surface resistivity of solid electrical insulating materials and the comparative tracking indices of solid insulating materials Test methods -- Part 1: Tests at power frequencies determi
Preparation and conditioning
All tests must be conducted under atmospheric conditions, specifically within a temperature range of 21 °C to 29 °C and a relative humidity of 45% to 70%, unless otherwise stated in the relevant specification standard or testing method Prior to measurements, the sample or test specimen should be pre-conditioned to achieve stability under these conditions For liquid or paste samples, ISO 15528 should be followed, and ISO 1513 should be applied for their preparation before testing.
For definitions of terms related to standard atmospheres, refer to ISO 558 The specified test atmosphere does not conform to either of the two standard atmospheres outlined in ISO 291, but it encompasses both ranges along with their tolerances.
All test method requirements are detailed in the description, with diagrams serving to illustrate a potential testing arrangement In the event of discrepancies between this standard and the IEC 60455-3 series specification sheets, the latter takes precedence Additionally, if another standard is referenced for a test method, it must be cited in the report.
Sequence of tests
To avoid unnecessary efforts, tests shall be carried out on the samples in the following sequence:
1) tests on individual components prior to mixing;
2) tests on reactive compound just after mixing (ready to use);
4) tests on cured compound after pre treatment (thermal, humidity, water etc.)
If the sample under test fails a test the following tests may become obsolete.
Test report
If not otherwise specified, the test report shall include the following data:
2) lot number or other identification;
3) confirmation of marking and labelling according to the material safety data sheet (MSDS);
5) major test parameters, including conditioning and calibration, if any;
6) processing conditions used to reactive compound;
7) copy of the technical data sheet (TDS) and MSDS
5 Methods of test for reactive compounds and their components
Flash point
For flash point temperatures of 79 °C and above, ISO 2592 should be utilized, while for temperatures below 79 °C, ISO 1523 must be applied using any closed-cup apparatus specified in Annex A of ISO 1523:2002 It is essential to read ISO 1523 in conjunction with ISO 3679 Two separate samples must be tested, and both flash point results should be reported along with references to the applicable standards.
Density
The method given in ISO 1675 shall be used Two measurements shall be made, and the two results of the density shall be reported.
Viscosity
Viscosity should be measured using an appropriate device at a temperature of (23 ± 0.5) °C unless specified otherwise For rotating devices, compliance with ISO 2555 (Brookfield type) or ISO 3219 (defined shear rate) is required If using efflux equipment, the testing method and flow cup must adhere to ISO 2431 Two viscosity measurements should be taken, and both results must be reported along with references to the applicable standards.
Viscosity after storing at elevated temperature
This method is not applicable to one-component systems or components containing hardener
Samples are stored for approximately 20 hours at a temperature of 100 °C in a sealed container After cooling to room temperature, the viscosity is measured, and the increase in viscosity is calculated using a specified equation.
Increase of viscosity in % = (η 2 – η 1 ) × 100 / η 1 where η 1 = dynamic viscosity before storing η 2 = dynamic viscosity after storing
Content of volatile organic components
This method is not applicable to one-component systems or components containing hardener
If not otherwise specified, the test shall be carried out in the following way:
The mass of an empty weighing bottle, measuring approximately 80 mm × 30 mm, is recorded to the nearest 0.001 g (denoted as m₁) A resin mass ranging from 0.4 g to 0.5 g (denoted as m₂) is then accurately weighed to 0.001 g and placed into the closed weighing bottle To dilute the resin, a few drops of toluene are added, and the liquid is evenly spread across the bottom of the weighing bottle with a gentle twisting motion.
The open weighing bottle is placed into an oven with forced air circulation for at least 2 h at
(110 ± 2) °C After cooling down to room temperature in a desiccator the weighing bottle is weighed again to 0,001 g (m 3 )
Isothermal increase of viscosity (processing time)
This method applies to PUR and EP resins, while gel time should be utilized for UP resins Unless stated otherwise, the test must be conducted as outlined.
All components and equipment must be at room temperature The resin components should be mixed following the manufacturer's guidelines, ensuring the mixing process does not exceed 3 minutes The timing begins once the last component is added and mixed.
The initial viscosity measurement is taken after 10 minutes, serving as the baseline value This measurement is repeated until the maximum specified viscosity is achieved, with the duration from the initial measurement to the maximum viscosity recorded as the processing time.
Shelf life
The shelf life is determined by measuring changes in specific characteristics, such as viscosity and gel time, after a defined storage period and temperature Viscosity, as per section 5.3, and gel time, according to section 5.23, are suitable indicators for this assessment Both the supplier and purchaser must agree on the temperature and end-point for testing Two measurements should be taken: one on fresh material and another on material stored under agreed conditions The results, which must reference the applicable standards, should include viscosity and/or gel time before and after storage, along with the storage duration and temperature, as well as the test temperature.
