what is Soot percentage test?

First, we will discuss how to measure soot in polyethylene pipes and fittings based on the ISO 6964 standard and the equipment needed to test the percentage of pipes. We also talk about soot and carbon black, which is present in polyethylene pipes and fittings and is very important. In the quality control of polyethylene pipes and fittings, testing and measuring the percentage of soot is one of the most important tests. It should be noted that performing this test requires high precision of the technician or operator. We recommend that if you are involved in the production of plastic products, click to buy مستربچ رنگی in different colors.

The reason for using carbon black in the production of polyethylene pipes and fittings

Polyethylene pipes usually spend a lot of time in the open air before being installed in the production unit and in the workplace. Also, many of these pipes are exposed to sunlight for a long time.

Ultraviolet uv rays that are present in the sunlight in a long period of time cause polyethylene chains to break and produce free radicals. The produced free radicals cause the development of destruction and with the passage of time, the flexibility and resistance of polyethylene pipes is lost.

In order to solve this problem, UV stabilizers are used. Carbon black or carbon black can be called as the best and cheapest UV stabilizer. The right amount of carbon black, which is usually 2 to 2.5% by mass, and its proper distribution in the pipe will provide long-term protection of the pipe against UV rays.

In order to declare the duration of resistance of the pipe against UV rays, it is necessary to conduct tests on the pipe. (You might be interested to learn more about Masterbatch Anti-UV.) Because according to some sources, if the amount of soot and its distribution is done according to the standards, the pipe will be resistant to UV rays for 50 years. According to some, in this condition, the pipe can be used for a maximum of two years. Therefore, it is not possible to recognize this issue only by relying on the percentage and dispersion of soot.

Therefore, it is necessary to add anti-ultraviolet materials to the composition of the raw materials of products that are exposed to sunlight in the warehouse or workplace (such as polyethylene joints). Soot has the property of absorbing ultraviolet rays. For this reason, in such cases, it is a suitable option for this work.

Reasons for using carbon black in polyethylene pipes

Carbon black is used in polyethylene pipes for the following reasons:

• Having the property of absorbing ultraviolet rays and protecting polyethylene against weathering
• Having an affordable price
• Convenient and easy measurement of soot amount
• Pipe coloring

Keep in mind that the low amount of carbon black in the final product will cause low resistance of the product against ultraviolet rays, and the excessive amount of carbon black in the product will increase the viscosity and thus reduce the processability of the final mixture. The right amount and the size of the soot will have a significant effect on the protection of the polymer against ultraviolet rays.

Note that the chemical structure of soot particles is very specific, which is why they tend to stick together. Therefore, their composition and mixing should be such that in addition to the particles being crushed and small, they also have a proper distribution in polyethylene. So, in addition to the appropriate amount of carbon black, this item will also complement the appropriate and desirable effectiveness in protecting the polymer.

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What standard is used for the soot percentage test?

The national standard 1990 and ISO 6964 is the basis for testing the percentage of soot in polyethylene pipes and fittings.

Necessary equipment for soot percentage test

The necessary equipment in the common method used to test and calculate the soot percentage are:

• Tubular electric furnace
• Silica gel used for drying nitrogen
• Dry nitrogen capsule including pyrogallol solution to purify it from oxygen
• Silica boat to keep the sample inside the oven
• Scale with accuracy of 0.001 (4 digits)
• desiccator

How to do the soot percentage test

To perform the test to determine the percentage of soot, first, the boat should be placed in the furnace at a temperature of 900 degrees for one hour. Then it is taken out and placed in a desiccator to cool completely. If needed and to keep the mass of the boat, it can be put in the oven again for 30 minutes. After the boat is cooled, record its weight.

At this stage, take a small amount of about one gram of the crushed pipe and record it accurately.

At this stage, the furnace must have a temperature of 550 degrees, so adjust it and put the boat and the sample in the beginning of the entrance of the furnace tube. Now it is necessary to connect the flow of nitrogen with a flow rate of 200 cubic centimeters per minute to the furnace for 5 minutes. So connect it and keep this position for 5 minutes.

After 5 minutes, the boat should be moved to the center of the furnace and the nitrogen flow should be halved; It means it should be set to 100 degrees. It takes 45 minutes to perform pyrolysis. So you have to wait 45 minutes at this stage.

After this time, the boat should be returned to the beginning of the mountain and placed under nitrogen gas with a flow rate of 100 for 10 minutes.

After 10 minutes, the boat should be removed and placed in a desiccator to cool. After the cooling phase, it is necessary to record its weight.

At this stage, the polymer in the sample is completely burned in the furnace, and the total of filler and soot remains. Now it is necessary to burn the soot to obtain the weight of the filler. The amount of soot is obtained from the difference between the two.

Now, at this stage, the oven should be placed at a temperature of 900 degrees and the cooled boat should be transferred to the oven. After the time passed when the soot was completely burned, so that there was no more soot, i.e. the black color of the soot was no longer visible, the boat is transferred to the desiccator and after it cools down, its weight is recorded. . Under these conditions, you will be able to determine the percentage of smoke.

After going through the above steps and completing the soot percentage test, you will be able to calculate the amount of smoke using the following formula:

It is necessary to repeat the test of the soot percentage of pipes and polyethylene fittings on 3 samples so that its average is determined and announced. Usually, the standard amount of soot percentage in most polyethylene pipes and fittings is something between 2-2.5 or 2-3%.

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