Electronic connectors are among the most demanding electrical applications for plastic materials. The material must pass the UL94 V-0 flammability rating, provide a sufficiently high CTI (comparative tracking index) to support creepage-distance design, withstand the high-temperature impact of SMT reflow soldering and chemical attack from fluxes and cleaning agents, and maintain accurate terminal positioning. Many engineers struggle to choose between FR PBT and PC/PBT. Selecting the wrong material can cause connector cracking, insufficient creepage distance, or even the rejection of an entire production batch.
Using SABIC’s two major engineering-plastics families—Valox™ FR PBT and Xenoy™ PC/PBT—as examples, this article systematically compares their performance differences, material-selection logic, and typical grades for electronic connector applications, helping manufacturers make more reliable material decisions.
1. Core Material Requirements for Electronic Connectors
Before comparing the materials, first identify the key criteria for evaluating connector materials. Different applications assign different priorities to these criteria, but the following seven are fundamental:
| Requirement | Description |
| UL94 flammability rating | V-0 is standard for most connectors; some thin-wall parts require 5VA or higher |
| CTI (comparative tracking index) | Determines creepage-distance design; a higher CTI allows a smaller, more compact connector |
| Heat resistance | Must withstand SMT reflow soldering (peak above 260°C) or wave soldering |
| Dimensional stability | Low moisture absorption and low warpage ensure terminal-position accuracy and assembly consistency |
| Chemical resistance | Resistance to fluxes, cleaning agents, lubricants, engine-compartment chemicals, etc. |
| Low-temperature toughness | Automotive and outdoor connectors must resist cracking at -40°C |
| Processing flowability | Small, precision connectors require excellent thin-wall filling and a low tendency to flash |
The performance of FR PBT and PC/PBT is compared below across these criteria.
2. Basic Comparison of FR PBT and PC/PBT
FR PBT (Represented by the SABIC Valox™ FR Series)
PBT is a crystalline engineering plastic with excellent electrical insulation, chemical resistance, low moisture absorption, and excellent flowability. Flame-retardant PBT can consistently achieve V-0 through the addition of brominated or phosphorus-based flame retardants, and the technology is highly mature.
Core advantages of Valox™ FR PBT:
- High CTI: Halogen-free grades typically achieve a CTI above 600 V, with some grades reaching even higher values, making them highly suitable for miniaturized, high-density connectors;
- Low moisture absorption: Moisture absorption is far lower than that of PA, providing excellent dimensional stability and high terminal-position accuracy;
- Excellent chemical resistance: Good resistance to fluxes, cleaning agents, lubricants, gasoline, and other chemicals;
- Good flowability: Suitable for thin walls, long flow paths, and multi-cavity molds.
Points requiring attention:
- Relatively low notched impact strength, with a particular tendency toward brittle cracking at low temperatures (-40°C);
- HDT (0.45 MPa) is typically around 200°C, and the long-term service temperature is approximately 120-140°C. Short-term heat resistance during SMT reflow soldering is acceptable, but grade selection requires careful attention.
PC/PBT (Represented by the SABIC Xenoy™ Series)
PC/PBT is an alloy of PC and PBT that combines the toughness of PC with the chemical resistance and crystallinity of PBT. Compared with neat PBT, PC/PBT offers greatly improved low-temperature impact performance while retaining good flame retardancy and processability.
Core advantages of Xenoy™ PC/PBT:
- Excellent low-temperature toughness: Maintains relatively high impact strength at -40°C and resists cracking, making it highly suitable for automotive, outdoor, and EV charging-station connectors;
- Balanced chemical resistance: Good resistance to most oils, fuels, and cleaning agents, although it is more sensitive than neat PBT to certain aggressive solvents;
- Good flame retardancy: Consistently achieves V-0, with mature halogen-free solutions available;
- Balanced overall performance: Provides a good balance of strength, toughness, heat resistance, and dimensional stability.
