Electrical insulating plastics should be selected against the electrical failure the part must prevent. A connector housing, terminal spacer and protective enclosure may all use an engineering polymer, but they do not have the same requirements. Start with the exact grade, operating environment and finished-part criteria. A high dielectric-strength value, a flame classification or the word “nylon” cannot answer all three.
Which electrical property does your part need?
Keep the test names separate when comparing quotations. UL Solutions describes distinct tests for volume resistance, surface resistance, dielectric breakdown and tracking. Ask for the method and specimen conditions beside the result, rather than accepting a column headed simply “insulation.”
| Propiedad | Question it helps answer | What to request |
|---|---|---|
| Volume resistivity | How strongly does the specimen resist current through its bulk? | Method, units, conditioning, temperature and electrode arrangement. |
| Surface resistivity | How does the specimen surface resist current? | Surface condition, humidity, method and measurement conditions. |
| Dielectric strength | Under the stated test conditions, when does breakdown occur through the specimen? | Specimen thickness, electrode geometry, test medium and voltage procedure. |
| Índice de seguimiento comparativo (CTI) | How does the material resist tracking in the specified surface test? | Exact grade and test record. Keep CTI separate from the assembly’s working-voltage rating. |
These measurements support material selection. They do not establish the allowable working voltage of a finished device. Geometry, creepage and clearance, contamination and the applicable equipment requirements still need review at assembly level.
CTI and dielectric strength are different evidence
A material can perform well in one electrical test without satisfying another requirement. Tracking concerns a conductive path developing under electrical stress and contamination; dielectric breakdown concerns failure across the tested insulating section. Substituting one result for the other can hide the actual failure mechanism.
Do not assign one tracking value to an entire polymer family. Toray’s TORELINA PPS tracking guide distinguishes grades developed for tracking resistance from other PPS grades. Those are named Toray materials, not reference values for every PPS compound offered by another supplier.
For a part exposed to condensation or cleaning residues, describe that exposure in the specification. For an internal spacer kept dry, define the intended environment rather than borrowing an outdoor tracking requirement without checking its relevance.
Narrow the material family, then approve the grade
Use the family name to organize a shortlist. Use grade-specific evidence to accept it. The following questions help turn a broad request into a comparable material proposal; the table does not assign electrical ratings to these families.
| Familia de productos candidatos | Question to settle before substitution |
|---|---|
| PA6 / PA66 | Are electrical and dimensional requirements satisfied in the specified moisture condition, not only on dry specimens? |
| PBT | Does the offered reinforced or flame-retardant grade have the required electrical data and recognition details? |
| PPS | Is tracking resistance documented for this grade, separately from its thermal or mechanical data? |
| PC or PC/ABS | Do the exact blend, color, wall thickness and exposure conditions match the proposed application? |
| PEI / PEEK | Is the offered material a molding grade, stock shape or additive material, and which records apply to that form? |
A higher material price does not resolve an undefined requirement. Compare the candidate with the drawing, intended exposure and available documentation before deciding whether a different polymer family is necessary. The centro de selección de materiales provides the broader mechanical, chemical and processing comparison.
Moisture, fillers and processing can change the decision
Ensinger’s electrically insulative materials guidance highlights moisture absorption as an influence on electrical properties, particularly for polyamides. Record whether the data describe dry material or another conditioning state. If service includes humid storage, condensation or washdown, request evidence relevant to that condition.
Also distinguish an insulating compound from a material intended to dissipate charge. A carbon-filled or ESD designation is not evidence of electrical isolation. Specify the required resistance behavior and verify the actual compound; the conductive and static-dissipative plastics guide addresses that different selection problem.
Do not transfer a material result between manufacturing routes without checking its scope. UL’s additive-manufacturing certification guidance discusses the influence of printing parameters on evaluated properties. A recognition record for a molded resin should not be treated as automatic approval for a printed prototype.
Read the recognition record as carefully as the datasheet
A UL Yellow Card records evaluated properties for a recognized polymeric material. Match the manufacturer and exact grade, then check the listed conditions. UL’s recognition abbreviations distinguish color, minimum thickness, flame classification, electrical temperature index and CTI.
Keep a flammability result separate from an electrical rating. A V-0 entry describes a response under the relevant flame test; it does not specify the voltage a finished connector may carry. Nor does a resin record by itself certify the complete component or device. For the other documents that accompany a purchase, use the material certification guide.
What to include in a material or part inquiry
- Electrical duty: intended voltage conditions and the properties or equipment requirements to be met.
- Environment: temperature, humidity, condensation, contamination, fluids and cleaning exposure.
- Definición de la pieza: current drawing, thinnest relevant section, mating conductors and mechanical loads.
- Material identity: required producer and grade, or a clearly defined substitution review; color and reinforcement.
- Supply route: pellets, machined stock or molded parts, estimated quantity and required documents.
- Aceptación: who approves the material and assembly, which checks apply, and the evidence required before repeat supply.
For a connector project, the Guía para el moldeado de conectores eléctricos covers inserts, geometry and manufacturing questions. Describe the missing decision in your inquiry so material selection and part-manufacturing requirements can be reviewed together.
Electrical insulating plastics FAQ
Which plastic is the best electrical insulator?
There is no universal choice. Define the electrical failure mode, humidity, temperature, geometry and required documentation, then compare exact grades under relevant test conditions.
Can a high CTI value replace dielectric-strength testing?
No. They address different behavior. Use the property and method required by the part and equipment specification; do not convert CTI into an assembly voltage rating.
Does a V-0 grade automatically suit a high-voltage connector?
No. Flammability, tracking, dielectric performance, geometry and finished-device evaluation are separate considerations. Check the exact grade record and the component requirements.
Can I approve a color or reinforcement change from the family name?
No. Confirm the offered formulation and applicable recognition or test records. Document an approved substitution rather than treating every PA66, PBT or PPS compound as interchangeable.
