ZMBT (MZ) Rubber Accelerator: Optimizing Scorch Safety & Cure Control
Product Name: Rubber Accelerator ZMBT (MZ)
Chemical Name: Zinc 2-mercaptobenzothiazole
CAS No.: 155-04-4
In the competitive landscape of rubber manufacturing, balancing cure rate with processing safety is the key to reducing scrap rates and ensuring consistent quality.
ZMBT Rubber Accelerator (often referred to as Accelerator MZ) stands out as a premier thiazole-class accelerator. Known for its ability to flatten the vulcanization curve and prevent premature curing (scorch), it is the preferred choice for manufacturers working with Natural Rubber (NR) and various Synthetic Rubbers (SBR, NBR) who require precise control over their production line.
What is ZMBT (MZ) and Why Use It?
Technically, ZMBT is the zinc salt of MBT. While it shares the fundamental accelerating properties of MBT, the presence of zinc modifies its activity, offering distinct advantages:
- Milder Reactivity: Unlike the aggressive onset of MBT, ZMBT provides a more gradual cure initiation.
- Enhanced Safety: It significantly extends the scorch time, making it ideal for complex molds or long flow paths.
- Latex Compatibility: ZMBT is widely used as a primary accelerator in latex compounding because it does not destabilize the emulsion.
It acts as a secondary accelerator or a standalone medium-speed accelerator, often paired with Thiurams (TMTD) or Guanidines (DPG) to create a synergistic, high-performance vulcanization system.
Technical Specifications (Typical Values)
Meets ASTM / ISO Industry Standards
| Property | Specification |
| Appearance | Pale yellow to light brown powder |
| Zinc Content | 15.0 – 18.0 % |
| Melting Point | > 250 °C (Decomposes) |
| Heating Loss | ≤ 0.5 % |
| Residue on Sieve (150 μm) | ≤ 0.5 % |
| Solubility | Insoluble in water; slightly soluble in organic solvents |
Tech Note: The high decomposition temperature ensures that ZMBT remains stable even during high-temperature mixing stages, preventing “dead compound” issues.
Key Performance Benefits
1. Superior Scorch Safety (Processing Latitude)
For extrusion and calendering processes, premature vulcanization is a costly disaster. ZMBT extends the scorch time (ts2), allowing the rubber compound to flow and fill molds completely before the crosslinking network forms.
2. Balanced Physical Properties
Compounds cured with ZMBT exhibit a uniform crosslink density, resulting in:
- High modulus stability (low reversion).
- Excellent aging resistance.
- Low compression set.
3. Low Odor & Eco-Friendly Processing
Compared to the sharp, sulfurous odor of MBT, ZMBT is significantly lower in odor. This improves the factory working environment and is critical for consumer-facing products where residual smell is a defect.
4. Versatile Synergies
ZMBT is a “team player” in formulation:
- With TMTD/TMTM: Boosts cure speed without sacrificing safety.
- With CBS/TBBS: Fine-tunes the induction period.
- With DPG: Activates the system for higher tensile strength.
Case Study: Upgrading Conveyor Belt Formulations
Challenge: A manufacturer of industrial conveyor belts (NR/SBR blend) faced issues with scorch during the calendering phase using a pure MBT system.
Solution: Replaced 50% of MBT with ZMBT (Ratio 1:1).
Lab Test Results:
| Metric | Original MBT System | Modified ZMBT System | Improvement |
| Scorch Time (t10 @ 130℃) | 6.5 min | 9.2 min | +41% (Safer) |
| Optimum Cure (t90) | 18.0 min | 19.5 min | Controlled |
| Tensile Strength | 18.6 MPa | 19.4 MPa | Improved |
| Compression Set | 38 % | 31 % | Better Recovery |
Outcome: The introduction of ZMBT eliminated scorch defects during the calendering process and improved the durability of the final belt.
Typical Applications
ZMBT is engineered for products that demand consistency and durability:
- Industrial Goods: Conveyor belts, transmission belts, and rubber hoses.
- Vibration Control: Engine mounts and shock absorbers (where modulus consistency is vital).
- Latex Products: Gloves, foam rubber, and threads.
- Footwear: Shoe soles and solid rubber sheets.
Sourcing Quality ZMBT: What Matters?
Not all ZMBT is created equal. To ensure your production line runs smoothly, prioritize sourcing from suppliers who guarantee:
- Fine Particle Size: Ensures rapid dispersion within the rubber matrix (no white spots).
- High Purity: Low free-MBT content reduces unpredictable scorch behavior.
- Regulatory Compliance: Material conforming to REACH, RoHS, and local environmental standards.
Looking to optimize your vulcanization system?
Contact us today for technical data sheets (TDS), safety data sheets (SDS), or a sample to test the difference ZMBT can make in your formulation.