高铁地铁内饰板用什么改性PP？在轨道车辆上，燃烧等级只是入场券，烟密度才是门槛。这篇把 TB/T 3237 与 EN 45545-2 两套体系的门限、六维工况、八项判据与验证顺序摆清楚，并说明哪四种情况下，这个件不该用改性PP。
一个做轨交内装的工程师发来一句话：同一块板子，换了家阻燃剂，燃烧等级还是那个等级，烟密度直接翻了一倍。
这句话把轨交内饰选型的真相说得很直白："不燃"只是入场券，烟密度才是门槛。
还有个常见现场：报告上燃烧等级好看，客户拿去做烟密度，过不去。回头查原因——送检的是原料粒子，装车的是"PP 蜂窝芯 + 玻纤蒙皮 + 贴面"三层结构，不是同一个东西。
这篇讲三件事：门槛怎么定、按什么顺序验，以及哪几种情况下它不该用改性PP。
一、工况六维拆解：轨交内饰板真正卡人的，是隧道里那五分钟
六维拆齐，材料方向基本就定了；而这六维里，只有合规是一票否决的那一维。
| 维度 | 轨交内饰板的实际工况 | 对材料的要求 |
|---|
| 温度 | 车内长期 20-25℃；暴晒停放时车顶与灯具附近更高；热塑 PP 蜂窝板公开资料标称 −40~+80℃ | 冷热循环后不翘曲、不脆裂 |
| 载荷 | 振动疲劳 + 装配应力；乘客倚靠与行李碰撞；座椅强度公开资料常按每座 100 kg 量级 | 刚性够、装配点不裂，靠结构分担 |
| 介质 | 中性清洁剂、消毒剂、湿气与冷凝 | PP 基体耐酸碱油脂较好，填充与阻燃体系另评 |
| 寿命 | 按车辆检修与大修周期，通常以年计 | 老化后力学与阻燃都不衰减 |
| 外观 | 多为"基材 + HPL / PVC 贴面或覆膜"，基材不外露 | 看平整度与贴面附着，不追镜面 |
| 合规 | 国内走 TB/T 3237-2010（动车组）或 TB/T 3138-2018；出口走 EN 45545-2 | 氧指数 + 燃烧等级 + 烟密度 + 烟毒四关 |
合规这一维的分量比其它任何件都重，原因在场景里。
地铁隧道只有与地面相连的通道作为出入口，排烟排热困难；地下供氧不足会让燃烧转向不完全燃烧，发烟量反而更大（据行业媒体公开资料，B 级）。火未必烧得多大，烟一定堆得住。
韩国大邱地铁火灾（2003 年）造成 198 人死亡。事后发现一个反直觉的现象：站台上一张桌子周围死了很多人——浓烟让站内漆黑，人在站立视野高度看不见地面，人群围着桌子打转，最后被烟气熏死。
日本消防部门试验：即使车厢被确认不易燃，起火后 2-5 分钟烟雾弥漫、看不清逃生出口，最慢 8 分钟出现有害气体，据公开科普资料留给大家的逃生时间只有 5 分钟（B 级）。
两条合起来："不易燃"和"能逃生"是两回事。 决定能不能走出车厢的是烟密度和烟毒。
所以轨交选材的提问顺序和汽车件是反的：不是先问强度，是先问氧指数、燃烧等级、烟密度、烟毒这四关，你这块板能过到哪一关。
二、三条路线怎么分：增强无卤阻燃PP、纯无卤阻燃PP、以及与酚醛玻璃钢铝蜂窝的分工边界
轨交内饰板能落在三条线上，没有"谁更强"，只有"卡在哪条线"。
| 路线 | 拿到什么 | 代价 / 短板 | 在轨交内饰上的位置 |
|---|
| 玻纤 / 矿物增强 + 无卤阻燃改性PP | 刚性、尺寸稳定、可注塑可模压；无卤体系发烟与毒性相对可控 | 阻燃剂加量 25-30%，力学必然让位；玻纤外露影响贴面 | 客室侧墙板、端墙板基材，隔板、风道、检修盖板 |
| 纯无卤阻燃 PP（含 PP 蜂窝芯 + 玻纤蒙皮的热塑夹层板） | 轻、可回收、可热熔焊接；公开资料标称 −40~+80℃ | 氧指数往上抬很吃力 | 行李架型材、内衬、盖板这类非承力件 |
| 酚醛 / 玻璃钢 / 铝蜂窝 / PC 的分工 | 酚醛芳纶蜂窝夹层耐火突出；SMC 模压成型效率高；铝蜂窝刚度好重量轻；PC 及合金做风口格栅与灯罩 | 热塑路线在关键防火区与承力位上让位 | 车头、车厢隔断等关键防火区；地板与电气柜；头罩、导流罩、座椅椅面 |
无卤要按量化定义卡，不能凭"无卤"三个字：溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm。灼热丝记准：GWIT 750 / 775℃；GWFI 850 / 960℃，对应 850℃ 灼热丝接触 30 s 不引燃——内饰板旁边的接线端子、灯具、线槽就靠这一条兜住。
烟密度有两套口径，别混用：建筑体系走 GB/T 8627 的烟密度等级 SDR（配合 GB 8624 分级），轨道交通走 GB/T 8323.2 的 NBS 烟箱法，按 Ds(1.5 min) / Ds(4 min) 判。客户说"烟密度过不去"时，先问是哪一套口径。
改性PP 在轨交内饰里的位置，先把边界说清楚。 据公开发表的轨道交通材料行业综述（B 级），头罩、侧墙板、门立柱罩、座椅椅面长期以玻璃钢为主；地板与电气柜多走铝蜂窝；内饰板与隔板常见 ABS；风口格栅与灯罩多见 PC 及合金。热塑性 PP 在可回收、可焊接、成型效率高这条线上——行李架型材、内衬、风道、检修盖板这类非承力件，以及 PP 蜂窝芯 + 玻纤蒙皮的热塑夹层板。一句话：改性PP 现在进的多数是中低危险等级、非承力、非关键防火区的内装位。 这条边界先讲明白，比事后解释"报告为什么过不去"有用。
三、★ 选型判据表：轨交内饰板的八项判据，每项都带验证方法
注意第三列：卡住人的常常不是"看哪项"，是"拿什么测、算不算过"。
| 指标 | 门限值 | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| 氧指数 LOI | 顶板 ≥35%；侧板、墙壁板 ≥32%；地板 ≥30%（TB/T 3237-2010，动车组） | GB/T 2406.2（塑料 / 橡塑）、GB/T 8924（FRP）等按材质分方法 | 富氧端续燃，侧墙板这一档过不去 | 无卤磷氮 / 膨胀阻燃 + 玻纤或矿物填充往上抬 |
