Carbon black
Carbon black
An amorphous carbon. Light, loose and very fine black powder, the specific surface area is very large, ranging from 10-3000m2 / g (measured using the automatic F-Sorb 2400 specific surface area tester BET method), is organic matter (natural gas, heavy oil, fuel oil, etc.) Products obtained by incomplete combustion or thermal decomposition under insufficient air conditions. Specific gravity 1.8-2.1 "Gas black" made from natural gas, "lamp black" made from oil, and "acetylene black" made from acetylene. In addition, there are "slot black" and "furnace black". According to the performance of carbon black, there are "reinforcing carbon black", "conductive carbon black", "wear-resistant carbon black" and so on. It can be used as a black dye, used to make Chinese ink, ink, paint, etc., and also used as a reinforcing agent for rubber. It is very important to study the specific surface area of ​​carbon black. Only the results of the BET method can be used to detect the specific surface area data of carbon black. There are many domestic instruments that can only be tested by the direct comparison method. . At present, the multi-point BET method is used uniformly for the specific surface area testing at home and abroad. The specific surface area measurement standards developed at home and abroad are based on the BET test method. Please refer to China's national standard (GB / T 19587-2004)-Gas adsorption BET principle Method for determining the specific surface area of ​​solid materials. The measurement of specific surface area is actually a time-consuming task. Due to the different adsorption capacity of the sample, the test of some samples may take a whole day. If the test process is not fully automated, then the tester ca n’t leave at all times. A high degree of concentration, observing the instrument panel, manipulating the knob, and a little inattention will lead to the failure of the test process, which will waste a lot of precious time of the tester. Only truly fully automated intelligent specific surface area tester products can meet the international standards of the test instrument industry. All similar international products are fully automated. Manually operated instruments have long been eliminated abroad. A truly fully automated intelligent specific surface area analyzer product frees testers from repeated mechanical operations, greatly reducing their work intensity, training is simple, and working efficiency is improved. The truly fully automated intelligent specific surface area analyzer product greatly reduces errors caused by human operations and improves test accuracy. Among several domestic manufacturers of specific surface area analyzers, only the F-Sorb 2400 specific surface area analyzer of Beijing Jinyi Spectrum Technology Co., Ltd. is an instrument that can truly realize the detection function of the BET method (both with direct comparison method), and the more important Beijing Gold F-Sorb 2400 specific surface area analyzer is the only fully automated and intelligent specific surface area detection equipment in China. Its test results are highly consistent with international standards, and its stability is also very good. At the same time, it reduces human errors. Improve the accuracy of test results. Detailed information on specific standards can be found on the relevant website
Pigment carbon black characteristics and application relationship •
1. Blackness and particle size Blackness is directly related to the particle size of carbon black. The smaller the particle size, the larger the specific surface area and the higher the blackness of carbon black. This is because although the primary particles have been fused into primary aggregates, their specific surface still works. If the primary particles are fine, the specific surface area of ​​the aggregates is larger. The displayed color is darker and has better UV protection. Since the fine particle carbon black has a higher light absorption rate than the coarse particle carbon black, the coloring power is stronger. However, when the particle diameter decreases, blue light is preferentially absorbed, so the hue becomes a brown phase.
The fine primary particles give carbon black a larger specific surface area, while increasing the difficulty of dispersion. Generally, surface treatment can adjust wettability and improve dispersion.
Carbon black particle size specific surface area and performance relationship performance high specific surface area small particle size low specific surface area large particle size performance high specific surface area small particle size low specific surface area large particle size main color blackness deeper and lighter coloring higher lower viscosity Higher and lower conductivity, higher and lower UV absorption, better and worse dispersion, more difficult, easier to wet, slower, faster, higher cost, lower
2. The structured carbon black particles not only exist in the form of primary particles, but also sinter into agglomerates during production. This aggregate is composed of primary particles through chemical bonding. In the process of coagulation, carbon black composed of a large number of branched primary aggregates is called high-structure carbon black. The carbon black composed of primary aggregates with fewer chain branches is called low-structure carbon black.
The structure of high-structure low-structure carbon black is the form of carbon black aggregates. In general, the more chain branches, the denser the structure is, the higher the structure is.
