飞机内饰件用什么改性PP？FST 三关里，垂直燃烧看得见，烟密度与烟毒看不见，也最容易被放到最后才想起来。这篇讲清 FST 的判定逻辑、玻纤芯效应为什么把阻燃加量推高，以及 PP 在航空内饰里真实能站的四个位置与进不去的四个位置。
一个做航空内饰配套的工程师跟我说过一句话：燃烧那关我们过了，烟密度也过了，一上烟毒测试就顶穿。
这句话我在不同客户那里听过好几遍，落点都一样。
航空内饰材料的 FST 三关——Flammability（燃烧）、Smoke（烟密度）、Toxicity（烟毒）——被低估的从来不是第一关。垂直燃烧有火焰、有烧焦长度，看得见；烟密度和烟毒是在密闭箱体里用光度计和气体分析仪读出来的数，看不见，也最容易被放到最后才想起来。
还有一个更隐蔽的现场：客户一次寄来三张报告，燃烧一张、烟密度一张、烟毒一张，单看每张都过；但三张是三个批次做的，按最终件结构整体送测，结论未必成立。
这篇讲这个件的三关为什么相互拉扯，以及改性PP 在航空内饰里能站在哪个位置。
一、工况六维拆解：卡住 PP 的不是温度
航空内饰件要分件位看。把六个数报齐，方向就出来了。
| 维度 | 件位的实际工况 | 对材料的要求 |
|---|
| 温度 | 客舱增压区是常温环境；地面停放按 −40℃ 到 +70℃ 量级的气候包线取；巡航阶段货舱与非增压区更冷 | 余量够：PP 熔点约 160-170℃，玻纤增强后变形温度上到 120℃ 档以上 |
| 载荷 | 多为非承力或次承力；真实载荷是振动、装配预紧力与自重；货舱衬垫还要扛装卸摩擦 | 刚性够用即可，不靠高刚性 |
| 介质 | 客舱清洁剂与消毒剂、饮料泼溅、湿度凝露；货舱另有冲洗水 | 耐化学 + 低吸湿 |
| 寿命 | 按机体大修周期设计，件级常按十年级计 | 长期老化后不脆化、不粉化 |
| 外观 | 可见区要 A 面，非可见区只看功能与尺寸 | 浮纤与色差 |
| 合规 | FST 法规与适航要求是主角 | 三关齐过，且按最终件结构整体判定 |
先记一句话：这个件上 PP 的耐热不是最卡的那一项。 客舱是常温环境，PP 熔点约 160-170℃ 有大量余量；把它挡在门外的是合规里的 S 和 T。
合规说三层。F 看 14 CFR 25.853（即 FAR 25.853，国内对应 CCAR 25.853），方法在附录 F 第一部分，即 60 秒与 12 秒垂直燃烧。S 看第五部分，平均 Ds 不超过 200，方法走 ASTM E662，另有 BSS 7238 与 AITM 2.0007A/B。T 对应 BSS 7239 与 ABD0031。
文字版结论：温度、载荷、介质、寿命四维，改性PP 靠玻纤增强加无卤阻燃体系基本应付得来；外观按可见区与非可见区分开看；只有合规是一票否决，且否决方式往往不是"不燃"，是烟密度和烟毒。
二、材料路线对比：三条路，各有各的边界
| 路线 | 拿到什么 | 代价 / 短板 | 常见件位 |
|---|
| 玻纤增强 + 无卤阻燃改性PP | 阻燃体系 + 刚性尺寸稳定 + 无卤口径（溴 <900 ppm、氯 <900 ppm、总和 <1500 ppm）；走常规注塑 | 玻纤带来"芯效应"，阻燃加量被推高，力学与烟密度两头受压 | 货舱衬垫、次结构件、非客舱小件、地面设备件 |
| 纯无卤阻燃 PP（不加玻纤） | 轻、加工窗口宽、配方简单 | 刚性撑不住大件，装配预紧下易变形 | 卡箍、夹子、盖板、护罩类小件 |
| 航空内饰主材（酚醛复合材料、PEI、PPS、PC 及复合结构） | 高要求件位的 FST 全套天然可达 | 加工路线、模具投入与成本结构完全不同 | 天花板、内墙板、隔板、厨房结构、大柜壁、结构地板、储物间 |
第三条路线值得单说。FAR 25.853 里，天花板、内墙板、隔板、厨房结构、大柜壁、结构地板、储物间这一档件位，除垂直燃烧外还要过烟密度、烟毒与热释放全套。
这条线就是改性PP 的现实边界：不是 PP 做不了件，是这些件位的判据组合把它挤到了非承力与次结构一侧。
反过来说，PP 在航空上本来就有位置——货舱衬垫与货舱容器、内饰饰条、卡箍夹子、风道、厨房周转箱、理线扎带，以及托盘桌、扶手、座椅小件、侧板这类低应力件。共同点是：强度不是关键判据。
文字版结论：三条路线是分工关系。改性PP 的现实位置在货舱侧、次结构装饰件、非客舱小件与地面设备；客舱高要求件位与结构承力位，走的是酚醛复合材料、PEI、PPS 这一路。两条路混着谈，选型一定走偏。
三、★ 选型判据表：六项判据，每项都带验证方法
这张表最该收藏。选料卡住常常不是不知道看哪项，是不知道拿什么测、测到多少算过。（标准号按通行引用，以件位要求与第三方报告为准）
| 指标 | 门限值 | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| 垂直燃烧（60 秒 / 12 秒档） | 60 秒档：平均烧焦长度 ≤152 mm、余焰 ≤15 s、滴落续燃 ≤平均 3 s；12 秒档：≤203 mm、余焰 ≤15 s、滴落续燃 ≤平均 5 s | 14 CFR 25.853 附录 F 第一部分；国内对应 CCAR 25.853、HB 5469 | 玻纤把熔体导到表面，烧焦超长；件位分类搞错用错门限 | 无卤磷氮膨胀体系 + 抑制熔滴；先按安装位置定档位 |
| 烟密度 Ds | 平均 Ds ≤200（辐射热通量 25 kW/m²，明火与非明火分别报） | ASTM E662；Boeing BSS 7238；Airbus AITM 2.0007A/B | 阻燃加量上去后烟密度同向抬高 | 无卤体系 + 抑烟组分（金属氢氧化物、硼酸锌类） |
| 烟毒（气体浓度） | 4 分钟采集：CO ≤3500、HCN ≤150、HCl ≤500、SO₂ ≤100、NOx ≤100、CO₂ ≤5000 ppm；HF 口径 100/200 ppm 两说 | Boeing BSS 7239；Airbus ABD0031 / AITM 3.0005；MD DMS 2294 | 含卤体系释放 HCl/HF，直接顶穿门限 | 走无卤路线；含卤省下的效率要在这里还回来 |