Points requiring attention:
- CTI is generally slightly lower than that of an equivalent neat PBT grade; halogen-free V-0 grades typically have a CTI in the 500-600 V range;
- Higher cost than neat PBT;
- Moisture must be strictly controlled during processing to prevent hydrolysis of the PC phase.
Summary of Key Differences
| Performance criterion | Valox™ FR PBT | Xenoy™ PC/PBT |
| UL94 flammability rating | V-0, V-2 | V-0, V-2 |
| CTI | Generally higher; halogen-free grades can reach 600 V+ | Slightly lower; typically 500-600 V depending on the grade |
| Low-temperature impact (-40°C) | Average; prone to brittle cracking | Excellent; retains toughness |
| Chemical resistance | Excellent | Good; slightly sensitive to certain solvents |
| Moisture absorption | Low | Slightly higher than PBT |
| Dimensional stability | Excellent | Good |
| Processing flowability | Good | Good |
| Cost | Lower | Higher |
3. SABIC Valox™ FR PBT in Connector Applications
Valox™ FR PBT is one of the most established flame-retardant PBT solutions for electronic connectors. It is widely used in consumer electronics, relays, coil bobbins, and small precision connectors.
Typical applications:
- USB connectors, FPC connectors, and board-to-board connectors;
- Relay housings and coil bobbins;
- Automotive fuse boxes and sensor connectors;
- Internal connectors for household appliances.
Material-selection considerations:
- High-density, miniaturized connectors: Give priority to high-CTI, halogen-free grades to reduce creepage-distance design constraints;
- Trade-off between halogenated and halogen-free grades: Halogenated grades cost less and provide high flame-retardant efficiency; halogen-free grades offer better CTI performance and meet environmental requirements for export products. If the customer accepts halogenated material, Valox™ halogenated FR PBT offers excellent value. If halogen-free material and high CTI are required, a halogen-free Valox™ grade is the first choice;
- Thin-wall parts: Select a high-flow grade to ensure complete filling and controllable flash.
Typical characteristics of Valox™ FR PBT:
The dimensional stability resulting from low moisture absorption keeps terminal insertion and retention forces stable over time, making the material suitable for connectors with extremely demanding electrical-contact reliability requirements.
4. SABIC Xenoy™ PC/PBT in Connector Applications
The core value of Xenoy™ PC/PBT lies in its balance of low-temperature toughness and overall performance. In many connectors exposed to vibration, drops, or low outdoor temperatures, the low-temperature brittleness of neat PBT can become a critical weakness. Xenoy™ directly addresses this limitation.
Typical applications:
- Automotive engine-compartment connectors and wire-harness connectors;
- EV charging-station connectors and internal charging-gun connectors;
- Outdoor base-station connectors and industrial-equipment connectors;
- Consumer-electronics connectors requiring impact testing at -40°C.
Material-selection considerations:
- Applications with specific low-temperature impact requirements: If the connector must pass a drop or impact test at -40°C, Xenoy™ PC/PBT is a safer choice than Valox™ FR PBT;
- Applications requiring both chemical resistance and low-temperature performance: Engine compartments involve both oil contamination and cold-start conditions, making Xenoy™ more reliable because of its balanced performance;
- Halogen-free V-0 requirements: Halogen-free flame-retardant Xenoy™ grades can consistently achieve V-0 while retaining excellent low-temperature toughness.
Note: Compared with neat PBT, Xenoy™ PC/PBT has a slightly lower CTI. Creepage distance must therefore be recalculated for miniaturized, high-density connectors. If the CTI margin is limited, a high-CTI Valox™ grade may still be required.