The effect of carbon black structure on performance performance high structure low structure performance high structure low structure dispersion is easier and harder conductivity higher and lower wetting slower and faster viscosity higher and lower main color blackness lower higher filling amount Higher gloss, lower higher tinting power, lower and higher
3. The production method of surface chemical carbon black is different, and its surface chemical properties are different. The surface of carbon black has different oxygen-containing functional groups (such as carboxyl group, lactone group, phenol group, carbonyl group, etc.). Generally, carbon black with high oxygen-containing functional groups has high volatile content, good color tone adjustability, and high fluidity. After the carbon black sample is heated to 825 ± 25oC, the carbon black volatile content is expressed as a percent weight loss. The more carbon black oxygen-containing genes, the greater the volatile content.
4. Hygroscopicity and density Carbon black is a substance with a large surface area, so it has certain hygroscopicity. The moisture absorption of medium carbon black is mainly determined by the surface area. Measures can be strengthened, especially during packaging, storage and transportation to reduce the hygroscopicity of the product. Because high moisture (hygroscopicity) will cause troubles in the processing process, it is required to have special packaging for certain varieties of carbon black.
Powdered pigmented carbon black or granular pigmented carbon black used in a given plastic blend depends on the type of dispersion and the characteristics of the resin, but the processing ability is also an important factor. Most current dispersion equipment can exert shear force , Enough to disperse the particles evenly.
• Application of carbon black in the plastic industry •
Prior to selection, its use must be determined, for example for coloring, UV protection, or electrical conductivity.
1. Carbon black for coloring Carbon black generally can better color plastics. Pigment carbon black can be selected according to coloring characteristics or physical and chemical properties. The choice of coloring carbon black is basically based on the blackness that the finished product must achieve set. Use extremely fine pigmented carbon black to achieve particularly high-level coloration; PE garbage bags, plastic bags, cable materials and other products only need a medium-level blackness, and can use carbon black varieties with low specific surface area and high structure ; When plastics are toned, small errors in carbon black weighing and batching will result in obvious color difference. Therefore, low-pigment carbon black with larger particle size and poor coloring power should be used, so that the amount of carbon black can be slightly Large, the weighing error is relatively small, and has the advantages of better dispersion and lower price.
For gray plastics, the use of fine-grained carbon black tends to appear brownish gray, while the use of coarse-grained pigmented carbon black produces a blueish gray.
Compared with other organic pigments, carbon black has better performance in addition to its difficulty in dispersion. The scientific blending amount of carbon black can provide better antistatic or electrical conductivity.
Carbon black is basically non-toxic, but it is relatively easy to fly and pollute, so it is often used in the form of masterbatch for the plastics industry, which eliminates pollution and improves the dispersion of carbon black in plastics.
Carbon black is used as a pigment for plastics. The commonly used dosage forms are powder and granular. Granular carbon black is less flying, but it is more difficult to disperse, so powder carbon black is used in plastic coloring.
Second, the application of ultraviolet protection One of the uses of carbon black in the plastics industry is to prevent ultraviolet aging. Because carbon black has high absorbency, it can effectively prevent the plastic from being oxidized and degraded by sunlight. The role of carbon black as an ultraviolet light stabilizer in plastics is: converting light energy into heat energy; protecting the plastic surface from radiation of a certain wavelength; intercepting atomic groups to produce an anti-aging effect, thereby preventing catalytic degradation. Ultraviolet rays are particularly harmful to polyolefins. Tests have shown that when the concentration of carbon black with a certain fineness is 2%, perfect ultraviolet shielding can be achieved.
The protective effect of carbon black on the ultraviolet aging of plastics depends on the particle size, structure and surface chemistry of carbon black.
When the particle size of carbon black is small, because of the increased surface area, its ability to absorb light or block light is increased, so the UV protection is enhanced, but the particle size is less than 20nm, and its protection tends to the same level, because the particle size is too small Scattering is reduced, and the light going forward threatens the stability of the polymer.
The structure is lower, that is, when the aggregate size is smaller, the geometric volume of the aggregate is smaller, which will enhance the protection of the polymer. This is also the reason why the carbon black with a lower structure is darker.
The surface of carbon black contains more oxygen groups, that is, when the volatile content is higher, it can eliminate the genes generated when the polymer is decomposed, so the protective effect is also enhanced.
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