The synergistic effect of carbon black plus talc can improve all aspects of rubber performance

 Reinforcing filler is one of the main raw materials of rubber industry.
The reinforcing agents used in the rubber industry are mainly carbon black, white carbon black, silicates, carbonates, metal oxides and certain organic substances. Their main role is to significantly improve the rubber's tensile strength, tear strength, fixed tensile stress, wear resistance and other properties.
The fillers used in the rubber industry are mainly inorganic fillers, such as talc, clay, calcium carbonate, attapulgite, metal oxides and hydroxides. It can play the role of increasing volume, reducing cost and improving rubber processing performance.
1. Carbon black reinforcing agent
Carbon black is made of hydrocarbon compounds by incomplete combustion or thermal cracking. It is mainly composed of carbon elements and exists in the form of sphere-like colloidal primary particles and aggregates. Its appearance is black powder. Generally processed into granular products with a diameter of 1~2mm.

Carbon black is the most important reinforcing agent in the rubber industry and the second largest rubber material after raw rubber. At present, more than 90% of carbon black consumption worldwide is used in the rubber industry. The degree of dispersion of carbon black in the compound affects its reinforcing properties. Experiments show that with the increase of carbon black dispersion rate, the constant tensile stress and Mooney viscosity of the compound decrease, the tensile strength and elongation at break increase, and the crack growth slows down. Therefore, improving the degree of dispersion of carbon black in the rubber compound is the key to ensuring a uniform rubber compound texture and excellent product performance.
2. Talc powder filler
Talc is a natural flaky mineral. Pure talc powder is a hydrous magnesium silicate composed of a brucite sheet sandwiched between two silicon dioxide sheets, and has a flaky shape.

Talc powder as a filler filled with organic polymer materials can improve the rigidity, dimensional stability and lubricity of products, prevent high temperature creep, reduce wear on molding machinery, and enable polymers to increase hardness and creep resistance through filling. At the same time, the thermal shock resistance of the polymer can also be improved, which can improve the plastic shrinkage rate, the bending modulus of elasticity and the tensile yield strength of the product.
3. Talc powder + carbon black synergy
The use of talc in carbon black reinforced rubber compounds can improve the properties of the rubber compounds and improve the quality of the products. The effect of talc powder + carbon black on the rubber compound is shown as the following 6 points:
（1）Rheological properties
The addition of talc to the carbon black compound results in a reduction in the viscosity of the compound, which in turn improves the in-mold fluidity and reduces the amount of extrudate shrinkage, which is beneficial to improve calendering performance and reduce heat generation.
（2）Reinforcement
Talc is not just a filler, it is also a reinforcing agent. Experiments have shown that the addition of talc to many carbon black elastomer compounds can increase the elongation at break of the elastomer due to talc.
（3）Cut/tear resistance
Cutting a tensile sample with a blade shows that talc powder greatly improves the toughness and durability of the elastomer. At relatively low elongation (<100%), the carbon black reinforced specimens will be completely broken, while the talc reinforced specimens can continue to stretch.
（4）Low air permeability
Talc powder can reduce the permeability of carbon black compound, because the flaky shape can hinder the diffusion of gas and liquid. It is currently used in tire innerliners to reduce air permeability.
(5) Weather resistance
Talc powder can reduce the volatilization of plasticizer of carbon black compound, thus giving excellent thermal stability and weather resistance, thus prolonging the service life of products. It can limit the migration of by-products to the surface, reduce its iridescent frost and yellowing, and improve the gray level of the car window seal.
（6）Dispersing aid
Talc is a dispersing aid for carbon black reinforcing tire tread compounds. It can improve the dispersibility of carbon black and other compounding agents and shorten the mixing time by 20%. In order to maintain the wear/abrasion resistance of the compound, the amount of talc powder should be limited to 5 parts
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