| 无卤量化定义 | 溴 <900 ppm、氯 <900 ppm、总和 <1500 ppm | 行业公开定量口径（原料筛查 + 批次复测） | 名义无卤、实际残留超标 | 阻燃剂与色母两端一起筛 |
| 灼热丝 | GWIT 750 / 775℃；GWFI 850 / 960℃；850℃ 接触 30 s 不引燃 | IEC 60695-2-12/13；GB/T 5169.12/13 | 导线穿舱、接线盒位这类带电气属性的件位不过 | 玻纤增强 + 无卤阻燃 |
| 力学（玻纤增强体系） | 长玻纤体系公开区间：拉伸 50-80 MPa、弯曲 80-120 MPa、缺口冲击 15-40 kJ/m²、HDT 120-180℃ | 素材库公开口径；短玻纤体系须另定门限 | 阻燃加量与玻纤同时上，缺口冲击掉得最快 | 按体系档位对 TDS，不拿长玻纤数据套短玻纤 |
这里有一句结构性判断必须讲清：PP 的阻燃剂加量普遍在 25-30% 这一档，而烟密度与烟毒往往正需要更高的加量。
玻纤还会把这件事推得更远。玻纤增强 PP 燃烧时存在"芯效应"——玻纤把熔体芯吸到表面，阻燃更难过。据公开产品资料（B 级），PP 加 20% 玻纤时无卤阻燃剂建议加到 30% 上下，加 30% 玻纤时也要 28% 这一档。
代价立刻显形。据同一批公开产品资料（B 级），PP + 30% 玻纤 + 24% 无卤阻燃的体系，拉伸强度落在 20 MPa 量级，缺口冲击只有 2-3.5 kJ/m² 量级——和长玻纤体系那组数不是一个档位。
文字版结论：六项里烟密度和烟毒最该放一起看，它们和阻燃加量同向变化。"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；而烟密度与烟毒又需要更高的加量。所以 FST 三关是相互拉扯的，不是分别达标就完事。 拿 TDS 先问清是长玻纤还是短玻纤体系，两组数不能互换。
四、这个件最常翻车的四类失效
失效一：燃烧过了，烟密度挂。 阻燃剂按"压住燃烧"选，没按"少产烟"选。磷氮膨胀体系加量抬上去后，不完全燃烧产物同步增多，烟密度与加量同向走——加得越多，越难过。
失效二：烟密度过了，烟毒挂 HCl 与 HF。 用了含卤阻燃。含卤效率高、加量少，燃烧释放卤化氢，HCl 与 HF 直接顶穿 BSS 7239 门限。有卤在 S 关省下的，要在 T 关还回去。
失效三：三张报告都对，拼到一个件上不成立。 三次送测用了三批料或三个配方。附录 F 要求按实际使用状态整体测试，夹层板这类装配单元不得拆层分开测——件结构一变，三份数据同时作废。
失效四（敢否定一个常见做法）：把 FST 当成三张独立的检测报告去凑，是错的。 行业里常见的是燃烧不过加阻燃剂、烟密度不过加抑烟剂、烟毒不过换体系，一轮一轮往下压。这条路在航空件上走不通——提高阻燃加量能压住燃烧，但往往同时抬高烟密度、恶化力学。三关要靠一套配方同时过，任何单项"加量解决"都会被另外两关打回来。
五、验证顺序：无卤筛查在前，烟毒排在力学之前
同行很少写这一段，但它是这个件能不能省下返工的关键。顺序错了，成本会在最后一步集中爆。
`
① 无卤筛查 溴 / 氯含量（各 <900 ppm，总和 <1500 ppm）
↓ 无卤口径不成立，后面几关都不用做
② 垂直燃烧 60 s（或 12 s）：烧焦长度 / 余焰 / 滴落续燃
↓ 不过 → 回 ① 复核体系与分散，不要直接加量
③ 烟密度 ASTM E662：平均 Ds ≤200，明火与非明火分别报
↓ 不过 → 多半是抑烟组分不够，在体系内重配
④ 烟毒 BSS 7239 / ABD0031：CO / HCN / HCl / HF / SO₂ / NOx
↓ 不过 → 多半有含卤残留，回 ①
⑤ 力学与老化 拉伸 / 弯曲 / 缺口冲击 / HDT；湿热与清洗剂浸泡保持率
↓
⑥ 整件与文件 按实际使用状态整件送测；件位分类、批次可追溯
`
烟毒排在力学之前，因为前三关是准入门：力学不过还能回去调结构，FST 不过这个件就出局。
反过来更常见：先把力学做漂亮，FST 留到最后送测。等烟密度或烟毒挂掉，前面的配方与工艺验证全部作废。
文字版结论：顺序是 无卤筛查 → 垂直燃烧 → 烟密度 → 烟毒 → 力学与老化 → 整件核对。每一步不过就退回上一级判断，而不是在本级继续加量：③ 不过退回体系重配，④ 不过退回 ①，因为多半是无卤被破了。
六、反向诚实：四种情况下，这个件不该用改性 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 |
|---|
| 件位在天花板、内墙板、隔板、厨房结构、大柜壁、结构地板、储物间这一档 | 除垂直燃烧外还要过烟密度、烟毒与热释放全套；高阻燃加量会把力学和烟密度一起拖下去 | 酚醛复合材料、PEI、PPS 等航空内饰主材路线 |
| 要求结构承力（座椅骨架、连接接头、承力支架） | 刚性与长期蠕变撑不到那一档，增强也抬不了量级 | PEI、PEEK、PPS、PAI 或金属 |
| 要求长期高低温循环 + 低吸湿 + 尺寸极稳 | 线膨胀与蠕变在长期循环下不占优，尺寸波动会传到装配 | 换高耐热工程塑料或复合结构 |
| 要求供应商提供适航取证支持、型号审定配套文件 | 材料供应商的角色是提供可用数据与批次一致性，取证责任在整机方与部件方 | 由部件方与整机方主导，材料方配合供数据 |
四种情况的共同点是：两个方向相反的要求同时要——高要求件位的 FST 全套 + 可接受的力学、结构承力 + 塑料件、长期尺寸稳定 + 改性PP。
在这类领域，我们只做两件事：给出可用的数据，做不到的明说。 关于适航，材料方不越位承诺任何取证结果。