Colour
The method given in ISO 6271 shall be used Two measurements shall be made, and the two results of colour shall be reported along with reference to the standard applied.
Softening temperature
The ISO 306 or ISO 4625 method must be utilized for testing Two measurements of the softening temperature are required, and both results should be reported, along with a reference to the applicable standard.
Ash content
The method given in ISO 3451-1, method A, shall be used Two measurements shall be made, and the two results of the ash content shall be reported.
Filler content
To be agreed between supplier and purchaser.
Chlorine content
Total chlorine content of unsaturated polyesters and epoxide resins
The method given in ISO 4615 shall be used Two measurements shall be made, and the two results of the total chlorine content shall be reported.
Inorganic chlorine content of epoxide resins and glycidyl esters
The method given in ISO 4573 shall be used Two measurements shall be made, and the two results of the inorganic chlorine content shall be reported.
Easily saponifiable chlorine content of epoxide resins and related
The method given in ISO 4583 shall be used Two measurements shall be made, and the two results of the saponifiable chlorine content shall be reported.
Tendency of cristallisation
This method is applicable to epoxy resins only
The method given in ISO 4895 shall be used Two measurements shall be made, and the two results shall be reported.
Epoxide equivalent of epoxide resins
The method given in ISO 3001 shall be used Two measurements shall be made, and the two results of the epoxide equivalent shall be reported.
Content of isocyanate
This method is applicable to polyurethane hardeners only
The method given in ISO 14896 shall be used Two measurements shall be made, and the two results shall be reported.
Water content (Karl Fischer method)
The method given in IEC 60814 shall be used Two measurements shall be made, and the two results of the water content shall be reported.
Hydroxyl value
Polyester resins
The method given in ISO 2554 shall be used Two measurements shall be made, and the two results of the hydroxyl value shall be reported.
Resins other than polyester
To be agreed between supplier and purchaser.
Acid value of polyester resins
The method given in ISO 2114 shall be used Two measurements shall be made, and the two results of the acid value shall be reported.
Amount of double bonds of unsaturated polyester and acrylate resins
To be agreed between supplier and purchaser.
Acid and acid-anhydride content of acid-anhydride hardeners
The ISO 2114 method is utilized for determining acid content, while the ISO 7327 method is employed for measuring anhydride content It is essential to conduct two measurements, and both results for acid value and/or anhydride content must be reported.
Amine value
The method given in ISO 9702 shall be used if not otherwise agreed between supplier and purchaser.
Pot life
General
The time which a particular method requires to achieve a viscosity of 50 Pas is measured The viscosity can be determined in any viscosimeter.
Resinous compounds for cable accessories
• beaker in accordance with ISO 7056, polyethylene, polypropylene or glass with dimensions: 70 mm to 100 mm diameter and 70 mm to 130 mm high;
The beaker shall be marked to a volume of (300 ± 25) ml
The beaker and a standard manufacturer pack shall be stored in an environmental chamber for 24 h at the temperature specified with a tolerance of − 0 2 K
The components shall be removed from the environmental chamber and start mixing immediately according to the supplier´s instructions The time starts at the commencement of mixing the components
Remove the beaker from the environmental chamber, and pour the mixed compound into the beaker up to the mark previously made
The test report shall include the following information:
– the time from the start of mixing until a viscosity of 50 Pas is reached is determined The pot life shall be rounded to the nearest of a second;
– the viscosimeter, test parameters and system used (e.g spindle size, rotation speed etc.) The viscosimeter with the system used shall be calibrated at 50 Pas.
Gel time
Unsaturated polyester based compounds
Gel time refers to the duration required for a reactive compound to transition into a gel state According to ISO 2535, testing should be conducted at a mutually agreed temperature between the supplier and purchaser It is essential to perform two measurements, and both gel time results must be reported alongside the test temperature.
Phenolic resin based compounds
The method given in ISO 9396 shall be used Two measurements shall be made, and the two results of the gel time shall be reported.
Other compounds
If applicable, the methods given in ISO 2535 or ISO 9696 or ISO 8987 shall be used.
Exothermic temperature rise
Unsaturated polyester based compounds
The method given in ISO 584 shall be used Two measurements shall be made, and the two results of the exothermic temperature rise shall be reported.
Resinous compounds for cable accessories
• beaker in accordance with ISO 7056, polyethylene, polypropylene or glass with dimensions: 70 mm to 100 mm diameter and 70 mm to 130 mm high;
• thermocouple made with twisted wires;
5.24.2.2 Preparation of the sample: Test at 23 °C
The beaker must be labeled to hold a volume of (300 ± 25) ml Additionally, a sufficient quantity of resinous compound components should be prepared, ranging from 400 ml to 700 ml, and stored for 24 hours at a temperature of (23 ± 2) °C.
