measure of the ease of flow of a molten polymer through a standardised capillary die under a defined load and temperature.

MFI is expressed in grams per 10 minutes (g/10 min). It is measured by Method A — the mass method — in which extrudate cut-offs are weighed to calculate the mass of polymer that flows through the die in 10 minutes.

MFI (g/10 min) = mass of extrudate (g) × [600 / cut time (s)]

Where cut time = interval between cuts (typically 5–30 seconds depending on MFI range)

What MFI tells you: A higher MFI indicates a lower-viscosity melt — which generally means lower molecular weight, more chain scission from thermal degradation, or higher levels of lubricants/processing aids. A lower MFI indicates higher viscosity — higher molecular weight polymer with better long-term mechanical properties.

💡 Terminology note: MFI (Melt Flow Index) and MFR (Melt Flow Rate / Melt Mass-Flow Rate) refer to the same measurement. ISO 1133 uses MFR officially; ASTM D1238 uses MFR or MFI. In India and commercial practice, MFI is the most commonly used term. This blog uses MFI throughout.

What is Melt Volume Rate (MVR)?

Melt Volume Rate (MVR) — also called Melt Volume-Flow Rate — is also defined in ASTM D1238 and ISO 1133, but measures the volume of polymer extruded rather than the mass. It is expressed in cubic centimetres per 10 minutes (cm³/10 min) and measured by Method B — the volume method.

In Method B (MVR), the apparatus measures the displacement of the piston using a position encoder rather than weighing cut-off samples. As the piston descends under the test load, the encoder records the distance travelled in a defined time, from which the extruded volume is calculated.

MVR (cm³/10 min) = A × L × [600 / t]

Piston cross-section area (cm²)

Piston travel distance (cm)

Travel time (seconds)

💡 MVR advantage for filled compounds: When a polymer compound contains fillers (glass fibre, carbon black, mineral fillers), the density varies significantly. MVR gives a more accurate and reproducible result for such materials because it is independent of density variation — it measures volume directly, not mass.

MFI vs MVR: Key Differences Side by Side

Parameter	MFI (Method A)	MVR (Method B)
Full name	Melt Flow Index / Melt Flow Rate (MFR)	Melt Volume Rate (MVR)
ISO 1133 term	Melt Mass-Flow Rate (MFR)	Melt Volume-Flow Rate (MVR)
ASTM D1238 method	Method A	Method B
Unit	g/10 min	cm³/10 min
Measurement principle	Cut & weigh extrudate samples	Piston position encoder — measures volume directly
Density dependence	Yes — result influenced by melt density	No — independent of melt density
Best for	Unfilled polymers, routine QC, IS 4984 HDPE pipe testing	Filled/reinforced compounds, density comparison, R&D
Accuracy for filled compounds	Lower — density variation affects result	Higher — volume is independent of filler density
Can calculate MVR from MFI?	Only if melt density is known: MVR = MFI / melt density	Directly measured
Instrument required	Any MFI tester (Method A or A&B models)	MFI tester with piston position encoder (Method A&B model)

Test Principle: What the MFI Apparatus Actually Measures

Despite its simplicity, the MFI test is a capillary rheometer operating at a single shear rate — a fundamental measurement of polymer viscosity under processing-like conditions. Here is what happens inside the apparatus:

🔥Barrel heating

The steel barrel is heated to the test temperature (e.g. 190°C for PE) and held stable within ±0.5°C. The polymer sample (3–5 g) is loaded and allowed to preheat for exactly 5–6 minutes to achieve temperature equilibrium.

⚖️Load application

A standardised dead-weight load (e.g. 2.16 kg, 5 kg, or 10 kg) is applied via a piston on top of the molten polymer, creating a defined pressure difference across the die.

🕳️Extrusion through die

Molten polymer is extruded through the hardened steel die (bore 2.095 mm dia × 8.000 mm long) under the applied pressure. The flow rate is determined by the polymer viscosity.

