Carbon black surface area definition - Database & Sql Blog Articles

Carbon black is a fine particulate material formed during the incomplete combustion of carbon-based fuels such as coal, petroleum, and biomass. Once released into the atmosphere, it absorbs sunlight, reducing the amount of solar radiation that reaches the Earth's surface. It is a black, powdery substance resulting from the partial combustion or pyrolysis of hydrocarbons under controlled conditions. Its primary composition is elemental carbon, with small amounts of oxygen, hydrogen, and sulfur. The particles are generally spherical, ranging in size from 10 to 500 micrometers. Many of them tend to aggregate, forming three-dimensional structures that resemble bonds or fibers. In the rubber industry, carbon black is used as a reinforcing agent and filler, enhancing the mechanical properties of the material. It is one of the oldest industrial products, widely used in rubber, paint, and ink manufacturing. One of the key characteristics of carbon black is its surface area, which plays a critical role in identifying and classifying different types of carbon black. Surface area is typically measured using gas-phase or liquid-phase adsorption techniques. The most common method is the low-temperature nitrogen adsorption (BET) method, which measures the total surface area of the carbon black, including both the external and internal surfaces. This method is highly accurate because nitrogen molecules can penetrate even the smallest pores within the carbon black structure. In recent years, macromolecular adsorption methods like CTAB (Cetyl Trimethyl Ammonium Bromide) have been introduced. These methods measure only the external surface area since CTAB molecules are too large to enter the micropores. For most carbon blacks used in rubber applications, where the polymer molecules are too large to enter the pores, the external surface area is more relevant for evaluating performance. The iodine absorption method is another commonly used technique in production control and product classification due to its simplicity and speed. However, it is sensitive to the oxidation level of the carbon black surface, which can affect the results. The BET method determines the total specific surface area (NSA), which includes both the external surface area (STSA) and the internal surface area from micropores. These micropores typically range in diameter from 2 to 50 nm. For carbon black used in rubber reinforcement, the external surface area is more important because the rubber molecules cannot access the internal micropores. The CTAB method, introduced in 1971, was designed to measure the external surface area by adsorbing CTAB onto the carbon black surface. Since CTAB molecules are larger (about 61.6 Å), they cannot enter the micropores, so this method provides an estimate of the accessible external surface. However, for some carbon blacks with larger or medium-sized pores (20–500 Å), CTAB may be able to enter, making this method less reliable for certain applications. To address these limitations, the t-method was developed by J.H. de Boer in 1965. This method calculates the external surface area based on the statistical thickness of the adsorbed layer of nitrogen. It involves plotting the relationship between the adsorption layer thickness and the volume of nitrogen adsorbed, then calculating the external surface area from this curve. Testing the external surface area of carbon black should follow established standards. In China, the GB/T 10722-2003 standard outlines the nitrogen adsorption method for determining both the total and external surface areas. This standard ensures consistency and accuracy in testing procedures. Modern instruments, such as the Jingbo Gaobo dual-site external surface measuring device, are designed to meet these standards. They can accurately measure both the total and external surface areas of carbon black, with a test repeatability of 1.5%, making them ideal for use in the carbon black industry.

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