机器人外壳用改性PP、扫地机结构件用改性PP，卡住你的往往不是"强不强"，是"跟多少种清洁剂打交道还不开裂"。这篇把 ESC（环境应力开裂）这条主线讲透：装配卡扣与螺丝柱为什么先裂、带应力的介质浸泡怎么验、增韧为什么和外观对拉，以及验证顺序为什么必须从介质浸泡开始。
"料没换，模具没动，装上去三个月，螺丝柱旁边裂了一条缝。"
一个做商用清洁机器人的技术员这么跟我说。首件检验全过，半年后一批件陆续返修。裂缝起点不在螺丝柱本体上，在它旁边那个尖角过渡处。断口很干净，没有明显变形——这不是撞裂的，是慢慢裂开的。
"扫地机也一样。"他说，"有几台是从台阶上翻下去摔裂的，有几台根本没摔过，就是天天用湿巾擦。"
一台被拖拽翻倒，一台被反复擦拭。听上去是两个问题，实际是同一件事的两面：室内服务设备的材料问题，不是"强不强"，是"跟多少种化学品打交道还不开裂"。
家用扫地机、擦窗机、商用清洁机器人、送餐与巡检服务机器人，长期接触的东西和工业设备不是一类——这是它们的头号工况。
一、扫地机与机器人外壳的工况六维：清洁剂这一维，才是室内服务设备的分水岭
结论先说：六维里温度和载荷是常规项，介质才是分水岭——室内服务设备天天擦的清洁剂，恰好是一类典型的环境应力开裂诱因。
| 维度 | 实际工况 | 对材料的要求 |
|---|
| 温度 | 室内常温为主；电池仓与充电座附近偏高；冬季运输与冷库可到 −20℃ 一级 | 低温不脆裂；贴近电池处另有耐温要求 |
| 载荷 | 碰撞（撞墙、被拖拽、翻倒）+ 跌落（台阶、桌面）+ 装配应力（自攻螺丝预紧、卡扣过盈） | 靠韧性吃碰撞，靠抗应力开裂吃装配与介质 |
| 介质 | 酒精、含氯消毒剂、表面活性剂清洗剂、精油类护理剂；日常擦拭反复出现 | 耐化学，重点是耐环境应力开裂 |
| 寿命 | 家用机常见按 3-5 年、商用机按 5-8 年设计；每天擦拭 1-3 次 | 介质与应力长期共同作用后不开裂 |
| 外观 | 浅色与白色高光件为主；色差、流痕、虎皮纹、缩水印都在客户眼里；免喷涂类划痕常按 dL < 1.5 口径（VW PV3952） | 外观体系与增韧体系必须配平 |
| 合规 | 内置电池的设备常要求 UL94 V-0（连厚度）；无卤量化；850℃ 灼热丝接触 30 s 不引燃；室内件另看气味 | 阻燃 + 无卤 + 低气味 |
文字版结论：温度这一维反而不是最难的，介质才是。 工业设备怕油、冷却液、切削液；服务设备怕清洁剂——成分更杂、接触更频繁，还常常"擦完不擦干"。选型的第一句不该问"要多强"，该问"这个件接触哪几种清洁剂、擦多少次"。
一个内行细节：这类件的开裂极少发生在平面上，几乎都从装配卡扣、自攻螺丝柱、壁厚突变的尖角起。这三处是应力集中区，而 ESC 的两个条件里，"应力"那一半是结构给的，不是材料给的。
二、材料路线对比：增韧阻燃PP、增韧PP加矿物填充、ABS 系、PC 系各管一段
结论先说：这四条路线不是替代关系，是分工关系——增韧阻燃 PP 赢在轻、绝缘、可做阻燃和成型自由，输在表面档次与承力。
| 路线 | 拿到什么 | 代价 | 适合哪一段 |
|---|
| 增韧阻燃改性 PP | 韧性、阻燃、轻量、成型自由，成本方向低 | 阻燃剂加量常落在 25-30% 一档，力学与韧性一起掉 | 室内非承力外壳、扫地机结构件 |
| 增韧 PP + 矿物填充 | 刚性提上来，收缩更均匀，尺寸更稳 | 冲击韧性下降；外观对流痕与缩水印更敏感 | 要尺寸稳定的结构件；浅色件要另配表面体系 |
| 阻燃 ABS 系（含 PC-ABS） | 表面与外观好、韧性高、免喷涂表现好 | 密度与成本上去；阻燃要另做体系 | 外观要求高、结构不太负重的壳体 |
| PC 与 PC 合金 | 刚性、耐温、抗冲击高一档，尺寸稳定性好 | 成本与密度更高；加工窗口更窄 | 局部承力件、耐温偏高件、精密装配件 |
文字版结论：PP 系接"轻、阻燃、成型自由、成本"；ABS 系接"表面好看"；PC 系接"更高一档的刚性与耐温"。 同一台机器上几种料各管一段是常态——碰撞缓冲件走 PP，面板走 ABS，滚刷电机座走 PC 加嵌件，谁也不是谁的替代品。