📏Measurement

Method A: Extrudate cut at defined intervals, each cut-off weighed on an analytical balance. Method B: Piston displacement measured by encoder — no cutting needed.

⚠️ Single shear rate limitation: MFI is a single-point viscosity measurement at one shear rate. Real processing involves a range of shear rates. Two polymers with the same MFI can behave very differently in a high-speed extruder. For full rheological characterisation (viscosity vs shear rate), a capillary rheometer is needed. MFI is a quality control tool — not a complete rheological characterisation.

ASTM D1238 and ISO 1133 — The Governing Standards

Two standards govern MFI and MVR testing worldwide:

📋 ASTM D1238

Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer

▸ Used widely in USA, India (IS references ASTM)

▸ Defines Method A (mass) and Method B (volume)

▸ Specifies test conditions for all major polymers

▸ Die bore: 2.095 mm × 8.000 mm

▸ Referenced by IS 4984, IS 4985, IS 14885

📋 ISO 1133

Plastics — Determination of the Melt Mass-Flow Rate (MFR) and Melt Volume-Flow Rate (MVR)

▸ International standard — used in Europe, globally

▸ Defines MFR (=MFI) and MVR

▸ Consistent die dimensions with ASTM

▸ Referenced by EN 12201, EN ISO 1133

▸ Part 1: Standard conditions; Part 2: Temperature-sensitive polymers

📋 Key difference: ASTM D1238 and ISO 1133 are essentially harmonised for standard polymers — the same die dimensions, same test conditions, same calculation. Results from ASTM D1238 and ISO 1133 are directly comparable for unfilled polymers. Minor differences exist for specific polymers like PVC and for stability test conditions (ISO 1133 Part 2).

Test Conditions: Temperature and Load for Every Major Polymer

MFI results are only meaningful when the test conditions are specified. The same polymer can give dramatically different MFI values at different temperatures and loads. Always report MFI with the full condition, e.g. MFI (190/5) = 0.8 g/10 min meaning 190°C temperature, 5 kg load.

Polymer	Standard	Temperature	Load	Typical MFI Range	Common Applications
HDPE — pipe grade	IS 4984 / ASTM D1238	190°C	5.0 kg	0.2 – 1.5 g/10 min	Pipe extrusion quality control
HDPE — general / film	ASTM D1238	190°C	2.16 kg	0.1 – 5.0 g/10 min	Blown film, injection moulding
LDPE / LLDPE	ASTM D1238 / ISO 1133	190°C	2.16 kg	0.3 – 30 g/10 min	Packaging film, coating
Polypropylene (PP)	ASTM D1238 / ISO 1133	230°C	2.16 kg	0.5 – 50 g/10 min	Fibres, injection, pipe
PVC (rigid)	ISO 1133	180°C	10 kg	Typically < 5 g/10 min	Pipe, profiles
ABS	ASTM D1238	220°C	10 kg	1 – 20 g/10 min	Injection moulding
Polycarbonate (PC)	ASTM D1238	300°C	1.2 kg	5 – 40 g/10 min	Optical, engineering
Nylon 6 (PA 6)	ISO 1133	235°C	1.0 kg	2 – 50 g/10 min	Fibres, engineering plastics
Nylon 66 (PA 66)	ISO 1133	275°C	1.0 kg	1 – 30 g/10 min	Engineering applications
POM (Acetal)	ASTM D1238	190°C	2.16 kg	1 – 30 g/10 min	Precision parts
EVA	ASTM D1238	190°C	2.16 kg	0.3 – 150 g/10 min	Adhesives, film
TPE / Elastomer	ASTM D1238	190°C	5.0 kg	Varies widely	Seals, hoses, overmoulding

⚠️ Always report conditions with results. An MFI value without temperature and load is meaningless. 'MFI = 0.8' tells you nothing. 'MFI (190°C / 5 kg) = 0.8 g/10 min per ASTM D1238' is a complete, auditable quality record.

