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DCBP (Bis(2,4-Dichlorobenzoyl) Peroxide, CAS 133-14-2): The Low-Temperature Peroxide for HTV Silicone Cable Jackets and Extruded Profiles
SEMITECH stocks DCBP as 50% paste in silicone fluid — the lowest-decomposition-temperature aromatic diacyl peroxide for HTV silicone rubber, with a 1-minute half-life at 124°C. Standard cure agent for thin-section extruded profiles in continuous hot-air vulcanisation tunnels. 25 kg pail, refrigerated transport for tropical destinations.
Contents
| 133-14-2 | 50% | 124°C |
|---|---|---|
| CAS number | In silicone fluid | t½ = 1 min |
Chemistry & Specifications
DCBP (C₁₄H₆Cl₄O₄, MW 380.0) is supplied as 50 wt% paste in methyl-silicone fluid. Key kinetics: t½ = 1 min at 124°C, 10 min at 95°C, 1 hour at 75°C — the lowest-temperature commercially-used silicone peroxide. Must be stored below 25°C; SADT = 50°C.
Cure Mechanism: Free-Radical Methyl-H Abstraction Crosslinking
Thermal homolysis generates 2,4-dichlorobenzoyloxy radicals, which abstract methyl-H from PDMS gum, forming Si-CH₂-CH₂-Si crosslinks.
- Loading 0.5–1.0 phr — thin-section extruded profiles (gaskets, tubing 1–5 mm)
- Loading 1.0–1.5 phr — standard HTV cable jackets (3–10 mm wall)
- Loading 1.5–2.5 phr — high-modulus calendered sheet and laminates
Continuous hot-air vulcanisation at 200–280°C; line speeds 5–15 m/min for thin sections, 2–8 m/min for thicker. Methyl-vinyl gum (0.1–0.5% vinyl) accepts lower loading (0.4–0.8 phr).
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Applications & Formulation Guidance
HTV cable insulation (largest application): 1.0–1.5 phr for 10–35 kV power cables, motor lead wire (Class H), and fire-survival cables. Extruded profiles: 0.5–1.0 phr for gaskets and tubing. Calendered sheet: 1.5–2.0 phr for Shore A 70+ thermal pads. Compression moulded parts: 0.8–1.5 phr, 3–10 min at 170–180°C. Not suitable for medical, food-contact, or optical silicone due to 2,4-dichlorobenzoic acid byproduct.
Procurement, Storage, Transport and SADT Compliance
CoA per batch: active oxygen ≥3.95%, assay ≥48% DCBP, water ≤0.5%, D90 ≤25 µm, SADT 50°C. 25 kg HDPE pail with breather valve. MOQ 200 kg. Lead time 2–4 weeks to Asia, 4–6 weeks to Europe/NA. UN 3106 / Class 5.2 Organic Peroxide Type C. Storage 5–25°C, never above 30°C. Shelf life 6 months refrigerated, 3 months ambient ≤25°C. Tropical-climate transport requires reefer container.
DCBP 50% Paste Specification Sheet
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Bis(2,4-dichlorobenzoyl) peroxide | — |
| CAS number | 133-14-2 | — |
| Molecular formula | C₁₄H₆Cl₄O₄ | — |
| Molecular weight | 380.0 g/mol | — |
| Form | 50 wt% paste in methyl-silicone fluid | — |
| DCBP assay (in paste) | ≥48% | ASTM E298 modified |
| Active oxygen (in paste) | ≥3.95% | Iodometric titration |
| Water content | ≤0.5% | Karl Fischer |
| Particle size (D90) | ≤25 µm | Laser diffraction |
| Appearance | Pale pink to off-white paste | Visual |
| Density (20°C) | 1.10–1.15 g/cm³ | ASTM D1475 |
| Half-life (124°C) | 1 minute | ASTM E2070 |
| Half-life (95°C) | 10 minutes | ASTM E2070 |
| Half-life (75°C) | 1 hour | ASTM E2070 |
| SADT (50 kg pkg) | 50°C | UN Test H.4 |
| UN classification | 3106 / Class 5.2 / Organic Peroxide Type C | — |
| Packaging | 25 kg HDPE pail with breather valve | — |
| Storage | 5–25°C, never above 30°C, no direct sunlight | — |
| Shelf life | 6 months refrigerated; 3 months ambient ≤25°C | — |
FAQ
+Why does my HTV cable extrusion show soft uncured cores?
The peroxide gel-time at tunnel temperature exceeds the cable's residence time. Solutions: reduce line speed 20–30%, raise tunnel temperature to 250°C, reduce wall thickness, or raise DCBP from 1.0 to 1.5 phr.
+Why does my DCBP paste develop hot spots in the warehouse?
Early warning of self-accelerating decomposition. Check if ambient exceeded 25°C, pails are stacked too tightly, breather valves are blocked, or shelf life expired. Move to refrigerated storage immediately; if pail >40°C and rising, evacuate and contact fire department.
+Can I use DCBP for moulded silicone food-contact parts?
No — 2,4-dichlorobenzoic acid byproduct (~0.5% residual) fails EU and FDA migration limits. Use Karstedt platinum addition cure for direct food-contact. DCBP-cured parts are acceptable for indirect food-contact after 4-hour post-cure at 200°C.