The components shall be mixed according to manufacturer’s instructions The time starts at the commencement of mixing the components
Pour the mixed components into the beaker until reaching the designated mark Insert the thermocouple vertically into the center of the mixture to a depth of (25 ± 5) mm below the surface, securing it in place with an appropriate device, such as a ring stand.
The temperature increase must be monitored, with the maximum rise and time to peak documented The test concludes once the highest temperature is achieved and a significant drop in temperature begins.
NOTE For ease of testing, the temperature can be recorded as a curve
The maximum temperature reached (rounded to the nearest °C) and the time to peak (rounded to the nearest min) shall be reported.
Other compounds
Method of test required, but not available.
Total volume shrinkage of epoxide and unsaturated polyester based
According to ISO 3521, two measurements of total volume shrinkage must be conducted and reported The report should include the test temperature, the density of the compound at that temperature, and the density of the specimen made from the cured compound.
Curing in presence of water
General
This test is specifically designed for polyurethane resinous compounds used in cable accessories It measures gas evolution and changes in physical structure during the curing process in the presence of water The formation of voids due to gas generation in the resin can result in electrical breakdown.
The density of the cured resin mentioned in the technical data sheet shall be > 1,05 g/cm 3
Apparatus and materials
• 250 ml PE squirt bottle with screw-on squirt cap;
• funnel that meets the requirements of 5.26.3;
• tubing, inner diameter corresponding to squirt cap tube outer diameter;
Pouring device
Use a funnel with a capability to fill the bottle within 30 s to 60 s at room temperature.
Procedure
Assemble the test apparatus according to Figure 1 Fill the graduated cylinder completely with water from the bucket Next, remove the squirt bottle from the squirt cap, which is marked at 100 ml and 200 ml, and fill it up to the appropriate mark.
100 ml mark with de-mineralized water
Allow the bucket, squirt bottle, and resinous compound to reach room temperature while still in their original packaging Open the compound package, start the stopwatch, and mix the components as per the manufacturer's instructions Pour the mixed compound into a closed funnel and immediately transfer it into the squirt bottle until the water level reaches the 200 ml mark, ensuring to pour in the center of the bottle and avoid contact with the inner walls.
Screw the cap onto the squirt bottle tightly to ensure a gastight connection, avoiding any deformation of the flexible tubing or bottle If deformation occurs, restart the test Allow the compound to cure for the manufacturer's specified pot life After one hour post pot life, measure the gas volume in the graduated cylinder and then empty the squirt bottle After allowing the resin to harden at room temperature for 24 hours, cut the specimen in half to inspect for blisters or cracks in the compound.
Test report
The following parameters shall be measured and reported:
• physical structure/presence of blisters or cracks or bubbles and/or inclusions;
• picture of the cut surface of the compound with scale.
Determination of the degree of curing
The reaction enthalpie of the uncured resin is determined by using DSC An amount of 10 mg has been found adequate
Unless stated otherwise, approximately 10 g of resin is cured according to the temperature and time conditions agreed upon by the supplier and purchaser The residual enthalpy is measured using a sample weighing around 10 mg.
The degree of curing is calculated as follows:
Degree of curing in % = 100 – H c × 100 / H u where
Curing in thick layer and emissions during curing
General
This test evaluates cured impregnating materials by assessing the curing condition of the specimen's top side, bottom side, and interior Additionally, it includes the measurement of emissions produced during the curing process.
Equipment
The following equipment shall be used:
– flat and smooth square pieces of aluminium foil, 0,1 mm to 0,15 mm in thickness and of
– a former made of metal or any other suitable solid material, (25 ± 1) mm in thickness and
The equipment required includes an oven featuring forced air circulation with a minimum of 8 fresh air changes per hour, specifically designed for drying and curing specimens Additionally, a balance with an accuracy of 0.01 g is essential for precise measurements.
Test specimen
To create a square mould from aluminium foil, first clean the foil thoroughly and then fold it around a former to achieve dimensions of approximately 45 mm on each side The mould should be dried at a temperature of (110 ± 5) °C for a duration of (10 ± 1) minutes, after which it must be cooled and stored in a desiccator.
The mass of the square mould shall be weighed to 0,01 g (m 1 ) A resin sample with a mass between 9,90 g and of 10,10 g shall be weighed to 0,01 g into the mould (m 2 )
The specimen must be cured at a mutually agreed temperature and duration between the supplier and purchaser After curing, it should be cooled to room temperature in a desiccator, and its mass should be measured to an accuracy of 0.01 g (m³) Finally, the aluminum foil is to be removed.