Method A vs Method B — When to Use Each

⚖️ Method A — Use When:

✓Testing unfilled or lightly filled polymers (HDPE, PP, LDPE, PVC)
✓Routine production QC — fast, simple, no encoder needed
✓IS 4984 HDPE pipe raw material and finished pipe testing
✓Comparing batches of the same polymer type and grade
✓Laboratory has basic analytical balance available
✓Budget-conscious operations needing reliable pass/fail results

📐 Method B — Use When:

✓Testing highly filled or reinforced compounds (glass-filled, mineral-filled)
✓Comparing polymers with very different densities (PE vs PA 6 vs PC)
✓Density data is needed for processing calculations
✓R&D and compound development requiring both MFI and MVR
✓Converting between MFI and MVR (melt density calculation)
✓Specification requires MVR in cm³/10 min (European polymer specs)

💡 Practical guidance for HDPE pipe manufacturers: For IS 4984 compliance testing of HDPE pipe-grade compound and finished pipe, Method A (MFI, g/10 min) at 190°C / 5 kg is the required method. Method B (MVR) is optional and provides additional information for compound development but is not specified in IS 4984.

Converting Between MFI and MVR

MFI and MVR are related through the melt density of the polymer at the test temperature. If you have one value, you can calculate the other — provided you know the melt density:

MFI = MVR × ρ_melt

g/10 min = cm³/10 min × g/cm³

MVR = MFI / ρ_melt

cm³/10 min = g/10 min ÷ g/cm³

Melt density reference values

Polymer	Test Temp.	Typical Melt Density	Notes
HDPE	190°C	0.74 – 0.76 g/cm³	Standard pipe/film grade
LDPE / LLDPE	190°C	0.74 – 0.76 g/cm³	Similar to HDPE
PP	230°C	0.73 g/cm³	Homopolymer and copolymer
ABS	220°C	0.98 – 1.02 g/cm³	Acrylonitrile-butadiene-styrene
PC	300°C	1.14 – 1.18 g/cm³	Polycarbonate

Worked example

Example: HDPE compound tested at 190°C / 5 kg. Melt density = 0.75 g/cm³.
Method A result: MFI = 0.90 g/10 min
Method B result: MVR = MFI / ρmelt = 0.90 / 0.75 = 1.20 cm³/10 min

Or conversely, if MVR = 1.20 cm³/10 min:
MFI = MVR × ρmelt = 1.20 × 0.75 = 0.90 g/10 min

💡 The Computerised Method A&B MFI Tester from International Equipments calculates and outputs both MFI (g/10 min) and MVR (cm³/10 min) simultaneously from a single test run — no manual conversion needed. Melt density is entered as a parameter and the instrument computes both values automatically.

How to Interpret MFI Values

What does MFI actually tell you about the polymer?

MFI Direction	Molecular Weight	Viscosity	Processing	Properties	Quality signal
Higher MFI →	Lower molecular weight	Lower melt viscosity	Easier to process	Weaker mechanical properties (generally)	May indicate thermal degradation
Lower MFI →	Higher molecular weight	Higher melt viscosity	Harder to process (higher pressures)	Better mechanical / ESCR properties	Preferred for pipe grade, load-bearing applications

MFI ratio — compound vs finished product

One of the most powerful uses of MFI testing in production is to compare the MFI of the raw compound (as received) against the MFI of the finished extruded pipe or moulded part. Any significant increase in MFI of the finished product indicates thermal degradation during processing — molecular weight has been reduced by chain scission at excessive barrel temperatures.

MFI ratio (pipe/compound)

< 1.20

✓ Acceptable — normal processing degradation

MFI ratio

1.20 – 1.40

⚠ Warning — check barrel temperatures

MFI ratio

> 1.40

✗ Reject — excessive thermal degradation

📋 IS 4984 requirement: The MFI of the finished HDPE pipe shall not exceed the MFI of the base compound by more than 20% (ratio > 1.20). This protects against processors using excessive temperatures that destroy molecular weight and reduce pressure resistance and ESCR.

