Rubber scorching refers to premature vulcanization, which is the early curing of rubber compounds during processes prior to vulcanization, including mastication, rubber storage, extrusion, calendering, and molding.
1. Improper formula design
The curing system is unbalanced, with excessive amounts of vulcanizing agents and accelerators.
2. Insufficient mastication and high processing temperature
For rubber types requiring mastication, inadequate mastication results in low plasticity and high hardness, causing a sharp temperature rise during mixing. High roll temperatures of mixers or other roller devices (such as re-mixers and calenders) and insufficient cooling can also trigger on-site scorching.
3. Poor heat dissipation during storage
Mixed rubber sheets that are too thick when discharged have poor heat dissipation. If stacked hastily without cooling, coupled with poor warehouse ventilation and high ambient temperatures, heat accumulation will occur and induce scorching.
4. Inadequate semi-finished product management
Poor management during rubber storage leads to natural scorching when the remaining scorch time is exhausted but the rubber is still left unused.
Causes difficulties in processing
Impairs the physical properties and surface smoothness of products
May even result in joint breakage of finished products
1. Optimize rubber formula design
Use a combination of multiple accelerators to suppress scorching. For high-temperature, high-pressure, and high-speed mixing processes, add an appropriate amount (0.3–0.5 parts) of anti-scorching agent.
2. Strengthen cooling control in processing
Strictly control machine and roll temperatures, and ensure sufficient cooling water circulation to keep operating temperatures below the scorching critical point.
Each batch of rubber should be tracked with a process card, follow the first-in first-out storage principle, and set a maximum storage time for each batch. Maintain good ventilation in the warehouse.
