新能源汽车电池包上盖用什么改性PP阻燃料？答案不是过个 V0，是 850℃ 灼热丝 30s 不引燃、RTI≥105℃、耐电解液与绝缘四关同时过。这篇讲清玻纤增强无卤阻燃 PP 怎么过三关，以及三种不该用改性PP 的工况。
一个主机厂负责电池包上盖的工程师跟我说：我们想把铝上盖换成塑料，减重和降本都要，阻燃你给个能过就行。
这话听着简单，坑在"就行"两个字。上盖不是过份阻燃报告就进得了包。行业里最常见的翻车现场有两种：V0 报告拍得漂亮，送第三方做 850℃ 灼热丝，直接引燃；或者装车跑了一年多，长期泡在 80-100℃ 里慢慢变脆。
这篇不讲"哪种料最好"，讲这个件最该先过的那几道关，以及哪几种工况下它压根不该用改性PP。
一、工况六维拆解：温度 / 载荷 / 介质 / 寿命 / 外观 / 合规
把上盖的工况拆成六维，六个数报齐，材料方向基本就定了。上盖用的改性PP阻燃料，硬线就两条——包内长期 80-100℃ 对应的 RTI≥105℃，和短路电弧对应的 850℃ 灼热丝。
| 维度 | 上盖实际工况 | 对材料的要求 |
|---|
| 温度 | 包内长期 80-100℃；短路 / 电弧产生 850℃ 级热点；夏季包体附近更高 | 长期耐热 RTI≥105℃；耐瞬时灼热丝 |
| 载荷 | 上盖非主承力，但要扛装卸、振动与螺栓紧固力 | 一定刚性 + 尺寸稳定，不靠高刚性 |
| 介质 | 电解液泄漏 / 冷凝、pack 内气氛、冷却液可能溅到 | 耐电解液、保持绝缘 |
| 寿命 | 整车生命周期（常按 10 年 / 数十万公里级设计） | 长期热老化后不脆化 |
| 外观 | 多为非外观件，表面要求低于外饰 | 关注浮纤与变形，可涂装 |
| 合规 | 车规安规：V0 + 850℃ 灼热丝 + RTI | 三关齐过，少一道都不行 |
六个维度里，温度和合规是"一票否决"性质的。原因很直接：包里长期 80-100℃，短期还有 850℃ 热点，材料撑不住这两档，其它维度再好也进不了包。
文字版结论：上盖工况的硬线就两条——包内长期 80-100℃ 对应的 RTI≥105℃，和短路电弧对应的 850℃ 灼热丝 30s 不引燃。耐电解液和绝缘是介质与安全的底，漏掉任何一项都算没过关。
二、材料路线对比：玻纤增强无卤阻燃 / 纯阻燃 / 金属上盖
上盖能落在三条路线上，没有"谁更好"，只有"卡在哪条线"。
| 路线 | 拿到什么 | 代价 / 短板 | 适用 |
|---|
| 玻纤增强 + 无卤阻燃改性PP | 同时过 V0、850℃ 灼热丝、RTI 三关；刚性与尺寸稳定 | 力学比纯 PP 降、成本高于纯阻燃；浮纤需控 | 主流非金属上盖 |
| 纯无卤阻燃 PP（不加玻纤） | 轻、过 V0；成本最低 | 850℃ 灼热丝与 RTI 两关常过不了；刚性撑不住装配 | 非包内主受热件 |
| 金属上盖（钢 / 铝） | 强度、耐热、阻燃天然达标 | 重、贵、成型与集成度低 | 高倍率 / 高安全冗余场景 |
先说无卤的量化定义，这是绕不开的硬指标：溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm。满足这条才叫无卤。
灼热丝指标也要记准：GWIT 750 / 775℃；GWFI 850 / 960℃。GWFI 850/960 这一档，正是上盖 850℃ 接触 30s 不引燃对应的判据。
文字版结论：上盖替代钢板或铝，玻纤增强无卤阻燃改性PP 可减重 50% 以上，成本比 PA66 体系低约 30%（据 B 级公开资料）。代价是力学要接受损失——这笔账后面算。
三、★ 选型判据表：五项判据，每项都带验证方法
下面这张表是全篇最该收藏的部分。注意第三列"验证方法·标准号"——选料卡住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，具体以牌号 TDS / 实测为准）
| 指标 | 门限值 | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| UL94 V-0（无熔滴引燃周边） | V-0（规定厚度，离火自熄、不引燃脱脂棉） | GB/T 2408 / IEC 60695-11-10（UL94） | 燃烧熔滴引燃周边 | 无卤膨胀阻燃 + 抑制熔滴 |