需要说清边界：增韧阻燃 PP 与"高光免喷涂外观件"天然对拉。 增韧靠弹性体分散相，填充靠矿物粒子，两者都让表面更难做平整；高光件要的恰好是表面细腻。两件事都要满，往往两头都不到位。
三、★ 选型判据表：机器人非承力外壳与扫地机结构件共用一张，每项都带验证方法
结论先说：这张表的价值在第四列——卡住你的通常不是"该看哪一项"，是"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 |
|---|
| 环境应力开裂 ESC（耐清洁剂） | 按件定：带应力试样在介质中到目标时长不开裂、无龟裂 | 弯条法 ASTM D1693（弯曲浸入 10% Igepal CO-630、50±0.5℃，记 F₅₀）；恒拉伸应力法 ISO 22088-3（40℃ 介质）；恒应变法 ISO 6252（三点/四点弯曲 + 介质，50-80℃，应变 1.0-2.0%） | 卡扣、螺丝柱、尖角处先裂 | 降内应力（模具、保压、退火）+ 改结构（去尖角、减过盈）+ 耐溶剂体系 |
| 缺口冲击（23℃） | 常见口径 ≥5-6 kJ/m²（件级按件定） | GB/T 1043.1 | 碰撞、搬运磕碰开裂 | 增韧体系 + 基材档位 |
| 低温冲击（−20℃） | 同类件常见按 −20℃ 缺口冲击 >3 kJ/m² 的口径；弯曲模量常见 ≥1667 MPa 一级 | GB/T 1843（等同 ISO 179 体系）/ GB/T 9341 | 冬季运输、冷库跌落脆裂；装配处变形 | 增韧加量与低温韧性一起调；填充量 + 基材档位 |
| 阻燃 | UL94 V-0，必须连厚度一起标 | GB/T 5169.16 / UL 94 | 档位与壁厚不匹配被打回 | 无卤阻燃体系 |
| 无卤量化 | 溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm | XRF / IC，参照 IEC 61249-2-21 口径 | 环保合规不达标 | 无卤体系，不用含卤协效剂 |
| 灼热丝 | GWIT 750/775℃、GWFI 850/960℃；850℃ 接触 30 s 不引燃 | GB/T 5169.12 / .13 | V-0 过了，灼热丝引燃 | 阻燃 + 填充协同 |
| RTI | ≥105℃ 起步（内置电池设备常用口径） | UL 746B | 长期服役后变脆开裂 | 耐热基材 + 填充 |
| 气味 | ≤3 级（室内件常用口径） | VDA 270 | 整机气味超标、客户投诉 | 低气味低 VOC 体系，控脱模剂与料温 |
| 耐候（擦窗机、户外服务机器人） | 氙灯老化 ΔE ≤3.0 | GB/T 16422.2 | 变色、粉化、失光 | 耐候抗 UV 体系 |
文字版结论：最该先做的是第一行，而它恰恰最常被排到最后——拉伸、冲击、阻燃都有现成报告，介质浸泡要自己定介质、定应力、定时间。但前面全过、介质这一关不过，等于整批方案作废。
四、常见失效与根因：四条现象，三条根因不在料上
结论先说：这四条里真正属于"料不行"的只有一条，另外三条分别是结构、工艺与外观体系的问题。
失效一：装着没裂，用一阵子从卡扣或螺丝柱裂开。 这是本篇的主线现象：介质渗透加上装配应力与内应力，数周到数月后起裂。先看裂缝起点——如果重复出现在同一条装配边或同一个尖角，先查结构，不是先换料。
失效二：跌落裂、卡扣断。 跌落分两段：常温跌落考整体韧性，低温跌落（冬季运输、冷库）考低温冲击。卡扣断多数不是韧性不够，是根部圆角太小、过盈量太大。判据写成"跌落后不裂 + 卡扣不断"，不是模量多少。
失效三：浅色高光件出流痕、虎皮纹、缩水印。 这一类几乎都和增韧剂、填充与浇口位置有关。同一个配方，深色件上什么都看不出，白件上一眼就现——白色件对表面缺陷的放大效应，是外观件选型里最容易被低估的一条。
失效四（敢否定一个常见做法）：出问题就去找"耐化学更高一档的牌号"。
