In order to study the effect of sample thickness on the vertical burning test of requirement set R26 in stan-dard EN 45545-2:2020+A1:2023 Railway applications-Fire protection on railway vehicles-Part 2:Requirements for fire behavior of materials and components,polycarbonate,polyamide and poly(1,4-butylene terephthalate)which are popularly used for electro technical and electronic components on railway vehicle were tested under different sample thicknesses.Using the test criteria of standard UL94,the test method of which is the same as the one of require-ment set R26,to classify the test results,it was showed that the flame-retardant classification rose from rating V-2 or V-1 to rating V-0 with the sample thickness increased.After reaching rating V-0,it kept at this classification as the sample thickness increased.The first reason of these results is that the ignition time increase with the sample thickness and the second one is that the burning rate decrease with the increase of the sample thickness.As a result,if one mate-rial could pass rating V-0 at two different thicknesses,thicker components made of the same material could also do it.This result is different from the rules 4.2(e)described in EN 45545-2:2020+A1:2023,which shows that a prod-uct meeting a requirement at two different thicknesses with identical formulation and density of each layer shall be considered to comply with the requirement of all intermediate thicknesses.In this study,the results not only comply to 4.2(e),but also indicate that thicker products could also meet the requirement,if two products at different thicknesses with identical formulation and density at each layer can pass rating V-0(test criteria of hazard level HL1 to HL3 for re-quirement set R26.This conclusion can be used for determining whether a product meets the requirement set R26.
Rolling StockNon-metalic MaterialsFire BehaviorVertical Burning TestSample Thickness
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