Fire hazard testing for electric and electronic products—Part 12: Glowing/hot-wire based test methods—Glow-wire flammability index (GWFI) test method for materials
GB/T 5169.12-2024 Fire hazard testing for electric and electronic products - Part 12: Glowing/hot-wire based test methods - Glow-wire flammability index (GWFI) test method for materials
1 Scope
This document specifies the details of the glow-wire test to be applied to test specimens of solid electrical insulating materials or other solid materials for flammability testing to determine the glow-wire flammability index (GWFI).
GWFI is the highest temperature, determined during this standardized procedure, at which the tested material does not ignite or, if it does, extinguishes within 30 s after removal of the glow-wire and is not totally consumed; and molten drips, if they occur, do not ignite the wrapping tissue.
This test method is a materials test carried out on a series of standard test specimens. The data obtained, along with data from the glow-wire ignition temperature (GWIT) test method for materials, IEC 60695-2-13, can then be used in a preselection process in accordance with IEC 60695-1-30[4] to judge the ability of materials to meet the requirements of IEC 60695-2-11.
Note: As an outcome of conducting a fire hazard assessment, an appropriate series of preselection flammability and ignition tests can allow a reduction of end product testing.
This document is primarily intended for use by technical committees in the preparation of safety publications in accordance with the principles laid down in IEC Guide 104 and ISO/IEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. Unless specifically mentioned or listed in the relevant standards, the requirements, test methods or test conditions of this document will not apply.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2918-2018 Plastics - Standard atmospheres for conditioning and testing (ISO 291:2008, MOD)
Note: There is no technical difference between the referenced content of GB/T 2918-2018 and the referenced content of ISO 291:2008.
ISO 13943:2023 Fire safety - Vocabulary
Note: There is no technical difference between the referenced content of ISO 13943:2023 and the referenced content of ISO 13943:2017.
IEC 60695-2-10 Fire hazard testing - Part 2-10: Glowing/hot-wire based test methods - Glow-wire apparatus and common test procedure
Note: GB/T 5169.10-2017, Fire hazard testing for electric and electronic products - Part 10: Glowing/hot-wire based test methods - Glow-wire apparatus and common test procedure (IEC 60695-2-10:2013, IDT)
IEC 60695-2-13 Fire hazard testing - Part 2-13: Glowing/hot-wire based test methods - Glow-wire ignition temperature (GWIT) test method for materials
Note: GB/T 5169.13-2024, Fire hazard testing for electric and electronic products - Part 13: Glowing/hot-wire based test methods - Glowing-wire ignition temperature (GWIT) test method for materials (IEC 60695-2-13:2021, IDT)
IEC 60695-4:2021 Fire hazard testing - Part 4: Terminology concerning fire tests for electrotechnical products
Note: GB/T 5169.1-2015, Fire hazard testing for electric and electronic products - Part 1: Terminology concerning fire tests (IEC 60695-4:2012, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13943:2023 and IEC 60695-4:2021 and the following apply.
3.1
combustion
exothermic reaction of a substance with an oxidizing agent
Note: Combustion generally emits fire effluent accompanied by flames and/or glowing.
[SOURCE: ISO 13943:2023, 3.62]
3.2
flame
rapid, self-sustaining, sub-sonic propagation of combustion in a gaseous medium, usually with emission of light
[SOURCE: ISO 13943:2023, 3.184]
3.3
flame event
sustained flaming and/or glowing combustion
3.4
flammability
ability of a material or product to burn with a flame under specified conditions
[SOURCE: ISO 13943:2023, 3.200]
3.5
glowing
luminosity caused by heat
[SOURCE: ISO 13943:2023, 3.220]
3.6
glowing combustion
combustion of a material in the solid phase without flame but with emission of light from the combustion zone
[SOURCE: ISO 13943:2023, 3.221]
3.7
ignition
DEPRECATED: sustained ignition
initiation of combustion
[SOURCE: ISO 13943:2023, 3.242]
3.8
ignition
DEPRECATED: sustained ignition
initiation of sustained flame
[SOURCE: ISO 13943:201 7, 3.243]
3.9
molten drip
falling droplet of material which has been softened or liquefied by heat
Note: The droplets can be flaming or not flaming.
[SOURCE: ISO 13943:2023, 3.307]
3.10
preselection
process of assessing and choosing candidate materials, components or subassemblies for making an end product
[SOURCE: IEC 60695-4:2021, 3.2.15]
4 Test specimens
4.1 Test specimen preparation
Test specimens shall be fabricated using the appropriate ISO method, e.g. casting and injection moulding in accordance with the ISO 294 series, compression moulding in accordance with ISO 293 or ISO 295, or transfer moulding to the necessary shape as specified in 4.2. Where this is not possible, the test specimen shall be cut and/or sliced from a representative sample of the material (for example, produced using the same fabrication process as would be used to mould a part of a product).
After any fabrication or cutting operation, all dust and any particles shall be removed from the surface; cut edges shall be fine sanded to a smooth finish.
4.2 Test specimen dimensions
The dimensions of the planar sections of the test specimens shall be at least 60 mm in length and 60 mm in width (measured inside the clamping areas) and shall be provided in all thicknesses under consideration. The preferred values of thickness include 0.1 mm ± 0.02 mm, 0.2 mm ± 0.03 mm, 0.4 mm ± 0.04 mm, 0.75 mm ± 0.15 mm, 1.5 mm ± 0.15 mm, 3.0 mm ± 0.25 mm, or 6.0 mm ± 0.4 mm.
Note: A set of 30 test specimens per thickness will, in general, be adequate to concurrently establish the GWFI and the glow wire ignition temperature, GWIT (see IEC 60695-2-13).
4.3 Testing ranges in formulations
4.3.1 General
The results of tests carried out on test specimen sets of different colour, thickness, density, molecular mass, anisotropic type/direction, additives, fillers, and/or reinforcements can vary. When agreed between the parties involved, the test programmes outlined in 4.3.2 and 4.3.3 may be employed in order to evaluate these variations.
4.3.2 Density, melt flows and filler/reinforcement
Test specimens covering all combinations of minimum and maximum levels of density, melt flows and filler/reinforcement content shall be provided and considered representative of the range if the test results yield the same GWFI. If the test results do not yield the same GWFI for all test specimens representing the range, evaluation shall be limited to the materials with the specific levels of density, melt flows and filler/reinforcement tested. In addition, test specimens with intermediate density, melt flows, and filler/reinforcement content shall be tested to determine the representative range for each GWFI determination. However, as an alternative, the least favourable performance of the specific levels of density, melt flows and filler/reinforcement tested shall be considered representative of intermediate levels without additional testing.
4.3.3 Colour
When evaluating a range of colours, test specimens that
a) contain no colouring,
b) contain the highest level of organic pigments/colorants/dyes and/or carbon black,
c) contain the highest level of inorganic pigments, and
d) contain pigments/colorants/dyes which are known to adversely affect flammability characteristics
are considered representative of the colour range if the test results yield the same GWFI.
If the colours do not yield the same GWFI, when evaluating a range of colours, the GWFI with the least favourable performance should yield the GWFI for an all colour range.
