In the formulation system of specialty High-Temperature Vulcanizing (HTV) silicone rubber, the vinyl content and Mooney rheology of the gum directly dictate the cure speed, mechanical strength, and extrusion appearance of the compounded stock. Conventional high-vinyl gums often suffer from broad molecular weight distribution and high volatility, leading to issues such as mill-sticking, rapid structuring, and post-cure blistering. As New Energy Vehicles (NEVs), ultra-thin flame-retardant sheets, and precision injection molding demand "high filler loading, fast curing, and low bleed," sourcing an MVQ gum with ~5% vinyl content, ≤2% volatiles, and a stable penetration of 600-900 has become a core challenge for domestic high-end compound localization.
Addressing this "high-vinyl processing balance" pain point,
Anhui IOTA Silicone Oil Co., Ltd. (IOTA) officially launches
Methyl Vinyl Silicone Rubber IOTA GUM 705 (MVQ Gum). Characterized by "semi-transparent appearance, density 0.97 g/mL, ~5% vinyl content, and penetration 600-900," and backed by "moderate crosslink density, excellent storage stability, and a 3-year shelf life," it serves as the "motherstock cornerstone" for specialty HTV compounds, high-strength flame-retardant stocks, and precision molded parts.
▎Molecular Architecture: Side-Vinyl Controlled Crosslinking
The core competitiveness of IOTA GUM 705 stems from its precisely tuned vinyl distribution and ideal rheological profile:
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Side Vinyl Supply (~5%): Approximately 5% vinyl (Vi) groups are introduced along the polymer chain. Without significantly increasing hardness, these groups provide ample crosslinking sites. Compared to standard 110-2 gum, 705 forms a denser network during peroxide curing, markedly improving tensile strength and tear resistance while retaining excellent resilience.
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Penetration 600-900 (Processing Sweet Spot): This metric places the gum neither in a flowing liquid nor a hard solid state, but in a "semi-plastic" zone. On a two-roll mill, 705 exhibits superior "body" and "mill-wrapping" characteristics—neither sticking to the rolls nor absorbing fillers too quickly—allowing fumed silica and additives to disperse uniformly and drastically reducing mixing-induced structuring risks.
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Low Volatility (≤2%): Volatile content (150℃/30min) is strictly capped at 2%, ensuring minimal residue post-cure. This meets the stringent requirements of electronic and electrical applications for low compression set and low outgassing.
▎Performance Leap: From General Compounding to Specialty Molding
Incorporating IOTA GUM 705 as the base gum enables qualitative leaps in downstream compounds:
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Specialty HTV Compounds: Serves as a high-strength base for formulating full-spectrum compounds (Shore A 50-80). Particularly suited for extruded wire/cable jackets and molded seals.
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Precision Injection Molding: Excellent flowability and moderate cure speed make it perfectly compatible with Liquid Injection Molding Systems (LIMS) for producing thin-walled, complex electronic connectors and medical components.
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High-Strength Flame-Retardant Systems: The high vinyl content provides abundant reactive sites for incorporating aluminum/magnesium hydroxides. This aids in forming dense ceramic-like char layers, enhancing the fire-resistance limit of UL94 V-0 rated silicones.
▎Application Penetration: From HV Connectors to Precision Seals
IOTA GUM 705 covers sectors demanding dual sensitivity to mechanical performance and processing efficiency:
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Organic Elastomer Base: Functions as the foundational polymer for functional silicones (conductive, thermal, FR), providing a stable crosslinking network skeleton.
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NEV Sealing Parts: Used in battery pack seals and HV relay gaskets, resisting long-term 200℃ thermal aging and electrolyte attack.
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Electronic Encapsulation: Acts as a base gum for electronic potting compounds, offering insulation and mechanical damping without long-term cracking.
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Processing Aid: Minor additions into difficult-to-disperse fluorosilicones or high-phenyl silicones improve filler wetting and dispersion.
▎IOTA Technical Guide: Temperature Control, Shelf-Life Management
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Raw Material Feed: Condition gum at ~25℃ prior to use to prevent moisture condensation affecting dispersion.
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Compounding: Recommended recipe: GUM 705 100phr / Fumed Silica 40-50phr / Structure Control Agent (e.g., IOTA R05) 3-5phr / Dicuperoxide (DCP) 0.5-1.0phr. Start with tight nip gaps; widen gradually after gum bands completely. Maintain roll temperature at 40-60℃.
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Curing: Primary cure 170-180℃×5-10min; Post-cure 200℃×2-4h to purge volatiles and stabilize properties.
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Safety Red Line: Non-hazardous chemical. Store in 25kg cartons (inner PE liner), moisture-proof, sun-proof, <40℃ sealed. Avoid direct co-storage with strong acids, bases, or peroxides. Shelf life 3 years; retest qualified for extended use.
Industry experts note that with the EV and energy storage boom, specialty HTV silicones are rapidly evolving towards "high strength, low volatiles, and easy processing." IOTA GUM 705, with its precise "~5% Vinyl + 600-900 Penetration" specs, fills a critical market gap in domestic mid-to-high vinyl gums. It not only boosts compounding efficiency but also reduces inventory pressure via its 3-year shelf life. This marks domestic HTV gums' readiness to compete head-to-head with international brands in the refined quality control arena.
