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Vulcanization and Foaming Mechanism of 1. Foam Adhesive Extrusion Tube

1. Coordination of vulcanization and foaming

The vulcanization speed should match the foaming speed. One side must not be significantly faster than the other.

Vulcanization speed is too fast: the foaming agent cannot be successfully decomposed due to the strong mechanical force of the vulcanized rubber.

Vulcanization speed is too slow: the foaming agent decomposes the gas to foam the rubber when the rubber is completely or close to and completely unvulcanized, but at the same time, the surface of the rubber compound is also broken by the gas, so that the surface of the rubber tube is uneven or has pores.

Comparison of the two speeds: Generally, the vulcanization speed should be slightly faster than the foaming speed, so as to ensure the smooth surface of the hose, and the foaming agent can smoothly decompose the gas to foam the rubber material.

2. Foaming process of hose

Microwave: The foaming of the hose is mainly completed by microwave heating. The heat radiation of microwave is used to heat the hose from the inside to the outside. When the inside of the hose starts to heat and foam, the relative temperature of the rubber material outside the hose is still low enough to completely vulcanize, resulting in the hose not being able to start. In this way, the heating method from the inside to the outside ensures that the hose can foam smoothly.

The heating and foaming of the rubber hose by microwave is also accompanied by vulcanization, but the vulcanization at this time does not reach the final vulcanization depth. After coming out of the microwave, it enters the hot air heating section to finish the final vulcanization of the hose. To complete the vulcanization and foaming of the hose.

2. formula design

1. Raw rubber

The choice of raw rubber mainly needs to consider the curing speed of the stiff fluidity.

Tightness: in order to achieve the required firmness, the rubber material is not allowed to deform due to the pressure of its own weight during the transmission of vulcanization. Raw rubber shall be of a higher Mooney grade.

Fluidity: In order to achieve the fluidity required for extrusion, the lower grade of Mooney is considered when choosing raw rubber.

Curing speed: because the foaming glue usually requires a faster curing speed, in order to meet the needs of curing speed, in the choice of raw rubber need to use a higher content of the third monomer brand.

We must choose according to the wall thickness and size of the hose. In general, raw rubber with a higher Mooney is used. You can also mix high-bottom Mooney.

2. Reinforcements

In general, we choose carbon black with better fluidity for the sake of the fluidity of the rubber material, such as Niriron N550R.

Note: For the fluidity of the compound, a certain amount of flow aids can also be added.

3. Vulcanization system

The vulcanization system of foam hose is usually required to be very fast. A large number of super-promotion and super-promotion must be used. Among them, TDEC(TL) effect is better. Fast scorch short. The disadvantage is that it is not safe to store.

In order to make it easier to decompose the gas to foam the rubber, we also pay attention to the crosslinking density when designing the vulcanization system. Crosslink density is too large to foam. Reducing the amount of sulfur, for example, is a better way.

4. Foaming agent

When selecting the foaming agent, attention should be paid to the foaming starting temperature and the maximum temperature of the foaming agent.

The decomposition temperature of the foaming agent is too low: it is easy to cause foaming before vulcanization, which is not conducive to the smooth surface of the hose.

The decomposition temperature of the foaming agent is too high: it is easy to lead to vulcanization after foaming, which is not conducive to the smooth foaming of the hose.

Note: The commonly used foaming agent is AC H OT microsphere foaming (Shanzhen Industrial sanesil FB66)

3. rubber refining

1. Cleaning

The cleaning of rubber mixing is particularly important. If the rubber mixing process is mixed with impurities or other rubber materials due to unclean appliances, the surface of the rubber hose is not smooth or the pores are not uniform after vulcanization.

2. Rubber material parking

After the compound is mixed (without adding vulcanization system and foaming agent), it is better to put it in place for 24 hours and then use it after re-refining and adding sulfur. The use of the compound after a certain period of time is conducive to the dispersion of the compounding agent.

4. process

1. Extruder

When starting to feed the extruder, the screw rotation speed should be slower. So as not to wear the screw due to the front end of the screw idling in the barrel.

Extruder temperature control, generally around 70 ℃. The temperature should be increased from the feeding section to the hose outlet. The temperature of the extruder can increase the plasticity of the compound and preheat the compound.

The temperature of the extruder has a great influence on the foaming of the hose. Proper preheating can help the microwave section to foam more quickly. However, if the extruder temperature is too high, it will affect the scorch of the compound, but it is not good for foaming.

The extrusion speed must match the conveying speed of the first vulcanization tank. If the extrusion speed is too fast, the hose will fall to the ground, while if the extrusion speed is too slow, the hose will be pulled with the conveying of the vulcanization tank and the hose will be thinned.

2. High temperature in the first section

The first section is called high temperature, which is shorter than the other three sections. Its function is to use the high temperature of this section to crust the skin of the hose, but not to have an effect on the inside of the hose.

3. Microwave section

In the microwave section, there is also hot air, but the most important is to use microwave radiation to heat the hose from the inside to the outside. A large number of microwaves make the inside of the compound heat up rapidly and cause the decomposition of the foaming agent to foam the hose. Since this section of heating is from the inside to the outside, so the decomposition of foaming is also from the inside to the outside. It avoids the inability to foam because the outside of the hose has been vulcanized.

4. Hot air

The third and fourth sections are hot air vulcanization. The rubber hose coming out of the second microwave vulcanization tank has been fully foamed, but the vulcanization depth is not enough, and the final vulcanization is carried out in the third and fourth sections. These two sections are mainly vulcanized rubber, of course, but also accompanied by a certain amount of foaming.

5. Cooling and shearing

The hose from the fourth section has completed all vulcanization and foaming and enters the cooling tank for water cooling. Cool and then cut to size to length. The finished product is finished.