1. Why should rubber be molded?

The purpose of rubber plasticization is to make rubber cut short macromolecular chain under mechanical, thermal and chemical action, so as to make rubber lose its elasticity temporarily and increase its plasticity

Meet the process requirements in the manufacturing process. Such as: make the mixture easy to mix, easy to calender, clear pattern, stable shape, increase the amount of molding, injection molding compound

Fluidity makes the compound easy to penetrate into the fiber, and improves the solubility and adhesion of the compound. Of course, some low viscosity, constant viscosity rubber sometimes may not be plasticized, domestic

Standard granulated rubber, Standard Malaysian Rubber (SMR).

2. What factors affect rubber plasticization in internal mixer?

The raw rubber produced by internal mixer is a kind of high temperature plastic refining, the lowest temperature is above 120 ℃, generally between 155 ℃ and 165 ℃. Raw rubber is subjected to high temperature and high strength in internal mixer cavity

Mechanical action, resulting in severe oxidation, can obtain ideal plasticity in a short time. Therefore, the main influencing factors of raw rubber plasticizing in internal mixer are as follows:

(1) Technical performance of equipment, such as speed, etc,

(2) Process conditions, such as time, temperature, wind pressure and capacity.

3. Why do all kinds of rubbers have different plasticizing properties?

The plasticization of rubber is closely related to its chemical composition, molecular structure, molecular weight and molecular weight distribution. Natural rubber and synthetic rubber due to the structure and properties

Generally speaking, natural rubber is easier to be molded than synthetic rubber. As far as synthetic rubber is concerned, isoprene rubber, chloroprene rubber are close to natural rubber, styrene butadiene rubber

Butyl rubber is the second, nitrile rubber is the most difficult.

4. Why is the plasticity of raw rubber used as the main quality standard of plastic rubber?

The plasticity of raw rubber is related to the difficulty of the whole manufacturing process of products, which directly affects the physical and mechanical properties of vulcanizates and the importance of product performance

Quality. If the plasticity of raw rubber is too high, the physical and mechanical properties of vulcanizate will be reduced. If the plasticity of raw rubber is too low, it will cause difficulties in processing and make the compound unstable

It is easy to mix evenly and calender. When pressing out, the surface of semi-finished products is not smooth and the shrinkage rate is large. It is difficult to master the size of semi-finished products. It is also difficult to rub the rubber into the fabric and make the fabric smooth

As a result, the adhesion between layers is greatly reduced. If the plasticity is not uniform, the processability and physical and mechanical properties of the compound will be inconsistent, even affect the performance

The performance of the products is inconsistent. Therefore, it is an important problem to master the plasticity of raw rubber.

5. What is the purpose of mixing?

Mixing is to mix raw rubber and various compounding agents together through rubber equipment according to the proportion of compounding agent specified in rubber compound formula, and make various compounding agents uniform

It is well dispersed in raw rubber. The purpose of mixing rubber compound is to obtain uniform physical and mechanical performance indexes, which meet the requirements of formula, so as to improve the quality of rubber compound

Under the process operation and ensure the quality requirements of finished products.

6. Why does the mixture agglomerate?

The causes of agglomeration are as follows: insufficient plastic refining of raw rubber, too large roll spacing, too high roll temperature, too large filling capacity, and coarse particles or agglomeration in powder compounding agent

Substances, gel and so on. The way to improve is to take the following measures according to the specific situation: fully plastic refining, properly adjust the roll distance, reduce the roll temperature, pay attention to the feeding method; powder mixing

Drying and screening; cut properly when mixing.

7. Why does too much carbon black in the compound produce "dilution effect"?

The so-called "dilution effect" is due to the excessive amount of carbon black in the compound formula, the rubber is relatively reduced in quantity, resulting in the tight connection between carbon black particles

Because of the existence of many large particles of carbon black, rubber molecules can not penetrate into carbon black

The interaction between rubber and carbon black is reduced and the strength is decreased when the particles are removed, which can not achieve the expected reinforcement effect.