文字版结论：件位落在客舱高要求档、要求承力、要求长期尺寸极稳、或要求材料方承担取证责任时，这个件不该用改性PP 硬撑。先说清楚，再谈折中；硬接下来的单子都要用返工还回去。
七、换料风险清单：多一条"FST 全套重做"
| 要动的项 | 需要确认什么 | 不做会怎样 |
|---|
| 模具收缩率 | 玻纤料收缩率与原方案不同，长件与装配面敏感 | 尺寸超差，装配对不上 |
| 浇口与排气 | 玻纤料流动差异大，熔接线位置会变 | 充填不足、熔接线强度弱 |
| 料温与模温 | 阻燃剂分解温度有限，玻纤料剪切生热更明显 | 局部过热、阻燃剂分解、浮纤 |
| 干燥 | 按具体体系定，阻燃料停留时间要控 | 银丝、气泡、降解 |
| 保压与脱模 | 收缩差异带来变形与顶白 | 变形、顶出拉伤 |
| 色差 | 非外观件也要先确认色板 | 批次色差争议 |
| 换料必须重做 FST 全套 | 阻燃体系一变，三关数据全部作废；件结构或饰面层一变同样重做 | 用旧报告交货，把风险留到客户端 |
| 验证顺序 | 无卤筛查 → 垂直燃烧 → 烟密度 → 烟毒 → 力学 → 整件 | 风险全压到最后一步爆发 |
要额外强调倒数第二行。换料必须重做 FST 全套，这是航空与轨交类件和普通件最大的差别。 普通件换料，改的是收缩率和外观；航空件换料，改的是一整套燃烧数据的有效性。
文字版结论：换料要动模具、工艺、色差、验证顺序四块，其中验证顺序和"FST 全套重做"最该先谈。跳过小样直接试模，等于把成本提前花出去；拿旧报告交新料，是把风险留给客户。
八、一页纸汇报对照表：五种场景直接上报
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 货舱衬垫、货舱地板下衬件 | 玻纤增强 + 无卤阻燃改性PP | 垂直燃烧 + Ds ≤200 | 14 CFR 25.853 附录 F；ASTM E662 | 件位分类、有无抗烧穿要求 |
| 非客舱小件（卡箍、夹子、盖板、护罩） | 纯无卤阻燃 PP 或低玻纤增强 | 无卤口径 + 垂直燃烧 | 同上 + 溴/氯含量筛查 | 装配预紧力、长期变形允收 |
| 客舱可见面装饰件（非高要求档） | 玻纤增强 + 无卤阻燃改性PP | 垂直燃烧 + Ds + 烟毒 | 同上 + BSS 7239 / ABD0031 | 是否落在高要求件位、饰面层整体判据 |
| 地面设备、工装与周转件 | 玻纤增强 + 无卤阻燃改性PP | 按客户内控的阻燃与烟密度 | 按客户指定标准执行 | 是否要走适航口径，多数不要求 |
| 客舱高要求件位、结构承力位 | 不该用改性PP | — | — | 走航空主材路线，另做方案 |
这张表让技术员能把结论直接往上报，不必重新组织语言。判断标准只有一条——客户拿它能不能在一次会议里把方向定下来。
九、这个件难在配平，不在换某一款料
航空内饰件最常见的翻车，不是垂直燃烧过不了，是燃烧过了、烟密度或烟毒挂掉。据公开检测机构资料（B 级），BSS 7239 的门限是 4 分钟采集下 CO ≤3500 ppm、HCN ≤150 ppm、HCl ≤500 ppm、SO₂ ≤100 ppm、NOx ≤100 ppm，与含卤体系直接冲突。
还有一条容易被忽略的公开事实：烟毒测试在很多机型上是整机厂的企业内控要求，不是强制法规项。 它不进法规清单，却进客户的验收清单。
结构性结论就一句：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。 而烟密度与烟毒又需要更高加量，玻纤的芯效应还把它继续往上推。
宁波市科隆新材料有限公司在这个件上常供的是玻纤增强无卤阻燃改性PP 方向，主要用来解决"三关一起过 + 尺寸稳定"这两件事；配方按件位与工况调，可以陪客户一起做无卤筛查、小样比对与试模，多品种小批量的件级需求也能接。
常见问答
问：有卤阻燃又便宜又高效，为什么航空件还要走无卤？
答：因为三关是一个整体。含卤加量少、效率高，垂直燃烧容易过；但燃烧释放卤化氢，HCl 与 HF 在烟毒那关直接顶门限。有卤在 S 关省下的，要在 T 关还回去。
问：烟密度不过，多加抑烟剂行不行？
答：不行。抑烟剂本身占配方空间，加进去会把阻燃加量、力学和流动一起挤。正确做法是回体系重配，在磷氮膨胀体系内部调比例与分散。
问：非承力小件能直接用不加玻纤的阻燃 PP 吗？
答：多数可以。卡箍、夹子、盖板这类装配预紧力不大，纯无卤阻燃 PP 刚性够用，而且少了芯效应，阻燃更容易过、烟密度也更好控。要确认的是长期变形允收。
问：三份现成的 FST 报告能直接拿来用吗？
答：要同时满足两条——报告对应最终件结构（含饰面层），以及配方与批次可追溯到本次供货。任一条不满足，报告只说明那个样品过了。
| 件位 | 关键判据 | 常规供应 |
|---|
| 货舱衬垫与次结构件 | 垂直燃烧 + Ds ≤200 | 玻纤增强无卤阻燃 PP，常规备货 |
| 非客舱小件 | 无卤口径 + 垂直燃烧 | 纯无卤阻燃 PP 或低玻纤增强方向 |
| 客舱可见面装饰件（非高要求档） | 垂直燃烧 + Ds + 烟毒 | 玻纤增强无卤阻燃 PP 方向 |
| 地面设备与周转件 | 按客户内控标准 | 按指定口径配方向 |
文字版结论：先问三关齐不齐，别只拿垂直燃烧报告谈；烟密度和烟毒是含卤体系最常挂的两关，也是加量上去后最容易失守的两关。换料必须重做 FST 全套，这条不能省。
十、最后说三句
第一，FST 三关里最难的不是"不燃"。 不燃看得见，烟密度和烟毒看不见，也最容易被排到最后才测——把顺序倒过来，是这类件最贵的错。
第二，三关是相互拉扯的，不是分别达标。 阻燃加量与力学反向，烟密度与烟毒又要求更高加量；玻纤的芯效应还把这个矛盾放大。一项不过就加量，另外两关会打回来。