这在清洁剂开裂这件事上多半是错的。ESC 是两个条件叠出来的：介质 + 应力。材料只改善"介质"那一半，而且改善有限——耐化学好一点的牌号，并不会让一个应力集中到极点的螺丝柱不裂。
真正的第一道解在应力和结构上： 加大根角与过渡圆角、把自攻螺丝柱改成嵌入铜螺母、把过盈量降到刚好、壁厚突变做成渐变；成型侧把保压和模温调到内应力更低的窗口，必要时加一道退火。这些做完，再谈换料。
五、清洁剂耐受与 ESC 怎么验：先分清"有没有应力"，再谈泡什么介质
结论先说：这个件最容易被验错的一点，是拿无应力试样去泡介质——无应力泡很久没事，带应力一周就裂，结论完全是两回事。
清洁剂的成分杂，验证要先做一件映射：这个件实际接触哪几类介质，分别对应哪种加速试验。
| 介质类型 | 为什么是 ESC 的典型诱因 | 常用验证口径 |
|---|
| 醇类（酒精、异丙醇） | 渗透快、降低表面能，配合装配应力诱发银纹 | 恒应变法（ISO 6252 口径）+ 反复擦拭循环 |
| 含氯消毒剂 | 强氧化性叠加极性介质，对聚烯烃表面与界面有侵蚀 | 带应力浸泡 + 老化后复测 |
| 表面活性剂清洗剂 | 表面活性剂在应力协同下诱发银纹扩展开裂（与洗涤设备内桶同类机理） | 弯条法 ASTM D1693：10% Igepal CO-630、50±0.5℃，记 50% 试样开裂时间 F₅₀ |
| 精油类／溶剂型护理剂 | 芳烃与萜类对聚烯烃渗透性强 | 恒拉伸应力法 ISO 22088-3：40℃ 介质中测断裂时间或临界应力 |
文字版结论：四行里只有第三行有现成的标准水溶液口径，另外三类都要按现场实际介质自己定。 定介质至少问清三件事：品牌型号、实际浓度、擦拭频率。拿"清洁剂"三个字去报试验，等于没报。
判据写成三要素：浸泡温度 + 浸泡时长 + 结果。 结果不写"合格"，写"开裂／未开裂 + 外观变化"。同一体系在 10% Igepal、50℃ 下未开裂时间可做到数百小时一级；这只是参考锚点，不是门限，门限要由实际擦拭频率和寿命反推。
两句提醒。 一是无应力与带应力试样的结果必须分开报。二是介质浸泡要在老化之后复测——热老化让材料变脆，UV 让表面体系变化，老化后的耐介质表现才是服役末期的表现。
六、验证顺序：先做带应力介质浸泡，最后才是整机运行
结论先说：这个件的验证顺序只有一条原则——把最可能一票否决、也最容易漏做的那一关，放在最前面。
`
① 带应力介质浸泡 按现场清洁剂映射介质；带应力试样；记"开裂／未开裂 + 外观变化"
↓ 不过，后面不用做；退回内应力与结构，再谈换料
② 跌落与卡扣冲击 常温 + −20℃ 低温 + 装配后整机跌落；卡扣与螺丝柱局部冲击
↓ 裂了或卡扣断，退回增韧加量、圆角与过盈量
③ 外观与色差 色板比对、色差、流痕/虎皮纹/缩水印 + 连续生产一致性
↓ 不过，退回表面体系、填充量与浇口位置
④ 阻燃 UL94 V-0（连厚度）、无卤三项、灼热丝 850℃ 接触 30 s、GWIT/GWFI
↓ 不过，退回阻燃体系
⑤ 老化后复测 热老化 + UV 后重做介质浸泡与冲击，看保持率
↓ 不达标，退回基材档位与稳定体系
⑥ 整机运行验证 清洁剂擦拭循环 + 整机碰撞与拖拽 + 连续运行
`
文字版结论：①和⑤最容易漏，也最贵。 跳过①等于把开裂留到装机三个月后；跳过⑤等于用新件的性能代表三年后的性能。最常见的错误是①没做、直接进②——用试模件做跌落，测出来的数没有代表性。
七、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"两个方向相反的要求同时要"，就说明这个件不该用改性PP 硬撑。
| 出现的情况 | 为什么改性PP不合适 | 该往哪走 |
|---|
| 要求长期高强度碰撞（重载机器人外壳，会被反复撞击） | 增韧与阻燃加量叠加后韧性有上限，反复大能量冲击下易出现裂口扩展 | 走玻纤／长玻纤增强的工程塑料壳体，或"金属骨架 + 塑料蒙皮"的分体结构 |
| 要求高光免喷涂 + 长期用溶剂型清洁剂擦拭 | 免喷涂要高光、少填料；长期擦拭又会带走表面体系并诱发应力纹，两个方向对拉 | 把外观件与擦拭面分开设计；或整件改走 ABS／PC-ABS 体系 |