| 850℃ 灼热丝 30s 不引燃 | GWFI 850 / 960℃；接触 30s 不起燃 | IEC 60695-2-12/13；GB/T 5169.12/13（GWIT/GWFI） | 灼热丝接触即引燃，进不了包 | 玻纤增强 + 无卤阻燃 |
| RTI 长期使用温度 | RTI ≥105℃（包内长期 80-100℃） | UL 746B 相对耐热指数（长期热老化外推） | 长期服役变脆开裂 | 玻纤增强 + 耐热体系 |
| 耐电解液 | 浸泡后力学与绝缘保持（行业通行浸泡评价） | 电解液浸泡 + 性能保持率评价 | 溶胀 / 开裂 / 绝缘下降 | 无卤体系 + 介质耐受设计 |
| 绝缘 | CTI / 绝缘电阻达标 | GB/T 4207 / IEC 60112（CTI） | 漏电起痕、击穿 | 无卤阻燃 + 绝缘厚度设计 |
文字版结论：五项里 850℃ 灼热丝和 RTI 是最该先看的两道——普通磷氮阻燃改性PP 只能勉强过 V0，这两关过不了。门限值和验证方法一起看，缺一项不判合格，比样件试出来再回头找原因省钱得多。
四、上盖最常翻车的四类失效与各自根因
失效一：850℃ 灼热丝引燃。 V0 过了，送测灼热丝直接挂。根因是普通磷氮阻燃改性PP 只够 V0，炭层和耐热撑不到 850℃ 热点；没上玻纤增强，热变形也兜不住。
失效二：长期热老化变脆开裂。 装车跑一两年后开裂。根因是 RTI 没到 105℃，包内长期 80-100℃ 让分子链慢慢降解，不是突然坏。
失效三：耐电解液后绝缘下降。 漏液或冷凝后绝缘电阻掉、甚至起痕。根因是阻燃体系的介质耐受没排够，只盯了阻燃忘了电解液。
失效四（敢否定一个常见做法）：为减重走纯无卤阻燃、不加玻纤。 有人觉得上盖越轻越好，干脆纯阻燃上。这是错的——纯阻燃只能勉强过 V0，850℃ 灼热丝与 RTI 两关过不了，没有玻纤补刚性，上盖在螺栓紧固和振动下还容易变形。上盖替代金属要的是"减重 + 过三关"，不是单纯轻。
五、验证顺序：先验灼热丝与 RTI，后验成型
这一段同行很少写，但它是换改性PP上盖料能不能省钱的关键。顺序错了，成本在最后一步集中爆。
`
① 小样物理比对 拉伸 / 弯曲 / 缺口冲击 / 收缩率 / 阻燃 V0
↓ 五项在门限内，才往下走
② 灼热丝 + RTI 850℃ 30s 不引燃；RTI≥105℃
↓ 这两关不过，后面全不用做
③ 短射试模 看充填、熔接线位置、浮纤
↓ 短射走通，才谈批量
④ 装车匹配 装配力、间隙、耐电解液浸泡
↓
⑤ 批量试产 + 客户端验证
`
文字版结论：验证顺序是 小样 → 灼热丝/RTI → 短射 → 装车 → 批量。灼热丝和 RTI 必须在短射之前过，因为它们最可能一票否决；过了再做模具侧的事，才不白花试模费。
六、反向诚实：三种工况下，这个件不该用改性 PP
前面讲"怎么做"，这里讲"什么时候别做"。这一段对选型判断价值最高。
| 出现的情况 | 为什么改性PP 不合适 | 该往哪走 |
|---|
| 要求长期工作温度 150℃ 以上 | 改性 PP 的耐热上限就在那条线附近，增强也抬不太多 | 换更高耐热的工程塑料或金属 |
| 要求 A 级表面 + 高阻燃同时满足 | 高表面要少填料少浮纤，高阻燃要高填充，两方向对拉 | 表面件与阻燃件分开设计，或换料 |
| 要求高速碰撞级结构强度 | 上盖是轻量盖，PP 韧性能量吸收补不了碰撞量级 | 回到结构方案或金属上盖 |
文字版结论：这三种工况的共同点是"两个方向相反的要求同时要"——长期高温 + 轻量、A 级表面 + 高阻燃、碰撞级强度 + 塑料上盖。任一出现就说明这个件不该用 PP 硬撑；先说清楚，再谈折中，硬接下来的单子最后都要用返工还回去。
七、换料风险清单：模具 / 料温 / 干燥 / 色差 / 验证顺序
决定试改性PP 之前，这张表建议先过一遍。客户真正顾虑往往不是性能，是"模具和工艺要不要改"。
| 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差，长件敏感 | 尺寸超差，装车对不上 |
| 浇口与排气 | 玻纤料流动差异，熔接线位置变 | 充填不足、熔接线弱 |
| 料温与模温 | 玻纤 + 阻燃体系窗口不同 | 浮纤、炭化、熔接线差 |
| 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 |
| 验证顺序 | 小样 → 灼热丝/RTI → 短射 → 装车 | 风险全压到最后一步爆发 |