Procedure
The specimen will be evaluated based on the condition of its top side, bottom side, and interior, using visual appearance and tackiness descriptions represented by the symbols in Tables 1, 2, and 3.
Table 1 – Condition of the top side
Table 2 – Condition of the bottom side
Table 3 – Condition of the interior
Not more than five voids 2
For the condition of the interior a statement shall be added whether the interior is uniform or not uniform
NOTE It can be necessary to cut the specimen, to bend the specimen with the fingers or to use a knife for describing the mechanical properties
The emissions shall be calculated by the following equation:
E = 100 – ((m 2 – (m 3 – m 1 )) × 100 / m 2 where m 1 = mass of the empty square mould m 2 = mass of the uncured resin (without mass of the square mould) m 3 = mass of the square mould with cured resin
6 Methods of test for cured reactive compounds
General
The cured compound is self-supporting and thus allows the preparation of rigid and flexible test specimens.
Test specimens
General
The term "test specimen" refers to solid parts of the cured material shaped according to the specific testing method In sections 6.2.2 to 6.2.4, these "test specimens" are simply called "specimens."
Preparation of the reactive compound
The reactive compound must be a uniform mixture of components as specified by the supplier Additionally, any drying, de-aerating, heating, and other treatment processes for the components and the compound should follow the supplier's guidelines It is also important to consider the potential for settlement when the compounds include fillers.
Preparation of test specimens
Specimens must be prepared according to the specific conditions outlined in the IEC 60455-3 specification sheet or as mutually agreed upon by the supplier and purchaser This preparation includes careful attention to the casting process, curing conditions, and the removal and cooling of the specimens Reactive compounds that cure at ambient temperature typically require several days or weeks to reach their final state; therefore, a defined degree of cure can be achieved by curing for 24 hours at ambient temperature followed by 24 hours at 80 °C, unless otherwise agreed Additionally, specimens should be cast to the specified dimensions and be free from defects such as voids, bubbles, nicks, and scratches, with machining processes conducted carefully to prevent excessive heating of the surfaces.
NOTE Removal of the cured compound from the mould is facilitated by the use of release agents and moulds made of chromium-plated or other adequate material.
Type and number of test specimens
The required type and quantity of specimens for a specific testing method are detailed in the test method or the relevant specification sheet of IEC 60455-3, or they can be mutually agreed upon by the supplier and purchaser.
Density
According to ISO 1183-1, two density measurements must be conducted It is essential to report the specimen's preparation method, dimensions, and the results of both density measurements.
Mechanical properties
Tensile properties
The ISO 527 method requires testing specimens to break within a time frame of (60 ± 15) seconds Specimens must be selected according to ISO 527 standards, with a total of five specimens tested The report should detail the preparation method, dimensions, specimen type, testing speed, and the five tensile property results Additionally, it should include tensile stress at yield, maximum load, and break, as well as percentage elongation at yield and break, and the modulus of elasticity.
According to ISO 37, testing must be conducted on five dumb-bell specimens The report should detail the preparation method, the type of dumb-bell specimen used, and the five tensile property results, including tensile strength, percentage elongation at break, and modulus of elasticity.
Compressive properties
The ISO 604 method must be utilized for testing, involving five specimens It is essential to report the preparation method, specimen dimensions, deformation rate, and the five results of the compressive properties The report should include compressive strength at maximum load, compressive yield stress, and the percentage of compressive strain at rupture, where applicable.
Flexural properties
According to ISO 178, the specified method must be applied with a relative movement rate between the loading nose and supports, ensuring that the specimen either ruptures or achieves its maximum load within the designated timeframe.
The flexural properties of five specimens will be tested, with a preparation time of (60 ± 15) seconds The report will detail the specimen preparation, dimensions, relative rate of movement, and the five results obtained It will also include the flexural stress at rupture or maximum load, the corresponding deflection, and the modulus of elasticity, as applicable.
Impact strength
The testing method outlined in ISO 179-1 or ISO 179-2 must be employed, involving the assessment of ten specimens It is essential to document the preparation method, dimensions, and type of specimen, along with the ten results obtained for impact strength.
The ISO 179-1 or ISO 179-2 method requires testing with a notched specimen, involving ten specimens in total It is essential to report the preparation method, dimensions, type of specimen, and the ten results of the impact strength.
Hardness
The ISO 2039-1 (ball indentation method) and ISO 868 (Shore D hardness) standards must be utilized for testing A minimum of five measurements should be conducted on one or more specimens It is essential to report the specimen preparation, dimensions, applied test load, and the five hardness results obtained.
The ISO 868 method, preferably using Shore A hardness, should be employed for testing A total of five measurements must be taken on one or more specimens It is essential to report the specimen preparation method, dimensions, the type of durometer used (A or D), and the five indentation hardness results.