第三，位置要说清楚。 改性PP 在航空内饰里的现实位置是货舱侧、次结构装饰件、非客舱小件与地面设备；客舱高要求件位与结构承力位，走的是酚醛复合材料、PEI、PPS 这一路。这一点不讲明白，方案从一开始就是歪的。
同批的《新能源汽车电池包上盖用什么阻燃PP》讲的是灼热丝与力学损失那笔账，这一篇讲的是烟密度与烟毒的判定逻辑，两篇的落点不一样，可以对着看。
附录 · 本篇引用的标准号与来源分级
A 级（法规原文 / 标准 / 专利）
- 14 CFR Part 25 附录 F 第一部分（60 秒与 12 秒垂直燃烧判据）、第四部分（热释放）、第五部分（Ds ≤200）
- ASTM E662；IEC 60695-2-12/13；GB/T 5169.12/13；HB 5469
- 专利 CN105542320A：抑烟剂路径；氢氧化物阻燃效率低、需大量添加导致力学变差
B 级（航空企业标准转述 / 行业综述 / 企业技术资料 / 素材库）
- Boeing BSS 7238、BSS 7239；Airbus ABD0031（AITM 2.0007A/B、AITM 3.0005）；MD DMS 2294——公开检测机构转述的烟毒门限，数值见第三节判据表
- 公开航空材料综述：PP 熔点约 160-170℃、拉伸约 30-40 MPa、件位集中在非结构低应力件
- 无卤阻燃剂企业公开产品资料：玻纤芯效应与阻燃加量档位；短玻纤体系拉伸 20 MPa 量级、缺口冲击 2-3.5 kJ/m² 量级
- 素材库 B 级条目：无卤量化定义、GWIT 750/775℃ 与 GWFI 850/960℃、长玻纤体系力学区间、阻燃剂加量 25-30%
关于我们
最麻烦的询盘是这一句：料没变，件出问题了。
料确实没变，变的是批次、干燥、模温、模具磨损，或者为了省钱动的某一项。参数是慢慢飘的，问题是一夜之间出来的。 放在航空这类件上还要再加一条——阻燃体系一动，FST 三关的数据全部作废。
宁波市科隆新材料有限公司，自产改性聚丙烯（PP）造粒，覆盖均聚 / 无规共聚 / 抗冲共聚三档基材，以及填充、玻纤增强、增韧、阻燃、低气味低 VOC、耐候、免喷涂耐划伤等改性方向；兼营各大石化厂 PP 树脂、副牌料与大包料。
What type of modified PP is used for aircraft interior parts? In the FST three tests, vertical burning is visible, while smoke density and smoke toxicity are not, and they are also the ones most easily remembered last. This article explains the logic of FST evaluation, why the glass fiber core effect drives up the flame retardant content, and the four real positions where PP can be used in aircraft interiors and the four positions where it cannot.
An engineer who works on aerospace interior components once told me: 'We pass the flammability test, we also pass the smoke density test, but as soon as it comes to the smoke toxicity test, we fail badly.'
I've heard this sentence several times from different clients, and the main point is always the same.
The three FST tests for aircraft interior materials—Flammability, Smoke, and Toxicity—are never ones where the first is underestimated. Vertical burning has flames and char length, which are visible; smoke density and toxicity are measured in a sealed chamber using photometers and gas analyzers, which are invisible and are most easily left until the last moment.
There is an even more hidden situation: a customer once sent three reports at a time — one for combustion, one for smoke density, and one for smoke toxicity. Each one looked fine on its own; however, the three were done for three different batches, so if tested together according to the final product structure, the conclusion may not hold.
This article explains why the three aspects of this matter pull against each other and the position modified PP can hold in aircraft interiors.
