In the molding and processing of plastic products, almost everyone has used black masterbatch for dyeing, anti-aging and conductive products. Many problems in use often perplex us.

1. What materials are black masterbatch made of?

The materials of black masterbatch are: A. carbon black; B. Carbon black carrier; C. Carbon black wetting agent; D. Carbon black dispersant; E. Other processing aids.

2. Please introduce carbon black for black masterbatch.

According to international classification, there are more than 30 varieties in China. It is mainly divided into rubber and non rubber. Wear resistant carbon black is mainly used in rubber carbon black, which can effectively improve the wear resistance of rubber tires; Among the non rubber carbon black, there are only several kinds of carbon black that can be used as black masterbatch. Trough carbon black is the most widely used in plastics, mainly due to its rich source, high purity and small particle size.

3. What's the matter with carbon black carrier?

Carrier is the material carrying carbon black. General plastic products use what raw materials, the carrier uses what raw materials. The black masterbatch produced in this way has good compatibility with plastic raw materials. 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 selected, because LDPE has the strongest carbon black bearing capacity and good processing performance. Other polyethylene HDPE and LLDPE can only produce low concentration black masterbatch. For PP (polypropylene) plastic products, only the black masterbatch with PP and LDPE as the carrier can be used, but the black masterbatch with HDPE, LLDPE and other plastics as the carrier cannot be used. Of course, there are also black masterbatches with recycled materials as carriers.

4. Why does carbon black need wetting agent?

The specific gravity of carbon black is about 2G / cm. Due to the small particle size of carbon black, the apparent density is very small, which appears fluffy and light. In order to process smoothly, the carbon black must be wetted first. The choice of wetting agent is very important. In order to reduce costs, many enterprises use white oil or paraffin products, which will seriously affect the strength of processed products.

5. What dispersants are used for carbon black masterbatch?

It is divided into organic dispersant and inorganic dispersant. High grade black masterbatch uses organic dispersant, which is mainly used for plastic products with high environmental requirements. Low grade black masterbatch uses inorganic dispersant, commonly calcium carbonate. Judging from the masterbatch packaging, only half a bag of 25kg must use inorganic dispersant; The organic dispersant bag is full of black. The use of inorganic dispersant can greatly reduce the cost of black masterbatch, but the fatal thing is that calcium carbonate can accelerate the aging of plastic products.

6. Does black masterbatch also need processing aids?

Of course. A smooth processing process requires the correct selection of antioxidants, internal lubricants, external lubricants, modifiers and antistatic agents.

7. What are the processing methods of black masterbatch?

There are three methods: single screw method, twin screw method and internal mixing method. Single screw method: after mixing the materials with a mixer, the materials are pulled and granulated by a single screw extruder. Generally, the carbon black concentration is 18-20%. The process is backward and the environmental conditions on the production site are poor. It is an obsolete process. It is not ruled out that some small factories that have just started still use this method for processing.

Twin screw method: after mixing the materials with a mixer, the materials will be pulled by a twin-screw extruder or granulated by water ring. Due to the limited mixing capacity of the twin-screw machine, the carbon black concentration of the masterbatch is generally 25-32%. Internal mixing method: after mixing the materials with the mixer, add them to the internal mixer for kneading, and then feed them into the twin-screw extruder by the feeder. After water ring or underwater granulation, the masterbatch generally has a carbon black concentration of 40-45%.

8. Does the processing method affect the properties of masterbatch?

yes. Obviously, the internal mixing method improves the bearing capacity of the carrier to carbon black, and the carbon black can enter the carrier more evenly. Giving full play to the mechanical kneading advantages of internal mixer, crushing the agglomerated particles, greatly reducing the agglomerated particle size of carbon black particles, and the carbon black particle size and its distribution in masterbatch are uniform, which can not be replaced by the other two methods.

9. What are the outstanding aspects of black masterbatch?

In the dyeing of plastic products, the black masterbatch only needs 0.6% - 0.8%, which will be extremely black, and it will not be darker if it is added more.

According to the test data, if the products used outdoors in Xinjiang need to rely on black masterbatch for anti-aging, as long as the high-quality black masterbatch (instead of the kind of recycled material as carrier, white oil wetting, calcium carbonate dispersion, etc.) is used, the content of carbon black in the products reaches 2-2.5%, that is, 5-6 parts (by weight) of masterbatch containing 40% carbon black per 100kg of raw materials, which plays a far more important role than any anti-aging products, The service life of the product can reach more than 10 years. This is why drip irrigation products, water delivery products and communication cable products are black. In addition, carbon black has a special contribution to the strength and conductivity of products.

10. It seems that so many copies of black masterbatch are not used in actual production?

you 're right. In actual production, about 2 parts of black masterbatch are generally used, and then anti-aging additives are added. The synergistic effect of anti-aging and carbon black is used to prevent aging, so as to reduce the product cost. In addition, the length of outdoor use and the requirements of product life also determine that the use amount of black masterbatch should be appropriately reduced, on the premise 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 (i.e. the part with high concentration of small pieces) is discontinuous in the product. At the boundary between the phases, the plastic molecules are the most vulnerable. They are directly hit by ultraviolet light and accelerate the oxygen aging reaction. At this time, carbon black is like an impurity in the product, so it's better not to add it.