GB/T 2951.8-1997 General test methods for cable insulation and sheathing materials Part 4: Specific test methods for polyethylene and polypropylene mixtures Section 1: Environmental stress cracking resistance test - Winding test after air heat aging - Melt index measurement method - Carbon black and
Some standard content:
National Standard of the People's Republic of China
Common test methods for Insulatingand sheathing materials of electric cablesPart 4: Methods specific tn polyethylene and polypropylene compoundsSection one: Resistance to euvironnental stress cracking-- Wrapping test after thernal ageing in air-Measurement of the melt flow index -- Carthn hlackand/or mineral tiller content measurement in PE1 Scope
GB/T 2951. 8—1997
idt IEC 811-4-1:1985
No.1(1988)1st Amendment
Replaces GB/T2951.1-94
GB/T 2951.36 --94
GB/T 2951.39-94
GB//2951.412951.42-94
GB/T2951 standard specifies the test methods for polymer insulation and sheath materials of power distribution cables and communication cables, including marine cables.
GB/T2951.8 standard specifies the test method for environmental stress cracking resistance, the winding test method after air heat aging, the melt index determination method and the test method for carbon black and/or mineral content. Applicable to polyethylene (PE) and polypropylene (PP) sheaths and insulation of wires and cables, including foam insulation and skin foam insulation. 2 Test principles
This standard does not specify all test conditions (such as temperature, duration, etc.) and all test requirements, which should be specified in the relevant cable product standards.
All test requirements specified in this standard can be modified in the relevant cable product standards to adapt to the requirements of special types of cables. 3 Scope of application
The test conditions and test parameters specified in this standard are applicable to the most commonly used types of insulation and sheath materials for cables, wires and cords. 4 Definitions
For the convenience of testing, it is necessary to distinguish between low-density, medium-density and high-density polyethylene (23°C): Low-density polyethylene
Medium-density polyethylene
High-density polyethylene
d: 0. 925 g/ein*
0. 9250.940 g/cm
Approved by the State Administration of Technical Supervision on October 28, 1997, and implemented on July 1, 1998
GB/T 2951.8 1997
Note: These densities d are for filling resin. The determination method shall be in accordance with the provisions of Chapter 8 of GB/T2951.3-1997. 5 Type test and other tests
The test methods specified in this standard are first used as type tests. The conditions for type tests and frequently performed tests (such as routine tests) for some test items are essentially different, and this standard has pointed out these differences. 6 Pretreatment
All tests should be carried out after the insulation and sheath materials have been stored for at least 16 hours after extrusion or vulcanization (or cross-linking). 7 Intermediate value
Arrange the test data that should be obtained in ascending or descending order. If the number of valid data is an odd number, the intermediate value is the middle value; if it is an even number, the intermediate value is the half-mean of the two middle values. 8 Environmental stress cracking resistance
8.1 Overview
These test steps are applicable to the original granular materials of cable sheaths. Step A is applicable to materials under less harsh cable use conditions and environments. Step B: Applicable to materials under more harsh cable use conditions and environments. 8.2 Test equipment
8.2.1 The pressing plate of the hot press to make the molded test piece should be large. 8.2.2 The thickness of the two hard metal templates is (6±0.5) mm and the area is about 200mmX230mm. Each plate should be drilled with a hole within 5mm from the edge to the center of the plate, and the overflow sensor should be placed in the hole. 8.2.3 The area of the isolation plate is about 200mm×230mm. For example, aluminum foil with a thickness of 0.1~0.2mm. 8.2.4 The size of the test piece made by the die is 150mm×180mm×(3.3±0.1)mm, and the inner corner radius is about 3mm. 8.2.5 The electric air box forces air circulation and is equipped with a program device with a cooling rate of (5±0.5)℃/h. 8.2.6 Clean, sharp, and undamaged dies and punching machines can punch out test pieces of (38.0±2.5)mm×(13.0±0.8)mm. 8.2.7 The diameter of the measuring surface of the pointer-type thickness gauge is 4~8mm, and the measuring pressure is 6~8N/cm. 8.2.8 The scoring device equipped with a blade is shown in Figure 1, and the shape and size of the blade are shown in Figure 2. 8.2.9 The bending clamping device shown in Figure 3 is symmetrically closed with a vise or other suitable device. 8.2.10 Transfer device As shown in Figure 4, transfer the bent specimens from the bending clamp to the brass groove specimen rack at one time. 8.2.11 The brass specimen rack with a roll as shown in Figure 5 can accommodate 10 bent specimens. 8.2.12 Hard glass test tubes as shown in Figure 6 with dimensions of 200 mm × g32 mm can accommodate the specimen rack containing the specimens. The test tube mouth is plugged with a cork wrapped in an aluminum box.