1. Six-Dimensional Analysis of Working Conditions: What’s Stalling PP Is Not Temperature
Aviation interior parts need to be looked at by individual components. Once all six numbers are reported together, the direction will become clear.
| Dimension | The actual working conditions of the component | Requirements for the materials |
|---|
| Temperature | The cabin pressurization area is a normal temperature environment; ground parking is based on a climate envelope of −40℃ to 70℃; during the cruise phase, the cargo hold and non-pressurized areas are colder. | Sufficient amount: PP melting point is about 160-170°C, and after glass fiber reinforcement, the deformation temperature rises above 120°C. |
| Load | Mostly non-load-bearing or secondary load-bearing; the actual loads are vibration, assembly pre-tightening force, and self-weight; cargo hold padding also has to withstand handling friction. | Stiffness is sufficient, no need for high rigidity |
| Medium | Cabin cleaners and disinfectants, beverage spills, humidity condensation; the cargo hold has additional wash water | Chemical resistant Low moisture absorption |
| Lifespan | Designed according to the major overhaul cycle of the airframe, component-level is generally counted in ten-year intervals. | Does not become brittle or powdery after long-term aging |
| Appearance | The visible area requires side A, while the non-visible area only considers function and size. | Floating Fibers and Color Difference |
| Compliance | FST regulations and airworthiness requirements are the main focus | Pass all three stages, and make an overall judgment based on the final item structure |
First, remember one thing: the heat resistance of PP on this part is not the most limiting factor. The cabin is a normal temperature environment, and PP has a melting point of about 160-170℃, leaving plenty of margin; what blocks it at the door are the S and T in compliance.
Compliance is described in three layers. F refers to 14 CFR 25.853 (that is, FAR 25.853, corresponding to CCAR 25.853 domestically), with methods in Appendix F Part I, namely 60-second and 12-second vertical burn tests. S refers to Part V, where the average Ds does not exceed 200, using the ASTM E662 method, with additional references to BSS 7238 and AITM 2.0007A/B. T corresponds to BSS 7239 and ABD0031.
Text version conclusion: In the four dimensions of temperature, load, medium, and lifetime, modified PP reinforced with glass fiber and halogen-free flame retardant systems can basically cope; the appearance should be considered separately for visible and non-visible areas; compliance alone is a veto, and the veto is often not due to 'non-flammability' but rather smoke density and smoke toxicity.
2. Comparison of material routes: three routes, each with its own boundaries
| Route | Get what | Cost / Shortcoming | Common part positions |
|---|
| Glass fiber reinforced halogen-free flame retardant modified PP | Flame-retardant system, rigid dimensional stability, halogen-free caliber (bromine <900 ppm, chlorine <900 ppm, total <1500 ppm); processed by conventional injection molding | Glass fibers bring a 'core effect,' raising the amount of flame retardant added, putting pressure on both mechanical properties and smoke density. | Cargo compartment linings, secondary structural components, non-cabin small parts, ground equipment parts |
| Pure halogen-free flame-retardant PP (without glass fiber) | Light, wide processing window, simple formulation | Rigid support cannot hold large items, and it is prone to deformation under assembly pre-tightening. | Small parts such as hose clamps, clips, cover plates, and guards |
| Aerospace interior main materials (phenolic composite materials, PEI, PPS, PC, and composite structures) | The full set of FST for high-demand parts is naturally reachable | The processing routes, mold investment, and cost structures are completely different. | Ceiling, interior wall panels, partitions, kitchen structure, large cabinet walls, structural floor, storage room |
The third route is worth mentioning separately. According to FAR 25.853, for ceiling panels, interior wall panels, partitions, galley structures, large cabinet walls, structural floors, and storage compartments, in addition to vertical burn tests, they must also pass the full set of smoke density, smoke toxicity, and heat release tests.
This line is the real boundary of modified PP: it's not that PP can't be used to make the parts, but the combination of criteria for these parts pushes it to the non-load-bearing and secondary structure side.
Conversely, PP already has applications in aviation — cargo hold liners and cargo containers, interior trim strips, hose clamps, air ducts, galley turnover boxes, cable ties, as well as low-stress components such as tray tables, armrests, small seat parts, and side panels. The common point is: strength is not the key criterion.
Text Version Conclusion: The three routes represent a division of labor. The practical position of modified PP is in cargo hold sides, secondary structural trim parts, non-cabin small parts, and ground equipment; cabin high-requirement parts and structural load-bearing positions use the route of phenolic composites, PEI, and PPS. Mixing the two routes in discussions will definitely lead to a biased selection.
3. ★ Selection Criteria Table: Six criteria, each with a verification method
This table is the most worth collecting. When selecting materials, it's often not that you don't know which item to look at, but that you don't know what to test or how much to test to pass. (The standard numbers are quoted according to common references, with the requirements per piece and third-party reports as the benchmark)
| Indicator | Threshold value | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Vertical burning (60 seconds / 12-second setting) | 60-second category: average char length ≤152 mm, afterflame ≤15 s, dripping combustion ≤ average 3 s; 12-second category: ≤203 mm, afterflame ≤15 s, dripping combustion ≤ average 5 s | 14 CFR 25.853 Appendix F Part I; domestic equivalents CCAR 25.853, HB 5469 | The fiberglass directs the melt to the surface, causing excessive charring; the part position classification is wrong, and the wrong threshold was used. | Halogen-free phosphorus-nitrogen intumescent system, inhibits molten droplets; first set the gear position according to the installation location |
| Smoke Density Ds | Average Ds ≤200 (radiant heat flux 25 kW/m², reported separately for open flame and non-open flame) | ASTM E662; Boeing BSS 7238; Airbus AITM 2.0007A/B | After increasing the flame retardant content, the smoke density rises in the same direction. | Halogen-free system, smoke-suppressing components (metal hydroxides, zinc borates) |
| Smoke toxicity (gas concentration) | 4-minute collection: CO ≤3500, HCN ≤150, HCl ≤500, SO₂ ≤100, NOx ≤100, CO₂ ≤5000 ppm; HF caliber 100/200 ppm two readings | Boeing BSS 7239; Airbus ABD0031 / AITM 3.0005; MD DMS 2294 | The halogen-containing system releases HCl/HF, directly piercing the threshold | Follow a halogen-free route; the efficiency saved from avoiding halogens needs to be returned here. |
| Halogen-free Quantitative Definition | Bromine <900 ppm, Chlorine <900 ppm, Total <1500 ppm | Industry Public Quantitative Caliber (Raw Material Screening Batch Retesting) | Nominally halogen-free, but actual residue exceeds the limit | Sift the flame retardant and color masterbatch together |
| Scorching thread | GWIT 750 / 775℃; GWFI 850 / 960℃; 850℃ contact for 30 s does not ignite | IEC 60695-2-12/13; GB/T 5169.12/13 | Wire routing through the cabin and junction box positions, these kinds of parts with electrical properties are not acceptable | Glass fiber reinforced Halogen-free flame retardant |
| Mechanics (Glass Fiber Reinforced System) | Open ranges for long glass fiber system: tensile 50-80 MPa, flexural 80-120 MPa, notched impact 15-40 kJ/m², HDT 120-180℃ | Public specifications of the material database; the short glass fiber system must have a separately defined threshold | When the flame retardant is increased along with the glass fiber, the notched impact drops the fastest | Compare TDS according to system levels, do not apply long glass fiber data to short glass fiber |
There is a structural judgment that must be made clear here: the amount of flame retardant added to PP is generally in the range of 25-30%, whereas smoke density and smoke toxicity often require a higher amount.
