基于EN45545-2:2020+A1:2023的材料厚度对垂直燃烧试验影响的研究(下)

Effect of the Material's Thickness on Vertical Burning Test Based on EN 45545-2:2020+A1:2023(Part 2 of 2)

为了研究EN 45545-2:2020+A1:2023《铁路应用机车车辆防火第2部分:材料和零件的防火性能要求》中材料厚度对R26要求的垂直燃烧试验的影响,选用铁路车辆低功率电工电子产品使用的不同厚度的聚碳酸酯、聚酰胺和聚对苯二甲酸丁二醇酯3种非金属阻燃材料进行试验,采用UL94垂直燃烧试验(测试方法同R26要求的垂直燃烧试验)的判定方法确定试验结果。试验结果表明,随着样品厚度的增加,阻燃等级由V-2或V-1等级上升至V-0等级,厚度继续增加,维持V-0等级不变。原因有2种:一是材料的点燃时间随着厚度的增加而逐步增加;二是材料厚度越大,燃烧速率越慢。因此,若相同材料的部件在2个不同的厚度达到V-0阻燃等级,则更厚的部件也能达到V-0阻燃等级。此规律与EN 45545-2:2020+A1:2023中4.2(e)的规定不同,后者规定具有相同组成和密度的不同厚度的2个产品均满足防火要求时,则处于二者之间的所有厚度的产品视为满足要求。试验结果表明,当组成和密度相同但厚度不同的2个产品均满足R26要求的危害等级时,不仅2个厚度之间的产品满足4.2(e)规定,更厚的产品也能满足要求。此规律可用于判定产品是否符合R26要求。

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.