Question & a knowledge of rubber products production

There are four purposes for storing the mixed rubber film after cooling: (1) to restore the fatigue of the rubber and relax the mechanical stress during mixing; (2) Reduce the shrinkage of rubber; (3) Make the compounding agent continue to diffuse during parking to promote uniform dispersion; (4) The bonding rubber is further formed between rubber and carbon black to improve the reinforcement effect.

2. Why strictly implement the segmented dosing and pressurization time?

Dosing sequence and pressurization time are important factors affecting mixing quality. Segmented dosing can improve the mixing efficiency and increase its uniformity, and there are special regulations on the dosing sequence of some chemicals, such as liquid softener shall not be added at the same time with carbon black to avoid agglomeration. Therefore, segmented dosing must be strictly implemented. The pressing time is too short, and the rubber and medicine can not be fully rubbed and kneaded, resulting in uneven mixing; If the pressure time is too long and the temperature of the mixing chamber is too high, the quality will be affected and the efficiency will be reduced. Therefore, the pressurization time must be strictly implemented.

3. What is the effect of rubber loading capacity on the quality of plastic mixing and mixing?

The rubber loading capacity refers to the actual mixing capacity of the internal mixer, which often accounts for only 50-60% of the total capacity of the mixing chamber of the internal mixer. If the capacity is too large, there is no sufficient gap in mixing, and sufficient mixing cannot be carried out, resulting in uneven mixing; If the temperature rises, it is easy to cause self sulfur of rubber; It will also cause motor overload. The capacity is too small, there is not enough friction resistance between rotors, and idling occurs, which also leads to uneven mixing, which affects the quality of compound and reduces the utilization rate of equipment.

4. Why should liquid softener be added at last when mixing rubber compound?

When mixing rubber, if liquid softener is added first, the raw rubber will expand too much, which will affect the mechanical friction between rubber molecules and fillers, reduce the mixing speed of rubber, and cause uneven dispersion and even agglomeration of powder. Therefore, the liquid softener is usually added last during mixing.

5. Why does the compound "self sulfur" after being placed for a long time?

The main causes of "self sulfur" during the placement of compound are: (1) too many vulcanizing agents and accelerators are used; (2) The rubber loading capacity is large, the temperature of the rubber mixer is too high, and the film cooling is not enough; (3) Or sulfur is added prematurely, resulting in uneven dispersion of chemicals, resulting in local concentration of accelerator and sulfur; (4) Improper parking, that is, the temperature of the parking place is too high, the air is not circulating, etc.

6. Why is there a certain wind pressure on the rubber mixture of internal mixer?

During mixing, in addition to raw rubber and medicine materials in the mixing chamber of the internal mixer, there are a considerable part of gaps. If the pressure is insufficient, the raw rubber and medicine materials will not get enough friction and kneading, resulting in uneven mixing; After increasing the pressure, the rubber will be subject to strong friction and kneading up, down, left and right, so that the raw rubber and the compounding agent can be mixed evenly quickly. Theoretically speaking, the greater the pressure, the better. However, due to the limitations of equipment and other aspects, in fact, the pressure cannot be unlimited. Generally speaking, the wind pressure is about 6kg / cm2.