The three types of vulcanization used in conveyor belt fabrication are hot vulcanization, cold vulcanization, and thermoplastic vulcanization. Each uses a different bonding mechanism and suits a different belt material and operating environment.
The Three Common Types of Vulcanization
Hot, cold, and thermoplastic vulcanization all create a continuous belt loop through molecular bonding. The chemistry, machinery, and application conditions differ significantly across each method.
Hot Vulcanization
Hot vulcanization uses raw rubber compounds, heat, and pressure to permanently cross-link polymer chains. It requires a belt vulcanizer press to apply the precise temperature and pressure profiles the process demands. It delivers 90% to 95% joint strength retention and suits heavy rubber and steel cord belts in mining, ports, and cement operations.
Cold Vulcanization
Cold vulcanization uses a two-part chemical adhesive that cures at room temperature without heat or machinery. It delivers 70% to 80% joint strength retention and suits fabric-ply belts in remote locations where transporting heavy equipment is not practical.
Thermoplastic Vulcanization
Thermoplastic vulcanization uses a rapid-cycle press to melt and fuse PVC or PU belt plies directly together without rubber compounds or adhesives. It delivers 85% to 90% joint strength retention and suits food processing and logistics lines where hygiene and fast turnaround are priorities.
How Hot Vulcanizing Works
Hot vulcanization runs through three stages, from joint preparation through to the controlled curing cycle under the press.
Step Cutting and Carcass Preparation
Belt ends are cut into overlapping steps or interlocking fingers to maximize bonding surface area. For fabric-ply belts, each layer is stripped back individually. For steel cord belts, the surrounding rubber is removed to expose the internal cables, which are then carefully interlaced.
Compound Layering
A hot-vulcanizing cement is applied as an initial tackifier. Uncured tie-gum rubber strips containing dormant sulfur compounds are laid between and over the joint surfaces.
Thermal Curing Under Pressure
The assembled joint goes into a heavy-duty belt vulcanizer. The press applies temperatures between 140°C and 160°C at pressures exceeding 100 PSI. Sulfur atoms form permanent cross-links between the polymer chains, converting the rubber into a tough, heat-resistant material. Dwell time runs 30 to 90 minutes, depending on belt thickness, followed by a controlled cooling cycle.
HoloBelt’s air-cooled and water-cooled splicing machines hold platen accuracy to ±2°C across the full joint surface, with CE certification for operations in Europe and North America.
How Cold Vulcanizing Works
Cold vulcanization relies on chemical bonding rather than heat, making it the practical choice for field repairs in remote locations.
Mechanical Buffing
Belt plies are stepped identically to the hot process. The exposed rubber surfaces are buffed using rotary wire brushes to create a textured surface that gives the adhesive something to bond to. Surface preparation here is more critical than in hot vulcanization because there is no molten rubber to fill voids.
Chemical Mixing and Application
A two-part adhesive consisting of a polyurethane or chloroprene base cement mixed with a hardener is applied rapidly across the buffed surfaces. The mixed compound has a limited working time, requiring fast and uniform coverage.
Ambient Curing
The prepared ends are aligned, pressed together, and rolled out from the center to the edges to expel trapped air. The hardener triggers a chemical curing reaction at room temperature. Full strength develops after 8 to 24 hours before the belt can safely return to tension.
Want a detailed breakdown of cold splicing parameters and joint strength specifications? Our splicing fundamentals and strength analysis cover the technical requirements for both methods.
Typical Equipment Used in the Process
Executing high-quality vulcanized splices requires purpose-built machinery designed for precise temperature control and uniform pressure delivery. The table below covers the core equipment used across hot and thermoplastic vulcanization processes.
| Equipment | Function |
| Sectional hot press | Aircraft-grade aluminum platens with internal heating elements and water-cooling channels |
| Thermoplastic air-cooled press | Rapid heating and cooling for PVC and PU belts, full cycle under 15 minutes |
| Hydraulic pressure pump | Delivers uniform clamping force to prevent localized delamination |
| Electronic control module | PLC-based automation of heat ramp-up, dwell times, and zone temperature monitoring |
| Industrial skiving knives | Precision stepped layer profiling for hot and cold splice preparation |
For a full overview of splicing tools and maintenance equipment, read our guide on conveyor belt splicing tools and equipment used in industrial fabrication environments.
How to Choose the Right Vulcanizing Method
Belt material is the primary decision factor. Environment and downtime constraints narrow the choice further.
- Steel cord belts require hot vulcanization. Cold bonding agents cannot anchor to steel cables reliably. Raw tie-gum rubber under hydraulic pressure is the only method that fully encapsulates the cord structure.
- Fabric-ply rubber belts suit both hot and cold vulcanization, depending on system tension. High-tension applications need hot vulcanization. Low to medium-tension systems can use cold bonding, particularly where remote access makes press equipment impractical.
- PVC and PU belts require thermoplastic vulcanization. Raw rubber compounds do not bond to synthetic plastics. The press heats the belt ends to their plasticization point, where the material fuses directly into a single piece on cooling.
- The temperature environment matters for cold vulcanization. Cold adhesives degrade above 75°C to 80°C and require ambient conditions between 15°C and 35°C to cure correctly. High humidity or freezing temperatures require a heated press.
- Downtime constraints favor thermoplastic vulcanization, where fast turnaround is critical. PVC and PU belts return to full tension in under an hour after the press cycle. Food processing and logistics lines benefit most from this. HoloBelt’s logistics conveyor solutions cover the integrated equipment used across these environments.
Reliable Cleat Welding Solution for Conveyor Belts Where HF Welding Is Not Applicable
LEARN MOREMatching the Right Method to Your Operation
Hot, cold, and thermoplastic vulcanization each solves a different problem. Getting the method right from the start reduces splice failures and extends belt service life across the full operating cycle.
Whether you need a full-scale in-house vulcanizing workshop or portable field equipment for on-site repairs, HoloBelt configures systems around your belt type, site conditions, and production volume.
Contact us today to discuss which method and equipment setup fits your operation.