文字版结论：换料要动的是模具、工艺、色差三块，最该先谈的是验证顺序。跳过小样直接试模，等于把成本提前花出去；跳过短射直接批量，一次失败就是整批损失。
八、一页纸汇报对照表：四种场景直接上报
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 常规非金属上盖 | 玻纤增强 + 无卤阻燃改性PP | V0 + 850℃ 灼热丝 + RTI≥105℃ | GB/T 2408；IEC 60695-2-12/13；UL 746B | 包内长期温度、是否接触电解液 |
| 高减重上盖 | 同上加高玻纤 | 减重 50% 以上；三关齐过 | 同上 + 短射试模 | 壁厚分布、螺栓位受力 |
| 耐电解液严苛件 | 无卤阻燃 + 介质耐受设计 | 浸泡后绝缘与力学保持 | 电解液浸泡评价 + CTI | 电解液种类、接触方式 |
| 高安全冗余件 | 金属上盖或高耐热体系 | 150℃ 以上仍稳 | 长期耐热外推 | 倍率、热失控边界 |
文字版结论：这张表让技术员能把结论直接往上报，不必重组织语言。判断标准只有一条——客户拿这张表，能不能一次会议里把材料方向定下来。
九、上盖三关一起过，难在配平，不在某一料
行业里上盖最常见的阻燃翻车，不是 V0 过不了，是 V0 过了、灼热丝或 RTI 挂了。据艾邦高分子《阻燃 PP 在 800V 高压平台新能源车应用解析》，电池箱体上盖的通行判据是 UL94 V-0 + 850℃ 灼热丝接触 30s 不引燃 + RTI 长期使用温度 ≥105℃（包内长期 80-100℃），普通磷氮阻燃 PP 只能勉强过 V0，后两道常过不了。
这里有个结构性判断必须讲清：PP 阻燃剂加量普遍在 25-30% 这一档，而工程塑料里不少体系远低于此。"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。 加量降不下来，力学损失就是必然的；想靠调配方"既要 V0 又要高抗冲又要便宜"，在 PP 上物理上互斥。
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；配方按件的工况调，可以陪客户一起做小样比对与短射试模，多品种小批量的件级需求也能接。
常见问答
问：无卤和有卤怎么选？只看成本行不行？
答：不行。有卤（溴系）效率高、加量少、成本低，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，而且对 850℃ 灼热丝不利。上盖三关里，有卤省下的力学常在灼热丝那关还回去。无卤更稳，代价是力学和成本要让。
问：纯阻燃不加玻纤，能不能更轻更便宜？
答：能轻能便宜，但过不了三关里的后两道。上盖要的是"减重 + 过三关"，不是单纯轻。玻纤在这的作用是补刚性和把耐热往上抬，不是可有可无。
问：阻燃剂加得多力学掉，是你们改性PP配方不行吗？
答：不是配方水平问题，是 PP 底子的结构。加量 25-30% 是 PP 绕不开的档，降不下来。能做的只是在这个前提下把界面和工艺配平，让损失可控。
| 工况 | 关键判据 | 常规供应 |
|---|
| 电池包上盖 | V0 + 850℃ 灼热丝 30s + RTI≥105℃ | 玻纤增强无卤阻燃 PP，常规备货 |
| 耐电解液上盖 | 浸泡后绝缘与力学保持 | 无卤阻燃 + 介质耐受方向 |
| 高减重上盖 | 减重 50% 以上、三关齐过 | 高玻纤无卤阻燃 PP 方向 |
文字版结论：上盖先问三关齐不齐，别只拿 V0 报告谈；灼热丝和 RTI 是普通阻燃 PP 最常挂的两关，体系要按这两关实测。换金属上盖和换改性PP，账要分开算——减重 50% 以上、成本比 PA66 低约 30%，是用玻纤增强无卤阻燃 PP 换金属才有的空间。
十、最后说三句
第一，上盖阻燃是三道关，不是一道 V0。 UL94 V-0 + 850℃ 灼热丝 30s + RTI≥105℃，少一道都不算过关；普通磷氮 PP 常卡在后两关。
第二，减重 50% 以上、成本比 PA66 低约 30%，是用玻纤增强无卤阻燃 PP 换金属上盖的账。 力学损失是结构性的、必然的，先认这笔账，再谈方案。
第三，验证顺序比验证项更重要。 小样 → 灼热丝/RTI → 短射 → 装车，灼热丝和 RTI 必须放在试模之前。
下一篇讲电池模组支架——那个件卡的是刚性和尺寸稳定，不是阻燃三关。
关于我们
"这个件用什么料？"
这是我们被问得最多的一句话，也是最不好一句话回答的一句。因为答案从来不是"用最好的"，是"用最合适的那一档"。