MFI as a Quality Control Tool

In a well-run plastic products manufacturing operation, MFI testing is performed at multiple control points:

Stage 1

Incoming raw material

Test every lot of polymer compound from the supplier. Verify MFI matches specification. Reject lots outside tolerance before they enter production.

Stage 2

After compounding / masterbatch

Verify the compound MFI after adding additives, fillers or masterbatch. Ensure blending has not shifted MFI outside the processing window.

Stage 3

Start-up sample (first extrusion)

Test the first pipe / film / moulded part of each production run. Confirm process is running at the correct temperature profile before committing to full production.

Stage 4

In-process monitoring

Test samples every 2–4 hours during continuous production. Detect drift from barrel temperature fluctuations, screw wear, or raw material variation.

Stage 5

Finished product

Test representative finished samples before dispatch. Compare MFI ratio (finished / compound) to detect processing degradation per IS 4984.

Stage 6

Customer / third-party verification

Incoming inspection by pipe buyers, BIS auditors, or export certification bodies. MFI is always one of the first tests run.

The Four MFI Tester Models from International Equipments

International Equipments manufactures four MFI tester models, covering the full range from basic production QC to computerised R&D laboratories:

KAYJAY/2005/CE Manual Method A — CE Certified ASTM D1238 Method A · ISO 1133

The original and most widely used model. Operator manually cuts extrudate at defined time intervals using a blade, then weighs each cut-off on an analytical balance. Ideal for laboratories with occasional MFI testing needs.

• Manual cut — operator cuts extrudate samples at timed intervals
• Digital temperature controller with ±0.5°C accuracy
• Load range: 1.2 kg to 21.6 kg (multiple standard loads available)
• CE certified — accepted for EU imports
• Supplied with: cutting blade, cleaning rods, die set, piston
• Standard for general purpose polymer QC

KAYJAY/2006/AC Manual Method A — Auto-Cut ASTM D1238 Method A

The most popular model for HDPE pipe manufacturers. The automatic cutter eliminates operator variability in cut timing — a major source of error in manual testing. A timer triggers the motorised cutter at the preset interval.

• Automatic motorised cutter — cuts at set time intervals automatically
• Eliminates operator timing error — more reproducible results
• Timer triggers cut every 5, 10, 15, 20 or 30 seconds (selectable)
• Digital temperature controller with ±0.5°C accuracy
• CE + ISO certified
• Recommended model for high-throughput production QC labs

Computerised Method A Computerised Method A — PC Output ASTM D1238 Method A · RS 232

For laboratories that need printed test certificates with full data — batch number, operator, date, test conditions, MFI result, and statistical summary. Required for BIS-accredited labs and export quality documentation.

• Microcontroller-based with RS 232 PC interface
• Interface software installs on user PC
• PC output: MFI value, temperature log, load, test date, operator name
• 10 specimens merged — mean and standard deviation calculated
• Printable test certificate with all test parameters
• Ideal for accredited testing laboratories with audit requirements

Computerised Method A&B Computerised Method A&B — MFI + MVR ASTM D1238 Method A & B · ISO 1133

The most advanced model in the range. The piston position encoder simultaneously outputs MFI and MVR from a single test — no manual conversion needed. Essential for compound development labs, filled polymer testing, and organisations supplying to European customers who require MVR data.

