电器外壳用阻燃PP，最容易走两个极端：档位选低了被整机安规打回，选高了阻燃剂加量上去、螺柱一拧就裂。这篇讲清 V-2 / V-1 / V-0 / 5VA 的实质差别，给出按安规距离与屏蔽倒推档位的方法、验证顺序、反向诚实段与换料风险清单。
"我们这个底座离带电件挺远的，外面还罩了一层，非要 V-0 吗？现在这个 V-0 的料，装上去一拧螺柱就裂。"
这句话我在展会上听过不止一次。问的人已经踩过坑：外壳和底座统一上了 V-0 料，阻燃那一关过了，装配那一关开始裂。反过来的一类也常见：外壳报的是 V-2，整机送检时被指出这个位置离载流连接件太近。
这两种翻车指向同一件事：阻燃等级不是"越高越安全"，它是从整机安规里"离火源多远、有没有屏蔽"倒推出来的一个位置参数。
一、这个件最容易倒的两件事：档位不够，和档位过高
结论先说：外壳、底座这个件，失效不在"烧不着"，在"档位没对上位置"。
档位不够表现很直接：件在整机送检时被卡。检测方看的是这个件离载流连接件的距离、载流多大、有没有人照管、有没有屏蔽挡板。
档位过高更隐蔽，因为它不发生在外壳上，而是发生在装配线上。料换了、阻燃剂加多了，外壳本体看着没事，螺柱根部、卡扣、超声线这些应力集中点开始发白开裂，或者整机跌落时底座先破。
第三类最容易被误判成"料太脆"。洗涤剂、油污、表面活性剂和装配应力一起作用，外壳装机几个月后从圆角处开裂——业内叫环境应力开裂，常规物性指标却往往合格。
一句判读：这个件要的不是最高的那一档，是对得上位置的那一档。 档位高一级，加量高一档，力学和韧性就多掉一截。
二、V-2、V-1、V-0 的差别不在"好不好"，在滴落物引不引燃脱脂棉
结论先说：这几档用同一套试样、同一套方法，差别只在两组数——燃烧时间多长，滴落物会不会引燃下方脱脂棉。
V 级垂直燃烧的试样是 125 mm × 13 mm 样条，20 mm 蓝色火焰接触两次、每次 10 s，再看余焰、余灼与滴落物是否引燃下方脱脂棉。据 UL 官网公开判定表与 GB/T 5169.16（idt IEC 60695-11-10）的口径：
| 等级 | 单次余焰时间 | 10 次施焰总余焰 | 第二次施焰后余焰+余灼 | 滴落物引燃下方脱脂棉 |
|---|
| V-0 | ≤10 s | ≤50 s | ≤30 s | 不允许 |
| V-1 | ≤30 s | ≤250 s | ≤60 s | 不允许 |
| V-2 | ≤30 s | ≤250 s | ≤60 s | 允许 |
最该记住的一行是 V-2 与 V-1 的对比：两者燃烧时间要求完全相同，差别只在滴落物允不允许引燃脱脂棉。 所以"V-2 比 V-1 差一大截"是误读——它俩差的就这一条，而这一条只在"滴落物会落到发热件上"的位置才致命。
再往上是 5VA 与 5VB：换 500 W、125 mm 大火焰，分界不在时间，在"烧不烧穿"——5VA 要求板状试样不出现孔洞，5VB 允许烧穿。
第二件必须记住的事：等级要和厚度一起报。 同一配方，1.5 mm 样条可能只到 V-2，做到 3 mm 就能上 V-0；不写厚度的"V-0"没法对到你的件上。
第三件事才是主线：这个等级在安规里不是"安全强度"，是位置参数。 家电安规按四件事分档：离载流/发热件多远、载流多大、有没有人照管、有没有屏蔽挡板。按 GB 4706.1 第 30 章的公开口径：
- 非金属外部件要过 550℃ 灼热丝（GB/T 5169.11）；但材料类别达到 HB40 以上，这一关可以免做。
- 有人照管的器具，支撑载流连接件的绝缘件、以及距这些连接件 3 mm 范围内的件：载流超过 0.5 A 按 750℃，其他按 650℃。
- 无人照管、载流超过 0.2 A 的：这些件和 3 mm 范围内的件，材料 GWFI 至少 850℃；或部件过 750℃ 且起燃不超过 2 s。
- 达不到的还有出口：连接件上方（直径 20 mm、高 50 mm 圆柱范围）的件做针焰试验；用隔离挡板屏蔽起来的件，不试验。
把这几条连起来，"要不要 V-0"的答案就变了——取决于离带电件多远（3 mm 是分界线）、载流多大（0.5 A 与 0.2 A 是两个岔口）、有没有屏蔽挡板。一个外面全罩住、离载流件挺远的纯外壳，和一个紧贴端子座的底座，本来就不该是同一档。
这也是这个件上最贵的一笔冤枉钱：很多外壳本来 V-2 就够，被"越高越安全"的思路推到 V-0，代价是三样一起上——加量更高、力学与韧性掉更多、成本往上走。
三、工况六维拆解：电器外壳、底座的六个维度，数字先报齐
结论先说：温度和位置这两维决定"要不要高等级"，介质和载荷这两维决定"能不能长期不开裂"，外观与合规是两个否决项。
| 维度 | 电器外壳 / 底座的工况 | 对材料的要求 |
|---|
| 温度 | 件内一般 40–80℃，靠近发热件处更高；小家电外壳一类件耐热常写到 120–150℃ | 热老化按 RTI ≥105℃ 口径；短期看灼热丝档位 |
| 载荷 | 自重 + 装配扭矩 + 卡扣预紧 + 整机跌落；螺柱与卡扣是应力集中点 | 要韧性与抗应力开裂，不是高刚性 |
| 介质 | 干区件是灰尘与手汗；湿区件长期接触洗涤剂、油污、表面活性剂 | 湿区件必须先过 ESC 这一关 |
| 寿命 | 按整机设计寿命计，湿区件叠加洗涤剂与温热长期作用 | ESC 看 F50 与 500 h 量级 |
| 外观 | 高光或免喷涂外壳，色差与表面缺陷直接被看见 | 填充与阻燃组分的表面影响要一并算 |
| 合规 | UL94 档位、灼热丝（550 / 650 / 750 / 850℃）、针焰、无卤量化、RTI | 少一条就不算过关 |
无卤是最容易被口头化的一条，它的量化定义是溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm，三条都满足才算。