Thermal properties
Bond strength at elevated temperature
The twisted coil test (method A) and the helical coil test (method B) outlined in IEC 61033 must be utilized The test temperature should align with the relevant specification sheet of IEC 60455-3 or be mutually agreed upon by the supplier and purchaser A total of five specimens are to be tested, and the method, types of enamelled winding wire used as substrate, along with the five results, must be documented.
Linear thermal expansion
The method given in ISO 11359-2 shall be used The kind of preparation, the dimensions of the specimen and the result shall be reported.
Thermal conductivity
To be agreed between supplier and purchaser.
Glass transition
According to ISO 11357-2, ISO 11359-2, or ISO 11359-3, two measurements must be conducted to determine the glass transition temperature It is essential to report the specimen preparation details, dimensions, the method employed (either A: DSC or DTA, B1: TMA in expansion mode, or B2: TMA in penetration mode), along with the two obtained results for the glass transition temperature.
6.5.4.2 Temperature of deflection under load
According to ISO 75, either Method A or Method B must be employed for testing Two specimens are required for the test, and it is essential to report the specimen preparation, dimensions, the method utilized, and the two results for the temperature of deflection under load.
The deflection temperature under load is similar to the glass transition temperature; however, ISO 75 methods do not permit the determination of temperatures below 40 °C It is recommended to use the methods outlined in section 6.5.4.1 for more accurate results.
Flammability
According to IEC 60695-11-10, both methods A and B must be utilized, with five specimens tested for each method Method B is applicable only if the results from method A fall below category V-2 It is essential to report the preparation details, dimensions of the test specimens, and the flammability results obtained from both methods A and B, if relevant.
Thermal shock
To be agreed between supplier and purchaser.
Dry heat resistance of resins for cable accessories – Method of test
This test is used to determine the effect of extended exposure to dry heat on loss of mass and impact strength
To ensure consistency, prepare the specimen from the same batch of resinous compound, following the manufacturer's instructions for preparation and curing For the loss of mass test, create a set of three test specimens with specified dimensions.
80 mm × 40 mm × 5 mm and individually identified b) Impact strength: a set of 5 test specimens shall be prepared in accordance with ISO 179
• analytic balance with accuracy of ± 1 mg;
• forced air oven with temperature control;
The test specimens, prepared in accordance with 6.5.7.2, shall be used as follows:
– The loss of mass specimen shall be marked individually Take the mass by weighing it individually to the nearest of 1 mg ( = mass m 1 )
All test specimens must be stored in a forced air oven for 28 days at a temperature of (120 ± 2) °C, ensuring that mechanical loading and direct contact between specimens are avoided Testing should be conducted on only one type of resinous compound at a time.
28 days, the set of test specimen shall be removed from the forced air oven
– The set of test specimen shall than be placed for 8 h in a desiccator and cooled to
– The loss of mass specimens shall be weighed individually to the nearest 1 mg (= mass m 2 ) immediately after removal from the desiccator
– The impact strength shall be measured in accordance with ISO 179
The percent loss of mass shall be calculated for each individual sample, in accordance with the following equation:
The test report shall include the following information:
– the average of percentage loss of mass;
– the average of the impact strength.
Wet heat resistance of resins for cable accessories
This test shall be carried out to the following requirements: a) the samples shall be prepared in accordance with the methods given in the relevant Part
3 sheet, to carry out the following tests: hardness, tensile and elongation, electric strength; b) final measurement of reference samples and treated samples shall be done the same day successively
The test sequence shall be as follows:
1) Preparation of the test specimen from the same lot of resinous compound
2) Immersion for 28 days at (70 ± 2) °C in water
3) Drying for 48 h at (60 ± 2) °C under vacuum
4) Drying 24 h at 80 °C with open ventilation slot
This test evaluates the resistance of resinous compounds to hydrolysis under the combined effects of water and temperature It assesses irreversible changes in mechanical properties through tensile and hardness tests, as well as electrical properties by measuring dielectric strength.