8-2.13 Reagents
Procedure A: 100% Igepal CO-630 (Antarox CO-630) or other reagents with the same chemical composition (see Notes 1, 2 and Appendix A).
Procedure B: 10% Igepalc O-630 (Antarox CO-630) aqueous solution (calculated by volume) or any other aqueous solution with the same chemical composition.
1 Reagent It can be used: - times.
2 In case of unexpectedly short expiration time, the water content of the reagent should be checked, because the activity of the reagent will increase significantly if the water content exceeds the specified expansion value by 1%.
3 The aqueous solution of Igepal C-630 or similar reagent should be prepared at 60-70°C with a stirrer, and the stirring time should be at least 1 hour. The reagent should be used within one week after preparation.
8.2.14 The heating container has sufficient size and depth to accommodate the glass tube with the test piece rack (as shown in Figure 6), and the temperature should be maintained at (50±0.5)°C by using suitable equipment. The heat capacity of the equipment should be large enough to ensure that the temperature does not drop below 49°C after the test tube is placed. Figure 1. Force frame made of \Gem\ blade, the blade is shown in Figure 2 (see also Appendix A) 19. n 2 9: 1
Rear chuck; 2— Loaded specimen; 3—Front chuck; 4—Screw; 5—Guide rod 1
Figure 5 Specimen rack
8.3 Preparation of test pieces
CB/T2951.8—1997
11, 75±0. 05
Inner width of specimen rack
Small unit: mm
Figure 6 Test tube and brass specimen rack with 10 specimens (as described in 8.2.11)
8.3.1 To prepare for the test, place a clean specimen rack as in 8. The isolation sheet described in 2.3 is placed on the template described in 8.2.2. (90 ± 1) g of granular material or powder is added to the die described in 8.2.1. This material forms a uniform thin layer in the die. Then another isolation sheet is placed and another template is added. No release agent is used. 8.3.2 The mold should be placed in the molding press described in 8.2.1. The mold base should be preheated to 170°C and the press should be closed with a force not greater than 1 kN.
8.3.3 When the temperature indicated by the sensor in the template reaches 165-170°C, a full pressure of 50-200 kN shall be applied to the mold by the press for 2 minutes. During this period, the temperature of the press shall be kept within the range of 165-170°C. At the end of the full pressure stage, heating shall be stopped and the mold can be removed from the press. It may also be cooled rapidly under full pressure. 8.4 Conditioning of the test piece
After removing the template without moving the spacer, the molded test piece shall be placed in the oven described in 8.2.5 to allow free circulation of air around the test piece. In this way, the molded test piece can be well placed on the horizontal heat-conducting surface so that the spacer and the polyethylene are in good contact. The temperature measured at a point not more than 5 mm above the center of the molded test piece surface shall be controlled as follows: For low-density polyethylene, the oven test temperature shall be maintained at (145 ± 2)°C, and for medium-density polyethylene, the test temperature shall be maintained at (155 ± 2)°C! For high-density ethylene, the test temperature shall be maintained at (165 ± 2) °C. The oven test temperature shall be maintained for 1 h and then reduced to (29 ± 1) °C at a rate of (5 ± 2) °C/h. The test piece may also be cooled on the press. The actual cooling rate shall be recorded on a plotter. Note: Whether the test piece needs to be conditioned is up to you. In case of dispute, the conditioned test piece shall be used. 8.5 Appearance inspection of the test piece
The surface of the test piece shall be smooth and free of bubbles, protrusions or depressions within 10 mm from the reverse edge of the test piece. 8.6 Test procedure
8.6.1 Preparation of test pieces
Use the die and punch described in 8.2.6 or other suitable device to cut 10 test pieces as specified in 8.6.2 at a distance greater than 25 mm from the edge of the test piece. When cutting the test pieces, the mesh between the holes left on the test piece shall not be damaged. The thickness of the specimen measured by the pointer thickness gauge described in 8.2.7 shall comply with the provisions of 8.6.2. The edges of the cut specimens shall be at right angles. Beveled edges may lead to erroneous results. 8.6.2 Notching and inserting the specimen
Before placing the specimen in the reagent, each specimen shall be notched using the notching device described in 8.2.8 (see Figure 7). The blade shall be sharp and undamaged and shall be replaced as required. Even in good conditions, the blade may only be notched a maximum of 100 times. Density of polyethylene protective material
0.940g/cm
>0. 940 g/cms
CB/T2951.81997
8+0~61
