Oct 10, 2026Material Guides
Polycarbonate Grade Selection: MFR, Viscosity, Datasheet
How to read a PC datasheet: MFR and viscosity windows, the seven fields that matter, compliance documents and batch-to-batch drift.
Polycarbonate Grade Selection: How to Read a PC Datasheet
Two polycarbonate grades can carry the same headline MFR and still behave differently on your production line.
This guide is written for procurement teams sourcing virgin polycarbonate and process engineers who must approve a grade before it reaches the mold. It explains what MFR actually measures, how viscosity ranges relate to part geometry, which datasheet fields matter, what compliance documents buyers should request and why batch-to-batch differences may appear after a grade has been approved.
What MFR Actually Tells You About a Polycarbonate Grade
MFR vs. MVR: Which Number Is on Your Datasheet?
Melt flow rate, or MFR, reports the number of grams of polymer extruded through a standard die in ten minutes.
Melt volume rate, or MVR, reports the volume of polymer extruded in cubic centimeters.
The two measurements are related through melt density, but they are not interchangeable. A datasheet that lists only “melt index” without stating whether the value is MFR or MVR cannot be compared reliably.
The test temperature and load must also be shown.
Polycarbonate is commonly tested at 300°C with a 1.2 kg load under ISO 1133 or ASTM D1238. Always confirm that the testing condition is printed on the datasheet you are reviewing.
If a supplier reports an MFR or MVR value without the testing condition, request the complete test information before comparing the grade with another material.
Why Viscosity Does Not Equal MFR
MFR is a single-point measurement taken under one specified set of conditions. Actual flow behavior inside a mold also depends on the molecular weight distribution and the material’s response to shear.
Two grades with the same MFR can therefore fill the same mold differently. One grade may show greater shear thinning, while another may require a higher barrel temperature to achieve the same cavity pressure.
A comparison based only on MFR is a useful starting filter, but it is not proof that two grades are equivalent.
Three Properties You Should Always Compare With MFR
Never evaluate MFR by itself. Compare it with at least the following three properties:
- Density — ISO 1183 or ASTM D792: Confirms that you are comparing the same material family and using appropriate feeding and weight assumptions.
- Notched impact strength — ISO 179 Charpy or ISO 180 Izod: Shows whether the required toughness is maintained after changing grades. The test method and notch type must be stated.
- Heat deflection temperature — ISO 75 or ASTM D648: Indicates whether the molded component can retain its shape at the required service temperature. Results measured at 0.45 MPa and 1.82 MPa are different and must not be compared as if they were the same.
A grade that matches the original material on MFR but has significantly lower notched impact strength should not be treated as an equivalent grade.
Medium vs. Low Viscosity: Matching the Grade to the Part
Thin-Wall and Long-Flow Parts
Low-viscosity polycarbonate grades flow farther before the melt freezes.
They are often suitable for:
- Thin-wall components
- Long flow paths
- Complex molded geometry
- Multi-cavity tools
- Components that would otherwise require excessive injection pressure
- Parts that cannot tolerate an unnecessarily high melt temperature
Lower viscosity can improve filling performance, but flowability must still be evaluated together with impact strength, heat resistance and the requirements of the finished component.
Thick Sections and Optical Parts
Medium-viscosity grades generally fill more slowly and may pack more evenly.
They are often considered for:
- Thick molded sections
- Parts with varying wall thickness
- Structural components
- Transparent components
- Optical parts that require controlled internal stress
- Parts that are sensitive to excessive shear
For transparent and optical applications, the grade with the highest flow is not automatically the best choice. The mold design, gate location, required appearance and acceptable level of internal stress must all be considered.
Evaluating WY-111BR
If you are evaluating Lihuayi Weiyuan WY-111BR, request the current manufacturer TDS and a batch-specific COA before comparing it with another grade.
The viscosity classification, processing method, application range and individual property values should be taken from the current manufacturer documentation rather than a third-party product listing.
Lema Plastic can provide the available document package and help identify any missing information before qualification.
A Simple Part-to-Grade Mapping Table
Part Characteristics | Viscosity Range to Start With | What to Confirm on the Datasheet |
|---|---|---|
Thin walls, long flow paths or complex geometry | Low | MFR test condition and impact retention after changing grades |
Variable wall thickness or structural components | Medium | Notched impact strength and heat deflection temperature |
Transparent or optical components | Medium | Light transmittance, haze and yellow index |
Parts requiring coating, printing or other secondary operations | Medium | The grade’s stated compatibility with the required secondary process |
The viscosity range in this table is only a starting point. The mold design, processing equipment and final performance requirements determine whether a grade is suitable.