文字版结论：温度和位置定档位、介质和载荷定寿命。把"这个件离带电件多远"当成要先报的参数，比先问用哪种料有用。
四、材料路线对比：无卤阻燃PP、有卤阻燃PP，以及和工程塑料的分工
结论先说：这不是"谁更好"的关系，是"哪一条的短板正好不在你这个件上"的关系。
| 路线 | 拿到什么 | 代价 | 适用位置 |
|---|
| 无卤阻燃PP（磷氮膨胀体系为主） | 过 V-0；抑烟表现好；满足无卤量化 | 加量普遍在 25–30% 这一档，力学与韧性掉得多；耐水与耐湿热要单独评估 | 外壳、底座、面板这类大件薄壁件 |
| 有卤阻燃PP（含卤阻燃剂 + 协效剂） | 效率高、用量低，V-0 相对容易做 | 加工受热释放卤化氢，腐蚀设备与模具；燃烧释放卤化氢与浓烟；灼热丝表现常被拖累 | 只在项目明确允许、且无出口环保要求时考虑 |
| ABS / PC-ABS / PBT | ABS 外观与韧性好、易做高光；PC-ABS 冲击与耐热更高；PBT 耐热耐化学、尺寸稳定更好 | ABS 耐热一般；PC-ABS 与 PBT 成本高 | 高光外观件、精密结构件、耐热耐化学位 |
还有一处必须讲透：PP 的阻燃剂加量普遍落在 25–30% 这一档，它带来的力学与韧性损失是 PP 的结构性问题，不是配方水平问题。 遇到"又要 V-0、又要高抗冲、还要便宜"三条同时提，先谈排序，再谈料。
五、★ 选型判据表：七项指标，每项都带验证方法
结论先说：第四列"验证方法·标准号"是这张表和普通物性表最大的差别——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。
| 指标 | 门限值（典型） | 验证方法 · 标准号 | 常见失效 | 通行解法 |
|---|
| UL94 垂直燃烧等级 | 按位置定：距载流连接件 3 mm 内需 V-0 或 V-1 以上；远离火源的纯外壳可落到 V-2 / HB40 档 | GB/T 5169.16（idt IEC 60695-11-10）；等级须连厚度标注 | 档位不够被打回；档位过高浪费力学与成本 | 按安规位置分档，同机不同件可不同档 |
| 灼热丝（外部件，部件口径） | 550℃；材料类别达 HB40 以上可免这一关 | GB/T 5169.11（idt IEC 60695-2-11） | 接触发热件起燃 | 材料类别选到 HB40 以上，直接免测 |
| 灼热丝（支撑载流件，按距离与载流分档） | 有人照管：距连接件 3 mm 内、>0.5 A 按 750℃，其他 650℃ | GB/T 5169.11 | 端子座附近件起燃 | 无卤阻燃 + 填充体系 |
| GWFI / GWIT（材料类别口径） | 无人照管、载流 >0.2 A：GWFI ≥850℃；或部件过 750℃ 且起燃 ≤2 s，或材料 GWIT 775℃ | GB/T 5169.12、GB/T 5169.13（idt IEC 60695-2-12 / 2-13） | 长期高温接触起燃 | 无卤阻燃 + 玻纤 / 矿物填充 |
| RTI 长期使用温度 | ≥105℃（按件内实际工况定） | UL 746B（长期热老化外推） | 长期服役后变脆开裂 | 耐热基材 + 填充 |
| 无卤量化 | 溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm | 卤素含量测试（XRF / IC），参照 IEC 61249-2-21 | 环保合规不达标 | 无卤阻燃体系，不用含卤协效剂 |
| 环境应力开裂 ESC | ASTM D1693 弯条法（10% Igepal CO-630、50±0.5℃，看 50% 试样开裂时间 F50）；或 ISO 22088-3 恒拉伸应力法；或 ISO 6252 恒应变法（50–80℃、应变 1.0–2.0%） | ASTM D1693 / ISO 22088-3 / ISO 6252 | 洗涤剂、油污 + 装配应力共同作用下开裂（料没错、件开裂） | 耐应力开裂体系 + 控装配应力 + 结构圆角 |
文字版结论：七项里 档位那一行与 ESC 那一行才是本篇主角——前者决定你花不花那笔冤枉钱，后者决定件装出去几个月后裂不裂。
六、常见失效与根因：四个现象，四条根因
结论先说：这四类里真正属于"料不行"的只有一类，另外三类分别是位置没倒推、加量代偿、介质与应力合谋。
失效一：整机送检被卡，材料要重新认证。 根因是选型时没先倒推安规位置——距载流件多远、载流多大、有没有屏蔽没问清就定了料。
失效二：阻燃档位一高，装配就裂。 根因是阻燃加量的结构性代价：PP 这一档加量普遍在 25–30%，加量上去，力学与韧性必然掉一截，表现就是螺柱根部发白开裂、跌落时底座先破。
失效三：装出去几个月后从圆角裂开，料检却是合格的。 根因是环境应力开裂：洗涤剂、油污、表面活性剂在装配应力协同下诱发银纹并扩展成裂纹。 先查件上有没有残余应力，再查料。
失效四（敢否定一个常见做法）：把所有塑料件统一采购成 V-0 料。 这是错的：它把不需要高档位的外壳一起推到高加量，力学、韧性、成本三样一起付；而高加量带来的填充与阻燃组分，会让湿润环境下的 ESC 风险更难控——为"统一省事"买的那一档，可能正好是让湿区件开裂的那一档。
七、验证顺序：按安规倒推，先定档位再定料
结论先说：这个件的验证顺序是倒着来的——先定整机安规要求（距火源多远、有没有屏蔽），再定阻燃档位，最后才轮到基材与填充。
`
① 先定安规位置 距载流/发热件多远（3 mm？）、载流多大（0.5 A / 0.2 A？）、
是否有人照管、有没有隔离挡板
↓ 这一步定了档位，后面才有意义
② 定阻燃档位 该位置要不要 V-0、要不要 GWFI 850℃、要不要针焰
③ 定基材与填充 均聚 / 抗冲共聚；矿物填充还是玻纤增强；无卤还是有卤