13.0±0.8
13. D± 0. 8
3. 0~3. 30
0, 50~-0, 65
0.300. 40
Put the 10 test pieces with the notches facing upwards into the bending clamp described in 8.2.9, then close the clamp with a vise or a constant speed electric press within 30~358 seconds,
take the bent test piece out of the clamp with the transfer tool described in 8.2.10 and put it into the brass groove test piece holder described in 8.2.11. If some specimens are too high on the specimen rack, they should be pressed down manually. After the specimens are bent for 5 to 10 minutes, insert the specimen rack into the test tube described in 8.2.12. The test tube should be filled with the appropriate reagents described in 8.2.13, and all specimens should be immersed in the reagents. Use corks to stopper the test tube. The test tube filled with reagents should be immediately placed in the heating container described in 8.2.11 and start counting the time. Care should be taken not to allow the specimen to avoid the test tube wall during the test.
8.7 Evaluation of test results
Usually, environmental stress cracking should start at the notch and develop at right angles to it. When the first crack appears on the specimen when inspected with normal vision or corrected vision without a magnifying glass, it indicates that the specimen has failed. Step A: After 24 hours of heating, there should be no more than 5 failed specimens in the container. If 6 specimens fail, it is considered as a failure to pass the test. It is allowed to cut 10 more specimens from a new specimen and repeat the test. No more than 5 specimens should fail in the repeated test. Step B: After 481 heating, there should be no specimen tip failure in the container. If one specimen fails, it is considered as a failure to pass the test. It is allowed to cut 10 more specimens from a new specimen and repeat the test. No one specimen should fail in the repeated test. 8.8 Test requirements and conditions for steps A and B
Test conditions and requirements
Test piece preparation:
Temperature,
Pressure, kn
Time, min
Test piece treatment:
Cold range, °C
Cooling rate, C/h
Test conditions:
Reagent concentration, %.%
Temperature, C
Step A
165--170
59～200
(145±2) to (30=9)
Requirement #
Test conditions and requirements
Time (minimum), five
Failure rate (maximum)
GB/T 2951.8—1997
Table (end)
5 specimens
*Igepal CO-630 or any other reagent with the same chemical composition. 9 Winding test after air heat aging
9.1 General
This method is used to determine the chemical resistance of polyethylene insulation materials. Procedure B
0 specimens
This test is applicable to products with a diameter not greater than 10 mma and/or a wall thickness less than 0.8 mm and a density not greater than 0.940 g/cm2.
For materials with a density greater than 0.940 g/cm2, the test method is under consideration. Note: Long-term qualitative tests are under consideration. 9.2 Test equipment
9.2.1 Smooth metal test rod and loading element. 9.2.2 Winding device, preferably with the function of mechanically driving the test rod. 9.2.3 Naturally ventilated electric heating box.
9.3
Take a 2m long sample from each cable or insulated core to be tested and cut a test piece of equal length for testing. Remove the sheath, braid (if any) and any filler that may be attached to the insulated core from the test piece. Leave the conductor in the insulation and calibrate the test piece. 9.4 Aging procedure
Hang the test piece prepared in accordance with the provisions of 9.3 vertically in the middle of a heating box that meets the requirements of 9.2.3, with each test piece at least 20mm apart. The space occupied by the test piece cannot exceed 2% of the volume of the test box. After aging for 14X24h at (100±2)℃, the test piece should be taken out of the test box immediately and placed at room temperature for at least 16h, avoiding direct sunlight. Note: If required by the relevant cable product standards, the aging time and/or aging temperature can be increased. 9.5 Test procedure
After aging in accordance with the provisions of 9.4, the test piece should be wound at room temperature. The conductor should be exposed at one end of the test piece. A load should be hung on the end (a tensile force of 15N/mm*±20% should be applied according to the cross-sectional area of the conductor). At the other end of the test piece, a winding device that meets the requirements of Article 9.2.2 should be used to roll the test piece on a metal test rod for 10 turns at a speed of about 1z/5s. The diameter of the mandrel should be 1 to 1.5 times the diameter of the test piece. Then remove the wound test piece from the mandrel, and then place the spiral test piece in a vertical state in the middle of a heating box that meets the requirements of Article 9.2.3 and is at a temperature of (70 ± 2) and kept for 24 h.