Glass fiber will also push this matter further. Glass fiber reinforced PP exhibits a 'core effect' when burning—glass fibers draw the molten core to the surface, making flame retardancy more difficult. According to publicly available product information (Class B), when PP contains 20% glass fiber, the recommended amount of halogen-free flame retardant is around 30%, and when it contains 30% glass fiber, it still requires around 28%.
The cost immediately becomes apparent. According to the same batch of publicly available product information (Class B), the PP 30% glass fiber 24% halogen-free flame retardant system has a tensile strength in the range of 20 MPa, and a notched impact strength of only 2-3.5 kJ/m²—which is not in the same league as the long glass fiber system.
Text version conclusion: Among the six items, smoke density and smoke toxicity should be looked at together, as they vary in the same direction as flame retardant loading. 'Adding more flame retardant will definitely reduce mechanical strength' is a structural issue of PP, not a formulation-level issue; meanwhile, higher amounts are needed for smoke density and smoke toxicity. Therefore, the three FST criteria are interdependent and cannot be simply considered as met individually. When referring to TDS, first clarify whether it is a long glass fiber or short glass fiber system, as the two sets of numbers are not interchangeable.
4. The Four Most Common Failure Types for This Component
Failure 1: The burning went too far, resulting in high smoke density. The flame retardant was chosen based on "suppress burning," not "reduce smoke generation." When the amount of the phosphorus-nitrogen intumescent system is increased, incomplete combustion products also increase accordingly, and smoke density rises along with the dosage—the more you add, the harder it is to control.
Failure 2: Smoke density is too high, smoke toxicity contains HCl and HF. Halogen-containing flame retardants were used. Halogen-containing ones are efficient, requiring a small amount, but burning releases hydrogen halides, and HCl and HF directly exceed the BSS 7239 threshold. Halogens saved in section S need to be returned in section T.
Invalidation Three: All three reports are correct, but combining them into one unit is not valid. The three tests used three batches of material or three formulations. Appendix F requires testing the overall performance according to the actual usage condition; assembly units such as sandwich panels must not be separated for layer-by-layer testing—once the structure of the unit changes, all three sets of data become invalid.
Invalid Four (Dare to challenge a common practice): Treating FST as three separate test reports to piece together is wrong. Common in the industry is to add flame retardants if combustion fails, add smoke suppressants if smoke density fails, change the formulation if smoke toxicity fails, and iteratively keep adjusting. This approach doesn't work for aerospace components—raising flame retardant content can control combustion, but it often simultaneously increases smoke density and worsens mechanical properties. All three criteria need to be met with a single formulation; any 'increased dosage to solve one issue' will be countered by the other two.
5. Verification sequence: Halogen-free screening comes first, followed by smoke toxicity before mechanical testing
Few peers write this section, but it is the key to whether this piece can avoid rework. If the order is wrong, the costs will accumulate and explode in the final step.
`
① Halogen-free screening Bromine / Chlorine content (each <900 ppm, total <1500 ppm)
↓ Halogen-free caliber is not established, the following stages do not need to be done
② Vertical burning 60 s (or 12 s): char length / afterflame / dripping combustion
↓ However → Back ① Review system and decentralization, do not increase the amount directly
③ Smoke Density ASTM E662: Average Ds ≤200, reported separately for flaming and non-flaming
↓ However → Most likely the anti-smoke component is insufficient and is being reconfigured within the system
④ Smoke and Toxic Substances BSS 7239 / ABD0031: CO / HCN / HCl / HF / SO₂ / NOx
↓ However → Most likely has halogen residues, return ①
⑤ Mechanics and Aging Tensile / Bending / Notched Impact / HDT; Retention after Humidity, Heat, and Detergent Soaking
↓
⑥ Whole Item and Documents: Submit the whole item for testing according to its actual usage status; item classification and batch can be traced
`
Smoking and drugs are placed before mechanics because the first three stages are entry-level: if you fail mechanics, you can still go back and adjust the structure; if you fail FST, this part is out of the game.
The reverse is more common: first get the mechanics done well, and leave FST for the final testing. If smoke density or smoke toxicity fails, all the previous formulation and process validations are invalidated.
Text version conclusion: The sequence is Halogen-Free Screening → Vertical Burning → Smoke Density → Smoke Toxicity → Mechanical and Aging → Whole Item Check. At each step, if it fails, it simply returns to the previous level for judgment, rather than increasing the amount at the current level: ③ If it fails, return to system reconfiguration; ④ If it fails, return to ①, because most likely the halogen-free property was compromised.