| 要求承力结构件（关节、臂、减速机安装位） | 承载看刚性、疲劳与蠕变，这三项都不是改性PP 的主场 | 回到结构方案：金属件、长玻纤 PP 结构件，或 PA／PBT 承力件 |
| 要求同一件同时满足 V-0 + 高光免喷涂 + 高抗冲 + 长期耐擦拭溶剂 | 四条同时要，配方里没有同时容纳它们的空间 | 把要求拆给不同件承担；或整件换材料体系 |
规律一致：不是改性PP 做不到某一项，是做不到"方向相反的两项同时满配"。 遇到这种情况，我们先讲清这条，再谈有没有折中的结构方案——硬接下来的单子，最后都要用返工和索赔还回去。
八、换料风险清单：增韧阻燃PP换料前先确认的七件事
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 | 增韧与填充后与原方案的差；装配间隙件尤其敏感 | 尺寸超差、装配对不上 |
| 浇口与排气 | 阻燃填充体系流动与产气不同；外观件对浇口位置极敏感 | 充填不足、流痕、熔接线弱 |
| 料温与模温 | 无卤体系热稳定窗口较窄，停留时间要控；模温影响表面 | 分解、表面缺陷、阻燃波动 |
| 干燥 | 按具体体系定，不可照搬原工艺 | 银丝、气泡 |
| 保压与脱模 | 保压决定内应力，脱模决定顶白与拉伤 | 内应力偏高，直接抬高 ESC 风险 |
| 色差 | 浅色与白色件必须先定色板；增韧与填充会让色差更难控 | 批次色差争议 |
| 验证顺序 | 带应力介质浸泡 → 跌落与卡扣冲击 → 外观与色差 → 阻燃 → 老化后复测 → 整机 | 风险全部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，最该先谈的是验证顺序，其次是保压。保压最容易被忽略——它不写在物性表里，却直接决定件里留了多少内应力，而内应力正是后面开裂的种子。
九、一页纸汇报对照表：机器人外壳 / 扫地机结构件分两栏
结论先说：判断这张表是否合格只有一条——客户拿它，能不能在一次会上把两个件的材料方向一起定下来。
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 【机器人】室内非承力外壳（含阻燃） | 增韧阻燃改性 PP | 带应力介质浸泡；UL94 V-0 连厚度；−20℃ 冲击 | ASTM D1693 / ISO 22088-3；GB/T 5169.16；GB/T 1843 | 接触哪几种清洁剂、擦拭频率 |
| 【机器人】浅色高光外观件 | 增韧 PP + 矿物填充，另配表面体系 | 色差、流痕、虎皮纹、缩水印；收缩率 | GB/T 17037.4；色板比对 | 色板、是否免喷涂 |
| 【机器人】长期高强度碰撞的重载壳 | PP 不优先：玻纤/长玻纤增强工程塑料，或金属骨架 + 塑料蒙皮 | 反复冲击后不开裂 | 按件台架与整机口径 | 冲击能量、碰撞频次 |
| 【扫地机】结构件、碰撞缓冲件 | 增韧改性 PP（含阻燃时加无卤体系） | −20℃ 低温跌落；卡扣与螺丝柱局部冲击 | GB/T 1843；整机跌落口径 | 运输温度、跌落高度、卡扣设计 |
| 【扫地机】承力位（滚刷电机座一类） | PP 不优先：PC 系或 PA/PBT + 金属嵌件 | 刚性、蠕变、装配精度 | 按件图与整机口径 | 载荷、拆装次数、精度要求 |
| 【扫地机／擦窗机】需户外或半户外 | 增韧耐候改性 PP（含阻燃时加无卤体系） | 氙灯老化 ΔE ≤3.0 | GB/T 16422.2 | 暴晒时长、是否沿海 |
文字版结论：同一台机器上"外壳走 PP、面板走 ABS、承力位走 PC 加嵌件"是正常配置。 靠的不是某一档更高，而是每个位置都对上它自己的第一约束。
十、机器人外壳与扫地机结构件上，最容易出问题的往往不是"强不强"
这类件上行业最常见的偏差有两类。一类是验证入口选错：拿无应力试样去泡清洁剂，或者只做拉伸冲击不做介质浸泡——ESC 是两个条件叠出来的，只验一半等于没验。 公开的加速试验口径是清楚的：ASTM D1693、ISO 22088-3、ISO 6252 三套体系，分别对应弯条法、恒拉伸应力法与恒应变法。