The resinous compound shall be prepared and cured in accordance with the manufacturer’s instructions
A set of 10 test specimens no 1B shall be prepared in accordance with 6.4.1.2 and ISO 527-1, ISO 527-2 and ISO 527-3 from blister free plates of resinous compound of thickness of (4 ± 0,2) mm
NOTE 1 For highly filled compound, specimens can be cast in a mould of adequate dimension for the test
A set of 5 test specimens shall be prepared in accordance with IEC 60093 for the electric strength tester
NOTE 2 IEC 60093 will be replaced by IEC 62631 in the future Users are encouraged to investigate the status of standardisation of IEC 62631 and the possibility of applying the standard Members of ISO and IEC maintain registers of currently valid International Standards
– hydrolysis vessel with a minimum capacity of 1 l for 5 test specimens each;
– forced air oven with temperature control;
The test specimens, shall be used as follows:
– A set of 5 mechanical test specimens shall be kept as reference samples They shall be stored in the test room at standard atmosphere 23/50 in accordance with ISO 291
A set of five mechanical and five electrical test specimens must be immersed in water within a hydrolysis vessel for 28 days at a temperature of 70 °C The specimens should be arranged to ensure they are fully surrounded by water, with a minimum water head of 10 mm, while avoiding any mechanical loading or direct contact between them Only one type of resinous compound should be tested at a time, and the water used must have a conductivity of less than 500 µS/m and a pH value of 7.0 ± 0.5 The hydrolysis vessel should be securely covered and placed in a heating cabinet maintained at (70 ± 2) °C for the entire duration After 28 days, the test specimens will be removed from both the heating cabinet and the hydrolysis vessel.
The test specimens must be placed in a dedicated heating/vacuum cabinet and dried for 48 hours at a temperature of (60 ± 2) °C under a vacuum of (1.5 ± 0.2) kPa Following this, they should be stored for 24 hours at (80 ± 2) °C with an open ventilation slot, and subsequently cooled to (23 ± 2) °C.
Test specimens must be conditioned for 24 hours in a 23/50 atmosphere according to ISO 291 prior to conducting hardness, tensile/elongation, and electric strength tests Both reference and wet aged mechanical test specimens will undergo hardness measurement, followed by tensile and elongation assessments.
The hardness test shall be carried out in accordance with ISO 868 on ends of the mechanical test specimens outside their clamping length and in the centre of their surfaces
The tensile and elongation test shall be carried out in accordance with ISO 527, with a jaw speed of 50 mm/min up to Shore D hardness 70
A jaw speed of 5 mm/min shall be applied if the Shore hardness is ≥ 70
The electrical test specimens shall be subjected to electric strength measurement in accordance with IEC 60093
For mechanical tests the following arithmetic mean for each property shall be calculated:
E 1 : value on the reference test specimens;
E 2 : value on the aged test specimens
The retained percentage of the values for these properties after the temperature/water exposure shall be calculated using the following equation:
For the electric strength test, the arithmetic mean of the test specimens shall be calculated and compared to the values in IEC 60455-3-8:2013, Table 2
The test report shall include the following information:
• retained percent of Shore hardness;
• retained percent of tensile strength;
• retained percent of elongation at break;
Loss of mass
This method applies to resinous compounds for cable accessories
– analytic balance with accuracy ± 1 mg;
– constant temperature oven with ventilation;
– desiccator with calcium dichloride as a drying agent
Three specimens with the dimension of 80 mm × 40 mm × 5 mm shall be conditioned for 24 h at standard atmosphere 23/50 in accordance with ISO 291 and individually identified
The three conditioned test specimens will be individually weighed to the nearest 1 mg (mass m1) and stored for one week at a temperature of (120 ± 2) °C in a vented oven After this period, they will be cooled in a desiccator Once removed from the desiccator, the test specimens will be weighed again to the nearest 1 mg (mass m2).
The percent loss of mass, M, shall be calculated for each individual sample, in accordance with the following equation:
The average value of the three measurements shall be reported.
Temperature index
The temperature index is influenced by the selected test criterion and the end-point criterion, leading to potential variations of 80 K or more for the same material.
The IEC 60216 method must be utilized, with test and end-point criteria aligning with the IEC 60455-3 specification sheet or mutually agreed upon by the supplier and purchaser Two test criteria are required, with a minimum of three exposure temperatures applied for each criterion, ensuring that the difference between consecutive temperatures does not exceed 20 K If the correlation coefficient falls below 0.95, an additional set of specimens must be tested at a different exposure temperature than the one initially selected.
ISO 2578 is a concise adaptation of IEC 60216, focusing solely on the essential information needed for conducting temperature index experiments and calculating results, making it a practical resource for laboratory use.
Each test criterion must include details on specimen preparation, type, dimensions, and the number of specimens tested Additionally, it should specify the exposure temperatures and reference the applicable standards The results should present the end-point times for each specimen, the time to end-point at various exposure temperatures, and a graph illustrating property values against the logarithm of the times to end-point Furthermore, a thermal endurance graph with a first-order regression line, the temperature index, and the correlation coefficient should also be included.
Chemical properties
Water absorption
According to ISO 62, Method 1 (water at 23 °C) and Method 3 (boiling water) should be employed for testing, with three specimens evaluated for each method It is essential to document the preparation type, specimen dimensions, and the three water absorption results obtained from both Method 1 and Method 3 Additionally, one untreated specimen must be retained for reference.