9.6 Evaluation of test results
After cooling to room temperature, the specimen shall be free of cracks when examined with normal or corrected vision without a magnifying glass. If one specimen fails, the test may be repeated once.
10 Determination of melt index
10.1 Overview
The melt index (MFI) of polyethylene and polyethylene blends refers to the amount of material extruded through a specified discharge die under load within 2.5 minutes or 10 minutes at 19VC temperature, as determined by the adopted method. Note: Melt index is not applicable to flame retardant ethylene. 10.2 Test equipment
GB/T 2951. 8—1997
The test equipment is mainly an extruder, and its general structure is shown in Figure 8. The polyethylene in the vertical cylinder is extruded by a piston through a discharge die at a controlled temperature. All surfaces in contact with the material on the test equipment should have a high finish. The main components of the test equipment are as follows: a) Steel cylinder
The steel cylinder is fixed vertically and has thermal insulation to work at 190. The length of the steel cylinder is at least 115mm, the inner diameter is between 9.5 and 10mm, and it meets the requirements of 10.2b). If the exposed metal surface area exceeds 4cm\, the base of the steel cylinder should be insulated, and polytetrafluoroethylene is recommended as the insulation material (about 3mm thick) to avoid sticking to the extrudate. b) Hollow steel piston
The length of the hollow steel piston is at least the same as that of the steel cylinder. The axis of the steel cylinder should coincide with the axis of the piston. The maximum effective length of the piston is 135mm. The length of the piston head is (6.35 ± 0.10) mm, and it should be (0.075 ± 0.015) mm smaller than the inner diameter of the steel cylinder at all points along the working length. In addition, to calculate the load (see 10.2c), the diameter of the piston head should be a known value with a tolerance of ± 0.025 mm. The lower edge of the piston has a fillet with a radius of 0.4 mu n, and the upper edge is ground to remove the sharp edges. The diameter of the piston above the piston head is reduced to about 9 mm, and there are bolts on the top of the movable cold to support the removable load. There should only be a thermal insulation layer between the piston and the load. e) Unloadable load on the top of the piston
The total weight of the load and the piston should be able to achieve the applied force P: When using method A (see 10.)
When using method ℃ (see 10.6)
d) Heater
Maintain the polyethylene in the steel cylinder at a temperature of (190±0.5). It is recommended to use an automatic control device.) Temperature measuring device
The temperature measuring device is as close to the discharge die as possible, but located inside the steel cylinder. This device should be calibrated to ensure that its temperature measurement is accurate to ±0.1℃. f) Discharge die
The length of the discharge die made of hardened steel is (8.000±0.025) mm, and its average inner diameter is between 2.090 mm and 2.100 mm and remains uniform over its length, with a deviation within the range of ±0.005 mm (see Figure 9). The discharge die should not extend beyond the base of the steel cylinder. g) Balance
accurate to ±0.0005 mm
10.3 Test
A sufficiently large sample of insulation or sheath shall be taken from one end of the cable or wire. The sample shall be cut into small pieces, the size of which shall not exceed 3 mm in any direction.
Note: If necessary, insulation may be taken from uninsulated wire cores. 10.4 Cleaning and Maintenance of Equipment
After each test, the equipment shall be cleaned.
When removing polyethylene from the surface or cleaning any part of the operating equipment, abrasives or similar materials that may damage the surface of the ring piston, steel cylinder or discharge die shall never be used.
Suitable solutions for cleaning the equipment are xylene, tetrahydronaphthalene or odorless gasoline. The piston shall be cleaned with a saturated solution while still hot, and the steel cylinder shall also be cleaned with a flannel soaked in a solution while still hot. The discharge die shall be cleaned with a tight-fitting brass reamer or wooden cork. Then immersed in a boiling solvent.