另一类是归因归错：把开裂全算在料上。公开机理是洗涤表面活性剂在应力协同下诱发银纹扩展开裂，这正是洗涤设备内桶的通行失效路径；而另一半原因往往是装配应力与残余应力。阻燃侧的门槛同样明确：UL94 V-0 连厚度、无卤三项、850℃ 灼热丝接触 30 s 不引燃。
通行解法两条：结构上把应力集中区做平（圆角、过渡、嵌入铜螺母、控过盈），成型上把内应力压低（保压、模温、必要时退火）。
宁波市科隆新材料有限公司在这两个件上常供的是自产改性聚丙烯（PP）造粒里的增韧 + 无卤阻燃方向：按接触的清洁剂清单给耐溶剂方向，按跌落高度与运输温度给增韧加量配平，按壁厚定 V-0 档位与无卤体系，重点解决"装配边开裂""跌落裂与卡扣断""浅色件表面难做"三件事。配方按件工况调，可陪客户做小样比对与介质浸泡对接，件级客户多品种小批量也能接。
我们接触到的这类询盘里，十次有七八次是先问"阻燃要 V-0"，很少有人第一句问"接触哪几种清洁剂"。而后者往往更早决定这个料能不能用。
常见问答
问：外壳开裂了，换一款耐化学更好的料，是不是就能解决？
答：不一定，甚至常常不能。ESC 是介质加应力叠出来的，材料只改善介质那一半。先查裂缝起点是不是在卡扣、螺丝柱或尖角上，再查保压与内应力，最后才谈换料。
问：清洁剂验证，拿无应力样条泡一下行不行？
答：不行。无应力试样泡很久可能不开裂，带应力试样一周就裂。判据要落在带应力试样上。
问：增韧剂加多一点，跌落和碰撞不是更保险？
答：要算兑换关系。增韧剂（POE、EPDM 一类）加量上去，刚性、尺寸稳定性与表面质量会跟着往下走，浅色高光件上尤其明显。加量由"低温冲击下限 + 刚性下限 + 外观上限"三条一起定。
| 工况 | 关键判据 | 自产常规供应 |
|---|
| 室内非承力外壳（含阻燃） | 带应力介质浸泡；V-0 连厚度；−20℃ 冲击 | 增韧 + 无卤阻燃改性 PP 方向 |
| 浅色高光外观件 | 色差、流痕、虎皮纹、缩水印 | 增韧 PP + 矿物填充 + 表面体系方向 |
| 扫地机结构件、缓冲件 | 低温跌落；卡扣与螺丝柱局部冲击 | 增韧改性 PP（含无卤阻燃档）方向 |
| 需户外或半户外件 | 氙灯老化 ΔE ≤3.0 | 增韧耐候（含无卤阻燃档）改性 PP 方向 |
最后说三句。
第一，这个件的头号工况是清洁剂，不是强度。第一句话该问"接触哪几种清洁剂、擦多少次"。
第二，开裂先从卡扣、螺丝柱和尖角起。ESC 的第一道解是降内应力、改结构，材料只是第二道。
第三，验证顺序比验证项更贵：带应力介质浸泡 → 跌落与卡扣冲击 → 外观与色差 → 阻燃 → 老化后复测 → 整机。①②不许跳。
关于我们
这三件事我们从不猜：耐温、寿命、用量。
没给使用温度，不猜；没给服役时长，不猜；没说月用量，也不猜。猜出来的方案，最后都要用返工和索赔还回去。
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 robot casing uses modified PP, and the structural parts of the vacuum cleaner use modified PP. What usually gets you stuck is not 'how strong it is,' but 'how many types of cleaning agents it can interact with without cracking.' This article thoroughly explains the main line of ESC (environmental stress cracking): why assembly snaps and screw posts crack first, how to test immersion in stressed media, why toughening affects appearance under tension, and why the verification sequence must start with media immersion.