| 燃烧性能等级 | A 级优先；供需一致时可选 B 级；C 级不合格 | UIC 564-2 第 7 章垂直燃烧 | 火焰蔓延、熔滴引燃下方 | 无卤膨胀阻燃 + 抑滴设计 |
| 烟密度 Ds | 有焰 / 无焰分别测：Ds(1.5 min) ≤100，Ds(4 min) ≤200（TB/T 3138-2018 口径 Ds(4)≤200，25 kW/m²、有引燃火焰模式） | GB/T 8323.2（NBS 烟箱法） | 换个阻燃体系烟密度翻倍，旧报告作废 | 低发烟体系 + 按件重测，不能沿用粒子数据 |
| 烟气毒性 | 8 种气体分别限值：CO、CO₂、HCl、HBr、HF、HCN、NOₓ、SO₂（公开资料典型值：CO <4000 mg/m³、HCl ≤150 mg/m³；质量 ≤100 g 的小件可豁免） | TB/T 3237 附录，烟箱内有焰燃烧同步采集（参照 ASTM E662） | 有卤体系放出 HCl / HBr，这一栏直接挂 | 无卤体系；先做元素筛查再送毒测 |
| 无卤量化定义 | 溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm | 元素分析（XRF 初筛 + 氧弹燃烧-离子色谱复核） | 名义无卤实测含卤，后续报告全废 | 供应商元素声明 + 进料批次筛查 |
| 灼热丝 | GWIT 750 / 775℃；GWFI 850 / 960℃；850℃ 接触 30 s 不引燃 | IEC 60695-2-12 / -2-13；GB/T 5169.12 / 5169.13 | 端子、灯具、线槽周边引燃 | 玻纤增强 + 无卤阻燃 |
| 力学与耐候 | 长玻纤 PP-LGF 公开区间：拉伸 50-80 MPa、弯曲 80-120 MPa、缺口冲击 15-40 kJ/m²、HDT 120-180℃、收缩 0.3-0.8%；矿物体系滑石粉常见 15-40 份 | GB/T 1040.2；GB/T 9341；GB/T 1043.1；GB/T 1634.2；氙灯 / 热老化按项目规定 | 装配点开裂、长期承压蠕变、老化后变脆 | 基材档位 + 填充与增韧配平，牺牲项按件排序 |
| 成品取样一致性 | 从成品取样；不能取成品时按实际应用状态制备 | TB/T 3138-2018 成品取样要求 | 粒子报告合格、复合板成品不合格 | 送检状态与装车状态一致，贴面 / 蒙皮一并计入 |
文字版结论：八项里烟密度和烟气毒性最该先看，它们是"燃烧等级一样、结果差好几倍"的那两项；无卤量化定义最便宜，元素筛查就能筛掉一批；氧指数决定这块板能上哪个位置。
PP 的阻燃剂加量普遍在 25-30% 这一档。"阻燃剂加得多、力学就一定掉"是 PP 的结构性问题，不是配方水平问题。 更棘手的是第三个变量——压低烟密度往往要更多阻燃剂，或者换一套体系，力学代价同时发生。 氧指数、烟密度、力学三者相互拉扯，不可能只动一个。
四、轨交内饰板最常翻车的四类失效与各自根因
失效一（敢否定一个常见做法）：只看燃烧等级报告选材。 很多料燃烧等级是同一个等级，烟密度能差好几倍；而隧道与地下区间这种密闭场景里，伤亡主要来自烟气造成的能见度丧失与毒性，不是火焰本身。同等燃烧等级的两块料，在轨交上不是同一档东西。
失效二：有卤体系过得了等级，过不了场景。 溴系效率高、加量少，等级容易做上去，但加工受热释放卤化氢腐蚀设备模具，燃烧释放卤化氢与浓烟（据公开资料）；轨交毒性试验直接对 HCl、HBr 设限值，禁限用物质清单里也明列高浓度卤素与多溴类物质。这个场景下，有卤路线是被明确规避的。
失效三：送检样条与装车件不是同一个东西。 烟密度与毒性试验对厚度、有焰 / 无焰模式、蒙皮与贴面状态极其敏感，复合板用单一材料报告顶替整件报告等于没做。TB/T 3138-2018 专门增加了成品取样要求（据公开标准解读，B 级）——这条修订本身就是冲这类问题来的。
失效四：为过氧指数加阻燃剂，烟密度反而更大。 阻燃与抑烟不是同一条曲线：公开技术资料提到，磷氮系有助于减少烟雾生成，而含卤阻燃剂可能增加烟密度（B 级）。氧指数抬上去的同时，烟密度可能跟着涨，力学同时掉。 正确动作是换体系，不是继续加量。
五、验证顺序：先无卤筛查，最后才是整件装车文件
这一段同行很少写，但它是换料能不能省钱的关键。
`
① 无卤筛查 溴 / 氯元素含量（XRF 初筛 + 离子色谱复核）
↓ 名义无卤实测含卤，退回换体系
② 燃烧等级 UIC 564-2 第 7 章垂直燃烧；A 级优先
↓ 判为 C 级，退回换阻燃体系
③ 氧指数 GB/T 2406.2 / GB/T 8924，按安装位置对档
↓ 侧墙板 ≥32%、顶板 ≥35% 对不上，退回改填充与体系
④ 烟密度 GB/T 8323.2，有焰 / 无焰分别测 Ds(1.5 min)、Ds(4 min)
↓ 轨交最常挂的一关，不过退回改体系
⑤ 烟气毒性 8 种气体分别对限值
↓ 不过退回，有卤体系通常卡在这里
⑥ 力学与老化 拉伸 / 弯曲 / 缺口冲击 / HDT + 氙灯或热老化
↓ 阻燃过关但力学塌到装配不住，退回重新配平
⑦ 振动疲劳 装车振动与装配应力模拟
↓
⑧ 整件装车文件 从成品取样、成品状态送检，与装车状态核对
`
每一级都有明确的"不过就退回上一级"判据。
文字版结论：顺序是 无卤筛查 → 燃烧等级 → 氧指数 → 烟密度 → 烟毒 → 力学与老化 → 振动疲劳 → 整件文件。
无卤筛查放最前，因为几分钟就能一票否决，成本也低；烟密度必须在力学之前过，因为改烟密度多半要动体系，一动体系力学就要重新配平；整件文件放最后，但取样状态要一开始就定死。
六、反向诚实：这四种情况，轨交内饰板不该用改性PP
前面讲"怎么做"，这里讲"什么时候别做"。
