In the molding of plastic products, black masterbatch has been used by almost everyone, for dyeing, anti-aging, conductive products and so on. However, various problems often arise during use, which bothers us. Today, Xiaobian will discuss some issues that everyone cares about, and hope to bring you benefits.
1. What is the composition of the black masterbatch?
The materials constituting the black masterbatch are: A. carbon black; B. carbon black carrier; C. carbon black wetting agent; D. carbon black dispersing agent;
Figure black masterbatch
2. What kind of carbon black is used for black masterbatch?
According to the international classification, there are more than 30 varieties in China. Mainly divided into two categories of rubber and non-rubber. In the carbon black for rubber, it is mainly wear-resistant carbon black , which can effectively improve the wear resistance of the rubber tire; in the non-rubber carbon black, there are only a few kinds of carbon black which can be used as the black masterbatch.
The grooved carbon black is most widely used in plastics, mainly due to its abundant source, high purity and small particle size. Among them, it is divided into high pigment carbon black (particle size 9-17mm), medium pigment carbon black (particle size 18-25mm) and low pigment carbon black (particle size 26-37mm) .
Prices vary widely due to different carbon black varieties. Carbon black particles are rarely present in primary particles due to their inherently active nature, and almost all have agglomerated particles in a certain range of particle sizes.
3. What is the carbon black carrier?
The carrier is a substance that carries carbon black. What kind of raw materials are used for general plastic products, and what raw materials are used for the carrier. The black masterbatch thus produced has good compatibility with the plastic raw material. For example, PS (polystyrene) plastic products, the black masterbatch carrier used is PS. For polyethylene plastic products, the carrier is polyethylene.
However, LDPE (high pressure polyethylene) is generally used because LDPE has the strongest ability to carry carbon black and has good processing performance. Other polyethylene HDPE and LLDPE can only produce low concentration black masterbatch. For PP (polypropylene) plastic products, only black masterbatch with PP and LDPE as the carrier can be used, but black masterbatch with HDPE and LLDPE and other plastics as the carrier cannot be used. Of course, the black masterbatch which uses the recycled material as a carrier is also used.
4. Why does carbon black require a wetting agent?
The carbon black has a specific gravity of about 2 g/cm. Since the carbon black has a small particle size, the density of expression is small and appears fluffy and seems to be very light. To process smoothly, the carbon black must be wetted first. The choice of wetting agent is critical. In order to reduce costs, there are not many enterprises that use a large amount of products such as white oil or paraffin, which seriously affects the strength of processed products.
5. Which dispersants will be used in the carbon black masterbatch?
Mainly divided into two types of organic dispersants and inorganic dispersants . The high-grade black masterbatch uses an organic dispersant, which is mainly used for the use of plastic products with high environmental requirements, such as drip irrigation products. The low-grade black masterbatch uses an inorganic dispersant, usually calcium carbonate.
It can be judged from the masterbatch packaging that 25 kg of only half a bag is definitely an inorganic dispersant; full bag is a black masterbatch using an organic dispersant. The use of inorganic dispersants can greatly reduce the cost of black masterbatch, but it is fatal that calcium carbonate has the effect of accelerating the aging of plastic products.
6. Does the black masterbatch require processing aids?
Of course you need it. Smooth processing requires the selection of the right antioxidants, internal lubricants, external lubricants, modifiers and antistatic agents.
7. What are the processing methods for black masterbatch?
There are three methods of processing: single screw method, twin screw method and dense love method .
Single-screw method : After mixing materials with a mixer, the granules are granulated by a single-screw extruder. The concentration of carbon black is generally 18-20%, the process is backward, and the environmental conditions at the production site are poor. Some small starters still use this method to process.
Twin-screw method : After mixing materials with a mixer, it is granulated by a twin-screw extruder or a water ring. Due to the limited mixing capacity of the twin-screw machine, the masterbatch generally has a carbon black concentration of 25-32%.
Mixing method : After mixing the materials with a mixer, kneading by adding an internal mixer, feeding the twin-screw extruder by a feeder, and cutting the pellets by water ring or underwater, the masterbatch generally has a carbon black concentration of 40- 45%.