Effect of liquid chemicals
The ISO 175 method must be followed, with the test liquid maintained at a temperature of (23 ± 2) °C and an immersion duration of (168 ± 1) hours (seven days) Three specimens should be tested for each liquid, and details regarding specimen preparation, dimensions, type of test liquid, and results for each specimen must be documented The results should include changes in appearance, dimensions, and mass for all three specimens, and one untreated specimen should be retained for reference.
Resistance to mould growth
According to IEC 60068-2-10, three specimens must be tested for resistance to mould growth as specified in section 6.7.1.3, and the results should be reported Additionally, one untreated specimen should be retained for reference.
Water vapour permeability
To be agreed between supplier and purchaser.
Electrical properties
Effect of water immersion on volume resistivity
The method given in IEC 60093 shall be used If IEC 60093 is not applicable for the material under test, then the following method may be used
IEC 60093 will soon be replaced by IEC 62631, prompting users to explore the standardization status of IEC 62631 and its potential applications ISO and IEC members keep updated registers of valid International Standards.
The following equipment shall be used:
• any commercially available tera-ohmmeter with an accuracy of ±10 %;
• a metal cylinder to be used as voltage electrode (top electrode) of at least 60 mm diameter having a mass to provide a pressure on the specimen of about 0,015 MPa;
• two conducting rubber disks having the same diameter as the top electrode and of 3 mm to 5 mm thickness with a maximum resistance of 1 000 Ω, and with a Shore A hardness of
• a metal cylinder having the same diameter as the top electrode and of about 70 mm height;
The specimen must be either a disk or a square, with its diameter or edge length exceeding that of the top electrode by a minimum of 10 mm Additionally, the thickness of the specimen should not surpass the specified limit.
3 mm and the flat surfaces shall be in parallel Three specimens shall be prepared
NOTE The specimen can be cast between plates, with a wound piece of enamelled round winding wire used as a spacer
The test setup involves placing the specimen between two metal cylinders, separated by rubber disks, as illustrated in Figure 1 The direct current (d.c.) test voltage will be set to achieve an electrical field strength not exceeding 1,000 V/mm The specimen will undergo testing both before and after immersion in demineralized water, with the water temperature specified unless stated otherwise.
The immersion temperature for the test shall be maintained at (23 ± 2) °C for a duration of (168 ± 1) hours Immediately after removing the specimen from the water, it should be blotted between filter papers to eliminate excess moisture before setting up the test Resistance measurements must be conducted (15 ± 1) minutes post setup, with readings taken (60 ± 5) seconds after electrification.
60 mm, resistivity shall be calculated as: ρ = (2,83 ⋅ R)/d where ρ is the resistivity (Ωm); d is the specimen thickness (mm);
For a different diameter D of the top electrode, replace the factor 2,83 by:
Three specimens will be tested, and the report will include details on the preparation method, electrode diameter, test specimen dimensions, test voltage, and the results obtained before and after immersion in water, along with the applicable standard The results will specifically include volume resistance and volume resistivity measurements.
Dielectric dissipation factor (tan δ) and relative permittivity (ε r)
The method given in IEC 60250 shall be used If IEC 60250 is not applicable for the material under test, then the following method may be used
The IEC 60250 standard will soon be replaced by IEC 62631, prompting users to explore the current status of IEC 62631 standardization and its potential applications For up-to-date information, members of ISO and IEC provide registers of valid International Standards.
Any commercially available and adequate impedance-meter may be used, indicating the dielectric dissipation factor (tan δ) and the relative permittivity (ε r )
A test specimen in accordance with 6.7.1.3 shall be used
The top electrode must have a minimum diameter of 40 mm and may be surrounded by a shield electrode, while the bottom electrode should exceed the top electrode's diameter by at least 20 mm and be applied concentrically Electrodes can be created using a conductive dispersion like graphite or silver, or by applying a metal foil no thicker than 0.005 mm, adhered with a drop of oil or another suitable method Testing should be conducted at a temperature of (23 ± 2) °C using a sinusoidal test voltage at a frequency of 1 kHz, with connections to the specimen following the testing device's instruction manual.
Two specimens will be tested, with details on preparation, dimensions, test temperature, electrodes used, test voltage, and frequency reported alongside the standard referenced The report will also include the dielectric dissipation factor and relative permittivity.
Breakdown voltage and electric strength
Breakdown voltage shall be measured by using IEC 60243-1 If IEC 60243-1 is not applicable to the material under test, Clauses 4 and 6 may be amended as below
The electrode arrangement shall be the ball-to-plate type The high-voltage electrode shall consist of a polished steel ball with a radius of (3 ± 0,000 5) mm for rigid material, and
For flexible materials, the required diameter is (10 ± 0.0005) mm, while polished steel balls with a surface roughness of less than 0.001 mm, commonly used in class III ball bearings, are readily available and suitable for this application The earth electrode must be a plate with a diameter of (75 ± 1) mm and rounded edges with a radius of (3 ± 0.1) mm For a complete test arrangement for flexible materials, refer to Figure 2, and for rigid materials, the configuration of the upper electrode and specimen is illustrated in Figure 3.
