Reasons and prevention methods for scorch

We know that the entire process from fkm raw materials to fkm rubber products generally goes through several stages, mainly including: fluoroelastomer raw rubber, mixing, vulcanization. Before the start of the vulcanization stage, we hope that the rubber will remain in the raw rubber state, that is, the rubber macro-molecule chain has not undergone a three-dimensional cross-linking reaction. If the rubber undergoes early vulcanization during the processing and storage before the vulcanization stage, we call this phenomenon scorch.

The factors that affect rubber vulcanization include formula, temperature, time, pressure, etc., among which the most critical factors are the first three. Of course, the formula here includes both the formula of raw materials and the formula of vulcanizers and accelerators. Below we analyze the causes of rubber scorch from three aspects:

 

1. Formula

The vulcanization system is improperly configured, and the specific manifestations include:

(1) The amount of vulcanizer and accelerator exceeds the standard;

(2) The critical reaction temperature of the vulcanizer and accelerator is too low, that is, the rubber molecular chain undergoes a three-dimensional cross-linking reaction at a lower temperature;

(3) The amount of anti-scorch agent is not used.

 

2. Temperature

(1) Processing temperature: The processing temperature is too high, and no effective cooling measures are taken during processing, resulting in excessive material temperature and vulcanization reaction;

(2) Storage temperature: The room temperature of the storage warehouse is too high and there are no cooling measures, and the materials are stacked too densely, resulting in the temperature not being able to drop quickly;

(3) Material sheet size: If the material sheet thickness is too thick, the material temperature will not be able to drop quickly, resulting in scorch.

 

3. Time

(1) Processing time: The processing time is too long and exceeds the material scorch time, resulting in scorch;

Storage time: The material consumption plan is not detailed enough, the storage management is poor, and the material is still piled up after the scorch time is exhausted. The first produced material is on the inside of the warehouse, and it cannot be taken out when needed, resulting in too long storage time.

 

4. Mold contamination

Bisphenol curable FKM or Peroxide curable FKM can't get touch with Sulfur. The rubber material will be scorch if the mold or production line isn't clean enough.

 

After understanding the causes of scorch, we can formulate targeted methods to prevent scorch, which are also explained from three aspects:

1. Formula:

(1) Rationally configure the vulcanization system and control the amount of vulcanizer and accelerator used;

(2) Try to use accelerators with high critical reaction temperatures;

(3) Use anti-scorching agents.

 

2. Temperature:

(1) Processing temperature: Control the temperature during mixing, and make sure to cool down the equipment temperature, especially the roller temperature;

(2) Storage temperature: Take timely cooling measures after mixing, such as storing in a cold storage as soon as possible, controlling the stacking height and gap when stacking, and reducing the temperature of the used materials as soon as possible;

(3) Material sheet size: The sheet size should not be too thick

 

3. Time:

(1) Processing time: Control the processing time, and the mixing time should not be too long;

(2) Storage time: Develop a detailed material use plan and storage rules, such as stacking the processed materials close to the outside of the warehouse for easy access when used. Plan production according to the amount of materials used to avoid long-term accumulation of unused materials.

 

4. Mold contamination

For Bisphenol curable FKM or Peroxide curable FKM,the production line must be strictly prevented from being contaminated by sulfur.

 

The material scorch time can be effectively extended by adjusting the formula, but it should also be noted that the scorch time cannot be extended blindly, because too long scorch time will seriously affect the vulcanization efficiency and thus greatly increase the cost of the factory. The correct approach should be to control the scorch time within a reasonable range, which will not affect the production efficiency of the enterprise while preventing scorch. Chengdu Crestmat Co., LTD, as a compounding rubber manufacturer with 20 years of production experience, has gained a good reputation in the industry with its advanced production technology and high-quality pre-sales and after-sales services, and can provide customers with FKM, HNBR, FVMQ, ACM, AEM and other products in one stop.