BEPS is a sulfur-rich diepithio monomer engineered for ultra-high refractive index (n<sub><sup> ≥ 1.70 @ 589 nm) UV/LED-curable optical systems.
Two epithio (thiirane) rings + central disulfide deliver 61 % sulfur by mass, giving:
n<sub><sup> ≈ 1.705 with Abbe number ≈ 23 – ideal for AR/VR pancake lenses, waveguide cores, high-n encapsulants
Dual cure mechanism: ring-opening (cationic) + disulfide addition → shrinkage < 1 %
Compatible with both radical & cationic photoinitiators (TPO, 6976, etc.)
Key Optical & Physical Data:
Refractive index (n<sub><sup>): 1.700 – 1.710
Abbe number (ν<sub>): 23 ± 1
Density: 1.34 g cm⁻³ (20 °C)
Viscosity (25 °C): 35 – 45 mPa·s (easy vacuum casting)
Melting point: < 25 °C (liquid at room temperature)
Volume shrinkage on cure: < 1 % (density dilatometry)
Glass-transition temperature (DSC, 2 % UVI-6976): 155 °C
1,1′-Thiobis(2,3-epithiopropane)
Cas:188829-97-2. Made in China.
Purity: ≥ 98 % (GC)
Refractive Index:1.70
Molecular Formula: C₆H₁₀S₃
Molecular Weight: 178.34 g mol⁻¹
Appearance: Colourless to light-yellow transparent liquid; faint sulfurous odour.