The material wasn't changed, the mold wasn't moved, and three months after it was installed, a crack appeared next to the screw post.
A technician who works on commercial cleaning robots told me this. The first batch passed inspection, but six months later, a batch of parts gradually needed repairs. The starting point of the crack was not on the screw post itself, but at the sharp corner transition next to it. The fracture is very clean, with no obvious deformation—it wasn't broken by impact, it cracked slowly.
"It's the same with the robot vacuums," he said. "Some of them fell off the steps and cracked, while others never fell at all and were just wiped daily with wet wipes."
One was dragged and overturned, and the other was wiped repeatedly. It sounds like two problems, but in fact, it's two sides of the same issue: the material problem of indoor service equipment, not about 'how strong it is,' but 'how many chemicals it can deal with without cracking'.
Household vacuum cleaners, window cleaning machines, commercial cleaning robots, and food delivery and inspection service robots are not the same type of things as industrial equipment—their primary operating conditions are entirely different.
1. The six-dimensional working conditions of the floor cleaning machine and robot shell: It's the dimension of cleaning agents that truly serves as the dividing line for indoor service equipment.
Conclusion first: In six dimensions, temperature and load are conventional factors, while the medium is the dividing line — the cleaning agents used daily on indoor service equipment happen to be a typical cause of environmental stress cracking.
