Melt Flow Rate according to the Standard INSO 6980-1,2
Melt Flow Rate (MFR) is a measure of the viscosity of a thermoplastic polymer in a specific temperature and pressure which is a function of the polymer’s molecular weight. Specifically stated, the amount of a thermoplastic polymer in grams which under the impact of a particular weight in a specific temperature passes through a die in 10 minutes time is called the melt flow rate of that polymer (gr/10 min). Using the results of this test, the behavior of materials inside an extruder is contemplated.
This test is carried out for raw materials and final products.
The amount of additives and fillers highly affects the melt flow index (MFI) of the materials. This test is carried out to analyze and use further information such as the following:
By measuring the MFI of materials and products and studying their differences, we can find out the burns rate of materials, the effect of the additives such as the effect of the masterbatch added to the colorless base materials, the destruction rate of materials by using non-oxidation methods, etc.
By observing the apparent surface of the production line in this machine, we can find out the rate of volatiles as well as the rate of other materials examined.
Carbon Black Content according to the Standard ISO 6964
Plastic pipes on their own are not resistant against the ultraviolet radiation emitted by the sun or other similar sources of light, and the damaging UV radiation would destroy them. Therefore, an anti-light screen of carbon black as anti-UV is used in these products to prevent the absorption of these radiations. To optimize the performance of this screen, at least 22% of carbon black should be spread quite uniformly inside the pipe.
If the amount is less than 2%, it will lead to disorder in the optimal performance of the anti-light screen. And if the amount is higher than 2.5%, it will cause disorder in other physical and mechanical characteristics of this product.
In this test, the amount of carbon in the raw material and also in the final product are determined. For this purpose, a specific amount of raw material is pyrolysed in pure nitrogen gas atmosphere in a furnace at a temperature up to 550 °C to determine the rate of carbon black in the sample.
The allowed rate of carbon in PE pipes is between 2 wt% and 2.5 wt% and should be distributed uniformly throughout.
In regions where the accumulated carbon is more than the allowed rate, there will be a stress concentration and the pipe will become vulnerable. If the amount of carbon is less than the allowed rate, the pipes’ strength against the sun’s UV radiations will decrease.
Dispersion of Carbon Black according to the Standard ISO 18553
This test will be carried out to ensure the uniform distribution and dispersion of carbon black throughout the pipe. In this test, a specific amount of the sample pipe is put in a certain time at a certain temperature, and then the result is examined by a microscope.
Density according to the Standard INSO 7090-1
Density of a material is the ratio of its mass to its volume at a specific temperature, which is expressed in units of gram to cubic centimeters.
The density number of a product shows the quality of the production process. The density of the raw material also affects the mechanical characteristics of the final product. Thus, the density of the raw material and of the product are determined by the dip coating method using an analytical scale and a fluid with a specified density according to the standard INSO 7090-1.
This feature can also be useful in determining uniformity in a sample.
Oxidation Induction Time according to the Standard ISIRI 7186
One of the important parameters in determining the efficiency of polymeric materials and parts is the oxidation induction time. This test is a qualitative measurement of the materials’ level of stability in the oxygen gas atmosphere, which can be used as one of the quality control tests carried out on the raw material to demonstrate the stability level of polyolefin blends before extruding and also after production in the final stage of use and under environmental conditions such as sunlight. The kinetics of the oxidation reaction is a function of the temperature and the intrinsic characteristics of the additives in the sample. Ram Plast Laboratory, with the differential scanning calorimetry (DSC) system, is capable of performing this test for all types of polyolefin according to the standard ISIRI 7186-6.
The destruction time for PE shouldn’t be less than 20 minutes.
Tensile Failure according to the Standard ISO 6259-1, 3
Using specialized laboratory systems, mechanical characteristics of PE pipes including maximum resistance against external load, the amount of length deformation in break point, maximum tensile strength and the tensile strength in yield point can be measured and considering the results of the above test, the performance of the product can be evaluated in operating conditions.
Longitudinal Reversion according to the Standard INSO 17614
In this test, a sample pipe with a specific length is put in an oven with a circulation of hot air for 1 hour. And after cooling in ambient air, the amount of length deformation in the sample after the heating, is measured with a caliper. The maximum allowed rate of deformation according to the standard is 3%.
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Volatile Content according to the Standard EN12099
The volatile content is measured in the raw material. If the raw material has a volatile content of over 350 ppn, the external surface of the pipes becomes improper during the production process. With this test, before production the raw material or the masterbatch which might cause the external surface of the pipes to become improper, is identified. If the volatile content is about 350 ppn, then the problem can be solved by heating the material.
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Hydrostatic Pressure according to the Standard ISIRI 12181-1, 2
One of the important parameters is studying physical and mechanical characteristics of thermoplastic pipes in order to determine the pressure stability of pipes under pressure and determine the life time of these pipes for long periods of use at various temperatures, which is carried out according to the standard ISIRI 12181-1. By conducting this test, the characteristics and pressure quality and life time of the pipes can be specified.
In this test, based on its size and the raw material type, the sample pipe is put at a 20 °C temperature for 100 hours, or at a 80 °C temperature for 165 hours or at a 80 °C temperature for 1000 hours, under a constant internal pressure, after soaking in a pool of water.
The product would be rejected in the event of any defect in the samples (burst, swelling, local inflation, leaks and hairline cracks).
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Burst according to the Standard ISIRI 12181-1,2
In this test, the pipe samples float in a pool at a constant temperature of 23 °C and are then put under an internal increasing pressure, so that in 60 to 70 seconds time, they swell and then burst.
A pipe produced with high quality material and made through a correct production process, will undergo plastic deformation and swell up. Afterwards, it will burst in the form of a beak, in which case the breaking plane is perpendicular to the length of the pipe.
A pipe that bursts or cracks longitudinally without swelling, is not usable.
Squeeze Off according to the Standard EN 12106
PE pipes used in gas supply are examined in this test. This method is used to block gas transmission lines in times of line repairs. In this test, the sample is frozen at a temperature of 0 °C; then it is squeezed in a squeezer machine for 1 hour and finally the hydrostatic test is carried out on it.
According to the standard, there shouldn’t appear any defects in the pipe.
Dimensions according to the Standard INSO 2412
Accurate determination of the pipe wall thickness is done using calibrated calipers in the cutting section and the external diameter of the pipe is measured using a psychometer along one branch of the pipe and the measured value is then reported.
According to the standard, the amount of deformation in the pipe section and deviation from ovality is measured after the production of the pipe. The allowed limit for such fluctuations is determined based on the pipe’s external diameter. It should be noted that PE pipes, due to their flexibility, are deformed during transportation and installation and this is resolved after the connection operations and in next stages after the implementation, when the fluid moves inside the pipes and exerts pressure, the pipes return to their original shape.
Ring Stiffness Test for Single-Walled PE Sewage Pipes according to the Standard ISIRI 11436
This test is carried out in order to structurally integrate PE single-walled sewage pipes.
ESCR according to the National Standard 7175-8
This test is used for LDPE raw materials and pipes. In this test, the raw material is shaped into a plate using HOT PRESS machine and some components of this plate or irrigation pipes are made from them. These components are excoriated so that there appears a stress concentration point and then they are put under thermal, chemical and mechanical stress and the test lasts for 1000 hours. The chemical stress is carried out using a 100% IGEPAL solution.
ESCR according to the Standard ISIRI 8988
It is solely used for LDPE pipes. By bending the pipe in two opposite directions a stress concentration point is made and the pipe is put under mechanical, thermal and chemical stress.