Carbon black is widely used in the rubber industry as a black powder with high surface area and high adsorption properties. Carbon black has a great impact on the properties of rubber, such as increasing strength, improving wear resistance, increasing hardness, etc. Therefore, the carbon black dispersion grade has an important impact on the rubber processing process and the performance of rubber products.
1. Definition and classification of carbon black dispersion grades.
Carbon black dispersion grade refers to the degree to which carbon black is evenly dispersed in rubber, which is one of the key factors affecting the performance of rubber. Carbon black dispersion grades are generally divided into five grades according to ASTM D2663 standards:
1.Excellent dispersion: carbon black is evenly dispersed in rubber, there is no agglomeration, and there are no obvious black and white spots.
2.Good dispersion: carbon black is evenly dispersed in rubber, there is no serious agglomeration, only a small number of black and white spots.
3.Medium dispersion: carbon black is unevenly dispersed in rubber, with obvious agglomeration, and there are more black and white spots.
4.Poor dispersion: Carbon black is heavily agglomerated in rubber, unevenly dispersed, and has a large number of black and white spots.
5.Extremely dispersed: Carbon black is very agglomerated in rubber, almost not dispersed, with a lot of black and white spots.
2. Influencing factors of carbon black dispersion grade.
1.Characteristics of carbon black itself.
Characteristics such as fineness, specific surface area, viscosity and size distribution of carbon black affect the dispersion of carbon black. Generally speaking, the smaller the fineness and the larger the specific surface area, the better the dispersion of carbon black, but too small a carbon black particle size can lead to agglomeration and even clotting.
2.Rubber formulation.
The composition and quality of the rubber formulation can also affect the carbon black dispersion. For example, vulcanizing agents, processing oils, and vulcanization activity in rubber affect the interaction of carbon black with rubber and thus the dispersion of carbon black.
3.Rubber processing technology.
The rubber processing process also has a strong influence on the carbon black dispersion grade. When rubber is processed, the carbon black should be mixed with the rubber so that the carbon black is evenly dispersed in the rubber. If the temperature is too high or too long during the stirring process, it will cause the carbon black to agglomerate in the rubber, reducing the carbon black dispersion grade. Therefore, scientific and reasonable technological measures should be taken in rubber processing to improve the dispersion grade of carbon black.
3. The relationship between carbon black dispersion grade and rubber processing technology.
In rubber processing, the carbon black dispersion grade directly affects the performance and quality of rubber, and the following will introduce the relationship between carbon black dispersion grade and rubber processing technology from the aspects of rubber mixing, extrusion and molding.
1.Rubber compounding.
Compounding is the core process of rubber processing, which has a great impact on the dispersion grade of carbon black and the quality and performance of rubber products. During mixing, the temperature, time and shear force during the mixing process should be controlled to ensure that the carbon black is fully dispersed and the chemical reaction between the rubber and the carbon black occurs. Too short a mixing time or too high a temperature will promote the aggregation of carbon black, resulting in a decrease in the carbon black dispersion grade, which will affect the quality of rubber products.
2.Rubber extrusion.
In the rubber extrusion process, the dispersion grade of carbon black has an important impact on the extrusion performance, appearance quality and hardness of rubber. If the carbon black dispersion grade is high, the surface of the rubber after extrusion is smooth and free of bubbles, and the performance indicators such as hardness, tensile and tear strength are also betterOn the contrary, a low carbon black dispersion grade will produce surface defects such as bubbles and shrinkage holes, which will significantly reduce the performance indicators of rubber products.
3.Rubber molding.
Rubber molding is the final process of rubber processing, and compression molding is one of the most widely used molding methods. The dispersion grade of carbon black has a greater impact on compression molding, because a higher dispersion grade of carbon black can better fill the voids in the rubber, so that the density of the product is more uniform and the binding force is stronger. On the contrary, a lower dispersion grade of carbon black will lead to defects such as unsmooth surface, high hollowness, and low strength.
Fourth, summary. Carbon black dispersion grades play an important role in rubber processing and the production of rubber products. The dispersion grade of carbon black is affected by a variety of factors such as the characteristics of the carbon black itself, rubber formula and processing technology. Therefore, in the process of rubber processing, scientific and reasonable technological measures should be taken to make the carbon black dispersed evenly to improve the quality and performance of rubber products.