Seven Fields to Check on Every Polycarbonate Datasheet
Before approving a PC grade, confirm that the datasheet includes the following information:
- Full grade designation and manufacturerA trade name or abbreviated family name is not enough. Confirm the complete grade designation and the legal manufacturer.
- MFR or MVR with complete test conditionsThe datasheet should identify the test standard, temperature and applied load.
- Density with test methodDensity should be reported with an ISO or ASTM method.
- Notched impact strengthConfirm the test method, specimen type, notch type and test temperature.
- Heat deflection temperatureThe applied load must be stated. Values measured at 0.45 MPa and 1.82 MPa are not interchangeable.
- Optical propertiesFor transparent components, review total luminous transmittance and haze according to ASTM D1003 or the applicable ISO equivalent.
- Yellow indexYellow index helps indicate whether an optical or appearance-critical component may show color variation or change over time.
Why Test Methods Matter More Than Headline Values
A tensile-strength value of “62 MPa” has limited meaning until you know:
- Which test method was used
- What specimen geometry was tested
- What test speed was used
- What conditioning procedure was applied
- Whether the result is typical or guaranteed
When comparing two suppliers, compare the test methods before comparing the reported values.
If one datasheet uses ISO methods and another uses ASTM methods, the results may still help with initial screening, but the conditions must be stated clearly.
When the testing conditions are missing, the value cannot be verified and should not be used as the basis for a material qualification decision.
Where to Cross-Check an Unfamiliar Grade
Public material databases can help you search by grade designation and compare published properties.
Common starting points include:
- UL Prospector
- MatWeb
- UL Product iQ for applicable UL recognition information
These databases are useful reference tools, but they are not substitutes for the manufacturer’s current datasheet or the COA for the material being supplied.
Use public databases to shortlist candidates and identify values that appear unusual. Complete the final qualification using manufacturer documentation, batch documentation and production testing.
How to Read a Translated Chinese Supplier Datasheet
Translation errors are a common source of incorrect material comparisons.
Watch for the following issues:
- “Melt index” translated without the test temperature and load
- Mechanical properties converted between MPa, kg/cm² or psi without a stated test method
- “Heat resistance” reported as a single temperature without a load or testing standard
- Compliance claims reduced to a statement such as “meets FDA” without naming the applicable regulation
- Missing distinction between typical values and guaranteed specifications
- Different grade names appearing in the title, table or document footer
These issues are not automatically reasons to reject a supplier. They are reasons to request a corrected datasheet before approving the material.
Food-Contact and UL Compliance: What Buyers Should Request
Food-Contact Documentation
For polycarbonate intended for food-contact applications, the relevant United States reference is FDA 21 CFR 177.1580.
For the European Union, the applicable framework includes Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food.
“Food grade” is not a complete compliance document.
Ask the supplier for a compliance statement that identifies:
- The exact material grade
- The applicable regulation
- The intended conditions of use
- Any relevant limitations
- Supporting migration data when required
- The document date and revision
Do not assume that a compliance statement for one grade automatically applies to another grade from the same product family.
UL Yellow Card Coverage
A UL Yellow Card applies to specific conditions, which may include:
- Exact grade designation
- Color
- Minimum tested thickness
- Flame classification
- Electrical properties
- Manufacturer and production location
Changing the grade, color or thickness may mean the existing UL recognition no longer applies.
If a component requires UL recognition, confirm the exact grade and color in UL Product iQ or the relevant UL documentation before purchasing the material.
RoHS and REACH SVHC Statements
RoHS and REACH SVHC statements are routine document requests for engineering-resin shipments.
Ask for a current version associated with the material being supplied. Avoid relying on a document retained from an older shipment or previous year when a newer revision is available.
Batch-to-Batch Color and Clarity
Why Yellow Index Can Drift
Yellow index variation may come from either the resin or the molding process.
Possible resin-related causes include:
- Base-polymer variation
- Additive variation
- Color formulation differences
- Regrind content
- Lot-to-lot material variation
Possible process-related causes include:
- Excessive melt temperature
- Long residence time
- Insufficient drying
- Material remaining in the barrel during production stops
- Contamination from a previous material or color
- Different machine conditions
If yellow index changes on one machine but not on another machine using the same material lot, the molding process should be investigated before the resin is identified as the cause.