6. Reverse honesty: In four situations, this part 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 items are located at this level in the ceiling, interior wall panels, partitions, kitchen structure, large cabinet walls, structural floors, and storage rooms | In addition to vertical burning, the full set of smoke density, smoke toxicity, and heat release must be tested; increasing flame retardant content will pull down both mechanical properties and smoke density together. | Phenolic composite materials, PEI, PPS, and other main material routes for aircraft interiors |
| Requires structural load-bearing (seat frame, connecting joints, load-bearing brackets) | The rigidity and long-term creep can't reach that level, and reinforcement can't increase the magnitude either. | PEI, PEEK, PPS, PAI, or metal |
| Requires long-term high and low temperature cycling, low moisture absorption, extremely stable dimensions | Thermal expansion and creep are not dominant under long-term cycling, and dimensional fluctuations will be transmitted to the assembly | Switch to high heat-resistant engineering plastics or composite structures |
| Require suppliers to provide airworthiness certification support and model approval supporting documents | The role of the material supplier is to provide available data and batch consistency, while the responsibility for verification lies with the complete machine side and the component side. | Led by the component side and the complete machine side, with the material side providing data support. |
The common point of the four situations is: requirements in two opposite directions must be met at the same time — full FST set of high-demand parts, acceptable mechanical and structural load-bearing, plastic parts with long-term dimensional stability, modified PP.
In this field, we only do two things: provide available data and clearly state what cannot be done. Regarding airworthiness, the materials side does not overstep by promising any certification results.
Text Version Conclusion: When a part falls into the category of high requirements for the cabin, requires load-bearing, long-term dimensional stability, or requires the material side to bear liability for evidence, this part should not use modified PP hard support. Clarify this first, then discuss compromises; all the orders that hard support is used for in the future will need to be reworked and returned.
7. Material Change Risk List: An additional item 'FST complete redo'
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The shrinkage rate of fiberglass material is different from the original plan, and long parts are sensitive to the assembly surface. | The dimensions are out of tolerance, and the assembly does not fit. |
| Gate and Venting | Fiberglass has large flow differences, and the weld line position will change. | Insufficient filling, weak weld line strength |
| Material Temperature and Mold Temperature | The decomposition temperature of the flame retardant is limited, and the shear heating of the glass fiber material is more pronounced. | Local overheating, flame retardant decomposition, floating fibers |
| Dry | According to the specific system, the residence time of the flame retardant must be controlled. | Silver threads, bubbles, degradation |
| Pressure Holding and Demolding | Shrinkage differences cause deformation and surface whitening | Deformation, extrusion strain |
| Color difference | Non-exterior parts also need to confirm the color swatch first | Batch color difference dispute |
| Changing materials requires redoing the entire FST set | If the flame retardant system changes, all data for the three stages become invalid; if the component structure or surface layer changes, they must also be redone. | Deliver with the old report, leave the risk to the client |
| Verification order | Halogen-free screening → Vertical burn → Smoke density → Smoke toxicity → Mechanical → Whole piece | All the risk is pushed to the final step before it explodes |
Special emphasis should be placed on the penultimate line. Changing materials requires redoing the entire FST set, which is the biggest difference between aerospace/rail transit parts and ordinary parts. For ordinary parts, changing materials affects shrinkage and appearance; for aerospace parts, changing materials affects the validity of an entire set of combustion data.
Text version conclusion: Changing materials involves four aspects: mold, process, color difference, and verification sequence, among which the verification sequence and 'full FST redo' should be discussed first. Skipping small samples and directly testing the mold is equivalent to spending the cost in advance; submitting old reports with new materials leaves the risk to the customer.
VIII. One-page report comparison table: Direct reporting for five scenarios
| Scene | Recommended Route | Key indicators | Verification standard | Conditions that need to be confirmed first |
|---|
| Cargo hold liners, cargo hold floor underlayment | Glass Fiber Reinforced Halogen-Free Flame Retardant Modified PP | Vertical burning Ds ≤200 | 14 CFR 25.853 Appendix F; ASTM E662 | Component classification, presence or absence of anti-burn-through requirements |
| Non-cabin small items (clamps, clips, cover plates, shields) | Pure halogen-free flame-retardant PP or low glass fiber reinforced | Halogen-free caliber Vertical burning | Same as above Bromine/Chlorine content screening | Assembly pre-tension, allowable long-term deformation |
| Cabin visible trim parts (non-high requirement grade) | Glass Fiber Reinforced Halogen-Free Flame Retardant Modified PP | Vertical burning Ds Smoke toxicity | Same as above BSS 7239 / ABD0031 | Whether it falls on high-requirement components, overall criteria for the surface layer |
| Ground equipment, tooling, and handling parts | Glass fiber reinforced halogen-free flame retardant modified PP | According to the client's internal control on flame retardancy and smoke density | Execute according to the customer's specified standards | Whether to follow airworthiness standards, mostly not required |
| Cabin high-demand component positions, structural load-bearing positions | Should not use modified PP | — | — | Take the aerospace main material route and make another plan |
This table allows technicians to report conclusions directly without having to reorganize their language. There is only one criterion for judgment — whether the client can use it to finalize the direction in a single meeting.
9. The difficulty with this piece lies in balancing it, not in switching to a certain type of material.
The most common failure of aircraft interior components is not that they fail vertical burn tests, but that they fail due to smoke density or smoke toxicity after passing the burn. According to data from public testing organizations (Class B), the threshold for BSS 7239 is CO ≤ 3500 ppm, HCN ≤ 150 ppm, HCl ≤ 500 ppm, SO₂ ≤ 100 ppm, NOx ≤ 100 ppm collected over 4 minutes, which directly conflicts with halogen-containing systems.
There is another publicly known fact that is easily overlooked: smoke and toxicity testing is an internal control requirement of the whole-vehicle manufacturer for many models, not a mandatory regulatory item. It is not listed in regulations, but it is included in the customer's acceptance checklist.
The structural conclusion is just one sentence: the flame retardant content in PP is generally in the range of 25-30%. The idea that 'more flame retardant means worse mechanical properties' is a structural issue of PP, not a problem at the formulation level. Moreover, higher dosages are needed for smoke density and toxicity, and the core effect of glass fibers further pushes it up.