| 出现的情况 | 为什么改性PP 不合适 | 该往哪走 |
|---|
| 项目被判为最高危险等级（EN 45545-2 的 HL3 类） | HL3 对氧指数、烟密度、毒性同时收紧，改性PP 体系抬不到那一档 | 酚醛 / 芳纶蜂窝夹层、金属蜂窝复合结构 |
| 件要承力并长期承受疲劳（车体结构、承力地板、座椅骨架） | 高填充下刚性可用，但长期疲劳与结构冗余不是它的场 | 铝蜂窝、金属结构、SMC 模压结构件 |
| 同时要超低烟密度 + 高刚性（车头、车厢隔断等关键防火区） | 抑烟与高刚性在 PP 上互相拉扯，加量与填充一起上，力学与工艺都撑不住 | 酚醛基夹层复材、SMC |
| 要求提供型式试验与认证支持 | 材料商能给的是材料数据与批次一致性，部件型式试验由部件方主导 | 由部件方牵头，我们配合提供材料侧数据 |
最后一条是合作边界：材料商提供数据与批次一致性，型式试验与认证由部件方主导，我们不做越位承诺。 需要哪些数据、按哪套体系出、以什么状态送检，可以在开样前一起列清单。
还有一条必须提醒：顶板那一档（氧指数 ≥35%）本身就是改性PP 的天花板附近。 遇到顶板件，先把氧指数可行性单独验一遍，再谈后面五关；顺序反了会浪费整轮打样。
七、换料要动什么：轨交内饰板换料风险清单
决定试改性PP 之前，这张表先过一遍。客户真正的顾虑往往不是性能，是"报告要不要重做"。
| 要动的项 | 需要确认什么 | 不做会怎样 |
|---|
| 模具收缩率 | 玻纤体系收缩率各向异性明显，长件敏感 | 尺寸超差，侧墙板拼缝对不上 |
| 浇口与排气 | 高填充 + 阻燃体系流动性差异大 | 充填不足、熔接线强度低 |
| 料温与模温 | 阻燃体系对停留时间敏感 | 浮纤、色差、气味、烟密度波动 |
| 干燥 | 按具体体系定，不能按普通 PP 的条件照搬 | 银丝、气泡、降解 |
| 保压与脱模 | 高填充体系收缩与顶出行为都变 | 变形、顶出拉伤、装配点开裂 |
| 色差 | 贴面件的基材色差会透出来 | 批次色差争议 |
| 阻燃与烟密度全套 | 换料必须重做全套：无卤筛查、燃烧等级、氧指数、烟密度、烟毒，一项都不能沿用旧报告 | 燃烧等级还一样、烟密度已经翻倍，装车文件失效 |
| 验证顺序 | 无卤筛查 → 燃烧等级 → 氧指数 → 烟密度 → 烟毒 → 力学老化 → 振动疲劳 → 整件文件 | 风险全压到最后一步集中爆发 |
文字版结论：轨交件换料比一般件多动一块——报告。阻燃与烟密度报告作废才是大头：同一块料换个阻燃体系，燃烧等级可能纹丝不动，烟密度已经不在同一档。所以这张表里最该先谈的是验证顺序。
八、一页纸汇报对照表：六种场景直接上报
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 客室侧墙板 / 端墙板基材 | 玻纤或矿物增强 + 无卤阻燃改性PP | 氧指数 ≥32%；Ds(1.5 min) ≤100、Ds(4 min) ≤200 | GB/T 2406.2；GB/T 8323.2 | 安装位置归属、贴面方式 |
| 行李架型材 / 内衬 / 盖板 | 纯无卤阻燃 PP 或热塑 PP 蜂窝复合板 | 氧指数与烟密度双过；−40~+80℃ 尺寸稳定 | GB/T 2406.2；GB/T 8323.2；成品取样 | 承载归属、是否需可回收 |
| 通风风道 / 检修盖板 | 阻燃 SMC 或增强无卤阻燃PP 按成型效率选 | 燃烧等级 A 级优先、B 级可协商 | UIC 564-2 第 7 章 | 批量与成型方式 |
| 顶板类件 | 先单独验氧指数可行性，再定路线 | 氧指数 ≥35% | GB/T 2406.2 或按材质对应方法 | 能否改填充 |
| 出口欧盟项目 | 先定 EN 45545-2 危险等级再选材 | 按 R1 或对应要求集：CFE ≥20 kW/m²、MARHE、Ds(4)、CITG 逐项 | ISO 5658-2；ISO 5660-1；ISO 5659-2；EN 17084 | 运营类别与设计类别（定 HL1/HL2/HL3） |
| 关键防火区（车头、隔断、承力地板） | 不走改性PP | — | — | 直接转酚醛夹层 / 金属蜂窝 / SMC |
文字版结论：这张表的作用是让技术员把结论直接往上报。判断标准只有一条——客户拿这张表，能不能在一次会议里把材料方向定下来。 特别注意第五行：国内 TB/T 的报告与 EN 45545-2 的报告互不等同，两套要分别做。
九、轨交内饰板上最容易出问题的，往往不是"料不够阻燃"
轨交内饰板上行业最常见的早期失效，不是燃烧等级过不去，是燃烧等级过了、烟密度或烟气毒性过不去。据公开标准资料，TB/T 3237-2010 对动车组内装材料的判定是四项并列：氧指数按安装位置分档（顶板 ≥35%、侧板与墙壁板 ≥32%、地板 ≥30%）、燃烧性能（UIC 564-2 第 7 章，须达 A 或 B 级）、烟密度（GB/T 8323.2，有焰 / 无焰分别测）、烟气毒性（8 种气体分别限值）。任一项不达标就进不了这套体系。
行业通行的做法是把三件事一起定：先用无卤元素筛查锁定体系，再按安装位置对氧指数档位，最后用低发烟体系把烟密度压下来。关键不在单看哪一项，而在氧指数、烟密度、力学能不能同时站在门限里——它们是对拉的。
宁波市科隆新材料有限公司在这个件上常供的是改性聚丙烯（PP）粒子里的无卤阻燃增强方向，按件的安装位置和门限档位给基材与填充配比，主要用来解决上面说的"等级过了、烟密度过不去"这件事；配方按件的工况调，可以配合做小样比对与打样共研，件级客户多品种小批量的需求也能接。
常见问答
问：燃烧等级一样的两块料，烟密度能差多少？
