PCT Polycyclohexylene Terephthalate Properties — Complete Engineering Data Sheet (2026)
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-06-10
PCT (polycyclohexylene-dimethylene terephthalate) is a high-temperature semi-crystalline polyester specifically developed for lead-free SMT (surface-mount technology) electronic connectors. It fills the performance gap between PBT (HDT 210 °C,...
PCT (polycyclohexylene-dimethylene terephthalate) is a high-temperature semi-crystalline polyester specifically developed for lead-free SMT (surface-mount technology) electronic connectors. It fills the performance gap between PBT (HDT 210 °C, insufficient for 260 °C reflow) and LCP (expensive, anisotropic) — offering LCP-level reflow survivability at approximately 60-70% of LCP's cost.
PCT's melting point of 290 °C gives it a 30 °C safety margin above the 260 °C peak reflow temperature, while its extremely low moisture absorption (0.06%) eliminates the blistering problems that plague PA66 connectors during reflow. These properties have made PCT the go-to material for mid-range electronic connectors, bobbins, relays, and switches that require reflow compatibility but do not justify the cost of LCP.
Celanese Thermx is the global market reference, widely specified by connector manufacturers in Japan (JST, JAE), Korea (KET, UJU), and China for consumer electronics, automotive ECU connectors, and appliance control boards. PCT competes directly with PA9T and PA46 in the mid-tier reflow-compatible connector material segment.
Processing: Melt temperature 295-310 °C, mold temperature 100-140 °C. Pre-drying at 120 °C for 4 hours is essential. PCT's crystallization rate is rapid — mold temperature must be maintained above 100 °C to achieve full crystallinity. A reverse barrel temperature profile is commonly used to manage the narrow processing window between melting and degradation (degradation onset ~320 °C).
Recommended Applications
PCT Polycyclohexylene Terephthalate is commonly specified for:
⚠ Not Recommended For
PCT Polycyclohexylene Terephthalate is not recommended for:
- Continuous outdoor UV exposure without UV coating (yellows and loses impact strength rapidly)
- Contact with aromatic hydrocarbons, ketones, or esters (causes environmental stress cracking)
- Steam sterilization above 120°C (use PSU or PPSU for autoclave applications instead)
Selection & Application Guide
Polycarbonate (PC) is the transparent engineering plastic with the highest impact strength — virtually unbreakable in thin sections. Choose PC over acrylic (PMMA) when impact resistance is needed; over PSU when lower cost and higher clarity matter and steam sterilization isn't required. PC's main limitations are poor chemical resistance to solvents and UV degradation without stabilization. For higher temperature or flame resistance, consider PC/ABS blend or Ultem.
Real-World Applications
PC's exceptional impact strength (850 J/m notched Izod) and optical clarity make it the standard for safety helmets, riot shields, and protective visors.
PC's optical clarity, impact resistance, and thermal stability for halogen bulb environments make it the dominant material for headlamp outer lenses worldwide.
PC and PC/ABS blends provide the combination of impact strength, flame retardancy (with additives), and surface finish quality for laptop, phone, and tablet housings.
PC's clarity for visual inspection, gamma sterilizability, and impact toughness suit it for IV components, blood centrifuge housings, and diagnostic device enclosures.
Processing & Cost Considerations
Manufacturing Tips
- PC processes at 280-320°C melt temperature with mold temperatures of 80-100°C. Thorough drying is essential (120°C for 3-4 hours to <0.02% moisture) — PC is very hygroscopic and even small amounts of moisture cause splay marks and reduced impact strength.
- PC has high melt viscosity — higher injection pressures and larger gates are needed compared to commodity plastics. Thin-wall molding may require fast injection speeds to prevent premature freeze-off.
- Design parts with uniform wall thickness to prevent sink marks and internal stresses. PC is notch-sensitive — avoid sharp internal corners (use R>0.5mm fillets) to maintain impact strength.
PC costs $5-12/kg — more than ABS ($2-5/kg) but less than PSU ($15-35/kg). PC/ABS blends offer a middle ground at $3-7/kg with better flow and processability. For applications requiring both transparency and impact resistance, PC has no cost-effective substitute. For opaque applications, PC/ABS is often a better value proposition.
Technical Properties
| Density | 1.44 g/cm³ (30% GF) |
|---|---|
| Tensile Strength | 120 MPa (30% GF) |
| Melting Point | 290 °C |
| Shrinkage Rate | 0.3% (30% GF) |
| Flexural Modulus | 8.5 GPa (30% GF) |
| Hdt | 260 °C at 1.82 MPa |
| Dielectric Constant | 3.5 at 1 MHz |
| Water Absorption | 0.06% (24h, 23 °C) |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Celanese Thermx PCT | |
| DuPont EccoTherm PCT | |
| SK Chemicals EcoPCT |
Frequently Asked Questions
How does PCT compare to LCP for SMT connectors?
PCT is 30-40% less expensive than LCP but has lower flow. LCP has a higher melting point and inherently better chemical resistance. LCP is highly anisotropic; PCT is more isotropic. Choose LCP for ultra-fine-pitch connectors (<0.5 mm pitch). Choose PCT for mid-pitch connectors where cost reduction is the priority and the additional LCP performance is not needed.
What are the disadvantages of PCT?
PCT's main limitations: (1) narrow processing window — degradation starts at ~320 °C, only 30 °C above melt temperature; (2) notch sensitivity — sharp corners can initiate cracks under impact; (3) limited resin suppliers — Celanese is the dominant global supplier.
What is the difference between PC and PMMA (acrylic)?
PC has much higher impact strength (850 J/m vs 16 J/m for PMMA) and higher service temperature (115°C vs 85°C). PMMA has better optical clarity (92% vs 88% transmission), better UV resistance, and lower cost. Choose PC when impact resistance is critical; PMMA for display applications where optical quality and UV stability matter more.
Can PC be autoclaved?
Not recommended. Standard PC softens and distorts at autoclave temperatures (134°C). It can withstand a few cycles but rapidly degrades. For steam sterilization, use PSU, PPSU, or Ultem instead. PC is compatible with EtO and gamma sterilization for single-use medical devices.
Why does PC stress-crack in the presence of solvents?
PC is highly susceptible to environmental stress cracking when exposed to solvents (gasoline, acetone, MEK) while under mechanical stress. The solvent migrates into the polymer at stress concentration points, causing microcracks that propagate rapidly. For solvent-exposed applications, specify stress-annealed parts or use a chemically resistant alternative (PPS, PPSU, or PEEK).
Is BPA-free polycarbonate available?
Yes. BPA-free copolyester alternatives (Tritan, PCTG) provide similar clarity and impact resistance without bisphenol-A. These materials are increasingly specified for food contact and children's products. However, they have lower temperature resistance than standard PC and may not be suitable for all PC applications.
What is PC/ABS blend and when should I use it?
PC/ABS blend combines PC's impact resistance and heat resistance with ABS's processability and lower cost. The blend offers better flow (easier thin-wall molding), lower melt temperature, and lower cost than pure PC. It is the dominant material for electronic device housings. Use pure PC when transparency is needed; PC/ABS for opaque structural and housing applications.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org