↓
④ 力学与韧性补偿 25–30% 阻燃加量的代价，用增韧与填充补回来
↓ 补不回来，退回 ② 重谈档位或改件结构
⑤ ESC 与老化 洗涤剂/油污 + 装配应力下的 ESC；热老化按 RTI 口径
↓ 湿区件这一关不过，前面全都不用做
⑥ 整机验证 灼热丝、针焰、整机认证
`
每一级都有"不过就退回上一级"的判据。最常见的错是跳过 ①② 直接进 ③，先挑一款看着顺眼的阻燃料，做出来再回头核对安规——这时档位、加量、结构都已定死，能改的只剩成本。
一句话收口：这个件是从安规往回推的，顺序反了的账最后都在整机认证和装配线上还。
八、反向诚实：这三种情况，这个件不该用改性PP
结论先说：只要出现"要 PP 拿不到的东西"，就不该硬撑——长期 150℃ 以上、5VA 级且壁厚受限、透明或高光外观，这三件事改性PP 都很难办。
| 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 | 耐热上限就在那条线附近，填充与玻纤增强往上抬也有边界 | 换更耐热的工程塑料或金属 |
| 要求 5VA 级且壁厚受限 | 5VA 要拿板试样烧、不许烧穿，靠的是高填充与高阻燃加量；薄壁下 PP 很难同时保住力学与这一档 | 换阻燃工程塑料（PC/ABS 类、PBT、PA 类）或金属 |
| 要求 透明或高光外观 | 25–30% 档的阻燃加量必然破坏透明与高光，矿物与阻燃组分的表面缺陷压不住 | 透明件走 PMMA / PC / 透明 ABS；高光件走 ABS / PC-ABS |
规律是一致的：只要出现"两个方向相反的要求同时要"，就说明这个件不该用 PP 硬撑——耐热与减填充、加量与减料、少填充与高填充，三组都是两头顶着。
九、换料要动什么：一张先看再动的清单
结论先说：客户真正的顾虑往往不是性能，是"我现在的模具和工艺要不要改"，这张表建议在决定试料之前先过一遍。
| 要动的项 | 需要确认什么 | 不做会怎样 |
|---|
| 模具收缩率 | 新料收缩率与原方案的差，有装配孔位的底座尤其敏感 | 尺寸超差，装配对不上 |
| 浇口与排气 | 阻燃填充料对浇口位置与排气更敏感 | 充填不足、烧焦、熔接线强度不足 |
| 料温与模温 | 无卤阻燃体系热稳定窗口较窄，停留时间要控 | 分解、表面缺陷、阻燃性能波动 |
| 干燥 | 按具体体系确认，不可照搬原工艺 | 银丝、气泡 |
| 保压与脱模 | 收缩差异带来变形与顶白 | 变形、顶出拉伤 |
| 验证顺序 | 安规位置 → 阻燃档位 → 基材与填充 → 力学补偿 → ESC | 风险全压到最后一步集中爆发 |
文字版结论：换料要动模具、工艺、外观三块，其中最该先谈的是验证顺序。跳过安规位置直接试模等于先花掉一笔试模费；跳过 ESC 直接批量，湿区件的问题往往几个月后才暴露。
十、一页纸汇报对照表（可以直接贴进 PPT）
结论先说：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。
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 纯外壳，远离载流/发热件 | 阻燃 PP 走低一档（V-2 或材料类别 HB40 以上） | 550℃ 灼热丝可免；V-2 或以上 | GB/T 5169.16、GB/T 5169.11 | 距载流件的距离、是否有人照管、有无挡板 |
| 底座、端子座，支撑载流 >0.2 A 或 3 mm 内 | 无卤阻燃 PP 走 V-0 + 850℃ 级 | GWFI ≥850℃；或 GWIT 775℃；V-0 | GB/T 5169.12 / .13 / .11、GB/T 5169.16 | 载流大小、照管状态、有没有屏蔽挡板 |
| 湿区件（控制面板、厨房小电周边） | 无卤阻燃 + 耐 ESC 体系 | ESC 按 F50 与加速时间看 | ASTM D1693 / ISO 22088-3 / ISO 6252 | 介质种类、装配应力、实际温度 |
文字版结论：同一台家电上，外壳走低一档、底座走 V-0 是正常配置；靠的不是档位高，而是每个位置都对上安规给它的那一条。
十一、这个件上最容易出问题的，往往不是阻燃
这类件上行业最常见的偏差有两类。一类是档位与位置没对上：公开的安规口径把要求按"距载流连接件的距离、载流大小、是否有人照管、有没有隔离挡板"来分，3 mm、0.5 A、0.2 A 就是那几个岔口，而现场常见做法是不问这些条件、直接按"越高越保险"定档。另一类是档位定高之后的代偿失效：PP 的阻燃剂加量普遍落在 25–30% 这一档，加量上去，力学与韧性必然掉一截，螺柱、卡扣先出问题。
判据层面，通行硬线是：外部件 550℃ 灼热丝（材料类别达 HB40 以上可免）；支撑载流件按距离与载流分到 650 / 750℃，无人照管的载流件按 GWFI 850℃ 或 GWIT 775℃；长期耐热按 RTI ≥105℃ 口径。
行业通行的解法是把顺序倒过来做：先由整机安规定位置条件，定出档位，再定基材与填充，用增韧补回阻燃加量的韧性损失，湿区件另加一道 ESC 评估——洗涤剂、油污、表面活性剂在装配应力协同下的开裂属于"料没错、件开裂"，只能在体系与结构两侧一起收。
宁波市科隆新材料有限公司在这个件上常供的是无卤阻燃改性PP 方向，按外壳、底座、湿区件三种位置给到对应的阻燃档位与填充/增韧配平，湿区件另配耐应力开裂体系，主要解决"档位与位置对不上、加量后装配开裂、装了几个月圆角开裂"这三件事；配方按件的工况调，可陪客户做小样比对与 ESC 验证，件级客户多品种小批量也能接。
常见问答
问：我能不能干脆全用 V-0，省得判断？
答：不建议。V-0 只对"离火源近、要屏蔽"的位置有意义，对远处的纯外壳是纯代价——加量更高、力学与韧性掉更多、成本更高。