8. Does the processing method have an effect on masterbatch performance?
Definitely. Among them, the dense method can improve the bearing capacity of the carrier to carbon black, and the carbon black can enter the carrier more uniformly. The mechanical kneading advantage of the internal mixer is utilized to break up the agglomerated particles, so that the agglomeration particle size of the carbon black particles is greatly reduced, and the particle size and distribution of the carbon black in the master batch are uniform, which cannot be replaced by the other two methods.
9. In what ways does the black masterbatch have outstanding performance?
In the dyeing of plastic products, the black masterbatch only needs 0.6%-0.8%, it will be very dark, and it will not be darker when added. According to the test data, if the products used outdoors in Xinjiang area need to rely on black masterbatch to prevent aging, as long as the use of high-quality black masterbatch (rather than returning material as carrier, white oil wetting, calcium carbonate dispersion, etc.) ).
The carbon black content in the product reaches 2-2.5%, that is, 5-6 parts by weight of the carbonaceous black containing 40% of the masterbatch per 100 kg of raw material, which plays a far greater role than any anti-aging product. Product life can reach more than 10 years.
This is why drip products, water products, and communication cable products are all black. In addition, carbon black has a special contribution to the strength of the product and the enhancement of conductivity.
Figure black masterbatch applied to pipe
10. It seems that there are not so many parts of black masterbatch used in actual production?
That's right. In actual production, about 2 parts of black masterbatch are generally used, and anti-aging additives are added to prevent aging by anti-aging and carbon black synergy to reduce product cost. In addition, the length of use in the outdoor, product life requirements, also determines the appropriate use of black masterbatch, provided that carbon black must form a continuous phase in the product, that is, there is a carbon black "film" to protect the plastic.
If too little black masterbatch is added, the carbon black phase (ie, the part with high concentration of the small piece) is discontinuous in the product. At the boundary between the phase and the phase, the plastic molecules are the most vulnerable, and are directly hit by ultraviolet light to accelerate the oxygen aging reaction. When carbon black is like impurities in the product, it is better not to add it. When the boundary between the phase and the phase is less than 280mm, the ultraviolet light can be avoided and the product is safe.
11. How to judge the quality of the black masterbatch from its appearance?
Good quality black masterbatch with mild luster and moderate hardness. If the oil is too bright, it means that the oil is too much, and the gloss is bleak, indicating that the carrier is a return material or an excess of calcium carbonate. A good quality black masterbatch is bitten with teeth and is soft and brittle.
Too soft indicates that the organic dispersant is too much, soft and loose, indicating that the carbon black concentration is low, and the calcium carbonate is more, the brittleness indicates that the carbon black content is too high, or the carrier is the return material.
12. What happens to the surface of the product after using the black masterbatch?
If the pockmark is a small pointed tip, indicating that the product processing equipment has limited ability to disperse the masterbatch, the carbon black agglomerated particles in the masterbatch cannot be sheared evenly, and the black masterbatch with a lower concentration should be used; or the masterbatch has too much carbonic acid. Calcium and excessive white oil are extruded by high-pressure single-screw and twin-screw machines to form small stiff blocks that cannot be dispersed. If the pockmark is concave, it is caused by the volatilization of small molecules in the masterbatch, indicating that there is more white oil.
13. Can the black masterbatch containing calcium carbonate be used?
To be comprehensive. First of all, if the calcium carbonate has a fineness of 1000 mesh and a content of less than 10% in the black masterbatch, it is a good choice for products that are not required for outdoor exposure, and the price is low. The appearance of the product is good, the carbon black is uniformly dispersed during processing, the blackness is not affected, and the influence on the product strength is small.
If the fineness of the calcium carbonate is less than 1000 mesh, the gloss may be dim, the surface may be rough, and the strength of the product may be lowered. If the amount of 1000-million calcium carbonate exceeds 10%, the surface of the product is dull and gray, and the blackness is insufficient, and the strength of the product is lowered.
Secondly, in any outdoor products with anti-aging requirements, it is not good to contain calcium carbonate, depending on the service life of the product.
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