NOTE 1 The ball-to-plate electrode arrangement gives, compared to a plate-to-plate set, a slightly increased field strength depending on the radius of the ball electrode and the thickness of the specimen
EXAMPLE For a radius of 10 mm and a thickness of 0,1 mm, the increase in field strength compared to that of plate-to-plate arrangement is about 10 %
NOTE 2 If a round cylindrical glass container of sufficient size is used to accommodate the test set-up and the fluid with the earth electrode at the bottom of it, such a container makes it possible to observe visually the process when the voltage is applied It also permits the earth connection and the fluid supply through the bottom electrode, with a fluid overflow at the top of the container, see Figure 2 If an elevated test temperature is required, such an arrangement allows the fluid to be used for heating purposes
The thickness of that part of the specimen which is subject to breakdown shall not exceed
1 mm The thickness of any two of the specimens of one set shall not vary by more than
Cured reactive compounds with a glass transition temperature exceeding 80 °C typically exhibit electric strength ranging from 50 kV/mm to 100 kV/mm, and in some cases, even higher for hot curing cycloaliphatic epoxide-based compounds Testing specimens thicker than 1 mm, arranged with electrodes as specified in IEC 60243-1 (e.g., 25/75 mm), may necessitate voltage levels surpassing 200 kV This situation can result in unavoidable flashover or partial flashover, leading to breakdowns outside the electrode area.
The specimen consists of a cylindrical rod made of cast compound, measuring approximately 30 mm in diameter and twice the assumed breakdown voltage in kilovolts in length It features a central lead wire with a steel ball fixed at one end, while the other end is fully embedded within the casting compound.
After removing the mould, the end of the specimen near the ball electrode must be ground to the specified thickness, polished, and coated with a conductive layer, such as a graphite or silver dispersion, which acts as the earth electrode Thickness control during grinding is achieved using a calibrated permeameter device An example of the specimen setup is illustrated in Figure 4, and this setup can be housed in a glass container, as shown in Figure 2.
For casting, a glass tube can be used as a mold, ensuring that the lead wire and ball electrode are properly centered A suitable lead wire can be made from a 3 mm diameter welding wire, with one end soldered to the ball electrode.
After testing, the cured compound is extracted at the breakdown point to measure the gap between the polished surface and the ball electrode This gap will be assessed using a micrometer probe and reported as thickness.
A specimen in accordance with 6.7.1.3 shall be used
The voltage increase rate must not exceed 500 V/s, and the test temperature should be maintained at (23 ± 2) °C unless specified otherwise The test is conducted with the specimen and electrodes submerged in a dielectric fluid, which is circulated to maintain the required temperature Unless stated otherwise, either unused mineral insulating oil per IEC 60296 or unused synthetic organic ester according to IEC 61099 should be used.
Five specimens will be tested, with detailed reporting on the specimen type, preparation method, dimensions, test temperature, ball electrode radius, and dielectric fluid used The results will include the breakdown thickness, breakdown voltage, and electric strength, along with references to the applicable standards.
Proof tracking index (PTI)
The testing method outlined in Clause 10 of IEC 60112:2003 requires three specimens to be evaluated using a proof voltage specified in the relevant specification sheet or mutually agreed upon by the supplier and purchaser It is essential to report the preparation method, dimensions of the specimens, and the three results of the Partial Discharge Inception Voltage (PTI) Additionally, the report must include the applied proof voltage and the number of drops recorded during the testing process.
Electrolytic corrosion
The visual method given in IEC 60426 shall be used Three specimens shall be tested The three results of electrolytic corrosion shall be reported
Figure 1 – Test apparatus for curing in presence of water test
Figure 2 – Test set-up for volume resistivity
Figure 3 – Example of electrode arrangement for flexible cured compound
Spherical top for high-voltage connection
Figure 4 – Example of electrode arrangement for rigid cured compound
Spherical cap for high-voltage connection
The manufacturer will provide the Material Safety Data Sheet (MSDS) for each component upon request, ensuring that the purchaser can safely transport, use, and dispose of the components and their packaging in the appropriate languages.
Further relevant information concerning health and safety linked to installation conditions shall be made available on request
[1] ISO 558:1980, Conditioning and testing – Standard atmospheres – Definitions
[2] ISO 2578:1993, Plastics – Determination of time-temperature limits after prolonged exposure to heat