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 flame retardant is used for the upper cover of new energy vehicle battery packs? The answer is not just passing V0, but withstanding a 850℃ glow wire for 30 seconds without igniting, RTI ≥105℃, and passing the four tests for resistance to electrolytes and insulation simultaneously. This article explains clearly how glass fiber-reinforced halogen-free flame retardant PP passes the three tests, as well as three conditions under which modified PP should not be used.
An engineer from an automaker responsible for the battery pack cover told me: We want to replace the aluminum cover with plastic, aiming for both weight reduction and cost reduction, and for flame retardancy, just make sure it passes.
This sounds simple, but the trick lies in the two words 'just needs to be'. The lid won't get into the package without an overly strict fire-retardant report. In the industry, there are two most common failure scenarios: A V0 report looks great, but when tested by a third party with an 850℃ glowing wire, it ignites immediately; or it's installed in the vehicle for over a year and slowly becomes brittle, having been constantly exposed to 80-100℃.
This article does not discuss 'which material is best'; it talks about the key checkpoints this part should first pass, and under which conditions it absolutely should not use modified PP.
1. Six-dimensional analysis of working conditions: Temperature / Load / Medium / Lifespan / Appearance / Compliance
Break down the working conditions of the upper cover into six dimensions; once the six numbers are reported, the material orientation is basically determined. The upper cover uses modified flame-retardant PP material, with only two hard limits—long-term 80-100℃ inside the package corresponding to an RTI ≥105℃, and the hot wire at 850℃ corresponding to a short-circuit arc.