Ningbo Kolon New Materials Co., Ltd. commonly supplies glass fiber reinforced halogen-free flame-retardant modified PP in this part, mainly used to address the two issues of 'passing all three checks together' and 'dimensional stability'; the formulation can be adjusted according to the part position and working conditions, and can accompany customers in halogen-free screening, small sample comparison, and mold testing. It can also handle part-level demands for multiple varieties and small batches.
Frequently Asked Questions
Q: There are halogen-containing flame retardants that are cheap and efficient, so why do aerospace components still use halogen-free ones?
Answer: Because the three stages are a whole. Adding a small amount of halogen is efficient, and vertical combustion is easy to pass; but burning releases hydrogen halides, and HCl and HF directly hit the threshold at the smoke toxicity stage. The halogen saved at the S stage has to be returned at the T stage.
Question: The smoke density isn't too high; can I just add more smoke suppressant?
Answer: No. The smoke suppressant itself takes up space in the formulation, and adding it would squeeze the amounts of flame retardant, mechanical properties, and flow. The correct approach is to readjust the system, adjusting the ratios and dispersion within the phosphorus-nitrogen intumescent system.
Question: Can non-load-bearing small parts directly use flame-retardant PP without glass fiber?
Answer: In most cases, it is possible. Clamps, clips, and cover plates have low assembly pre-tightening force. Pure halogen-free flame-retardant PP has sufficient rigidity, and with less core effect, it is easier to meet flame retardancy requirements and better control smoke density. What needs to be confirmed is the allowable long-term deformation.
Q: Can three ready-made FST reports be used directly?
Answer: Both conditions must be met — the report must correspond to the final product structure (including the surface layer), and the formulation and batch must be traceable to this supply. If either condition is not met, the report will only state that that particular sample passed.
| position | Key criterion | Regular supply |
|---|
| Cargo hold lining and secondary structural components | Vertical burning Ds ≤200 | Glass fiber reinforced halogen-free flame retardant PP, regular stock |
| Non-cabin small items | Halogen-free caliber Vertical burning | Pure halogen-free flame-retardant PP or low glass fiber reinforced direction |
| Cabin visible trim parts (non-high requirement grade) | Vertical burning Ds Smoke toxicity | Glass fiber reinforced halogen-free flame-retardant PP direction |
| Ground Equipment and Turnover Items | According to the customer's internal control standards | Align the direction according to the specified caliber |
Text version conclusion: First, check if all three barriers are in place, don't just rely on the vertical burning report; smoke density and smoke toxicity are the two tests that often fail in halogen-containing systems, and they are also the easiest to fail when the amount is increased. Changing the material requires redoing the full FST test set, this step cannot be skipped.
Ten, Lastly, say three sentences
First, the hardest part in the three FST stages is not the 'non-flammable' test. The non-flammable aspect is visible, but smoke density and smoke toxicity are not visible, and they are also most likely to be tested last—reversing the order is the most expensive mistake for this kind of component.
Second, the second and third stages are interdependent, not individually achieving standards. Increasing the amount for flame retardancy works against mechanical strength, while smoke density and smoke toxicity require even higher amounts; the core effect of glass fibers further amplifies this conflict. If one criterion fails, you increase the amount, but the other two stages will push back.
Third, the position must be clearly explained. The actual position of modified PP in aircraft interiors is on the cargo compartment sides, secondary structure trim parts, small non-cabin components, and ground equipment; for cabin high-demand parts and structural load-bearing positions, materials like phenolic composites, PEI, and PPS are used. If this point is not clarified, the plan is flawed from the start.
The batch of "What flame-retardant PP is used for the top cover of new energy vehicle battery packs" talks about the account of hot wire and mechanical loss. This one talks about the logic of determining smoke density and smoke toxicity. The focus of the two articles is different, and they can be compared side by side.
Appendix · Standard Numbers and Source Classification Referenced in This Article
Class A (Regulation Original Text / Standard / Patent)
- 14 CFR Part 25 Appendix F Part I (60-second and 12-second vertical burn criteria), Part IV (heat release), Part V (Ds ≤200)
- ASTM E662; IEC 60695-2-12/13; GB/T 5169.12/13; HB 5469
- Patent CN105542320A: Smoke suppressant pathway; hydroxide flame retardants have low efficiency and require large amounts, leading to poor mechanical properties
Level B (Restatement of Aviation Enterprise Standards / Industry Overview / Enterprise Technical Information / Resource Library)
- Boeing BSS 7238, BSS 7239; Airbus ABD0031 (AITM 2.0007A/B, AITM 3.0005); MD DMS 2294 —— thresholds for smoke toxicity as quoted by public testing agencies, values are listed in the criteria table in Section 3
- Overview of publicly available aviation materials: PP melting point is about 160-170°C, tensile strength is about 30-40 MPa, components are mainly concentrated in non-structural low-stress parts
- Halogen-free flame retardant companies publicly disclose product information: fiberglass core effect and flame retardant addition levels; short fiberglass systems have tensile strength on the order of 20 MPa and notched impact strength on the order of 2-3.5 kJ/m²
- Material library Level B entries: halogen-free quantification definition, GWIT 750/775°C and GWFI 850/960°C, mechanical range of long glass fiber systems, flame retardant addition 25-30%
About Us
The most troublesome inquiry is this one: the material hasn't changed, but the part has a problem.
The material indeed hasn't changed; what has changed are the batch, drying, mold temperature, mold wear, or sometimes one of these is altered to save money. The parameters drift gradually, but the problems appear overnight. When it comes to aviation parts, one more thing needs to be added — once the flame retardant system is altered, all three FST data sets become invalid.
Ningbo Cologne New Materials Co., Ltd. produces modified polypropylene (PP) granules, covering homopolymer, random copolymer, and block copolymer base materials, as well as modifications including filled, glass fiber reinforced, toughened, flame-retardant, low odor and low VOC, weather-resistant, and scratch-resistant without coating; it also deals in PP resins from major petrochemical plants, off-spec materials, and bulk materials.