答：差好几倍是常见的。烟密度跟阻燃体系与成炭方式直接相关，而燃烧等级只看离火后自熄与滴落。轨交上这两项必须同时看，只拿燃烧等级报告谈选材，是在拿隧道里的能见度做赌注。
问：有卤体系又便宜又好过，轨交上能不能用？
答：不建议。加工受热释放卤化氢腐蚀设备模具，燃烧释放卤化氢与浓烟；轨交毒性试验直接对 HCl、HBr 设限值。省下的那一块，通常要在毒性那一关还回去。
问：阻燃剂加到 25-30%，力学掉是你们配方不行吗？
答：不是配方水平问题，是 PP 的结构性问题，加量降不下来。能做的只是把界面与填充配平，让损失可控。而想把烟密度压得更低，加量还要往上走。
问：国内做了 TB/T 的检测，出口项目能不能直接用？
答：不能。国内走 GB/T 8323.2 加 UIC 564-2；EN 45545-2 走 ISO 5658-2、ISO 5660-1、ISO 5659-2、EN 17084，并先按运营类别与设计类别定 HL1/HL2/HL3。两套要分别做。
| 工况 | 关键判据 | 常规供应 |
|---|
| 客室侧墙板 / 端墙板基材 | 氧指数 ≥32%；Ds(1.5 min) ≤100、Ds(4 min) ≤200 | 无卤阻燃增强 PP 方向，常规备货 |
| 行李架 / 内衬 / 盖板 | 氧指数与烟密度双过、尺寸稳定 | 无卤阻燃 PP 与增强方向 |
| 出口项目件 | 按 EN 45545-2 要求集与危险等级逐项 | 无卤阻燃增强 PP 方向，配合材料侧数据 |
想提醒一句：件出问题，最常见的错法是先换料。烟密度超标、氧指数不够、毒性超限，每一条的原因都不止一个。先定位，再换料；顺序反了，往往换了几轮还在原地。
十、最后说三句
一，轨交内饰板上，"不燃"只是入场券，烟密度才是门槛。 隧道与地下区间的疏散条件决定了：真正让人走不出车厢的是烟气的能见度与毒性，不是火焰本身。
二，氧指数、烟密度、力学三者是对拉的，不可能只动一个。 阻燃剂加量 25-30% 是 PP 绕不开的档，力学损失是结构性的；想把烟密度再压下去，往往要更多加量或换体系，代价同时发生。先把这笔账认下来，再谈方案。
三，验证顺序比验证项更重要。 无卤筛查 → 燃烧等级 → 氧指数 → 烟密度 → 烟毒 → 力学与老化 → 振动疲劳 → 整件文件。无卤筛查放最前，烟密度必须放在力学之前，取样状态一开始就定死。
关于 PP 在轨交内饰里的位置，我们把边界说在前面：它现在主要落在中低危险等级、非承力、非关键防火区的内装位上；车头、车厢隔断、承力结构这些位置，该走酚醛夹层、金属蜂窝与 SMC，我们不硬接。
关于我们
关于我们，四句话：
一、宁波市科隆新材料有限公司，自产改性聚丙烯（PP）造粒——均聚 / 无规共聚 / 抗冲共聚；
二、改性方向：填充、玻纤增强、增韧、阻燃、低气味低 VOC、耐候、免喷涂耐划伤；
三、各大石化厂 PP 树脂贸易；
四、副牌料、大包料现货。
What type of modified PP is used for high-speed rail and metro interior panels? On rail vehicles, the fire rating is just a ticket to enter, while smoke density is the actual threshold. This article clarifies the thresholds, six-dimensional conditions, eight criteria, and verification sequences of the TB/T 3237 and EN 45545-2 systems, and explains in which four situations this component should not use modified PP.
An engineer who works on subway interior finishes sent a message: The same board, with a different flame retardant added, keeps the same fire rating, but the smoke density doubled.
This sentence puts the truth about subway interior selection very bluntly: 'Non-flammable' is just the entry ticket, while smoke density is the real threshold.
There is another common scenario on site: the report shows a good combustion rating, but when the customer uses it to test smoke density, it fails. Checking the reason later — the sample sent for testing was raw material granules, while what was loaded onto the vehicle was a three-layer structure of 'PP honeycomb core, fiberglass skin, and laminate,' not the same thing.
This article talks about three things: how to set the threshold, in what order to test, and in which cases modified PP should not be used.