8. How does the structure of carbon black affect the properties of the compound?

Carbon black is produced by thermal decomposition of hydrocarbons. When the raw material is natural gas (mainly composed of aliphatic hydrocarbons), the six membered ring of carbon is formed

When it is heavy oil (with high content of aromatic hydrocarbon), because it already contains six membered rings of carbon, it will be further dehydrogenated and condensed to form polycyclic aromatic compounds, thus forming the structure of carbon atom

Hexagonal network structure layer, which has 3-5 overlapping layers, becomes crystal. The spherical particles of carbon black are composed of several groups of such crystals with no definite standard orientation

The crystal is amorphous. There are unsaturated free bonds around the crystal, which make the carbon black particles agglomerate with each other and form different number of branched small chains, which is called carbon black

The structure of carbon black.

The structure of carbon black varies with different preparation methods. Generally, the structure of furnace carbon black is higher than that of trough carbon black. The structure of acetylene carbon black is the highest

If the content of aromatic hydrocarbon is high, the structure of carbon black is high and the yield is high; otherwise, the structure is low and the yield is low. The smaller the diameter of carbon black particles is, the smaller the size of carbon black particles is

The higher the structure is. In the same particle size range, the higher the structure is, the easier it is to press out, and the surface of the product is smooth and the shrinkage is small. The structure of carbon black can be determined by its oil absorption value

In the case of the same particle size, large oil absorption value means high structure, otherwise it means low structure. Carbon black with high structure is difficult to disperse in synthetic rubber, but it is soft

Synthetic rubber needs carbon black with higher modulus to improve its strength. Fine particle high structure carbon black can improve the wear resistance of tread rubber. The advantage of low structure carbon black is that it breaks

It has high strength, high elongation, low tensile strength, low hardness, soft compound and low heat generation, but its wear resistance is worse than that of high structure carbon black with the same particle size.

9. Why does carbon black affect the scorch property of rubber compound?

The influence of structure of carbon black on scorch time: the higher the structure, the shorter the scorch time; the smaller the particle size of carbon black, the shorter the scorch time. Effect of surface properties of carbon black particles on coke burning

Influence: mainly refers to the surface oxygen content of carbon black, high oxygen content, low pH value, acidic, such as black tank, long scorch time. Effect of carbon black dosage on scorch time

Large amount of carbon black can obviously shorten the scorch time because the increase of carbon black and the formation of bound rubber tend to promote scorch. Effect of carbon black on Mooney coke in different curing systems

The effect of burning time is different.

10. What is one-stage mixing and what is two-stage mixing?

The first stage mixing is to mix the plasticized rubber and various compounding agents (for some compounding agents which are not easy to disperse or have less dosage, they can be made into mother gum in advance) one by one according to the requirements of the process specification

Adding, that is, mixing the master compound in the internal mixer, and then adding sulfur or other vulcanizing agents and some super accelerators that should not be added in the internal mixer.

In short, a period of mixing is not in the middle of the park and a complete mixing.

In the second stage of mixing, all kinds of compounding agents except vulcanizing agent and super accelerator are mixed with raw rubber evenly to make master rubber, which is cooled down and stored for a certain time,

Then, the vulcanizing agent is added to the internal mixer or open mixer for supplementary processing.

11. Why should the film be cooled before storage?

The temperature of the film cut down by the tablet press is very high. If it is not cooled immediately, it is easy to produce early vulcanization and viscose, causing trouble to the next process. I

The factory comes down from the press, immerses the isolation agent through the film cooling device, blow dry and slice, which is for this purpose. The general cooling requirement is to cool the film to 45 ℃ in order to cool the film

In this case, the parking time should not be too long, otherwise it will cause frost spray.

12. Why should the sulfur adding temperature be controlled below 100 ℃?

This is because when sulfur and accelerator are added to the compound, if the temperature exceeds 100 ℃, it is easy to cause early vulcanization (scorch). In addition, in the high

Sulfur dissolves in rubber at low temperature, and condenses on the surface of rubber after cooling, resulting in frost spray and uneven sulfur dispersion.

溫下硫磺溶介在橡膠內，冷卻后硫磺凝集在膠料表面，造成噴霜，而且會造成硫磺分散不勻。