Detail of GB/T 42924.4-2023

Introduction of GB/T 42924.4-2023

GB/T 42924.4-2023 Plastics- Smoke generation- Determination of the corrosivity of fire effluents- Part 4 : Dynamic decomposition method using a conical radiant heater Warnings 1. Avoidance of misleading This standard method of test shall be used solely to measure and describe the properties of materials, products or systems in response to heat or flame under controlled laboratory conditions and shall not be considered or used by itself for describing or appraising the fire hazard of materials, products or systems under actual fire conditions or as the sole source on which regulations pertaining to corrosivity of fire effluents are based. 2. Avoidance of danger to test operators The test procedures involve high temperatures and combustion products. Therefore, conditions exist for burns, ignition of extraneous objects or clothing, and inhalation of combustion products. Use eye protection, and use protective gloves for insertion and removal of test specimens. Do not touch either the cone heater or the associated fixtures while hot, except with the use of protective gloves. Vent the combustion products flowing through the exposure chamber through a properly designed exhaust system. Vent the captured combustion products in a smoke hood at the end of a test. Check the exhaust system for proper operation before testing, and discharge into a building exhaust system with adequate capacity. Make provisions for collecting and venting any combustion products that for whatever reason fail to be collected by the normal exhaust system of the apparatus. 1 Scope 1.1 This document specifies a test method for measuring the corrosive effect, by loss of metal from a target, of the combustion effluents of plastic materials or products. 1.2 The test method is intended for the evaluation of materials or products, for additional data to assist in the design of products, and for development and research purposes. 1.3 The method provides corrosion results for plastic materials or product specimens limited to a maximum size of 100 mm × 100 mm in area. The results of this method have not been investigated with respect to correlation to actual fires. 1.4 The method measures the increase in electrical resistance of a metal circuit. Such increase is related to the decrease in conductive cross-sectional area resulting from the metal loss due to corrosion. 1.5 The method is applicable to measuring and describing the response of materials and/or products to heat and flame under controlled conditions but is not applicable to describing or appraising the fire hazard or fire risk of materials under actual fire conditions. However, results of this test may be used as elements of a fire hazard or risk assessment as they relate to a particular end use. 2 Normative references The following referenced documents are indispensable for the application 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 16172-2007 Test method for heat release rate of building materials (ISO 5660-1:2002, IDT) GB/T 42924.1-2023 Plastics - Smoke generation - Determination of the corrosivity of fire effluents - Part 1 : General concepts and applicability (ISO 11907-1:2019, MOD) Note: There is no technical difference between the referenced contents in GB/T 42924.1-2023 and those in ISO 11907-1:2019. 3 Terms and Definitions For the purposes of this document, the following terms and definitions defined in GB/T 42924.1-2023 and the followings apply. 3.1 corrosion the reaction of a metallic material with its environment, resulting in a measurable change of the material and possibly in an impairment of the functioning of a metal part or of an entire system Note: In most cases, the reaction is electrochemical. In others, however, it may be chemical (non-electrochemical) or physical 3.2 corrosion damage the physical and/or chemical damage or impaired function caused by chemical action 3.3 corrosion by metal loss the loss of metal on a target, expressed as reduction in thickness of the target metal 3.4 corrosion testing device equipment used to determine corrosion in this standard 3.5 corrosion target the sensor used to determine, under specified test conditions, the degree of corrosion damage Note: This sensor can be a product, a component or a reference material used to simulate them. 3.6 irradiance (at a point on a surface) the radiant flux incident on an infinitesimally small element of the surface containing the point, divided by the area of that element Note: The specimen, once ignited, is also heated by its own flame. 3.7 exposure chamber the enclosure in which a target is exposed to combustion products 3.8 environmental chamber the enclosure used to expose the targets to high humidity and temperature after the exposure to combustion products 3.9 sustained flaming existence of a flame on or over the surface of the specimen for a minimum period of time (over 10 s) Note: For flaming of less than 10 s, the flaming is considered transitory or flashing. 3.10 fire effluent the totality of gases and/or aerosols (including suspended particles) created by combustion or pyrolysis 3.11 fire model a laboratory process, including the apparatus, the environment and the test procedure, intended to represent a certain phase of a fire 3.12 fire scenario a detailed description of conditions, including environmental, of one or more stages from before ignition to completion of combustion in an actual fire at a specific location, or in a real-scale simulation 4 Symbols specific to this test method For the purpose of this document, the following symbols apply. A0: Initial electrical resistance of the corrosion, Ω. A1: Electrical resistance of the corrosion target at the end of 1 hour exposure to combustion, Ω. A24: Electrical resistance of the corrosion target at the end of 24 hours in the environmental, Ω. C: Corrosion of a target, nm. C1: Corrosion of a target at the end of 1 hour exposure to combustion products, nm. C24: Corrosion of a target at the end of 24 hours in the environmental chamber, nm. m: Specimen mass, g. mi: Initial specimen mass, g. mf: Final specimen mass, g. m70: 70 % of the total mass loss, g. td: Sampling time, s. qv: Volumetric sampling rate of combustion products, m 3 /s. 5 Principle 5.1 This test method is used to determine the corrosive effect of combustion products from burning plastic materials. Corrosion is determined by the reduction in thickness of the metal on standardized targets, which is directly related to the increase in electrical resistance of the target due to the decrease in conductive cross-sectional area. These targets are not necessarily representative of the intended end use. 5.2 The test is conducted in two parts. In the first part, two weight loss tests are conducted by exposing the test specimen to a recommended irradiance of 50 kW/m2, or to other heating fluxes up to 100 kW/m2 relevant to particular scenarios. A spark igniter is used to ignite the combustible vapours. The combustible mass loss is determined as the average mass loss of the two tests. In the second part, the specimen is subjected to the same irradiance as before. The products of decomposition or combustion are channeled through a funnel, and a portion of the products continuously flows through an exposure chamber, which holds the corrosion targets, until the specimen has lost 70 % of the loss measured in the two preliminary tests. The corrosion of the corrosion target is determined by exposure of the target to combustion products for 1 hour, followed by 24 hour exposure of the corrosion target to a controlled humidity and temperature environment in a separate chamber. The increase in electrical resistance of each target is monitored and the reduction in thickness of the metal on the target is calculated from the increase in electrical resistance. This reduction in thickness is referred to as corrosion by metal loss. 5.3 Additional guidance for testing is given in Annex A and in GB/T 42924.1-2023.

Contents of GB/T 42924.4-2023