问：V-0 一定比 V-2 安全吗？
答：不能这么比。V-2 允许滴落物引燃脱脂棉，所以不能用在"滴落物会落到发热件或易燃物上"的位置；但一个外面全罩住、离载流件很远的外壳，用 V-2 并不构成风险。等级是位置参数，不是安全分数。
问：外壳装好几个月后从螺柱处裂开，是不是料太脆？
答：先别换料。这类开裂八成是环境应力开裂，常规物性指标查不出来；判据按 ASTM D1693（10% Igepal CO-630、50℃）或 ISO 22088-3 走，同时把装配扭矩与圆角核一遍。
| 工况 | 关键判据 | 常规供应 |
|---|
| 纯外壳（远离载流/发热件） | V-2 档可用；550℃ 灼热丝可免 | 无卤阻燃改性PP，低档位配平方向 |
| 底座 / 端子座（3 mm 内或支撑载流 >0.2 A） | GWFI ≥850℃、GWIT 775℃、V-0 | 无卤阻燃改性PP，高灼热丝档方向 |
| 湿区件（控制面板、厨房小电周边） | ESC 按 F50 与加速时间 | 无卤阻燃 + 耐应力开裂体系方向 |
最后说三句。 第一，阻燃档位是从安规倒推出来的位置参数，离带电件多远、载流多大有没有挡板要先问清。第二，V-2 与 V-1 的燃烧时间要求完全相同，差的只是滴落物允不允许引燃脱脂棉。第三，验证顺序比验证项更贵：安规位置 → 阻燃档位 → 基材与填充 → 力学补偿 → ESC。
下一篇讲开关插座面板——那个件的难点落在矿物填充配平与电气性能上。
关于我们
选型卡住，通常卡在很具体的一步。
是不知道该用均聚还是抗冲共聚，是增韧了又怕划痕发白，是玻纤料收缩各向异性压不住公差——说清卡在哪一步，比说"要一种好料"有用得多。
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。
The appliance casing uses flame-retardant PP, which is prone to two extremes: if the grade is chosen too low, the whole device will fail safety certification; if chosen too high, the amount of flame retardant increases, and the posts crack as soon as you screw them in. This article explains the real differences between V-2 / V-1 / V-0 / 5VA, provides a method to deduce the grade based on safety distances and shielding, and gives the verification sequence, reverse honesty section, and a risk checklist for material substitution.
Our base is quite far from the live parts, and it even has an extra layer on the outside. Do we really need V-0? With the current V-0 material, it cracks as soon as you screw in the stud.
I have heard this sentence more than once at the exhibition. The people asking have already hit the pitfalls: the shell and base are both made of V-0 material, so the flame-retardant part is fine, but cracks start to appear during assembly. The opposite situation is also common: the shell is rated V-2, and when the whole machine is submitted for inspection, it is pointed out that this spot is too close to the current-carrying connector.
These two types of accidents point to the same thing: the fire resistance rating is not 'the higher, the safer.' It is a positional parameter inferred from the overall equipment safety regulations based on 'how far it is from the fire source and whether there is shielding.'
1. The two things that are easiest to fail in this matter: not enough gears, and gears too high
Conclusion first: The failure of the casing and base parts is not due to 'not being able to ignite,' but because 'the gear position did not align correctly.'