1. Six-Dimensional Analysis of Working Conditions: What really traps people with subway interior panels is those five minutes in the tunnel
Once the six dimensions are fully analyzed, the direction for materials is basically set; among these six dimensions, only compliance is the one that can veto everything.
| Dimension | Actual operating conditions of rail transit interior panels | Requirements for the materials |
|---|
| Temperature | Inside the car it is long-term 20-25°C; when parked in direct sunlight, the area near the roof and lights is higher; the publicly available data for thermoplastic PP honeycomb panels indicates −40 to 80°C | Does not warp or crack after hot and cold cycles |
| Load | Vibration fatigue; assembly stress; passenger leaning and collision with luggage; seat strength public data is often based on 100 kg per seat | Sufficient rigidity, assembly points do not crack, relying on the structure to bear the load |
| Medium | Neutral cleaners, disinfectants, moisture, and condensation | PP substrate has good resistance to acids, alkalis, and grease; filling and flame-retardant systems are evaluated separately. |
| Lifespan | Based on the vehicle maintenance and overhaul cycle, it is usually calculated in years | After aging, both mechanical properties and flame retardancy do not degrade |
| Appearance | Mostly 'substrate HPL/PVC laminate or film-coated', with the substrate not exposed | Check the flatness and veneer adhesion, without pursuing a mirror finish |
| Compliance | For domestic use, follow TB/T 3237-2010 (EMU) or TB/T 3138-2018; for export, follow EN 45545-2. | Oxygen Index Combustion Rating Smoke Density Smoke Toxicity Four Levels |
The weight of the compliance dimension is heavier than any other component, and the reason lies in the context.
Subway tunnels only have passages connected to the surface as entrances and exits, making smoke and heat exhaust difficult; insufficient underground oxygen can cause combustion to become incomplete, resulting in even more smoke (according to publicly available information from industry media, level B). The fire may not burn very large, but the smoke will definitely accumulate.
The Daegu subway fire in South Korea (2003) caused 198 deaths. Afterwards, a counterintuitive phenomenon was discovered: many people died around a table on the platform — the thick smoke made the station pitch black, people standing at eye level could not see the ground, and the crowd circled around the table, eventually being suffocated by the smoke.
Japanese fire department experiment: Even if the cabin is confirmed to be non-flammable, smoke spreads and the escape exits are obscured within 2-5 minutes after a fire starts, and harmful gases appear no later than 8 minutes. According to publicly available popular science information, the escape time provided to everyone is only 5 minutes (Class B).
Combine the two: 'non-flammable' and 'can escape' are two different things. What determines whether you can get out of the carriage is smoke density and smoke toxicity.
So the order of questions for material selection in rail transit is the opposite of that for automotive parts: instead of asking about strength first, you first ask about the four criteria of oxygen index, combustion rating, smoke density, and smoke toxicity, and see which level this board can pass.
2. How the three routes are divided: enhanced halogen-free flame-retardant PP, pure halogen-free flame-retardant PP, and the division of responsibilities with phenolic glass fiber reinforced aluminum honeycomb
The interior panels of rail transit can fall on three lines; there is no 'who is stronger,' only 'which line it is stuck on.'
| Route | Get what | Cost / Shortcoming | Position on rail transit interior |
|---|
| Glass fiber / mineral reinforced halogen-free flame-retardant modified PP | Rigid, dimensionally stable, suitable for injection molding and compression molding; halogen-free system with relatively controllable smoke and toxicity | Flame retardant dosage 25-30%, mechanical properties will inevitably give way; exposed glass fibers affect the veneer | Cabin side wall panels, end wall panel substrates, partitions, air ducts, inspection cover panels |
| Pure halogen-free flame-retardant PP (including thermoplastic sandwich panels with PP honeycomb core and glass fiber facing) | Lightweight, recyclable, and hot-melt weldable; publicly available data indicates −40~80℃ | Raising the oxygen index is very strenuous | Non-load-bearing components such as luggage rack profiles, linings, and cover plates |
| Division of labor of phenolic / fiberglass / aluminum honeycomb / PC | Phenolic aramid honeycomb core has outstanding fire resistance; SMC molding is highly efficient; aluminum honeycomb has good stiffness and light weight; PC and alloys are used for air vent grids and lampshades | The thermoplastic route yields at key fire protection areas and load-bearing positions | Key fire prevention areas such as the front of the vehicle and compartment partitions; the floor and electrical cabinets; head covers, fairings, and seat surfaces |
Halogen-free must follow the quantitative definition card; you cannot rely on just the three words 'halogen-free': Bromine <900 ppm, Chlorine <900 ppm, total of both <1500 ppm. Remember the glow wire test: GWIT 750 / 775℃; GWFI 850 / 960℃, corresponding to a glow wire of 850℃ contacting for 30 s without igniting — this is what protects the terminals, lamps, and wiring ducts next to the interior panels.
There are two standards for smoke density, do not mix them: the building system follows the smoke density grade SDR of GB/T 8627 (in conjunction with GB 8624 classification), while rail transit follows the NBS smoke chamber method of GB/T 8323.2, judged by Ds(1.5 min) / Ds(4 min). When a customer says 'the smoke density doesn't pass,' first ask which standard they are referring to.
The position of modified PP in rail transit interiors should first clarify the boundaries. According to publicly published industry reviews of rail transit materials (B-level), headliners, sidewall panels, door pillar covers, and seat surfaces have long been primarily made of fiberglass; floors and electrical cabinets mostly use aluminum honeycomb; interior panels and partitions commonly use ABS; air vent grilles and lamp covers are often PC and alloys. Thermoplastic PP, along the lines of being recyclable, weldable, and highly efficient to mold, is used for non-load-bearing parts like luggage rack profiles, linings, air ducts, and maintenance access panels, as well as thermoplastic sandwich panels with PP honeycomb cores and glass fiber skins. In short: most of the modified PP currently used is in low to medium hazard, non-load-bearing, non-critical fire zone interior positions. Clarifying this boundary first is more useful than explaining afterward why a report doesn’t pass.
