Choose a polycarbonate grade by matching the manufacturing process and the part’s service requirements, then checking the candidate grade’s documents and testing the finished part. “PC” identifies a polymer family; it does not establish that two grades are interchangeable. A transparent molded cover, a reinforced housing and an outdoor extruded sheet need different evidence.
This guide addresses the selection decision. For the material definition, classification and notch-sensitivity references, use the PC material page. The matrix below is a screening tool, not a commercial grade recommendation or an approval of a particular part.
Define the part before comparing grades
Write a short requirement sheet before asking for a grade. Include the manufacturing method, drawing revision, minimum and maximum wall thickness, required appearance, service temperature, mechanical loads, assembly method and expected contact with chemicals or cleaners. Specify which requirements are mandatory and which can be traded against cost or cycle time.
Use measurable acceptance criteria where your specification already defines them. For example, “transparent” is incomplete without the thickness and an optical acceptance method. “Impact resistant” needs the test method, specimen or part geometry and the temperature of the test. If the customer has not defined a pass criterion, agree it before the trial rather than selecting whichever material produces the most attractive datasheet.
Do not transfer a requirement from a different component merely because both use PC. A molded housing and a continuously extruded profile can have different processing and appearance constraints. Keep the decision connected to the actual part.
Use a process and performance matrix
Covestro’s published range distinguishes general-purpose, impact-modified, flame-retardant and reinforced PC families. It also identifies grades by processing method. These distinctions justify screening by application rather than choosing by a single “best PC” label. Check the current manufacturer’s documentation for any candidate; historical range guides are background references, not proof of present availability.
| Part requirement | Candidate direction | Decision evidence |
|---|---|---|
| Transparent injection-molded cover | PC intended for injection molding with the required optical characteristics | Optical test thickness, flow information, surface appearance and a molded-part trial |
| Outdoor extruded sheet | Extrusion grade with documented weathering or UV provisions | Extrusion suitability, color and optical retention under the intended exposure |
| Stiff, dimensionally controlled housing | Compare reinforced and unreinforced candidates | Stiffness, shrinkage, appearance and assembly checks on the actual geometry |
| Part with a fire classification requirement | Grade with an applicable documented classification | Exact grade, color, thickness and classification scope |
| Highly loaded or impact-critical part | Candidate supported by appropriate mechanical test data | Load case, temperature, notch geometry and part testing |
The “candidate direction” column starts an investigation; it does not select a resin automatically. If a grade meets the stiffness requirement but cannot deliver the required appearance, it fails the combined specification. Record that reason instead of hiding it behind a favorable average score.
Injection molding and extrusion are different decisions
A current Covestro ET3113 product reference identifies an extrusion PC with high viscosity and UV stabilization. The 2405 product reference separately provides optical measurements and processing guidance. These are examples of the information supplied for specific grades, not PLAXRAW stock listings.
For an injection-molded part, record the machine, tooling, fill length and wall section alongside the supplier’s processing instructions. For extrusion, record the intended sheet or profile, die and line conditions. Do not assume a grade proven on one process is qualified on the other.
Keep drying instructions associated with the exact candidate and dryer type. Use the supplier’s current guidance as the starting point; the guide does not prescribe one drying temperature or one melt temperature for every PC.
Compare datasheets on the same basis
Build a comparison sheet with one column per candidate and rows for the actual decision criteria. Each numeric entry should carry its unit, test standard, test temperature, specimen thickness and conditioning where relevant. Mark missing information as missing rather than substituting a value from another grade.
MFR and MVR are reported in different units. Record the temperature and load with each measurement and do not rank candidates using numbers taken under different conditions. For a deeper discussion of batch comparison, see melt-flow consistency.
Separate three kinds of evidence: a typical datasheet value, a supplier’s agreed specification, and a result from your part trial. They answer different questions. A typical value describes a published test; it does not certify every shipment or the geometry you plan to make.
Check the requirements that cannot be inferred from PC
For fire performance, request the relevant listing or report and confirm its scope against the part specification. A favorable rating at one thickness is not a substitute for evidence at another. For chemical exposure, ask for guidance appropriate to the grade and the intended substance, concentration, temperature and contact time.
For food-contact, medical or other regulated use, request application-specific documents for the destination market. Neither the family name nor an unrelated grade’s approval establishes compliance. If the document is absent, keep that candidate unqualified for that requirement.
The existing material reference discusses notch sensitivity. In this selection workflow, its practical use is to flag sharp features and assembly stresses for the part trial; do not carry a laboratory threshold over to every commercial grade.
Run a controlled trial and keep the decision record
Use the following sequence as a proposed engineering workflow, adapted to your product specification:
- Keep the established material as a control and identify the candidate by manufacturer, grade and lot.
- Record processing conditions, preparation, drying and additive or color packages.
- Produce parts using an agreed trial plan; document adjustments instead of changing several variables silently.
- Check dimensions, appearance and assembly, then the required mechanical, environmental and compliance tests.
- Record failures as well as successes, and agree what evidence is still missing.
- Approve the combined material/process specification only through your normal qualification procedure.
If dimensional behavior is the concern, consult warping and shrinkage in injection molding. If a different polymer family is being considered, use the ABS reference to structure a separate comparison; it is not an automatic substitute for PC.
Prepare a useful material enquiry
Include the part or application, process, drawing constraints, mandatory properties, current material if known, required documents and proposed trial quantity. State whether you need a transparent, colored, reinforced or fire-classified candidate. List unresolved requirements so the technical discussion can address them.
After defining the evidence needed, discuss material selection. This guide supplies a selection framework, not a claim that PLAXRAW holds a particular grade or can certify your finished part.
Technical references and authorship
Prepared as PLAXRAW reference guidance on 5 October 2026. The selection workflow is an editorial synthesis; it is not a report of a PLAXRAW production trial or a named engineer’s independent qualification.
- Covestro — Engineering Thermoplastics: Products and Grades: background on PC grade families and processes.
- Covestro — Makrolon 2405: example of optical and processing documentation for a specific grade.
- Covestro — Makrolon ET3113: example of an extrusion and UV-stabilized grade.
Use current candidate documents for the purchasing and qualification decision; manufacturer examples in these sources do not establish PLAXRAW supply availability.
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