In LED filament and filament-like (G4/G9, corn-light strip) packaging, the refractive index match between encapsulant and sapphire chip (nD≈1.77) or phosphor glass directly dictates light extraction and long-term yellowing. Conventional methyl silicones often suffer from higher RI (>1.43), poor thixotropy causing edge-collapse on fine filaments, and post-bake hazing/cracking. As LED filaments evolve toward "thinner wires, higher lumen, full-wrap without dam," sourcing a methyl-type dual-pack with nD 1.41, strong thixotropy, and split-cure no-crack profile has become the core challenge for domestic filament-gum substitution.
Addressing this "low-RI + thixotropic + filament-specific" pain point,
Anhui IOTA Silicone Oil Co., Ltd. (IOTA) officially launches
Low-Refractive Methyl Encapsulant Silicone IOTA 34387. Characterized by "A 8000 / B 20000 mPa·s (25℃), 1:1 mix, mixed visc 15000 mPa·s, nD 1.41, Shore A 45, tensile 5MPa, elong 100%, transmittance 92%, CTE 200ppm," and backed by "thixotropic dam-free + split-cure no-crack/no-haze + methyl backbone heat resistance," it serves as the "optical encapsulation anchor" for LED filament gum, MCOB half-wrap, and fine-wire faux-filament.
Molecular Architecture: Low-RI Logic of Methyl Addition Network
The core competitiveness of IOTA 34387 stems from its precisely tuned dual-pack addition-cure methyl polysiloxane topology:
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Methyl Backbone Locks Low RI: Vi-terminated PDMS base + H-PDMS crosslinker + Pt catalyst; all-methyl substitution naturally anchors nD 1.41 (0.13 below phenyl 1.54), better stress match to phosphor/glass coating, less interface total-reflection loss.
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Thixotropic Structure Dam-Free: A-side pre-mixed with fumed silica/polyurea thixotrope; quiescent yield high, no sag on Φ0.5-1.0mm filament; full-wrap in one pass, no PPA dam; half-wrap self-forms lens arc, no collapse at 150℃.
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Split Cure Releases Stress: 80℃/1h pre-gel avoids lead-frame thermal mismatch; 150℃/3h post-cure completes dehydrogenative network, bubble-free, transparent, no ring-crack at Cu/Al/glass interface.
Performance Leap: From "Dam Dispensing" to "Full-Wrap Self-Form"
Incorporating IOTA 34387 enables qualitative leaps in filament packaging:
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Filament Full-Wrap: Tungsten/molybdenum wire coated uniformly 360°, replaces dam+refill, lifts yield.
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Half-Wrap Lens: MCOB half-wrap self-levels into lens curvature, partially replaces PC lens.
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Heat/Haze Resist: 250℃-class junction conduction tolerance; 85℃/85%RH 1000h transmittance ≥92%, no yellowing; -40~150℃ 200 cycles no crack.
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Phosphor Friendly: Low YAG/nitride settling, minimal CCT drift, fits filament direct-phosphor coating.
Application Penetration: From Filament to Decorative Wire
IOTA 34387 covers lighting scenes most sensitive to "low-RI + thixotropy + fine-wire wrap":
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LED Filament: Retro filament bulbs, G4/G9, corn-light strips.
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MCOB/Molding: Half-wrap lens forming, integrated surface-source edging.
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Decorative Lighting: Flexible filament tape, neon-filament, low-voltage ambient wire.
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Specialty Encaps: Light-guide edge caps, micro-indicator optical domes.
IOTA Technical Guide: 1:1 Weigh, Split Degas
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Mix: A:B by 1:1 mass (±1%), planetary stir 2-3min, vacuum degas (-0.095MPa, 5-10min).
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Pre-treatment: Bake filament frame 150℃×30min to remove moisture; dispense at dewpoint ≤-20℃, class 10k.
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Cure Profile: 80℃×1h (pre-gel) + 150℃×3h (post-cure); no direct 150℃ ramp (lead thermal stress).
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Red Lines: Avoid N/P/S/alkyne/organotin/condensation sulfurs (Pt poison); reseal A/B separately, moisture-proof; pot life ≥4h @25℃.
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Storage: Original sealed, <25℃ dry cool, 12-month shelf (per MSDS); non-haz.
Industry experts note that as LED filaments shift from "decor retro" to "main-lighting substitute," encapsulant has upgraded from "just transparent" to "low-RI match + thixotropic form + long-term anti-haze" trinity. IOTA 34387 aligns with domestic first-line filament gum specs via "nD 1.41 + thixotropic full-wrap + 1:1 addition," removing the dam step from the line and holding the 250℃ junction redline with methyl backbone. This marks domestic low-RI methyl encapsulants' readiness to replace imports in the filament niche.