It is recommended to clean the equipment regularly (e.g. once a week for equipment in common use), and thoroughly clean the insulation board, the discharge die baffle and the steel cylinder. If they are assembled together, they can be disassembled and cleaned (see Figure 8). 10.5 Method A
10.5.1 General
Method A is suitable for determining the melt index of polyethylene samples with unknown MFI. 10.5.2 Test procedure
GB/T 2951. 8— 1997
The test equipment should be cleaned (see 10.4). The temperature of the steel cylinder and the piston should be maintained at (190 ± 0.5) ° C for 15 minutes before the test begins, and this temperature should be maintained during the polyethylene extrusion. The recommended temperature measuring device (see 10.2e)) is a mercury-in-glass thermometer permanently covered in the steel cylinder (see Note). It is recommended to use a low melting point alloy (Zhengde alloy) to improve contact. Note: If other temperature measuring equipment is used, it should be tested at a temperature of (190 ± 0.5) °C and in accordance with 10.2e> mercury thermometer for calibration, at this time the mercury thermometer should be placed in the steel cylinder and inserted into the polyethylene material to an appropriate depth, then a sample should be added to the steel cylinder (see Table 1) and the unloaded piston should be re-inserted into the top of the steel cylinder. 6 minutes after the addition of the material, the temperature of the steel cylinder should rise to (190 ± 0.5) ℃, and a load should be applied to the piston to extrude the polyethylene through the discharge die. At the discharge die, a short section of the extruded material should be cut off at a certain time with an appropriate sharp tool as a "take-off amount" at a time. The extrusion speed is measured by cutting the extruded material, and the time for each take-off is listed in Table 1. Several times of material should be taken within 20 minutes of the material being added to the steel cylinder. The first take-off and any take-off containing air bubbles should be measured. The remaining several times of taking the material (at least three times) should be weighed separately, accurate to mg+ and the average weight calculated. If the difference between the maximum and minimum weights measured is greater than 10% of the average value, the test result shall be invalidated and a new sample shall be taken for the test.
10.5.3 Evaluation of test results
MFI shall be calculated to two significant figures (see Note 1) and expressed as MFI.190.20.A (see Note 2). MFI.190.20.A=
where: MFI - grams per 10 min
m - average weight of the sample;
- sample interval, 5.
1The MFI of polyethylene may be affected by previous heat treatment and mechanical treatment, especially oxidation, which may cause a decrease in the MFI. Usually, oxidation occurring during the test will cause a systematic decrease in the weight of successive samples. This phenomenon will not occur in polyethylene containing antioxidants. 2MFI melt index:
190 test temperature, +
20 (or 50) - the approximate load applied to the melt, expressed as V. 10.6 Method C
10.6.1 Overview
Method C is applicable to the determination of polyethylene samples with an MFI less than 1. The measurement method is the same as that of Method A. 10.6.2 Test procedure
The test procedure is the same as that of Method A.
The time interval for taking the material and the weight of the sample put into the cylinder are as specified in Table 1. 10.6.3 Evaluation of the test results
The MFI should be recorded to two significant figures (see Note 1 above) and expressed as MFI.190.50.C (see Note 2 above). MFI. 190. 50. C _ 150 Xm
Note: The results indicated by the symbol C obtained with a heavier load (50N) and a shorter sampling time (150s) are essentially the same as those indicated by the symbol A and weighing A. However, there is no direct correlation between the symbols A and C. 1. Sample sampling interval and weight of sample put into the steel tube for methods A and C Melt index IF
Weight of sample put into the tube, g
Time interval of sampling,
CB/T 2951.8 -1997
11 Determination of carbon black and mineral filler content in polyethylene 11.1 Sampling
Take a sufficient weight of insulation and sheath sample from one end of the cable. Cut the sample into small pieces, the size of which should not exceed 5mm in any direction. 11.2 Test Procedure
Heat a combustion boat about 75 mm long until it is red hot, then cool it in a desiccator for at least 30 min and weigh it to the nearest 0.(1001 g) Place a (1.0 ± 0.1) g ethylene sample in the combustion boat and weigh them together to the nearest 0.0001 t. Subtract the weight of the combustion boat to obtain the weight of the ethylene sample (weight A) to the nearest 0.0001 g. Place the combustion boat containing the sample in the middle of a hard glass, quartz or ceramic combustion tube. The inner diameter of the tube is about 30 mm and the length of the tube is (400 + 50) mm. Then insert a thermometer with a temperature range of 300 to 550 ° C and a tube for nitrogen supply at one end of the combustion tube so that the end of the thermometer is in contact with the combustion boat. Nitrogen with an oxygen content of less than 0.5% is (1 .7±0.3)L/rmin flow rate through the combustion tube, and maintain this flow rate during the subsequent heating process. ; When in doubt, the nitrogen content should be limited to 0.01%. The combustion tube is fed into the furnace, and the outlet of the tube is connected in series to two condensers containing trichloroethylene. The first condenser is cooled with solid carbon dioxide, and the outlet pipe of the second condenser should be connected to a ventilation tree or the outdoor atmosphere. Alternatively, the outlet diameter of the combustion tube can be connected to the outdoor atmosphere.
