Technical datasheet
- Typical values for comparing and selecting grades
- Published by the resin supplier and updated at their discretion
- Not a commitment that every lot meets each value
Engineering
How to Read a Plastic Material Datasheet
A datasheet is a set of test results under controlled conditions. It is the best starting point for choosing a resin, and a poor predictor of your part unless you know what each number was measured on.
What a datasheet is
Test bar results, not part performance
Every value comes from a standard specimen, molded and tested a standard way.
A resin datasheet lists properties measured on standardized test specimens: bars, plaques, and discs molded under controlled conditions and tested by published methods from bodies such as ISO and ASTM. That standardization is what makes grades comparable. It is also why a datasheet cannot tell you directly how your part will behave.
Your part has different wall sections, weld lines where flows meet, gates that orient the molecules or fibers, corners that concentrate stress, and a service life with heat, chemicals, and sustained loads. None of that is in a test bar. The datasheet tells you what the material can do under ideal and repeatable conditions. Design and molding decide how much of that reaches the part.
Read it as a screening tool. It is excellent for ruling grades out and building a shortlist, and it should be followed by part level testing for anything that matters.
The properties
What the common values mean, and what to watch
Grouped the way most datasheets present them.
| Property | What it measures | Watch out for |
|---|---|---|
| Melt flow rate or index | How easily the melt flows under a set load and temperature | Higher flow fills thin walls more easily but often comes with lower toughness within a family |
| Tensile strength | Stress at yield or at break when a bar is pulled | Check whether the value is at yield or at break. They are not the same design limit |
| Tensile or flexural modulus | Stiffness under a small load | Stiffness falls as temperature rises. A room temperature value can flatter a hot application |
| Elongation at break | How far the bar stretches before it breaks | A guide to ductility. Snap fits and living hinges depend on it |
| Notched impact strength | Energy to break a notched bar in one blow | Sensitive to temperature and notch shape. Sharp corners in your part act like the notch |
| Heat deflection temperature | Temperature at which a loaded bar bends a set amount | A short term comparison point, not a safe continuous use temperature |
| Relative thermal index | Long term temperature limit for retaining properties, where listed | Tied to a specific thickness and color. Check the listing, not only the datasheet |
| Flammability rating | How a specimen burns and self extinguishes in a standard test | Valid only at the listed thickness and for the listed grade and color |
| Mold shrinkage | How much a test plaque shrinks after molding, along and across the flow | Your part shrinks differently. Filled grades shrink less along the flow than across it |
| Processing guidance | Drying, melt temperature, and mold temperature recommendations | Useful for the molder. Drying guidance matters most for moisture sensitive resins |
The traps
Mistakes that come from reading a datasheet literally
Most material surprises trace back to one of these.
Treating typical values as guaranteed minimums. Datasheet values are usually averages, not specification limits
Comparing a value tested by an ISO method with one tested by an ASTM method. Specimens and conditions differ, so the numbers are not directly comparable
Reading dry values for a moisture sensitive resin. Nylons are often listed dry as molded and conditioned, and they behave differently
Using a single room temperature value for a part that runs hot or cold
Ignoring time. Sustained loads cause creep, and repeated loads cause fatigue, neither of which a short test shows
Assuming weld lines are as strong as the bar. They are often weaker, especially in filled grades
Assuming a color or additive change leaves properties untouched. Pigments and flame retardants can shift them
Forgetting chemical exposure. Cleaners, oils, and fuels can crack a part under stress that the datasheet never tested
A working method
From requirements to a tested grade
Use the datasheet where it is strong, and test where it is not.
- 1
Write the requirements first
Loads, temperatures, chemicals, appearance, flammability, and regulatory needs, before opening any datasheet.
- 2
Screen by family
Rule out resin families that cannot meet the temperature, chemical, or stiffness needs.
- 3
Compare like with like
Compare grades on the same test method, units, and conditioning state.
- 4
Ask for more data
Request curves over temperature, creep data, and chemical resistance from the resin supplier.
- 5
Check processability
Ask your molder whether the flow, drying, and shrink behavior suit your geometry.
- 6
Test real parts
Mold samples and test them in the conditions the product will actually face.
Two kinds of document
Datasheet versus specification
They look similar and are used very differently.
Material specification
- Agreed limits that each lot must meet
- Often backed by a certificate of analysis per lot
- What your drawing should reference for critical parts
FAQ
Questions about material datasheets
Why do two datasheets for similar grades show different values?
The grades may genuinely differ, or the values may come from different test methods, specimen sizes, or conditioning. Check the method and conditions beside each value before concluding one grade is better.
Can I use the datasheet shrinkage to size my tool?
It is a starting point. Real shrinkage depends on wall thickness, flow direction, gate location, and process settings. Toolmakers combine the datasheet value with their experience and often leave critical features steel safe.
Is a generic datasheet for a resin family good enough?
For early screening, yes. For final selection, use the datasheet for the exact grade, because grades within one family can differ widely in flow, toughness, and heat resistance.
What should I ask the resin supplier beyond the datasheet?
Property curves over temperature, creep and fatigue data, chemical resistance for your specific fluids, regulatory statements, and whether the grade is expected to remain available.
Keep reading
Related guides
Materials and the properties behind them.
Injection molding materials
Common resins and where each fits.
MaterialsMelt flow index
What the flow value means for filling your part.
Melt flow indexHygroscopic resins
Why some resins must be dried before molding.
Hygroscopic resinGlass filled vs unfilled
How fibers change stiffness, shrink, and warp.
Glass filled vs unfilledNylon 6 vs nylon 66
Two close grades and how moisture affects both.
Nylon 6 vs nylon 66Is mold flow analysis worth it?
Where good material data matters most.
Mold flow analysisNext step
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