3. ★ Selection Criteria Table: Eight criteria for rail transit interior panels, each with a verification method
Pay attention to the third column: what's often trapping people is not 'which item to look at,' but 'what to use to measure and whether it counts.'
| Indicator | Threshold value | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Oxygen Index LOI | Roof panel ≥35%; side panels, wall panels ≥32%; floor panels ≥30% (TB/T 3237-2010, EMU) | GB/T 2406.2 (Plastics / Rubber-Plastics), GB/T 8924 (FRP), etc., are methods classified by material | Oxygen-rich end continuous burning, this section of the side wall panel cannot pass | Halogen-free phosphorus-nitrogen / intumescent flame retardant Fiberglass or mineral filling lifts upwards |
| Fire performance rating | Priority for Grade A; Grade B can be chosen when supply and demand match; Grade C is not qualified | UIC 564-2 Chapter 7 Vertical Burning | Flames spread, molten drops ignite below | Halogen-free flame retardant with anti-drip design |
| Smoke Density Ds | Flame / Flameless measurement respectively: Ds(1.5 min) ≤100, Ds(4 min) ≤200 (TB/T 3138-2018 caliber Ds(4) ≤200, 25 kW/m², with igniting flame mode) | GB/T 8323.2 (NBS Smoke Chamber Method) | Changing the flame-retardant system doubled the smoke density, and the old report is invalid. | Low smoke system: reweigh per item, particle data cannot be reused |
| Smoke toxicity | Limit values for 8 gases: CO, CO₂, HCl, HBr, HF, HCN, NOₓ, SO₂ (typical values from public sources: CO <4000 mg/m³, HCl ≤150 mg/m³; small items with mass ≤100 g may be exempt) | TB/T 3237 Appendix, simultaneous collection of flame combustion inside the smoke box (refer to ASTM E662) | If there is a halogen system releasing HCl / HBr, this column is filled directly. | Halogen-free system; first conduct elemental screening, then send for toxicity testing |
| Halogen-free Quantitative Definition | Bromine <900 ppm, Chlorine <900 ppm, Total of both <1500 ppm | Elemental analysis (XRF preliminary screening, oxygen bomb combustion - ion chromatography verification) | Nominally halogen-free but tested to contain halogen, subsequent reports are all void | Supplier Element Declaration Incoming Batch Screening |
| Scorching thread | GWIT 750 / 775℃; GWFI 850 / 960℃; 850℃ contact for 30 s does not ignite | IEC 60695-2-12 / -2-13; GB/T 5169.12 / 5169.13 | Ignition around terminals, lamps, and cable ducts | Glass fiber reinforced Halogen-free flame retardant |
| Mechanics and Weather Resistance | Long glass fiber PP-LGF open range: tensile 50-80 MPa, flexural 80-120 MPa, notched impact 15-40 kJ/m², HDT 120-180℃, shrinkage 0.3-0.8%; mineral system talc powder commonly 15-40 parts | GB/T 1040.2; GB/T 9341; GB/T 1043.1; GB/T 1634.2; Xenon lamp / Heat aging according to project specifications | Assembly point cracking, long-term stress creep, brittleness after aging | Substrate level Balance filling and toughening, rank sacrifice items by piece |
| Finished product sampling consistency | Sample from finished product; if finished product cannot be obtained, prepare according to actual application conditions | TB/T 3138-2018 Finished Product Sampling Requirements | Particle report qualified, composite board finished product unqualified | The inspection status is consistent with the loading status, and the facing/skin is counted together. |
Text version conclusion: Among the eight items, smoke density and smoke toxicity should be looked at first, as they are the two items where 'the combustion level is the same, but the results differ by several times'; halogen-free quantification is the cheapest, as a simple elemental screening can eliminate a batch; the oxygen index determines which position this board can be used in.
The flame retardant content in PP is generally in the range of 25-30%. 'Adding more flame retardant will definitely reduce mechanical properties' is a structural issue of PP, not a formulation-level issue. What’s more tricky is the third variable—reducing smoke density often requires more flame retardant, or switching to a different system, with mechanical performance being affected at the same time. The three factors of oxygen index, smoke density, and mechanical properties interact with each other; it is impossible to change only one.
4. The Four Most Common Failures of Rail Transit Interior Panels and Their Root Causes
Invalid point one (daring to question a common practice): Selecting materials solely based on the fire rating report. Many materials have the same fire rating, but the smoke density can differ several times; in confined environments like tunnels and underground sections, casualties mainly come from visibility loss and toxicity caused by smoke, not the flames themselves. Two materials with the same fire rating are not equivalent when it comes to rail transit.
Failure 2: Halogen-containing systems can meet the grade but fail the scenario. Brominated compounds are highly efficient and require small amounts, so achieving the grade is easy, but during processing they release hydrogen halides when heated, which corrode equipment and molds, and when burned, they release hydrogen halides and dense smoke (according to public information); transit toxicity tests directly set limit values for HCl and HBr, and the list of prohibited substances also explicitly lists high-concentration halogens and polybrominated compounds. In this scenario, halogen-containing routes are explicitly avoided.
Failure 3: The sample submitted for inspection is not the same as the installed part. Smoke density and toxicity tests are extremely sensitive to thickness, flaming/non-flaming modes, and the state of the skin and facing. Replacing the complete part report with a report on a single material for composite panels is equivalent to not testing at all. TB/T 3138-2018 specifically added requirements for sampling finished products (according to publicly available standard interpretations, Class B) — this revision itself is aimed at addressing this kind of issue.
Failure 4: Adding flame retardants to increase the oxygen index actually increases the smoke density. Flame retardancy and smoke suppression are not the same curve: public technical data indicate that phosphorus-nitrogen systems help reduce smoke generation, while halogen-containing flame retardants may increase smoke density (Class B). As the oxygen index rises, smoke density may also increase, and mechanical properties simultaneously degrade. The correct action is to change the system, not to continue increasing the amount.
5. Verification sequence: first the halogen-free screening, and finally the complete loading documentation
This part is rarely written by peers, but it is key to whether changing materials can save money.