Heat the tube to 300~350 in 10 minutes and then heat it to about 450℃ for another 10 minutes. After the third 10 minutes, heat it to (500+5). Then keep it at this temperature for 10 minutes. Then disconnect the outlet pipe from the condenser (if any), take the combustion tube with the combustion boat out of the furnace, and cool it for 5 minutes. min, the nitrogen flow rate is the same as before. Then take the combustion boat out of the combustion tube through the nitrogen inlet, cool it in the dryer for 20~～30 min and re-weigh it, and measure the weight of the residue to an accuracy of 0.00018 (residue weight B). Then, put the combustion boat into the combustion tube again, and replace the nitrogen with air or oxygen at a temperature of (500±20) and pass it into the combustion tube at an appropriate speed to burn the residual carbon black. After the test device is cooled, take out the combustion boat and weigh it, and measure the weight of the residue to an accuracy of 0.0001g (residue weight C).
11.3 Method of expressing test results
Carbon black content
A×100%
Mineral filler content=
Filling content-
GB/T 2951. 8-1997
Figure 8 Melt index tester (shown is a steel cylinder with a small outer diameter, a fixed plate A for the discharge die and an insulating plate B)9.5~:0
Figure 9 Discharge die (example of a small outer diameter steel cylinder and a fixed discharge die)Instrument
GB/T2951.8-—1997
Appendix A
(Suggestive Appendix)
Apparatus and reagents only
Address for purchasing the test instruments described in 8.2.8, 8.2.9 and 8.2.10:Messrs Cuslon Scientific Instruments Inc.541 Deven Street
Arlington, NJ
Address for obtaining the test instruments:
American Societyfor Testing and Materials (ASTM)1916 Race Street.Philadelphia 19103,Pa
Address for purchasing 100% IGEPALCO-630 reagent with a density of 1.06 at 25C:GAF Corp.Dyestuff and Chemical Div.140 West 51 Street
NewYork,VY10020
The water content of the reagent must be less than 1% because it is hygroscopic and should be stored in a sealed metal or glass container.2 Test procedure
The test procedure is the same as for method A.
The time intervals for taking the sample and the weight of the sample to be placed in the cylinder shall be as specified in Table 1. 10.6.3 Evaluation of test results
The MFI shall be recorded to two significant figures (see Note 1 above) and expressed as MFI.190.50.C (see Note 2 above). MFI. 190. 50. C _ 150 Xm
Note: The results indicated by the symbol C obtained with a heavier load (50 N) and a shorter taking time (150 s) are essentially the same as those obtained with method A and expressed by the symbol A. However, there is no direct correlation between the symbols A and C. 1. Time interval for taking materials and weight of test materials put into steel tube for method A and method C Melt index IF
Weight of test materials put into steel tube, g
Time interval for taking materials,
CB/T 2951.8 -1997
11 Determination of carbon black and mineral filler content in polyethylene 11.1 Sampling
Take a section of insulation and sheath test samples of sufficient weight from one end of the cable. Cut the test samples into small pieces, the size of which should not exceed 5mm in any direction. 11.2 Test Procedure
Heat a combustion boat about 75 mm long until it is red hot, then cool it in a desiccator for at least 30 min and weigh it to the nearest 0.(1001 g) Place a (1.0 ± 0.1) g ethylene sample in the combustion boat and weigh them together to the nearest 0.0001 t. Subtract the weight of the combustion boat to obtain the weight of the ethylene sample (weight A) to the nearest 0.0001 g. Place the combustion boat containing the sample in the middle of a hard glass, quartz or ceramic combustion tube. The inner diameter of the tube is about 30 mm and the length of the tube is (400 + 50) mm. Then insert a thermometer with a temperature range of 300 to 550 ° C and a tube for nitrogen supply at one end of the combustion tube so that the end of the thermometer is in contact with the combustion boat. Nitrogen with an oxygen content of less than 0.5% is (1 .7±0.3)L/rmin flow rate through the combustion tube, and maintain this flow rate during the subsequent heating process. ; When in doubt, the nitrogen content should be limited to 0.01%. The combustion tube is fed into the furnace, and the outlet of the tube is connected in series to two condensers containing trichloroethylene. The first condenser is cooled with solid carbon dioxide, and the outlet pipe of the second condenser should be connected to a ventilation tree or the outdoor atmosphere. Alternatively, the outlet diameter of the combustion tube can be connected to the outdoor atmosphere.