| Dimension | Actual operating conditions of the upper cover | Requirements for the materials |
|---|
| Temperature | Inside the package long-term 80-100℃; short circuit / arc generates 850℃ level hotspots; even higher near the package in summer | Long-term heat resistance RTI ≥ 105℃; resistant to instantaneous hot wire |
| Load | The upper cover does not bear the main load, but it must withstand handling, vibration, and bolt tightening forces | Certain rigidity, dimensionally stable, not relying on high rigidity |
| Medium | Electrolyte leakage / condensation, atmosphere inside the pack, coolant may splash | Resistant to electrolyte, maintains insulation |
| Lifespan | Vehicle lifecycle (typically designed for 10 years / hundreds of thousands of kilometers) | Does not become brittle after long-term thermal aging |
| Appearance | Mostly non-exterior parts, with surface requirements lower than exterior trim | Pay attention to floating fibers and deformation, can be coated |
| Compliance | Automotive and safety regulations: V0 850℃ glowing wire RTI | All three barriers must be passed; missing even one is not acceptable. |
Among the six dimensions, temperature and compliance are of a 'veto' nature. The reason is straightforward: if the package is at 80-100℃ for a long time, and has 850℃ hotspots for a short term, the material cannot withstand these two extremes; no matter how good the other dimensions are, it still can't be included in the package.
Text version conclusion: There are only two hard lines for the upper cover condition——long-term 80-100℃ inside the package corresponds to RTI ≥ 105℃, and a short-circuit arc corresponds to a 850℃ glowing wire not igniting for 30 seconds. Resistance to electrolyte and insulation are the basis of the dielectric and safety; missing any one of them is considered a fail.
2. Comparison of material routes: glass fiber reinforced halogen-free flame retardant / pure flame retardant / metal cover
The top cover can fall on three routes; there is no 'which is better', only 'which line is stuck'.
| Route | Get what | Cost / Shortcoming | Applicable |
|---|
| Glass Fiber Reinforced Halogen-Free Flame Retardant Modified PP | Simultaneously passes V0, 850°C glow wire, and RTI tests; rigid and dimensionally stable | Mechanical properties are lower than pure PP, and costs are higher than pure flame retardant; floating fibers need to be controlled | Mainstream non-metallic cover |
| Pure halogen-free flame-retardant PP (without glass fiber) | Light, exceeds V0; lowest cost | 850℃ hot wire and RTI often fail both tests; the rigid support can't hold the assembly | Non-package main heat-receiving component |
| Metal top cover (steel/aluminum) | Strength, heat resistance, and flame retardancy naturally meet the standards | Heavy, expensive, low maturity, and low degree of integration | High magnification / high safety redundancy scenario |
First, let's talk about the quantitative definition of halogen-free, which is an unavoidable hard standard: bromine <900 ppm, chlorine <900 ppm, and the total of both <1500 ppm. Only if this condition is met can it be called halogen-free.
The scorching wire index also needs to be recorded accurately: GWIT 750 / 775℃; GWFI 850 / 960℃. The GWFI 850/960 level is exactly the criterion corresponding to the upper cover not igniting when in contact at 850℃ for 30 seconds.
Text version conclusion: Replacing the cover with steel plate or aluminum, glass fiber reinforced halogen-free flame-retardant modified PP can reduce weight by more than 50%, and the cost is about 30% lower than the PA66 system (according to publicly available B-level information). The trade-off is that the mechanical properties will suffer — this calculation will be done later.
