Application of black masterbatch in plastic products

Time:2021-08-24 11:31:47 / Popularity: / Source:

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

1. What materials are black masterbatch made of?

Materials that make up 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 my country. Mainly divided into two categories: rubber and non-rubber. Among carbon blacks for rubber, wear-resistant carbon blacks are mainly used, which can effectively improve abrasion resistance of rubber tires. Among carbon blacks for non-rubbers, there are only a few types of carbon blacks that can be used as black masterbatches. Channel carbon black is the most widely used in plastics, mainly due to its abundant source, high purity, and small particle size.

3. What is carbon black carrier?

Carrier is substance that carries carbon black. Generally, what raw materials are used in plastic products, and what raw materials are used in carrier. Black masterbatch manufactured in this way has better compatibility with plastic raw materials. Such as: PS (polystyrene) plastic products, black masterbatch carrier used is PS.
For polyethylene plastic products, carrier is polyethylene. However, LDPE (High Pressure Polyethylene) is generally selected because LDPE has the strongest carbon black carrying capacity and good processing performance. Other polyethylene HDPE and LLDPE can only produce low-concentration black masterbatch.
For PP (polypropylene) plastic products, only black masterbatches with PP and LDPE as carriers can be used, but black masterbatches with HDPE, LLDPE and other plastics as carriers cannot be used. Of course, there is also a black masterbatch with recycled materials as a carrier.

4. Why does carbon black need a wetting agent?

Specific gravity of carbon black is about 2g/cm. Due to small particle size of carbon black, apparent density is very small, and it appears fluffy and seems very light. For smooth processing, carbon black must first be wetted. Choice of wetting agent is very critical. In order to reduce costs, there are not a few companies that use a large amount of products such as white oil or paraffin, which will seriously affect strength of processed products.

5. What dispersants are used in carbon black masterbatch?

There are two types of 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, and calcium carbonate is commonly used. It can be judged from packaging of masterbatch that if there is only half a bag of 25 kg, inorganic dispersant must be used; full bag is black masterbatch with organic dispersant.
Use of inorganic dispersants can greatly reduce cost of black masterbatch, but fatal thing is that calcium carbonate has effect of accelerating aging of plastic products.

6. Does black masterbatch also need processing aids?

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

7. What are processing methods for black masterbatch?

There are three types: single screw method, twin screw method and internal mixing method. Single-screw method: After mixing materials with a mixer, they are pelletized by a single-screw extruder. Generally, carbon black concentration is 18-20%. Process is backward and environmental conditions of production site are poor. It is an eliminated process and cannot be ruled out. Some start-up small factories still use this method for processing.
Twin-screw method: After materials are mixed by a mixer, they are pelletized by a twin-screw extruder or water ring. Due to limited mixing capacity of twin-screw machine, masterbatch generally has a carbon black concentration of 25-32%. Internal mixing method: After mixing materials with a mixer, adding them to internal mixer for kneading, they are fed into twin-screw extruder from feeder, and pelletized by water ring or underwater. Masterbatch generally has a carbon black concentration of 40- 45%.

8. Does processing method affect performance of masterbatch?

Yes it is. Obviously, internal mixing method improves carrier's carrying capacity for carbon black, and at the same time, carbon black can enter carrier more uniformly. Taking advantage of mechanical kneading of internal mixer to crush agglomerated particles, agglomerated particle size of carbon black particles is greatly reduced. Particle size and distribution of carbon black in masterbatch are uniform, which cannot be replaced by the other two methods.

9. In what respects does black masterbatch have outstanding performance?

In dyeing of plastic products, black masterbatch only needs 0.6%-0.8%, it will be extremely black, and it will not be blacker if you add more.
According to test data, for products used outdoors in Xinjiang, if you need to rely on black masterbatch to prevent aging, you only need to use high-quality black masterbatch (not kind of carrier, white oil wetting, calcium carbonate dispersion, etc.) , content of carbon black in product reaches 2-2.5%, that is: every 100 kilograms of raw materials, there are 5-6 parts (weight) of 40% carbon black masterbatch, which far exceeds any anti-aging product, product life can reach more than 10 years.
This is why drip irrigation products, water delivery products, and communication cable products are all black. In addition, carbon black has a special contribution to increase of product strength and conductivity.

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

That's right. In actual production, about 2 parts of black masterbatch is generally used, anti-aging additives are added to use synergistic effect of anti-aging and carbon black to prevent aging, so as to reduce product costs.
In addition, length of outdoor use and product life requirements also determine appropriate reduction in amount of black masterbatch used. Premise is that carbon black must form a continuous phase in product, that is, there is a carbon black "film" to protect plastic.
If too little black masterbatch is added, carbon black phase (that is, part with high concentration of small chips) is not continuous in product. At boundary between phase and phase, plastic molecules are the most fragile and are directly hit by ultraviolet light, which accelerates oxygen aging reaction. When carbon black is like an impurity in product, it is better not to add it.

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