A brief introduction of tests

Quality Control Tests on Raw materials and Polyethylene Pipes

The raw materials of polyethylene pipe's manufacturing including polyethylene or masterbatch have been tested before using, and after confirmation, they have been applied in pipe's manufacturing:

1 -  The tests related to raw materials

  1 - 1 MFR Test

According to INSO 6980-1, polyethylene granules must be tested in 190 degrees Celsius and the weight of 5 kilograms. After filling the device with about 3-8 grams of materials, the materials are heated for about 5 minutes and the test starts. The device cuts automatically every 2 minutes. As the result of MFR test is reported in gr/10min, the weight of 5 cuts from the output of device indicates the value of MFR test. The allowed value in the standard of INSO 14427 has been reported between 0.15 – 0.7gr/10min, and there isn’t any distinction between the materials of PE80 and PE100. However, this value is desirable when it is between 0.15-0.23 for PE100 materials. 

 

  1 - 2 OIT Test

According to the national standard of 7186-6, polyethylene granule must be tested in 200 degrees Celsius with the purge of oxygen gas for 20 minutes. During this time, the polyethylene must not be at risk of thermal destruction and oxidation. Although the value of thermal stability has been reported equal to 20min, this test is performed in the laboratory of Resa Louleh Pasargad for more than one hour for getting more information about the quality of raw materials. 

  1 - 3 Density Test

The density of polyethylene granule is also tested according to the national standard of 7090-1, and the allowed value is more than 0.941 g/cm³ according to INSO 14427.

  1 - 4 Carbon black content test

If the raw materials are black, Carbon black content test is performed on the raw materials according to ISO 6964. In this test, 1gr of material is burned inside the furnace in 550 degrees and nitrogen gas environment with high purity in order to determine the percentage of black carbon. According to INSO 14427, the allowed value is between 2-2.5%. 

 

  1 - 5 Carbon black dispersion and distribution  test

Like 4.1 part, for black raw materials, the Carbon black dispersion is measured according to ISO 18553/INSO 20059. By providing some thin films of materials and examining them by a microscope, the carbon particles are measured and counted then the degree of dispersion is determined. According to the standard of INSO 14427/ISO 4427, the allowed value has been reported equal to 3 or less than it. 

  1 - 6 ESCR Test

This test must be done by the manufacturer of raw materials and mentioned in datasheet of raw materials. 

 

2 - The tests related to the polyethylene pipe

  2 - 1 MFR Test

 

According to INSO 6980-1, polyethylene pipes must be tested in 190 degrees Celsius and the weight of 5 kilograms. After filling the device with about 3-8 grams of materials (the pipe is being cut into cubic shapes), the materials are heated for 5 minutes and the test starts. The device cuts automatically every 2 minutes. As the result of MFR test is reported in g/10min, the weight of 5 cuts from the output of device indicates the value of MFR test. It is noteworthy that value of MFR of pipe must not be different from MFR value of raw materials more than 20%.

According to INSO 14427, for multilayer pipes, the MFR test must be performed in each layer separately, and the results of each layer must be recorded.

 

  2 - 2 OIT Test

According to INSO 7186-6, polyethylene pipes must be tested in 200 degrees Celsius with the purge of oxygen gas for 20 minutes. During this time, the pipe must not be at risk of thermal destruction and oxidation.

According to INSO 14427, for multilayer pipes, the OIT test must be performed in each layer separately, and the results of each layer must be recorded.

  2 - 3 Density Test 

The density of polyethylene pipe is also tested according to INSO 7090-1, and the allowed value is more than 0.941gr/cm³ according to the standard of INSO 14427.

 

  2 - 4 Carbon black content test

The allowed amount of carbon black in polyethylene pipes is between 2-2.5% according to INSO 14427/ISO 4427. This test is done similar to the method in part 1.4. Now, as the natural materials are being used in Iran and due to use of masterbatch for providing carbon black in the pipes, this value is more dependent on full mixing of materials by masterbach.

 

  2 - 5 Carbon black dispersion and distribution test

The Carbon black dispersion is measured according to ISO 18553/INSO 20059. By providing thin films from six different points of the pipe and examining them by a microscope, the carbon particles are measured and counted then the degree of dispersion is determined. According to INSO 14427/ISO 4427, the allowed value has been reported equal to 3 or less than it. 

 

  2 - 6 Tensile Test

To do a tensile test according ISO 6259/INSO17140, the samples are cut depending on the thickness by CNC device.

The pipes with the thickness of 5 mm, more than 5 mm, and the samples with the thickness of more than 12mm are called Type 2, Type 1, and Type 3, respectively.

After putting the samples in two jaws of tension device, they are stretched at a specified speed. According to ISO 4427/INSO 14427, the value of excessive length before the sample's rupture must be more than 350%. 

  2 - 7 Hydrostatic Pressure test

 

According to ISO 1167/INSO 12181, polyethylene pipes must undergo a specified pressure during a specified time and a determined temperature. This test is performed in three ways: 100 hours in the temperature of 20 degree, 165 hours in the temperature of 80 degree, and 1000 hours in the temperature of 20 degree. and the applied pressure is calculated for each specified pipe according to following formula:

 

 

e_min: minimum thickness

 

dem: pipe's diameter

 

σ: value of tension

 

Tension amounts in MPa

 

The kind of pipe	100 hours in 20degree	165 hours in 80degree	1000hours in 80degree
PE100	12.4	5.5	5
PE80	9	4.6	4
PE63	8	3.5	3.2

 

  2 - 8 Heat reversion test

According to ISO 2505/INSO 17614, a pipe with 20cm length is selected, and 10cm in its length is marked from two ends of the pipe by observing the equal distance. The pipe is put in an oven under a temperature of 110degree, and after one or two hours (depending on the thickness of pipe), it is brought out from the oven to become cold. After the pipe is cooled, the length change must not be more than 3%.

 

  2 - 9 Structural Integration test

According to the standard of INSO 14427, a structural integration test must be done on the pipes with co-extruded layers after a bending (ISO 13968).