The insufficient gear levels are reflected very directly: the part gets stuck when the whole machine is sent for inspection. The inspectors look at the distance of this part from the current-carrying connector, how much current it carries, whether anyone is supervising, and whether there is a protective shield.
Higher gear levels are more concealed because they don't occur on the casing but on the assembly line. When materials are changed or more flame retardant is added, the casing itself looks fine, but the roots of the studs, clips, and ultrasonic weld lines—these stress concentration points—start to whiten and crack, or the base breaks first when the whole device is dropped.
The third category is most easily misjudged as 'the material is too brittle.' Detergents, grease, surfactants, and assembly stress work together, causing the casing to crack at the corners a few months after installation — in the industry, this is called environmental stress cracking, even though conventional physical property indicators are often within specifications.
A judgment: What this part requires is not the highest grade, but the grade that matches the position. If the grade is one level higher and the quantity is increased by one level, the strength and toughness will drop accordingly.
2. The difference between V-2, V-1, and V-0 is not about 'good or not,' but whether the drips ignite the cotton wadding.
Conclusion first: For these few tests using the same set of samples and the same methods, the only differences are two sets of numbers — how long the combustion lasts and whether the dripping material will ignite the absorbent cotton below.
The V-level vertically burning specimen is a 125 mm × 13 mm strip, with a 20 mm blue flame applied twice, each time for 10 seconds, and then observing whether the remaining flame, afterglow, or drips ignite the cotton below. According to the public determination table on UL's official website and the scope of GB/T 5169.16 (idt IEC 60695-11-10):
| Level | Single Residual Flame Time | Total Residual Flame from 10 Flame Applications | After the second flame application, residual flame and residual burn | Dripping substances ignite the cotton below |
|---|
| V-0 | ≤10 s | ≤50 s | ≤30 s | Not allowed |
| V-1 | ≤30 s | ≤250 s | ≤60 s | Not allowed |
| V-2 | ≤30 s | ≤250 s | ≤60 s | Allow |
The line that should be remembered most is the comparison between V-2 and V-1: both have exactly the same burn time requirements, the only difference is whether the dripping material is allowed to ignite the cotton. So the idea that "V-2 is much worse than V-1" is a misreading—they only differ in this one aspect, and this aspect is only critical in places where "the drips can fall on heated components."
Above that are 5VA and 5VB: switching to 500 W, 125 mm large flames, the distinction is not in time, but in "whether it burns through" — 5VA requires the board-shaped sample not to have holes, while 5VB allows burning through.
The second thing to remember: the rating must be reported together with the thickness. For the same formula, a 1.5 mm sample strip may only reach V-2, while a 3 mm strip can reach V-0; a 'V-0' without specifying the thickness cannot be applied to your part.
The third thing is the main line: this level in safety regulations is not "safety strength," but a position parameter. Household appliance safety regulations are classified according to four things: how far it is from current-carrying/heating parts, the amount of current carried, whether there is supervision, and whether there is a shield panel. According to the public wording of Chapter 30 of GB 4706.1:
- Non-metallic exterior parts must pass a 550°C glowing wire test (GB/T 5169.11); however, if the material category reaches HB40 or above, this step can be exempted.
- Devices that are monitored by someone, insulating parts supporting current-carrying connectors, and parts within 3 mm of these connectors: For current exceeding 0.5 A, use 750℃; for others, use 650℃.
- Unattended, carrying a current exceeding 0.2 A: these parts and parts within a 3 mm range, material GWFI at least 850°C; or parts exceeding 750°C with an ignition time not exceeding 2 s.
- The parts that cannot be reached should also be tested: perform a needle flame test on the parts above the connector (cylindrical area with a diameter of 20 mm and a height of 50 mm); parts shielded by an isolation baffle are not tested.
Connecting these few items together changes the answer to 'whether to V-0'—it depends on how far it is from live parts (3 mm is the dividing line), the current amount (0.5 A and 0.2 A are two different points), and whether there is a shielding baffle. A fully enclosed external shell, which is quite far from the live parts, and a base that is right next to the terminal block, should not be in the same category in the first place.
This is also the most expensive wasteful expense for this part: the shell was originally enough with V-2, but the idea of 'the higher, the safer' pushed it to V-0, and the cost was all three increasing together—higher quantities, more degradation in mechanics and toughness, and rising costs.
3. Six-dimensional breakdown of working conditions: six dimensions of the electrical enclosure and base, report the numbers first
Conclusion first: The two dimensions of temperature and position determine 'whether a high grade is needed,' the two dimensions of medium and load determine 'whether it can remain crack-free for a long time,' and appearance and compliance are two veto items.
| Dimension | Operating conditions of electrical appliance casing/base | Requirements for the materials |
|---|
| Temperature | Generally, the inside parts are 40–80℃, higher near the heating elements; for small appliance housings and similar parts, the heat resistance is often specified as 120–150℃. | Thermal aging is judged according to RTI ≥105°C; in the short term, look at the glowing wire level |
| Load | Self-weight Assembly torque Clip pre-tightening Whole machine drop; Studs and clips are stress concentration points | What is needed is toughness and resistance to stress cracking, not high rigidity. |
| Medium | Dry area parts are exposed to dust and hand sweat; wet area parts are in long-term contact with detergents, grease, and surfactants | Wet area components must first pass the ESC checkpoint |
| Lifespan | Based on the designed service life of the whole machine, the wet area components are subjected to the long-term effects of detergents and warm water. | ESC looks at F50 and 500 h scale |
| Appearance | Highlight or paint-free shell, color difference and surface defects are directly visible | The surface effects of filler and flame-retardant components should be considered together |
| Compliance | UL94 rating, glowing wire (550 / 650 / 750 / 850℃), needle flame, halogen-free quantification, RTI | Missing even one means you haven't passed. |
Halogen-free is the easiest to be verbalized. Its quantitative definition is bromine <900 ppm, chlorine <900 ppm, and the total of both <1500 ppm; all three conditions must be met to qualify.
