PAR Polymer: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-06-10
Polyarylate (PAR) is a wholly aromatic polyester developed by Unitika (Japan) and marketed as U-Polymer since 1973. It uniquely combines the high heat resistance of polysulfone (Tg 193 °C) with the transparency of polycarbonate and inherent UV...
Polyarylate (PAR) is a wholly aromatic polyester developed by Unitika (Japan) and marketed as U-Polymer since 1973. It uniquely combines the high heat resistance of polysulfone (Tg 193 °C) with the transparency of polycarbonate and inherent UV resistance without requiring UV stabilizer additives — a rare combination for outdoor transparent applications, automotive lighting reflectors, and medical devices requiring repeated autoclave sterilization.
Unitika U-Polymer is one of Japan's lesser-known but strategically important specialty polymers. Unlike polycarbonate which yellows significantly after UV exposure without UV stabilizers, PAR's molecular structure contains an intrinsic UV-absorbing benzophenone moiety — there is no stabilizer to leach out or degrade over time. This makes PAR ideal for LED lighting lenses, automotive headlamp reflectors, and outdoor sensor housings requiring 10+ year outdoor lifespans.
U-Polymer offers a continuous service temperature of 150 °C — well above polycarbonate (120 °C) and approaching polysulfone (160 °C) — while maintaining 87% visible light transmission. Its excellent flow characteristics enable molding of thin-wall parts down to 0.5 mm, critical for compact connector housings. The material is inherently flame-retardant (UL 94 V-0 at 1.5 mm) without halogen or phosphorus additives.
Processing: Melt temperature 340-370 °C, mold temperature 120-150 °C. Pre-drying at 140 °C for 5 hours is essential — PAR hydrolyzes if processed with moisture. High-temperature machine capability (ceramic heaters, capable of 380 °C) is required.
Technical Properties
| Density | 1.21 g/cm³ |
|---|---|
| Tensile Strength | 70 MPa |
| Melting Point | N/A (Amorphous, Tg 193 °C) |
| Shrinkage Rate | 0.6-0.8% |
| Flexural Modulus | 2.3 GPa |
| Hdt | 175 °C at 1.82 MPa |
| Light Transmission | 87% (visible spectrum) |
| Uv Resistance | Excellent (inherent UV absorber) |
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 |
|---|---|
| Unitika U-Polymer U-100 | |
| Unitika U-Polymer P-1001 |
Frequently Asked Questions
How does PAR compare to polycarbonate for outdoor transparent applications?
PAR outperforms PC in three key aspects for outdoor use: (1) inherent UV resistance — no stabilizer additives needed, no yellowing over time; (2) higher heat resistance (Tg 193 °C vs 147 °C for PC); (3) better chemical resistance to cleaning agents and automotive fluids. PC is 50-70% less expensive and offers better impact resistance.
Why is Unitika the only major commercial producer of polyarylate?
PAR's niche position between PC (lower cost, better impact) and PSU/PES (higher heat, opaque) means its addressable market is smaller than either. Unitika commercialized U-Polymer in 1973 and optimized the manufacturing process, though the high processing temperature (340-370 °C) limits the number of molders who can work with the material.
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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