| Dimension | Actual operating conditions | Requirements for the materials |
|---|
| Temperature | Mainly room temperature indoors; higher near the battery compartment and charging dock; during winter transport and in cold storage can reach −20°C, Grade 1 | Not brittle at low temperatures; there are additional temperature requirements near the battery |
| Load | Collision (hitting walls, being dragged, tipping over) Fall (steps, table surface) Assembly stress (self-tapping screw pre-tightening, interference fit of clips) | Rely on toughness to withstand collisions, rely on stress resistance to prevent cracking during assembly and with media |
| Medium | Alcohol, chlorine-containing disinfectants, surfactant cleaning agents, essential oil-based care products; recurring with daily wiping | Chemical resistant, with a focus on environmental stress cracking resistance |
| Lifespan | Home machines are commonly designed for 3-5 years, commercial machines for 5-8 years; wipe 1-3 times a day | The material does not crack after long-term combined action of medium and stress |
| Appearance | Light colors and white highlight parts are the main focus; color differences, flow marks, tiger stripes, and shrinkage marks are all noticed by customers; for scratch-resistant coatings, scratches are generally within dL < 1.5 caliber (VW PV3952) | The appearance system and the toughening system must be balanced |
| Compliance | Devices with built-in batteries often require UL94 V-0 (including thickness); halogen-free quantification; 850℃ glow-wire contact for 30 seconds without ignition; see indoor parts for odor separately. | Flame retardant, halogen-free, low odor |
Text version conclusion: Temperature is not the most difficult factor; the medium is. Industrial equipment is sensitive to oil, coolant, and cutting fluid; service equipment is sensitive to cleaners—whose compositions are more complex, contact is more frequent, and they are often 'not wiped dry after wiping.' The first question in selection should not be 'how strong does it need to be,' but 'which cleaners will this part come into contact with, and how many times will it be wiped?'
An insider detail: Cracking in this type of part rarely occurs on flat surfaces; it almost always starts from assembly clips, self-tapping screw posts, or corners with abrupt changes in wall thickness. These three locations are areas of stress concentration, and in the two conditions of ESC, the 'stress' part is provided by the structure, not by the material.
2. Comparison of material routes: toughened flame-retardant PP, toughened PP with mineral filler, ABS series, PC series, each pipe in one section
Conclusion first: These four routes are not alternatives, but complementary in their roles—toughened flame-retardant PP excels in being lightweight, insulating, flame-retardant, and having molding freedom, but it falls short in surface quality and load-bearing capacity.
| Route | Get what | Cost | Suitable for which section |
|---|
| Toughened flame-retardant modified PP | Toughness, flame retardant, lightweight, molding freedom, low cost orientation | The amount of flame retardant is usually around 25-30%, causing both mechanical strength and toughness to decrease. | Non-load-bearing interior casing, robotic vacuum components |
| Toughened PP Mineral Filled | Increased rigidity results in more uniform shrinkage and more stable dimensions. | Impact toughness decreases; appearance is more sensitive to flow marks and sink marks | Structural parts with stable dimensions; Light-colored parts require additional surface systems |
| Flame-retardant ABS series (including PC-ABS) | Good surface and appearance, high toughness, good performance without painting | Density and cost go up; flame retardancy requires a separate system | Enclosures with high appearance requirements and relatively low structural load |
| PC and PC Alloy | Higher level of rigidity, temperature resistance, and impact resistance, with good dimensional stability | Higher cost and density; narrower processing window | Local load-bearing components, high-temperature-resistant components, precision assembly components |
Text version conclusion: PP series is characterized by 'lightweight, flame-retardant, easy molding, cost-effective'; ABS series is 'good surface appearance'; PC series offers 'higher-level rigidity and heat resistance.' On the same machine, it is normal for different materials to be used for different parts—collision buffers use PP, panels use ABS, roller brush motor housings use PC with inserts; none of them is a substitute for the others.
It is necessary to clarify the boundaries: toughened flame-retardant PP is naturally at odds with 'high-gloss no-spray appearance parts.' Toughening relies on elastomer dispersed phases, and filling relies on mineral particles; both make the surface harder to smooth. High-gloss parts, on the other hand, require precisely a fine surface. Trying to satisfy both often results in neither being done properly.
3. ★ Selection Criteria Table: The robot's non-load-bearing shell and the sweeper's structural components share one table, with each item accompanied by a verification method
Conclusion first: The value of this table lies in the fourth column — what usually holds you back is not 'which item to look at,' but 'what to measure with and how much counts as passing.'