Drying Before Molding
Polycarbonate absorbs moisture. Moisture present during melting can cause:
- Silver streaks
- Haze
- Bubbles
- Surface defects
- Reduced impact strength
- Polymer degradation
Drying conditions vary by grade and equipment. Follow the drying instructions in the grade’s own processing guide and verify the material using an appropriate moisture measurement rather than relying only on drying time.
Incoming Inspection for Optical or Appearance-Critical Parts
For grades used in optical or appearance-critical applications, consider including the following checks in incoming inspection:
- Yellow index
- Haze
- Light transmittance
- Color difference
- Pellet appearance
- Batch number
- COA review
- Packaging condition
Use the same instrument and measurement conditions for every lot. Comparing different batches using one controlled method is generally more useful than comparing measurements generated by different instruments or laboratories.
Substitution Limits: When a Similar PC Grade Is Not Equivalent
Equivalent MFR, Different Molecular Weight Distribution
A common substitution failure occurs when a replacement grade matches the original material on MFR and passes a short molding trial but later fails in service.
Possible problems include:
- Reduced low-temperature impact strength
- Stress cracking
- Warpage
- Different packing behavior
- Increased internal stress
- Changes in surface appearance
- Unstable cycle time
The datasheet values may appear similar while the molecular weight distribution and real processing behavior remain different.
Optical Parts Are the Hardest to Substitute
Transparency, haze and yellow index can be difficult to stabilize after changing grades.
For an optical component, conduct appearance and performance trials using the actual production mold before committing to a large-volume order.
The evaluation should include the real wall thickness, gate design, surface finish, processing window and final lighting conditions.
Qualification Checklist Before Approving a Substitute
Checks That Can Be Completed on the Production Site
- Part weight
- Critical dimensions
- Appearance compared with the approved sample
- Cycle time
- Filling behavior
- Molding defects
- Color match under the standard light source
- Ejection and mold-release behavior
- Assembly performance
Checks That May Require Laboratory Testing
- Notched impact strength
- Heat deflection temperature
- Light transmittance
- Haze
- Yellow index
- Tensile properties
- Flexural properties
- Application-specific chemical resistance
- Food-contact migration
- Flame classification or other regulatory requirements
A successful short molding trial should not replace the required laboratory testing.
When We Would Advise Against Changing Grades
A substitution may not be worthwhile even when the headline datasheet values are similar.
We may advise against changing the grade when:
- An optical part is already covered by an approved customer specification
- The replacement is not covered by the required UL recognition
- A food-contact application lacks matching compliance documents
- The component performs a safety-critical function
- The existing approval process would cost more than the expected material saving
- The replacement cannot be tested using the actual production mold
- The supplier cannot provide complete and current documentation
In these situations, the cost and risk of requalification may be greater than the purchasing benefit.
Frequently Asked Questions
Can two polycarbonate grades with the same MFR be treated as equivalent?
No. Matching MFR values are only a starting point. Compare impact strength, heat resistance, density, optical properties, molecular weight distribution and application-specific requirements before approving a substitute.
Is MFR the same as viscosity?
Not exactly. MFR is a single-point flow measurement under specified test conditions. Actual viscosity and mold-filling behavior depend on temperature, shear rate and molecular weight distribution.
What information must accompany an MFR value?
The datasheet should state whether the value is MFR or MVR, the test standard, test temperature and applied load.
Which properties matter most for transparent polycarbonate parts?
Light transmittance, haze, yellow index, impact strength and internal stress are particularly important. Evaluate the material using the actual production mold whenever possible.
What food-contact documents should a buyer request?
Request a grade-specific compliance statement naming the applicable regulation and conditions of use. Supporting migration data should also be requested when required by the regulation or application.
Does a UL Yellow Card cover every color and thickness?
No. UL coverage may depend on the exact grade, color and tested thickness. Confirm the applicable listing before approving the material.
What documents should accompany each polycarbonate shipment?
Depending on the application, buyers may request the batch COA, current TDS, SDS, RoHS statement, REACH SVHC statement and any required food-contact or UL documentation.
When should a polycarbonate grade not be substituted?
Avoid substitution when required compliance coverage is missing, the application is safety-critical, the customer specification does not permit the change or the replacement cannot be tested properly.
Need Help Reviewing a Polycarbonate Datasheet?
If you have a polycarbonate grade and are not sure whether its datasheet contains enough information, send the document to Lema Plastic.
We can help you identify:
- Missing test conditions
- Properties that cannot be compared directly
- Required compliance documents
- Potential substitution risks
- Information that should be confirmed on the batch COA
For WY-111BR or another polycarbonate grade, contact us to request the current product documentation, availability and quotation.
Contact Lema Plastic to review your PC grade requirements.