Text version of the conclusion: Temperature and position determine the setting, while the medium and load determine the lifespan. Considering 'how far this part is from the live part' as a parameter to report first is more useful than asking which material to use first.
4. Comparison of material routes: halogen-free flame-retardant PP, halogen-containing flame-retardant PP, and the division of labor with engineering plastics
Conclusion first: this is not about 'who is better,' it is about 'which one's shortcomings just happen not to be in your part.'
| Route | Get what | Cost | Applicable Location |
|---|
| Halogen-free flame-retardant PP (mainly phosphorous-nitrogen intumescent system) | Passed V-0; good smoke suppression performance; meets halogen-free quantification | The dosage is generally in the 25–30% range, with significant reductions in strength and toughness; water resistance and heat-moisture resistance need to be evaluated separately. | Large thin-walled parts such as shells, bases, and panels |
| Halogenated flame-retardant PP (contains halogenated flame retardant and synergist) | High efficiency, low usage, V-0 is relatively easy to achieve | Processing releases hydrogen halides when heated, corroding equipment and molds; burning releases hydrogen halides and thick smoke; hot wires often show being affected. | Consider only when the project explicitly allows it and there are no export environmental requirements |
| ABS / PC-ABS / PBT | ABS has good appearance and toughness, and is easy to polish; PC-ABS has higher impact and heat resistance; PBT has better heat and chemical resistance, and better dimensional stability | ABS has average heat resistance; PC-ABS and PBT are expensive | Highlight exterior parts, precision structural components, heat- and chemical-resistant positions |
There is one more point that must be made clear: the amount of flame retardant added to PP generally falls in the 25–30% range, and the resulting loss in mechanical strength and toughness is a structural issue of PP, not a formula-level problem. When faced with the simultaneous demands of "V-0, high impact resistance, and low cost," we first discuss the priorities, then the material.
5. ★ Selection Criteria Table: Seven indicators, each with a verification method
Conclusion first: The biggest difference between this table and a regular physical property table is the fourth column 'Verification Method · Standard Number' — the common problem is often not that you don't know which item to look at, but that you don't know what to measure or what measurement count as passing.
| Indicator | Threshold Value (Typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| UL94 Vertical Burning Rating | Based on position: Within 3 mm of current-carrying connectors, V-0 or V-1 or above is required; for an outer shell away from fire sources, it can go down to V-2 / HB40 level. | GB/T 5169.16 (idt IEC 60695-11-10); the grade must be indicated along with the thickness | Returned due to insufficient grade; too high a grade wastes mechanics and costs | Classified by safety regulation position; different parts of the same machine can have different classifications |
| Incandescent wire (external component, component caliber) | 550℃; materials of category HB40 or above can skip this step | GB/T 5169.11 (idt IEC 60695-2-11) | Ignition upon contact with heating element | If the material category is selected as HB40 or above, testing is directly waived. |
| Hot wires (supporting current-carrying components, categorized by distance and current) | Supervised: Within 3 mm of the connector, >0.5 A at 750°C, others at 650°C | GB/T 5169.11 | Ignition near the terminal block | Halogen-free flame retardant Filling system |
| GWFI / GWIT (Material Category Caliber) | Unattended, current >0.2 A: GWFI ≥850℃; or component over 750℃ and ignition ≤2 s, or material GWIT 775℃ | GB/T 5169.12, GB/T 5169.13 (idt IEC 60695-2-12 / 2-13) | Ignition upon long-term high-temperature exposure | Halogen-free flame retardant Glass fiber / mineral filled |
| RTI long-term use temperature | ≥105℃ (determined according to the actual working conditions inside the item) | UL 746B (Long-Term Thermal Aging Extrapolation) | Brittle and cracked after long-term service | Heat-resistant substrate Filling |
| halogen-free quantification | Bromine <900 ppm, Chlorine <900 ppm, Total of both <1500 ppm | Halogen content testing (XRF / IC), according to IEC 61249-2-21 | Environmental compliance not up to standard | Halogen-free flame retardant system, does not use halogen-containing synergists |
| Environmental Stress Cracking (ESC) | ASTM D1693 Bent Strip Method (10% Igepal CO-630, 50±0.5℃, observe the time for 50% of samples to crack F50); or ISO 22088-3 Constant Tensile Stress Method; or ISO 6252 Constant Strain Method (50–80℃, strain 1.0–2.0%) | ASTM D1693 / ISO 22088-3 / ISO 6252 | Cracking under the combined effects of detergent, grease, and assembly stress (material is fine, part cracks) | Stress corrosion cracking system Control assembly stress Structural fillet |
Text version conclusion: Among the seven items, the gear row and the ESC row are the main focus of this article—the former determines whether you spend that unnecessary money, and the latter determines whether it will crack a few months after being installed.
6. Common Failures and Root Causes: Four Phenomena, Four Root Causes
Conclusion first: Among these four categories, the only one that truly belongs to 'bad material' is one category; the other three are respectively 'position not back-calculated,' 'compensation by increasing quantity,' and 'collusion of medium and stress'.
Failure 1: The whole machine was blocked during inspection, and the materials need to be re-certified. The root cause is that during the selection process, the safety standard positions were not considered first—how far they are from current-carrying parts, how much current they carry, and whether there is shielding were not clarified before the materials were finalized.