Heat the tube to 300~350 in 10 minutes and then heat it to about 450℃ for another 10 minutes. After the third 10 minutes, heat it to (500+5). Then keep it at this temperature for 10 minutes. Then disconnect the outlet pipe from the condenser (if any), take the combustion tube with the combustion boat out of the furnace, and cool it for 5 minutes. min, the nitrogen flow rate is the same as before. Then take the combustion boat out of the combustion tube through the nitrogen inlet, cool it in the dryer for 20~～30 min and re-weigh it, and measure the weight of the residue to an accuracy of 0.00018 (residue weight B). Then, put the combustion boat into the combustion tube again, and replace the nitrogen with air or oxygen at a temperature of (500±20) and pass it into the combustion tube at an appropriate speed to burn the residual carbon black. After the test device is cooled, take out the combustion boat and weigh it, and measure the weight of the residue to an accuracy of 0.0001g (residue weight C).
11.3 Method of expressing test results
Carbon black content
A×100%
Mineral filler content=
Filling content-
GB/T 2951. 8-1997
Figure 8 Melt index tester (shown is a steel cylinder with a small outer diameter, a fixed plate A for the discharge die and an insulating plate B)9.5~:0
Figure 9 Discharge die (example of a small outer diameter steel cylinder and a fixed discharge die)Instrument
GB/T2951.8-—1997
Appendix A
(Suggestive Appendix)
Apparatus and reagents only
Address for purchasing the test instruments described in 8.2.8, 8.2.9 and 8.2.10:Messrs Cuslon Scientific Instruments Inc.541 Deven Street
Arlington, NJ
Address for obtaining the test instruments:
American Societyfor Testing and Materials (ASTM)1916 Race Street.Philadelphia 19103,Pa
Address for purchasing 100% IGEPALCO-630 reagent with a density of 1.06 at 25C:GAF Corp.Dyestuff and Chemical Div.140 West 51 Street
NewYork,VY10020
The water content of the reagent must be less than 1% because it is hygroscopic and should be stored in a sealed metal or glass container.2 Test procedure
The test procedure is the same as for method A.
The time intervals for taking the sample and the weight of the sample to be placed in the cylinder shall be as specified in Table 1. 10.6.3 Evaluation of test results
The MFI shall be recorded to two significant figures (see Note 1 above) and expressed as MFI.190.50.C (see Note 2 above). MFI. 190. 50. C _ 150 Xm
Note: The results indicated by the symbol C obtained with a heavier load (50 N) and a shorter taking time (150 s) are essentially the same as those obtained with method A and expressed by the symbol A. However, there is no direct correlation between the symbols A and C. 1. Time interval for taking materials and weight of test materials put into steel tube for method A and method C Melt index IF
Weight of test materials put into steel tube, g
Time interval for taking materials,
CB/T 2951.8 -1997
11 Determination of carbon black and mineral filler content in polyethylene 11.1 Sampling
Take a section of insulation and sheath test samples of sufficient weight from one end of the cable. Cut the test samples into small pieces, the size of which should not exceed 5mm in any direction. 11.2 Test Procedure
Heat a combustion boat about 75 mm long until it is red hot, then cool it in a desiccator for at least 30 min and weigh it to the nearest 0.(1001 g) Place a (1.0 ± 0.1) g ethylene sample in the combustion boat and weigh them together to the nearest 0.0001 t. Subtract the weight of the combustion boat to obtain the weight of the ethylene sample (weight A) to the nearest 0.0001 g. Place the combustion boat containing the sample in the middle of a hard glass, quartz or ceramic combustion tube. The inner diameter of the tube is about 30 mm and the length of the tube is (400 + 50) mm. Then insert a thermometer with a temperature range of 300 to 550 ° C and a tube for nitrogen supply at one end of the combustion tube so that the end of the thermometer is in contact with the combustion boat. Nitrogen with an oxygen content of less than 0.5% is (1 .7±0.3)L/rmin flow rate through the combustion tube, and maintain this flow rate during the subsequent heating process. ; When in doubt, the nitrogen content should be limited to 0.01%. The combustion tube is fed into the furnace, and the outlet of the tube is connected in series to two condensers containing trichloroethylene. The first condenser is cooled with solid carbon dioxide, and the outlet pipe of the second condenser should be connected to a ventilation tree or the outdoor atmosphere. Alternatively, the outlet diameter of the combustion tube can be connected to the outdoor atmosphere.