3. ★ Selection Criteria Table: Five criteria, each with a verification method
The table below is the most important part of the entire article to keep. Pay attention to the third column "Verification Method · Standard Number" — 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 measure or what measurement counts as passing. (Standard numbers are cited according to common usage; specific details should be based on the grade TDS / actual measurements)
| Indicator | Threshold value | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| UL94 V-0 (no flaming drips ignite surroundings) | V-0 (specified thickness, self-extinguishing when removed from flame, does not ignite cotton wadding) | GB/T 2408 / IEC 60695-11-10 (UL94) | Burning molten droplets ignite the surroundings | Halogen-free flame retardant with anti-drip |
| 850℃ glowing wire 30s does not ignite | GWFI 850 / 960℃; does not ignite after 30s of contact | IEC 60695-2-12/13; GB/T 5169.12/13 (GWIT/GWFI) | The hot wire ignites on contact and cannot enter the packet. | Glass fiber reinforced Halogen-free flame retardant |
| RTI long-term use temperature | RTI ≥105℃ (long-term 80-100℃ inside the package) | UL 746B Relative Heat Resistance Index (Long-term Thermal Aging Extrapolation) | Brittle and cracked from long-term use | Glass fiber reinforced heat-resistant system |
| Electrolyte-resistant | Mechanical and Insulation Retention After Soaking (Industry Standard Soaking Evaluation) | Electrolyte Soaking Performance Retention Evaluation | Swelling / Cracking / Insulation Decrease | Halogen-free system Medium resistance design |
| Insulation | CTI / Insulation Resistance Meets Standard | GB/T 4207 / IEC 60112 (CTI) | Tracking and breakdown due to leakage | Halogen-free flame retardant Insulation thickness design |
Text version conclusion: Among the five items, the 850℃ glowing wire test and RTI are the two that should be looked at first — ordinary phosphorus-nitrogen flame-retardant modified PP can barely pass V0, and cannot pass these two tests. The threshold values and verification methods should be considered together; missing either one means it is not qualified. This is much more cost-effective than testing the sample first and then going back to find the reason.
4. The Four Most Common Types of Failures of the Cover and Their Respective Root Causes
Failure 1: Ignition by 850°C glowing wire. V0 passed, but when tested, the glowing wire ignited directly. The root cause is that ordinary phosphorus-nitrogen flame-retardant modified PP is only enough for V0; the char layer and heat resistance cannot withstand 850°C hotspots. Without glass fiber reinforcement, it also cannot prevent thermal deformation.
Failure mode 2: Brittle cracking due to long-term thermal aging. Cracks appear after one or two years of usage in the vehicle. The root cause is that the RTI did not reach 105°C, and long-term exposure to 80-100°C inside the package gradually degrades the molecular chains, rather than sudden failure.
Failure 3: Decreased insulation after electrolyte exposure. Insulation resistance drops or even leaves marks after leakage or condensation. The root cause is that the dielectric resistance of the flame-retardant system was insufficiently tested; only flame retardancy was focused on, while electrolyte resistance was overlooked.
Ineffective Point Four (Daring to Challenge a Common Practice): To reduce weight, use purely halogen-free flame retardant material without adding fiberglass. Some people think the lighter the cover, the better, so they go for purely flame-retardant material. This is wrong — purely flame-retardant materials can barely pass V0, cannot pass the 850℃ glowing wire test and RTI requirements, and without fiberglass to reinforce rigidity, the cover is prone to deformation under bolting and vibration. The goal of replacing a metal cover is 'weight reduction while passing all three tests,' not just being light.
5. Verification sequence: a priori hot wire and RTI, a posteriori molding
This part is rarely written about by peers, but it is key to whether modifying PP cover materials can save money. If the order is wrong, the cost will concentrate and explode at the final step.
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① Sample physical comparison Tensile / Bending / Notched impact / Shrinkage / Flame retardant V0
↓ Only if all five items are within the threshold, proceed further
② Glowing wire RTI 850℃ 30s does not ignite; RTI ≥105℃
↓ If you can't pass these two levels, you don't need to do the rest.
③ Short shot test molding – Check the filling, weld line position, and floating fibers
↓ Short-shooting needs to work first before talking about mass production
④ Loading Match Assembly force, clearance, resistance to electrolyte immersion
↓
⑤ Batch trial production Client-side verification
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Text Version Conclusion: The verification sequence is small sample → hot wire/RTI → short shot → loading → mass production. Hot wire and RTI must pass before the short shot, because they are most likely to result in a veto; only after passing them should the mold-side work be done, so as not to waste mold trial costs.