Failure 2: When the flame-retardant level is high, the assembly cracks. The root cause is the structural cost of increasing flame retardant: for PP, this level of increase is generally 25–30%. With the increase, the mechanical properties and toughness inevitably drop, manifested as whitening and cracking at the base of the studs, and the base breaking first when dropped.
Failure 3: After being assembled and used for a few months, it cracked from the rounded corners, but the material inspection was qualified. The root cause is environmental stress cracking: detergents, grease, and surfactants, combined with assembly stress, induce silver streaks that expand into cracks. First, check whether there is residual stress in the part, and then check the material.
Invalid point four (daring to contradict a common practice): Purchasing all plastic parts as V-0 material. This is wrong: it pushes enclosures that don’t require high-grade material to high amounts, making you pay for mechanics, toughness, and cost all together; and the additives brought by the high-grade material, such as fillers and flame retardants, make the ESC risk harder to control in humid environments—the grade chosen for "uniform convenience" might just be the one that causes parts in wet areas to crack.
7. Verification sequence: Follow safety regulations in reverse, set the gear position first, then determine the material.
Conclusion first: The verification sequence for this part is reversed — first determine the overall equipment safety requirements (distance from fire source, whether there is shielding), then determine the flame retardant grade, and only finally consider the base material and filling.
`
① First determine the position of the safety device: how far from the current-carrying/heating components (3 mm?), and what current it carries (0.5 A / 0.2 A?).
Is someone taking care of it, and is there a partition or barrier?
↓ This step sets the gear, only then does what comes next have meaning
② Fixed flame-retardant level At this position, is V-0 needed, is GWFI 850℃ needed, is the needle flame needed
③ Base Material and Filling: Homopolymer / Impact Copolymer; Mineral Filled or Glass Fiber Reinforced; Halogen-Free or Halogen-Containing
↓
④ Mechanical and toughness compensation: Make up for the cost of a 25–30% increase in flame retardant by toughening and filling.
↓ Cannot be made up, return ② renegotiate the grade or change the part structure
⑤ ESC and Aging Detergent/Oil Stains ESC under assembly stress; thermal aging according to RTI specifications
↓ If you can't pass this wet area section, you don't need to do any of the previous parts.
⑥ Complete Machine Verification Incandescent Wire, Needle Flame, Complete Machine Certification
`
Each level has a criterion of 'just return to the previous level.' The most common mistake is skipping ①② and going straight to ③, picking a flame retardant that looks satisfactory, making it first, and then going back to check the safety standards—by then, the grade, dosage, and structure are already fixed, and the only thing that can be changed is the cost.
In one sentence: This part is backwards from the safety certification, and the accounts in reverse order are eventually reconciled on the complete machine certification and assembly line.
8. Reverse Honesty: In these three situations, this part should not use modified PP
Conclusion first: As long as 'things that PP cannot achieve' appear, you shouldn't force it—long-term over 150°C, 5VA grade with limited wall thickness, transparent or high-gloss appearance, these three things are very difficult for modified PP to handle.
| 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 upper limit is around that line, and raising the fill and glass fiber reinforcement also has boundaries. | Switch to more heat-resistant engineering plastics or metals |
| Requires 5VA grade and limited wall thickness | For 5VA, the board sample needs to be burned without burning through, which relies on high filler content and increased flame retardant; under thin walls, it’s very difficult for PP to maintain both mechanical properties and this level. | Replace with flame-retardant engineering plastics (PC/ABS type, PBT, PA type) or metal |
| Requires a transparent or glossy appearance | A flame retardant addition of 25–30% will inevitably damage transparency and high gloss, and the surface defects of the mineral and flame retardant components cannot be suppressed. | Transparent parts use PMMA / PC / transparent ABS; high-gloss parts use ABS / PC-ABS |
The pattern is consistent: whenever there are 'two opposite requirements at the same time,' it indicates that this part should not be forcibly made with PP — heat resistance versus reduced filling, increased amount versus reduced material, low filling versus high filling; all three sets are contradictory at both ends.
9. What to touch when changing materials: a checklist to look at before taking action
Conclusion first: the customer's real concern is often not performance, but 'Do I need to change my current mold and process?' This table is recommended to be reviewed before deciding to test the material.
| 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 the new material differs from the original plan, and the base with assembly holes is particularly sensitive. | The dimensions are out of tolerance, and the assembly does not fit. |
| Gate and Venting | Flame-retardant fillers are more sensitive to gate positions and venting | Underfill, burn marks, insufficient weld line strength |
| Material Temperature and Mold Temperature | Halogen-free flame retardant systems have a relatively narrow thermal stability window, so the residence time must be controlled. | Decomposition, surface defects, and fluctuations in flame retardant performance |
| Dry | Confirm according to the specific system, do not directly copy the original process | Silver threads, bubbles |
| Pressure Holding and Demolding | Shrinkage differences cause deformation and whitening on the surface | Deformation, extrusion strain |
| Verification order | Safety regulation position → Flame retardant gear → Base material and filling → Mechanical compensation → ESC | All the risks are concentrated to explode at the final step |
Text version conclusion: Changing materials involves three aspects: mold, process, and appearance, among which the order of verification should be discussed first. Skipping safety position and directly trying the mold is equivalent to spending a mold trial fee first; skipping ESC and going directly to mass production, problems with wet area parts often only emerge several months later.
10. One-page report comparison table (can be directly pasted into PPT)
Conclusion first: There is only one criterion for judgment — can the client use this form to finalize the direction of the materials in a single meeting.