• Piston position encoder — measures both MFI (g/10 min) AND MVR (cm³/10 min) simultaneously
• Melt density entered as parameter — automatic MFI↔MVR conversion
• Full PC output with both values, graphs, and statistics
• 10 specimen statistical analysis with mean, std dev, min, max
• Ideal for filled compound testing, compound development, R&D
• Most advanced model — covers all ASTM D1238 and ISO 1133 requirements

🔗 Related Products:

→ Melt Flow Index Tester — all 4 models — KAYJAY/2005/CE · KAYJAY/2006/AC · Computerised Method A · Computerised Method A&B

Tips for Accurate and Reproducible MFI Results

1Dry hygroscopic polymers before testing. Nylon (PA), PET, PC and POM absorb moisture from the air. Undried samples give high MFI values due to hydrolytic chain scission at test temperature. Dry at the manufacturer's recommended temperature (e.g. PA 6: 80°C for 4h) before MFI testing.
2Use the correct preheat time — exactly 5–6 minutes. Too short = barrel not at equilibrium, extrudate is at wrong temperature. Too long = thermal degradation of the sample in the barrel, falsely high MFI. Set a timer; don't estimate.
3Clean the die and barrel after every test. Residual degraded polymer from the previous test contaminates the next, particularly if different polymers are tested in sequence. Use the cleaning rod and fresh cotton swabs. Never use a metal tool inside the die bore — it will scratch and widen the bore.
4Use the right sample mass (3–5 g, typically). Too little sample means the barrel empties before sufficient cuts are made. Too much creates excessive back-pressure. Load approximately 3–5 g for most polymers — the barrel should not be completely emptied in less than 10 cut intervals.
5Check barrel and die temperature calibration regularly. Temperature drift of even ±2°C can shift MFI results significantly, particularly for polymers like PP where viscosity is highly temperature-sensitive. Calibrate with a NIST-traceable thermometer at least monthly.
6Discard the first cut for high-MFI materials. For polymers with MFI > 20 g/10 min, the initial extrudate contains pre-heated polymer from the preheat period. Discard the first cut and collect only subsequent cuts for weighing.
7Always run at least 3 cut-offs per specimen and average. Single cut-off results have high uncertainty. Three or more cuts from the same specimen, averaged, give the MFI for that specimen. For statistical reporting, test 5–10 specimens and report mean ± standard deviation.
8Compare MFI (compound) vs MFI (finished pipe) — it is a mandatory check. This ratio is the best single indicator of processing quality. A ratio > 1.20 triggers investigation; > 1.40 triggers batch rejection under IS 4984.

Key Takeaways

✓MFI (Melt Flow Index, g/10 min) and MVR (Melt Volume Rate, cm³/10 min) are both measured by the MFI tester — MFI by Method A (mass, cut & weigh), MVR by Method B (volume, piston encoder).
✓MFI is the standard for routine production QC and IS 4984 HDPE pipe testing. MVR is better for filled/reinforced compounds and European polymer specifications.
✓The two are related by melt density: MFI = MVR × ρmelt. The Computerised Method A&B tester calculates both simultaneously.
✓Always specify test conditions with results: temperature, load, and standard (e.g. 'MFI (190°C / 5 kg) = 0.8 g/10 min per ASTM D1238').
✓Higher MFI = lower molecular weight = lower viscosity = generally weaker mechanical properties. For HDPE pipes, lower MFI = better pressure resistance and ESCR.
✓The MFI ratio (finished pipe / raw compound) must not exceed 1.20 per IS 4984. A higher ratio indicates thermal degradation during extrusion.
✓International Equipments manufactures four MFI tester models from basic manual (KAYJAY/2005/CE) to computerised Method A&B — all CE and ISO certified.

✉ Choose the right MFI tester for your lab. Contact International Equipments to discuss your application, polymer types, and throughput requirements — our engineers will recommend the most appropriate model from the four available. Request a free quote →

Frequently Asked Questions

Common questions about MFI, MVR, ASTM D1238, test conditions, and MFI tester selection.

What is Melt Flow Index (MFI) and how is it measured?+

MFI (Melt Flow Index), also called MFR (Melt Flow Rate), measures the ease of flow of molten polymer through a standard die under a defined load and temperature. It is measured per ASTM D1238 Method A or ISO 1133 by extruding polymer through a 2.095 mm die at a set temperature and load, then cutting and weighing the extrudate at timed intervals. Result is in grams per 10 minutes (g/10 min). Higher MFI = lower molecular weight = more flow.