`
① Halogen-free Screening Bromine / Chlorine Content (XRF Preliminary Screening, Ion Chromatography Verification)
↓ Nominally halogen-free, actual measurement contains halogen, return for system replacement
② Combustion level UIC 564-2 Chapter 7 Vertical burning; Class A preferred
↓ Rated as C, returned to replace the flame-retardant system
③ Oxygen index GB/T 2406.2 / GB/T 8924, ranked according to installation position
↓ Side wall panel ≥32%, top panel ≥35% do not match, return for modification of filling and system
④ Smoke density GB/T 8323.2, with flame / without flame, measure Ds(1.5 min) and Ds(4 min) respectively
↓ The most common level people fail in rail transit, but it reverts to system modification
⑤ Fume Toxicity The eight gases each with respect to the limit values
↓ But going back, the brine system usually gets stuck here
⑥ Mechanics and Aging Tensile / Bending / Notched Impact / HDT Xenon Lamp or Thermal Aging
↓ Passed flame retardant test but collapsed mechanically and couldn't be assembled, returned for rebalancing
⑦ Vibration Fatigue Vehicle Loading Vibration and Assembly Stress Simulation
↓
⑧ Complete loading documents: sampling from finished products, inspection of finished product status, and verification with loading status
`
Each level has clear 'just go back to the previous level' criteria.
Text version conclusion: The sequence is halogen-free screening → combustion rating → oxygen index → smoke density → smoke toxicity → mechanical properties and aging → vibration fatigue → complete document.
Halogen-free screening is placed first, as it can be rejected in minutes and costs are low; Smoke density must be passed before mechanics, because changing smoke density usually requires system movement, and once the system is moved, the mechanics must be rebalanced; The entire document is placed last, but the sampling status must be fixed from the start.
6. Reverse Honesty: In these four situations, interior panels of rail transit should not use modified PP
Earlier we talked about 'how to do it,' here we talk about 'when not to do it.'
| The situation that occurred | Why is modified PP not suitable? | Which way should I go? |
|---|
| The project has been classified as the highest risk level (HL3 class of EN 45545-2) | HL3 tightens the limits on oxygen index, smoke density, and toxicity simultaneously, and the modified PP system cannot reach that level. | Phenolic / aramid honeycomb core, metal honeycomb composite structure |
| Components must bear loads and endure long-term fatigue (vehicle body structure, load-bearing floor, seat frames) | It can be used under high filling for rigidity, but long-term fatigue and structural redundancy are not its field. | Aluminum honeycomb, metal structures, SMC molded components |
| At the same time, it should have ultra-low smoke density and high rigidity (key fire prevention areas such as the front of the vehicle and compartment partitions). | Flame retardancy and high rigidity pull against each other in PP; increasing the amount together with fillers overwhelms both mechanical properties and processing. | Phenolic-based sandwich composites, SMC |
| Request provision of type testing and certification support | What the material supplier can provide is the material data and batch consistency, while the component type tests are led by the component party. | Led by the component side, we will cooperate by providing material-side data. |
The last point is the collaboration boundaries: material suppliers provide data and batch consistency, while type testing and certification are led by the component party. We do not make overstepping commitments. What data is needed, according to which system it should be issued, and in what condition it should be submitted for inspection can all be listed together before sample approval.
There is one more thing that must be reminded: the top-tier level (oxygen index ≥35%) is already near the ceiling for modified PP. When encountering top-tier parts, first separately check the feasibility of the oxygen index before discussing the following five steps; if the order is reversed, it will waste the entire round of sampling.
7. What needs to be moved during material replacement: Risk checklist for subway interior panel replacement
Before deciding to try modified PP, go through this table first. The client's real concern is often not performance, but whether the report needs to be redone.
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The shrinkage of the glass fiber system is significantly anisotropic, and long parts are sensitive. | The dimensions are seriously off, and the side wall panels do not align at the seams. |
| Gate and Venting | High filling Large differences in flow properties of flame-retardant systems | Insufficient filling, low weld line strength |
| Material Temperature and Mold Temperature | Flame-retardant system is sensitive to residence time | Floating fibers, color difference, odor, smoke density fluctuation |
| Dry | Determine according to the specific system; it cannot be copied according to the conditions of ordinary PP. | Silver threads, bubbles, degradation |
| Pressure Holding and Demolding | Both the shrinkage and ejection behavior of the high-fill system changed | Deformation, ejection tear, assembly point cracking |
| Color difference | The color difference of the substrate of the veneer will show through. | Batch color difference dispute |
| Complete set of flame retardant and smoke density | Material changes require a complete redo: halogen-free screening, combustion rating, oxygen index, smoke density, and smoke toxicity; not a single item can use the old report. | The burning level is still the same, but the smoke density has doubled, and the loading documents are invalid. |
| Verification order | Halogen-free screening → Burning level → Oxygen index → Smoke density → Smoke toxicity → Mechanical aging → Vibration fatigue → Complete document | All the risks are concentrated to explode at the final step |
Text version conclusion: For rail transit parts, changing the material involves more effort than for general parts — report. The major issue is that the flame retardant and smoke density reports become invalid: if the same material is changed to a different flame retardant system, the combustion rating may remain unchanged, but the smoke density is no longer in the same range. Therefore, what should be discussed first in this table is the verification sequence.
VIII. One-Page Report Comparison Table: Six Scenarios for Direct Reporting
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Cabin side wall panel / end wall panel substrate | Glass fiber or mineral reinforced halogen-free flame-retardant modified PP | Oxygen index ≥32%; Ds(1.5 min) ≤100, Ds(4 min) ≤200 | GB/T 2406.2; GB/T 8323.2 | Installation location attribution, veneering method |
| Luggage Rack Profiles / Linings / Cover Plates | Pure halogen-free flame-retardant PP or thermoplastic PP honeycomb composite panel | Both oxygen index and smoke density pass; −40~80℃ dimensional stability | GB/T 2406.2; GB/T 8323.2; Finished product sampling | Bearing ownership, whether it needs to be recyclable |
| Ventilation Duct / Maintenance Cover Plate | Flame-retardant SMC or reinforced halogen-free flame-retardant PP selected according to molding efficiency | Burning level: Priority to Grade A, Grade B negotiable | UIC 564-2 Chapter 7 | Batch and molding method |
| Top plate components | First test the feasibility of the oxygen index separately, then decide on the route. | Oxygen index ≥35% | GB/T 2406.2 or according to the corresponding method for the material | Can the filling be changed? |
| Export EU Project | First determine the hazard level according to EN 45545-2, then select the material | According to R1 or the corresponding set of requirements: CFE ≥20 kW/m², MARHE, Ds(4), CITG item by item | ISO 5658-2; ISO 5660-1; ISO 5659-2; EN 17084 | Operation Category and Design Category (set HL1/HL2/HL3) |
| Key fire prevention areas (cab, partition, load-bearing floor) | Does not use modified PP | — | — | Direct transfer phenolic laminate / metal honeycomb / SMC |
Text version conclusion: The purpose of this table is to allow technicians to report conclusions directly upward. There is only one criterion for judgment—whether the customer can determine the direction of the materials in a single meeting using this table. Pay special attention to the fifth row: domestic TB/T reports and EN 45545-2 reports are not equivalent and must be done separately.
