PE pipe than PVC pipe more environmental protection characteristics, began to gradually replace PVC pipe into the mainstream pipe market.
For this emerging material, it is necessary to conduct a comprehensive examination of its performance, in order to determine its scope of use, to ensure that it can better serve us.
Materials and methods
1. Material analysis
Through the analysis of antioxidants, some factors affecting the use of antioxidants were found, including: in the construction process to pay attention to the timing of antioxidant addition, adding the timing is too early or too late, the anti-oxidation effect is not much effect;
Also control the amount of antioxidants added because the amount of antioxidants is not directly proportional to the antioxidant effect.
After more than a certain amount may promote oxidation effect: the synergy of antioxidants, when two or more of the antioxidant mixed use, the antioxidant effects tend to be alone than a stronger antioxidant effect of use: avoid such as Co, Cu, Fe, Mn, Ni ion of mixed with the transition elements, because of the transition elements ion has a strong promote oxidation effect, which helps the oxidant;
In the use of the process to avoid the light, heat, oxygen and so on.
Through the analysis of PE pipe, find some characteristics of PE pipe, including: temperature, PE pipe is generally used in a temperature range of 60~C ~ 60~C, the temperature is too low or too high will have some influence on the use of PE pipe;
Good resistance to stress cracking: high corrosion resistance, can withstand a variety of chemical medium corrosion, no decay and other phenomena;
Aging resistance, normal service life up to 5O years, will not be damaged by ultraviolet radiation;
Good winding performance, easy to complete, can bypass obstacles for construction;
Light weight, easy to handle and install, can reduce the handling and installation costs;
Weather resistance, 8O℃ hydrostatic strength, no rupture, no leakage, fracture shrinkage rate is greater than or equal to 350%, at 200 ℃ oxidation induction is greater than or equal to 10 minutes.
Therefore, these factors should be selected in the selection of materials to avoid some conditions and climate that affect the test results of materials, so as to make the test results conform to statistics.
2. Material selection
Because of the need for a comparative test, four groups were selected for the comparative test.
Each group selected 1O PE tubes of the same length for testing. The first group was the standard group and randomly selected the same batch of qualified PE tubes with antioxidant added.
The second group was the experimental group, randomly selected the same batch of qualified PE tubes without antioxidant.
The third group was the standard control group, randomly selected different batches of qualified PE pipes with antioxidant added.
The fourth group was the experimental control group, which randomly selected different batches of qualified PE pipes without added antioxidant.
3. Experiment preparation
The four groups of materials were uniformly placed in the laboratory under the same environmental conditions for the test to ensure the same test environment, so that the final test results will also conform to the normal distribution and statistics, in order to exclude the influence of different environmental conditions on the test data, and reduce the error rate.
4. Test standards
There are many standards for testing PE pipes, such as aging test, physical properties test, and so on, each of which contains many different test methods.
If all of them are selected, the first is the cost is too large, the second is not necessary, so it is necessary to select the most suitable test standard and test method that can best reflect the impact of antioxidant cutting on the service life of PE pipe according to the characteristics of PE pipe and the characteristics of antioxidant.
4. Selection of test methods
Through the above analysis of the test standard, we decided to conduct the test of PE pipe through two test methods, which can cover both the PE pipe and the use of antioxidant characteristics.
(1) oxidation induction phase test
Pyris 1 DSC (power compensated differential scanning calorimeter) was used to determine the oxidation induction period of polymer materials.
PE tube samples were heated to a predetermined temperature (200 degrees) for 5 minutes under inert gas environment, and then changed to the oxygen state to determine the time required for degradation of the samples.
(2) endurance test
Photoaging, especially the sun exposure to PE pipe has a great impact, the intensity of ultraviolet will cause direct damage to the pipe.
(3) chemical stability test
PE pipe has a good stability, chlorine, oxygen gas, acid, alkali and so on have a good chemical resistance, but benzene, gasoline, carbon tetrachloride and so on have a certain impact on PE pipe.