What is MVR and how does it differ from MFI?+

MVR (Melt Volume Rate) measures the volume of polymer extruded in 10 minutes, in cm³/10 min, using Method B. Unlike MFI (which weighs cut-off samples), MVR directly measures piston displacement using a position encoder. MVR is more accurate for filled/reinforced compounds where density varies, and for comparing polymers of very different densities. The two are related by: MFI = MVR × melt density (g/cm³).

What are the standard test methods for MFI and MVR?+

ASTM D1238 (Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer) and ISO 1133 (Plastics — Determination of the Melt Mass-Flow Rate and Melt Volume-Flow Rate of Thermoplastics). Both define Method A (mass-based MFI) and Method B (volume-based MVR) with standardised die dimensions (2.095 mm dia × 8.000 mm long) and test conditions for all major polymers.

What test conditions are used for HDPE, PP, and PVC MFI testing?+

Standard conditions per ASTM D1238 / ISO 1133: HDPE pipe grade (IS 4984) — 190°C / 5.0 kg; HDPE general — 190°C / 2.16 kg; PP — 230°C / 2.16 kg; LDPE / LLDPE — 190°C / 2.16 kg; PVC (rigid) — 180°C / 10 kg; ABS — 220°C / 10 kg; PC — 300°C / 1.2 kg; Nylon 6 — 235°C / 1.0 kg. Always report conditions with results.

When should I use Method A (MFI) vs Method B (MVR)?+

Method A (MFI): use for unfilled polymers, routine production QC, IS 4984 HDPE pipe testing, basic batch-to-batch comparison. Method B (MVR): use for highly filled or reinforced compounds (glass-filled, mineral-filled), comparing polymers of very different densities, European specifications requiring MVR in cm³/10 min, and R&D compound development requiring both values simultaneously.

What does a high MFI value mean for polymer quality?+

Higher MFI = lower molecular weight = lower melt viscosity. For HDPE pipe grade material, a higher-than-specified MFI indicates thermal degradation during extrusion — molecular weight has been reduced by chain scission, reducing pressure resistance and ESCR. The IS 4984 MFI ratio check (finished pipe / raw compound < 1.20) detects this. For packaging films, MFI indicates processability vs mechanical property trade-offs.

How do you convert between MFI and MVR?+

MFI (g/10 min) = MVR (cm³/10 min) × melt density (g/cm³). Typical melt densities: HDPE at 190°C ≈ 0.75 g/cm³; PP at 230°C ≈ 0.73 g/cm³. Example: MVR = 1.20 cm³/10 min × 0.75 = MFI 0.90 g/10 min. The Computerised Method A&B MFI Tester from International Equipments calculates both values automatically — no manual conversion needed.

What are the four MFI tester models from International Equipments?+

1. KAYJAY/2005/CE — Manual Method A with manual cut, CE certified, basic model. 2. KAYJAY/2006/AC — Manual Method A with motorised auto-cut at set intervals, eliminates operator timing error, most popular for pipe QC. 3. Computerised Method A — PC output of all test parameters via RS 232, printable certificate, 10-specimen statistics. 4. Computerised Method A&B — piston encoder measures both MFI and MVR simultaneously, auto-converts, most advanced for filled compounds and R&D. All are CE and ISO certified.

What is the die specification for ASTM D1238 MFI testing?+

The standard die bore is 2.095 mm ± 0.005 mm diameter and 8.000 mm ± 0.025 mm long, machined from hardened steel. The piston diameter is 9.474 mm ± 0.007 mm. The die bore must be cleaned after every test with the cleaning rod. The bore must be inspected and replaced when wear causes it to exceed 2.105 mm — a worn bore gives falsely high MFI results. Never use metal tools inside the die bore.

Melt Flow Index (MFI) vs Melt Volume Rate (MVR):What's the Difference and When to Use Each