6. Reverse honesty: Under three working conditions, this part should not use modified PP
Earlier, we talked about 'how to do it'; here, we talk about 'when not to do it.' This section is the most valuable for making selection decisions.
| The situation that occurred | Why is modified PP not suitable? | Which way should I go? |
|---|
| Requires a long-term operating temperature above 150℃ | The heat resistance limit of modified PP is around that line, and reinforcement doesn't raise it much. | Switch to higher heat-resistant engineering plastics or metals |
| Requires Class A surface, high flame retardancy while meeting the requirements | High surface requires less filler and less floating fiber, high flame retardancy requires high filling, biaxial drawing | Design the surface parts and flame-retardant parts separately, or change the material |
| Requires high-speed collision-level structural strength | The upper cover is a lightweight cover, and the PP toughness cannot absorb the collision energy. | Return to the structural plan or metal cover |
Text Version Conclusion: The common point of these three working conditions is that there are "simultaneous requirements in opposite directions"—long-term high temperature but lightweight, A-grade surface but high flame retardancy, crash-level strength but plastic top cover. The presence of any of these indicates that this part should not be strictly made of PP; clarify this first before discussing compromises. Any orders forced through will eventually need to be reworked and returned.
7. Material Change Risk List: Mold / Material Temperature / Drying / Color Difference / Verification Sequence
Before deciding to try modified PP, it is recommended to go through this table first. Customers' real concern is often not performance, but whether 'the mold and process need to be changed'.
| Items to be moved | What needs to be confirmed? | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The shrinkage rate of glass fiber material differs from the original plan, sensitive for long parts | The dimensions are off, and they don't fit on the truck. |
| Gate and Venting | Differences in fiberglass flow cause changes in weld line positions | Insufficient filling, weak weld lines |
| Material Temperature and Mold Temperature | Glass fiber Different flame-retardant system windows | Floating fibers, carbonization, and fusion line defects |
| 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 whitening on the surface | Deformation, extrusion strain |
| Color difference | Non-exterior parts also need to confirm the color swatch first | Batch color difference dispute |
| Verification order | Sample → Heating wire/RTI → Short shot → Loading | All the risk is pushed to the final step before it explodes |
Text version conclusion: Material change affects three aspects: molds, processes, and color differences. The part that should be discussed first is the verification sequence. Skipping the small sample and going straight to molding is equivalent to spending the cost in advance; skipping the short shot test and going straight to batch production means that a single failure will result in the loss of the entire batch.
8. One-page report comparison table: Direct reporting for four scenarios
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Conventional non-metallic cover | Glass Fiber Reinforced Halogen-Free Flame Retardant Modified PP | V0 850℃ glowing wire RTI≥105℃ | GB/T 2408; IEC 60695-2-12/13; UL 746B | Long-term temperature inside the pack, and whether it comes into contact with electrolyte |
| High weight-reduction upper cover | Same as above, with increased fiberglass | Lose more than 50% of weight; pass all three levels | Same as above Short-shot mold testing | Wall thickness distribution, bolt position stress |
| Electrolyte-resistant critical component | Halogen-free flame retardant Medium tolerance design | Insulation and mechanical retention after soaking | Electrolyte Soaking Evaluation CTI | Types of electrolyte and contact methods |
| High-security redundant components | Metal upper cover or high heat-resistant system | Stable above 150° C | Long-term heat resistance extrapolation | Rate, thermal runaway boundary |
Text version Conclusion: This form allows technicians to directly report conclusions without relying on organizational language. There is only one criterion — can the client take this form and determine the material direction in one meeting?
9. The top cover passes all three stages together; the difficulty lies in matching, not on a single material
The most common flame-retardant failure in the industry is not that V0 fails, but that V0 passes, or the hot wire or RTI fails. According to Aibang Polymer's "Analysis of Flame-Retardant PP Applications in 800V High-Voltage Platforms for New Energy Vehicles," the passing criteria for the battery casing cover are UL94 V-0 + 850°C hot wire contact for 30 seconds without ignition + long-term RTI usage temperature ≥105°C (in-pack long-term 80-100°C). Ordinary phosphorus-nitrogen flame-retardant PP can barely pass V0, and the last two layers often fail.