(4) short-term strength test
In the actual environment, due to the occurrence of geological disasters such as foundation subsidence, earthquake, tsunami, etc., the case of the pipeline facing this degree of deformation without fracture should also be taken into account.
After five tests on all four groups of materials, the following conclusions were drawn:
From the above experimental data, it can be concluded that:
1, at least 12 times measured the gap of continuous growth, test a week after the first group of two sample crack growth does not occur, the second group of four sample crack growth, the third group of 3 of them have taken place in a sample crack growth, the fourth group of crack growth happened three sample, one sample crack growth.
2. In the test of hydrostatic strength at 20 ° c, annular stress at 9 ° MPa and 100H, the four groups of materials did not break or leak;
80 degrees Celsius, hydrostatic strength hoop stress is 4.6 MPa, 165 h test, first, three groups of materials not rupture, leakage occurs, the second, four groups each have two material fracture, leakage phenomenon: 80 degrees Celsius, hydrostatic strength hoop stress is 4.0 MPa, 100 h test, first, three groups of materials not rupture, leakage occurs, the second, four groups each have 1 root material fracture, leakage phenomenon.
3, pipe is greater than or equal to 3.56 J/m in total energy after aging, hydrostatic strength at 80 degrees, hoop stress is 4.6 MPa, 165 h experiment, the first group of specimens rupture, leakage does not occur, the second group of the specimen have seven root fracture, leakage, the third group of the specimen 2 root fracture, leakage, a fourth group of samples eight root fracture, leakage.
4, can be a variety of chemical corrosion resistance, but the chemical material such as benzene, gasoline, carbon tetrachloride influence on PE pipe, the first group have 2 sample rupture, leakage occurs, a second group of seven root sample rupture, leakage occurs, the third group has four specimens rupture, leakage occurs, the fourth group is eight specimens rupture, leakage.
5. In the strength test, the flexibility of PE pipe makes it able to bend, so there is no phenomenon of rupture and leakage before the critical value, and after the critical value, eight out of ten cases of rupture and leakage occur in the pipes of the four groups of samples.
discuss
Antioxidants are chemicals that, when present in a polymer, inhibit oxidation, thereby extending its life.
Antioxidant 1010 is used in the polymerization, molding and final use of PE, PVC, ABS resin and rubber.
Antioxidant 1076 is used in polyolefin, polyester and petroleum products.
Antioxidant 264 is widely used in cosmetics, animal and vegetable oils and fats in China.
Antioxidant 2246 is often used in light-colored rubber products, can prevent cellulose resin, ABS resin photoaging and thermal aging: antioxidant 3(X)0 is often used in white, transparent products.
It has a significant antioxidant effect on polyethylene wire and cable, and can be Shared with carbon black to enhance its own antioxidant: antioxidant 3300 has the effect of long-term and lasting protection of products: antioxidant DLP and antioxidant 1010, antioxidant 1076 have a good synergistic effect.
The ideal antioxidant should meet the following requirements:
1. High antioxidant capacity;
2, the processing performance is good, in the high temperature heating is not volatile, not easy to decompose;
3. Insoluble in water and oil;
4, antioxidant itself should be non-toxic, colorless;
The price must be good and reasonable.
But this is an ideal, in reality, no antioxidant can meet these conditions, in practice, all the use of other antioxidants to share, in order to produce synergies, to improve their antioxidant capacity.
Different antioxidants have different effects.
Even the same antioxidant ACTS differently in different polymers.
Tests have shown that antioxidants do not change the outcome of polymer products, so they should be added early, and sometimes later, depending on the polymer.
In addition to the addition of antioxidants should not be too much, too much antioxidant on the antioxidant effect of the action will have the opposite effect.
Finally, through the experiment, we came to the conclusion that antioxidant can improve the stability of pE pipe and prolong the service life of pE pipe.