9. The part of rail transit interior panels that is most prone to problems is often not 'insufficient flame retardancy of the material'
The most common early failure of rail transit interior panels in the industry is not failing the flammability rating, but failing the smoke density or smoke toxicity even if the flammability rating is passed. According to publicly available standard materials, TB/T 3237-2010 stipulates four parallel criteria for the evaluation of interior materials in EMU trains: oxygen index varying by installation position (ceiling ≥35%, side panels and wall panels ≥32%, floor ≥30%), combustion performance (UIC 564-2 Chapter 7, must reach Class A or B), smoke density (GB/T 8323.2, measured separately for flaming and non-flaming), and smoke toxicity (limits for eight specific gases). Failure in any one of these criteria means the material cannot enter this system.
The common industry practice is to determine three things together: first, use halogen-free elements to screen and lock in the system; then classify the oxygen index according to the installation position; and finally, use a low-smoke system to reduce the smoke density. The key is not in looking at any single item alone, but whether the oxygen index, smoke density, and mechanical properties can all simultaneously stay within the thresholds—they are in opposition to each other.
Ningbo Kolong New Materials Co., Ltd. commonly supplies halogen-free flame-retardant reinforced modified polypropylene (PP) particles for this component. The base material and filler ratio are determined according to the component's installation position and threshold settings. They are mainly used to address the issue mentioned above, that 'the rating is exceeded, but the smoke density does not pass.' The formulation can be adjusted according to the working conditions of the component and can be used for sample comparison and joint development. They can also accommodate component-level customers with small batches of various varieties.
Frequently Asked Questions
Q: For two materials with the same combustion rating, how much can the smoke density differ?
Answer: Being off by several times is common. Smoke density is directly related to the flame-retardant system and the carbonization method, while the combustion rating only considers self-extinguishing and dripping after being removed from the flame. In rail transit, both of these factors must be considered simultaneously; discussing material selection based solely on the combustion rating report is like gambling with visibility in tunnels.
Question: With a halogen system that is cheap and good, can it be used on rail transit?
Answer: Not recommended. Processing releases halogen acids when heated, which can corrode equipment and molds, and burning releases halogen acids along with thick smoke; subway toxicity tests directly set limits for HCl and HBr. The savings from that part usually have to be compensated for at the toxicity stage.
Question: If the flame retardant is added to 25-30%, is the drop in mechanical properties due to your formulation being inadequate?
Answer: It's not a formula-level problem, it's a structural issue with PP, and increasing the amount won't reduce it. All that can be done is to balance the interface with the filler to keep the loss controllable. If you want to further reduce smoke density, the amount will have to go up.
Question: If TB/T testing is done domestically, can it be used directly for export projects?
Answer: No. Domestically, follow GB/T 8323.2 plus UIC 564-2; EN 45545-2 follows ISO 5658-2, ISO 5660-1, ISO 5659-2, EN 17084, and first determine HL1/HL2/HL3 according to operational category and design category. The two sets need to be done separately.
| Operating condition | Key criterion | Regular supply |
|---|
| Cabin side wall panel / end wall panel substrate | Oxygen index ≥32%; Ds(1.5 min) ≤100, Ds(4 min) ≤200 | Halogen-free flame-retardant reinforced PP direction, regular stock |
| Luggage rack / Lining / Cover plate | Dual oxygen index and smoke density, dimensionally stable | Halogen-free flame-retardant PP and reinforcement direction |
| Export project items | Itemized according to EN 45545-2 requirements set and hazard levels | Halogen-free flame-retardant reinforced PP direction, combined with material-side data |
I want to give a reminder: When something goes wrong, the most common mistake is to change the material first. Excess smoke density, insufficient oxygen index, or excessive toxicity—each of these issues has more than one possible cause. First identify the cause, then change the material; if you reverse the order, you often end up changing materials several times and still stay in the same place.
Ten, Lastly Say Three Sentences
1. On rail transit interior panels, 'non-combustible' is just a ticket to entry, while smoke density is the threshold. The evacuation conditions of tunnels and underground sections determine that what really prevents people from getting out of the carriage is the visibility and toxicity of the smoke, not the flames themselves.
Second, the three factors—oxygen index, smoke density, and mechanical properties—are interrelated, and it's impossible to change just one. Adding 25-30% flame retardant is an unavoidable threshold for PP, and the loss in mechanical properties is structural; if you want to further reduce smoke density, you usually need to add more or change the system, and the cost occurs at the same time. Acknowledge this fact first before discussing a plan.
3. The order of verification is more important than the verification items. Halogen-free screening → Combustion rating → Oxygen index → Smoke density → Smoke toxicity → Mechanics and aging → Vibration fatigue → Complete documentation. Halogen-free screening should be listed first, smoke density must be placed before mechanics, and the sampling state should be fixed from the beginning.
Regarding the position of PP in rail transit interiors, let's clarify the boundaries first: it is currently mainly used in interior parts that are of low to medium risk, non-load-bearing, and not critical fire zones; for areas like the front of the train, car compartment partitions, and load-bearing structures, phenolic sandwich, metal honeycomb, and SMC should be used—we do not forcibly apply PP there.
About Us
About us, four sentences:
1. Ningbo Kelong New Materials Co., Ltd., self-produced modified polypropylene (PP) pelletizing—homopolymer / random copolymerization / impact-resistant copolymerization;
2. Modification directions: filling, glass fiber reinforcement, toughening, flame retardant, low odor and low VOC, weather resistance, scratch resistance without coating;
3. PP resin trade of major petrochemical plants;
4. Side牌料 and large package料 in stock.