5. FR PBT vs. PC/PBT: Connector Material-Selection Decision Matrix
To help engineers make a quick assessment, the following matrix summarizes the recommended direction for typical connector applications:
| Connector type | Key requirements | Recommended material | Reason for recommendation |
| Consumer-electronics connectors (USB, FPC, board-to-board) | High CTI, thin walls, cost sensitivity | Valox™ FR PBT | High CTI, low moisture absorption, and good flowability; suitable for miniaturization |
| Automotive engine-compartment connectors | Heat resistance, oil resistance, and low-temperature impact performance | Xenoy™ PC/PBT | Good low-temperature toughness and balanced chemical resistance |
| EV charging-station/outdoor connectors | Halogen-free V-0, low-temperature performance, and weather resistance | Xenoy™ PC/PBT | Excellent low-temperature impact performance and consistent flame retardancy |
| Relay housings/coil bobbins | High CTI and dimensional stability | Valox™ FR PBT | Low moisture absorption and excellent electrical performance |
| Industrial-equipment connectors | Chemical resistance, flame retardancy, and mechanical strength | Depends on the specific service conditions | Either material may be used; immersion testing in the relevant medium is required |
| Automotive fuse boxes/sensor connectors | Heat resistance, dimensional stability, and electrical performance | Valox™ FR PBT | High CTI and low moisture absorption ensure long-term reliability |
6. Selection Under the Halogen-Free Trend
Halogen-free electronic connectors have become a global trend. Products exported to the EU, in particular, are generally required to meet halogen-free requirements under RoHS and REACH. When choosing between FR PBT and PC/PBT for a halogen-free solution, both CTI and low-temperature impact performance must be considered:
- Valox™ halogen-free FR PBT: Offers a clear CTI advantage (above 600 V) and good dimensional stability, making it suitable for high-density connectors. However, its low-temperature toughness is inferior to that of PC/PBT, and it may fail impact testing at -40°C.
- Xenoy™ halogen-free PC/PBT: Offers excellent low-temperature impact performance and consistent flame retardancy, but its CTI is slightly lower. If the connector has sufficient creepage-distance margin, Xenoy™ is the more balanced choice.
Recommendation:
If the customer requires halogen-free material and CTI > 600 V, give priority to Valox™ halogen-free FR PBT. If the customer requires halogen-free material and impact performance at -40°C, give priority to Xenoy™ PC/PBT. If both requirements are stringent, evaluate specific grades together with the material supplier and, if necessary, consider modified PBT/PC or the addition of special additives.
7. Processing Precautions
Valox™ FR PBT Processing Guidelines
- Drying: 120-130°C for 3-4 hours; control moisture content below 0.02%;
- Processing temperature: Barrel temperature 240-260°C; avoid exceeding 270°C, which may cause the flame retardant to decompose;
- Mold temperature: 60-80°C to ensure sufficient crystallization and dimensional stability;
- Shutdown purging: Purge the barrel with PP or PS to prevent residual material from decomposing at high temperature.
Xenoy™ PC/PBT Processing Guidelines
- Drying: 110-120°C for 3-4 hours; because the PC phase has a high risk of hydrolysis, moisture must be strictly controlled;
- Processing temperature: Barrel temperature 250-270°C; the nozzle temperature should not be too high;
- Mold temperature: 60-80°C; a higher mold temperature helps improve surface quality and dimensional stability;
- Shutdown purging: Purge with PC or general-purpose ABS to prevent degradation of residual PC/PBT.
Both materials are relatively sensitive to shear. A moderate screw speed and back pressure are recommended to avoid the buildup of shear heat caused by high-speed injection.
8. Conclusion
FR PBT and PC/PBT each have an irreplaceable role in electronic connector applications. Valox™ FR PBT excels in CTI, chemical resistance, and dimensional stability, making it the first choice for miniaturized, high-density connectors; Xenoy™ PC/PBT excels in low-temperature toughness and balanced overall performance, making it a reliable choice for connectors used in automotive, outdoor, and vibration-prone environments. The key to material selection is not which material is better, but which risk poses the greater concern for your connector—insufficient creepage distance or low-temperature cracking.
We specialize in SABIC Valox™ FR PBT and Xenoy™ PC/PBT plastic resin pellets. We offer multiple halogenated and halogen-free V-0 grades, supported by TDS documents, UL Yellow Cards, and RoHS/REACH declarations. If you are developing electronic connectors, relays, or automotive electronic components, please provide your product drawings, certification requirements, and service conditions. We will recommend the most suitable grade based on your actual needs and arrange sample testing.