Heat the tube to 300~350 in 10 minutes and then heat it to about 450℃ for another 10 minutes. After the third 10 minutes, heat it to (500+5). Then keep it at this temperature for 10 minutes. Then disconnect the outlet pipe from the condenser (if any), take the combustion tube with the combustion boat out of the furnace, and cool it for 5 minutes. min, the nitrogen flow rate is the same as before. Then take the combustion boat out of the combustion tube through the nitrogen inlet, cool it in the dryer for 20~～30 min and re-weigh it, and measure the weight of the residue to an accuracy of 0.00018 (residue weight B). Then, put the combustion boat into the combustion tube again, and replace the nitrogen with air or oxygen at a temperature of (500±20) and pass it into the combustion tube at an appropriate speed to burn the residual carbon black. After the test device is cooled, take out the combustion boat and weigh it, and measure the weight of the residue to an accuracy of 0.0001g (residue weight C).
11.3 Method of expressing test results
Carbon black content
A×100%
Mineral filler content=
Filling content-
GB/T 2951. 8-1997
Figure 8 Melt index tester (shown is a steel cylinder with a small outer diameter, a fixed plate A for the discharge die and an insulating plate B)9.5~:0
Figure 9 Discharge die (example of a small outer diameter steel cylinder and a fixed discharge die)Instrument
GB/T2951.8-—1997
Appendix A
(Suggestive Appendix)
Apparatus and reagents only
Address for purchasing the test instruments described in 8.2.8, 8.2.9 and 8.2.10:Messrs Cuslon Scientific Instruments Inc.541 Deven Street
Arlington, NJ
Address for obtaining the test instruments:
American Societyfor Testing and Materials (ASTM)1916 Race Street.Philadelphia 19103,Pa
Address for purchasing 100% IGEPALCO-630 reagent with a density of 1.06 at 25C:GAF Corp.Dyestuff and Chemical Div.140 West 51 Street
NewYork,VY10020
The water content of the reagent must be less than 1% because it is hygroscopic and should be stored in a sealed metal or glass container.0
Figure 9 Discharge die (Example of small outer diameter steel cylinder and fixed discharge die) Apparatus
GB/T2951.8--1997
Appendix A
(Suggestive Appendix)
Instruments and reagents only
Address for purchasing the test instruments described in 8.2.8, 8.2.9 and 8.2.10: Messrs Cuslon Scientific Instruments Inc. 541 Deven Street
Arlington, NJ
Address for obtaining test instruments:
American Society for Testing and Materials (ASTM) 1916 Race Street. Philadelphia 19103, Pa
Address for purchasing the reagent of 100% IGEPALCO-630 with a density of 1.06 at 25C: GAF Corp. Dyestuff and Chemical Div. 140 West 51 Street
NewYork,VY10020
The water content of the reagent must be less than 1% because it is hygroscopic and should be stored in a sealed metal or glass container.0
Figure 9 Discharge die (Example of small outer diameter steel cylinder and fixed discharge die) Apparatus
GB/T2951.8--1997bZxz.net
Appendix A
(Suggestive Appendix)
Instruments and reagents only
Address for purchasing the test instruments described in 8.2.8, 8.2.9 and 8.2.10: Messrs Cuslon Scientific Instruments Inc. 541 Deven Street
Arlington, NJ
Address for obtaining test instruments:
American Society for Testing and Materials (ASTM) 1916 Race Street. Philadelphia 19103, Pa
Address for purchasing the reagent of 100% IGEPALCO-630 with a density of 1.06 at 25C: GAF Corp. Dyestuff and Chemical Div. 140 West 51 Street
NewYork,VY10020
The water content of the reagent must be less than 1% because it is hygroscopic and should be stored in a sealed metal or glass container.
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