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Pure casing, away from current-carrying/heating components | Flame-retardant PP drops by one grade (V-2 or material category above HB40) | 550℃ glowing wire test can be avoided; V-2 or above | GB/T 5169.16, GB/T 5169.11 | Distance from the current-carrying parts, whether someone is supervising, whether there are barriers |
| Base, terminal seat, supporting current >0.2 A or within 3 mm | Halogen-free flame-retardant PP, V-0, 850℃ grade | GWFI ≥850℃; or GWIT 775℃; V-0 | GB/T 5169.12 / .13 / .11, GB/T 5169.16 | Current carrying capacity, tube lighting status, presence of shielding baffle |
| Wet area components (control panel, kitchen small appliances) | Halogen-free flame retardant, ESC-resistant system | ESC press F50 to check with acceleration time | ASTM D1693 / ISO 22088-3 / ISO 6252 | Medium type, assembly stress, actual temperature |
Text version Conclusion: For the same appliance, lowering the casing by one level and setting the base to V-0 is a normal configuration; It's not about the higher setting, but about aligning every position with the safety code setting for it.
11. The most common issues with this part are often not flame-retardant
The most common industry deviations in these types of parts are twofold. One type is the setting position not aligned: public safety standards classify requirements by "distance from current-carrying connectors, current-carrying magnitude, whether someone is supervising it, and whether there is an isolation baffle." 3mm, 0.5A, 0.2A are those forks, and the common practice on site is to ignore these conditions and simply set the settings by "the higher the the safer." The other type is compensation failure after setting the settings: PP flame retardant dosages generally fall around the 25–30% range. When increased, mechanical and toughness inevitably drop, causing problems in studs and clips first.
At the criterion level, the standard standard is: external components with 550°C hot wire (exempted for material categories above HB40); Support current-carrying components are divided by distance and current-carrying at 650/750°C; unattended current-carrying components are rated at GWFI 850°C or GWIT 775°C; Long-term heat resistance is at RTI ≥105°C diameter.
The industry's common solution is to reverse the order: first, set the position conditions for the whole machine and set the levels, then determine the substrate and filler, use toughening to compensate for the toughness loss from flame retardant additions, and add an additional ESC evaluation for wet-zone components—cracking under the combined assembly stress of detergent, oil stains, and surfactants is considered "cracking of the material is correct, part cracks" and can only be collected on both sides of the system and structure.
Ningbo Kelong New Materials Co., Ltd. commonly supplies halogen-free flame-retardant modified PP for this part, with corresponding flame-retardant levels and filling/toughening balances for housing, base, and wet zone parts. Wet zone parts are also equipped with a stress-resistant cracking system, mainly solving three issues: 'mismatch between grade and position, cracking after adding parts, and cracking at rounded corners after several months of installation.' The formula can be adjusted according to the working conditions of the part, and can accompany customers for sample comparison and ESC verification. For part-level customers, we can also accept small batches of multiple varieties.
FAQ
Question: Can I just use all V-0 to avoid judgment?
Answer: Not recommended. V-0 only matters for locations "close to fire sources and shielded," while for distant pure casings, it's a pure cost—higher weight, more mechanical and toughness loss, and higher cost.
Question: Is V-0 always safer than V-2?
A: Not that comparison. V-2 allows droplets to ignite the absorbent cotton, so it can't be used where "drips will land on heating or flammable parts"; But for a shell that is fully covered and far from the current-carrying parts, using V-2 does not pose a risk. Grade is a position parameter, not a safety score.
Question: After the shell is installed for several months, if it cracks at the stud, is the material too brittle?
Answer: Don't change the material yet. Eighty percent of these cracks are due to environmental stress, and conventional physical properties cannot be detected; Criteria should be based on ASTM D1693 (10% Igepal CO-630, 50°C) or ISO 22088-3, and the assembly torque and fillet core should be checked.
| Operating Conditions | Key Criteria | Conventional Supply |
|---|
| Pure Enclosure (away from current-carrying or heating parts) | V-2 levels are usable; 550°C hot wire can be removed | halogen-free flame-retardant modified PP; low-level trimming direction |
| base/terminal block (within 3 mm or support current carrying >0.2 A ) | GWFI ≥850°C, GWIT 775°C, V-0 | halogen-free flame-retardant modified PP; high heat wire direction |
| wet zone components (control panel, kitchen small electrical peripheral) | ESC F50 and acceleration time | halogen-free flame retardant + stress-resistant cracking system direction |
Finally, three final words. First, the flame-retardant level is a position parameter derived from the safety standard. You need to first clarify how far it is from the live part, how much current it carries, and whether there is a baffle. Second, the combustion time requirements for V-2 and V-1 are exactly the same; the only difference is whether droplets are allowed to ignite the degreased cotton. Third, the verification order is more expensive than the verification items: safety standard position → flame-retardant level → substrate and filler → mechanical compensation → ESC.
Next article will talk about switches and socket panels—the challenge of that part lies in mineral filling trimming and electrical performance.
About Us
Selection gets stuck at a very specific step.
is it that you don't know whether to use homopolymer or impact-resistant copolymer, whether it's toughening but worried about whitening scratches, or that the shrinkage anisotropy of fiberglass material can't withstand tolerances—clearly explaining where the stucks are is much more useful than saying "I want a good material."
Ningbo Kelong New Materials Co., Ltd. produces modified polypropylene (PP) pelletizing and covers 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 spraying and scratch resistance; Also engaged in PP resin, sub-brand materials, and large packaging materials for major petrochemical plants