There is a structural judgment that must be clarified: PP flame retardant dosage is generally in the 25-30% range, while many engineering plastics systems fall far below this. "The more flame retardant added, the more mechanical degradation" is a structural issue with PP, not a formulation level issue. If the dosage cannot be reduced, mechanical losses are inevitable; If you want to adjust the formula to "have V0, high impact resistance, and low cost," the PP is physically mutually exclusive.
Ningbo Kelong New Materials Co., Ltd. commonly supplies glass fiber reinforced halogen-free flame-retardant modified PP for this part, mainly to solve the problem of "passing all three checks together + dimensional stability"; The formula can be adjusted according to the working conditions of the part, and we can accompany customers for small-scale sample comparison and short shot mold testing, and can also handle multi-variety, small-batch part-level requirements.
FAQ
Q: How do you choose halogen-free or halogen-free? Is it okay to just look at cost?
Answer: No. Halogen (bromine-based) is highly efficient, requires less dosage, and is low-cost, but during processing, it releases hydrogen halide and corrodes molds when heated, and combustion releases hydrogen halide and thick smoke, which is also unfavorable for the 850°C hot wire. Among the three checkpoints of the top cover, the mechanical savings from halogen often return at the heat wire stage. Halogen-free is more stable, but the trade-off is mechanics and cost.
Question: Can pure flame-retardant without adding glass fiber be lighter and cheaper?
A: It can be lightweight and cheap, but it can't pass the last two stages of the three stages. The top cover needs to be "weight reduction + passing the three tests," not simply lightness. The role of glass fiber here is to add rigidity and raise heat resistance, not to be optional.
Question: How much flame retardant is added to remove it? Is it because your modified PP formula isn't good?
Answer: It's not a matter of formulation level, it's the structure of the PP base. Adding 25-30% is an unavoidable barrier for PP—it can't be reduced. All you can do is balance the interface and process under this premise to keep losses controllable.
| Operating Condition | Key Criteria | Conventional Supply |
|---|
| Battery Pack Cover | V0 + 850°C Hot Wire 30s + RTI≥105°C | Glass Fiber Reinforced Halogen-Free Flame-Retardant PP, Regular Stock |
| Electrolyte-Resistant Upper Cover | Insulation and mechanics maintained after immersion | Halogen-free flame retardant + medium tolerance direction |
| High weight reduction cover | Weight reduction over 50%, all three tests passed | High glass fiber halogen-free flame retardant PP direction |
Text version conclusion: First ask if the top cover has all three checkpoints, don't just use the V0 report for discussion; Hot wire and RTI are the two most common hurdles for ordinary flame-retardant PP; the system must be tested according to these two tests. Replacing the metal top cover and switching to modified PP should be calculated separately—reducing weight by over 50%, cost about 30% lower than PA66, which is the only way to replace metal with glass fiber reinforced halogen-free flame-retardant PP.
Ten, three final words
First, the flame retardant upper cover has three levels, not just one V0. UL94 V-0 + 850°C hot wire 30s + RTI≥105°C—even one less step doesn't pass; Ordinary phosphorus and nitrogen PP often gets stuck in the last two stages.
Second, reducing weight by more than 50% and costing about 30% less than PA66 is the process of replacing the metal cover with glass fiber reinforced halogen-free flame-retardant PP. Mechanical losses are structural and inevitable; acknowledge this first, then discuss the solution.
Third, the order of validation is more important than the validation items. Sample → hot wire/RTI → short shot → for vehicle installation; hot wire and RTI must be placed before mold trials.
Next article will talk about battery module brackets—the part is stuck in rigidity and dimensional stability, not flame retardant triple barriers.
About Us
"What material is used for this part?" "
This is the question we get asked the most, and also the one we rarely answer. Because the answer has never been 'use the best,' but 'the most suitable grade.'
Ningbo Kelong New Materials Co., Ltd. produces its own modified polypropylene (PP) pelletizing, covering three grades: homopolymer, random copolymer, and impact-resistant copolymer substrates, as well as modification directions such as filling, glass fiber reinforcement, toughening, flame retardant, low odor and low VOC, weather resistance, no coating and scratch resistance; Also engaged in PP resin, sub-brand materials, and large package materials for major petrochemical plants