| Indicator | Threshold (typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Environmental Stress Cracking ESC (resistant to cleaners) | Set by item: Stress-bearing specimens do not crack or develop crazing when immersed in the medium for the target duration | Bent strip method ASTM D1693 (bending immersed in 10% Igepal CO-630, 50±0.5℃, recorded as F₅₀); constant tensile stress method ISO 22088-3 (40℃ medium); constant strain method ISO 6252 (three-point/four-point bending, medium, 50-80℃, strain 1.0-2.0%) | Clips, screw posts, and sharp corners crack first | Reduce internal stress (mold, holding pressure, annealing) Modify structure (remove sharp corners, reduce interference fit) Solvent-resistant system |
| Notch Impact (23°C) | Common caliber ≥5-6 kJ/m² (for piece level, determined per piece) | GB/T 1043.1 | Collision, bumps and cracks during handling | Toughening System Substrate Grade |
| Low-temperature shock (-20°C) | Common specifications for similar parts: notch impact at −20℃ >3 kJ/m²; bending modulus commonly ≥1667 MPa, grade 1 | GB/T 1843 (equivalent to ISO 179 system) / GB/T 9341 | Winter transportation, cold storage brittle fracture; deformation at assembly points | Toughness enhancement and low-temperature toughness are adjusted together; filler amount base material grade |
| Flame retardant | UL94 V-0, the thickness must also be indicated | GB/T 5169.16 / UL 94 | Rejected due to mismatch between gear position and wall thickness | Halogen-free flame retardant system |
| halogen-free quantification | Bromine <900 ppm, Chlorine <900 ppm, Total of both <1500 ppm | XRF / IC, in accordance with IEC 61249-2-21 caliber | Environmental compliance not up to standard | Halogen-free system, no halogen-containing synergists needed |
| Scorching thread | GWIT 750/775℃, GWFI 850/960℃; 850℃ contact for 30 s does not ignite | GB/T 5169.12 / .13 | V-0 passed, incandescent wire ignites | Flame retardant Fillers synergy |
| RTI | ≥105℃ Starting (Common specification for devices with built-in batteries) | UL 746B | Brittle and cracked after long-term service | Heat-resistant substrate Filling |
| smell | Level ≤3 (common caliber for indoor components) | VDA 270 | Excessive odor from the entire machine, customer complaints | Low-odor, low-VOC system, release agent control and material temperature |
| Weather-resistant (window cleaning robots, outdoor service robots) | Xenon lamp aging ΔE ≤ 3.0 | GB/T 16422.2 | Discoloration, chalking, loss of gloss | Weather-resistant UV system |
Text version conclusion: The thing that should be done first is the first line, but it is precisely the one most often put last—there are existing reports for stretching, impact, and flame retardancy, but for media immersion, you have to determine the medium, the stress, and the time yourself. If everything else passes but this media test does not, it amounts to the entire batch of plans being invalid.
4. Common Failures and Root Causes: Four phenomena, three root causes are not related to the material
Conclusion first: Among these four items, only one truly belongs to 'material is not good'; the other three are issues with structure, craftsmanship, and appearance system.
Failure 1: The assembly doesn't crack initially, but after some use, it splits from the clip or screw post. This is the main phenomenon discussed in this article: medium penetration combined with assembly stress and internal stress causes cracks to appear after several weeks to months. First, look at the starting point of the crack—if it repeatedly appears on the same assembly edge or at the same sharp corner, check the structure first, not the material replacement.
Failure 2: Drop cracks and broken clips. Drops are divided into two types: normal temperature drops test overall toughness, while low temperature drops (winter transportation, cold storage) test low-temperature impact. Most clip breaks are not due to insufficient toughness, but because the root fillet is too small and the interference fit is too tight. The criterion is written as 'no cracks after dropping, clips do not break,' not based on modulus.
Failure three: Flow marks, tiger stripes, and sink marks on light-colored highlights. This type is almost entirely related to toughening agents, fillers, and gate locations. With the same formulation, nothing is visible on dark-colored parts, but it is immediately apparent on white parts—the magnifying effect of white parts on surface defects is one of the most easily underestimated aspects in appearance part selection.
Failure Four (Daring to question a common practice): When problems arise, go find a 'higher chemical-resistant grade'.
This is mostly wrong when it comes to detergent cracking. ESC arises from the combination of two conditions: the medium and the stress. Materials only improve the 'medium' part, and the improvement is limited—a grade with better chemical resistance does not prevent a screw post with stress concentrated to the extreme from cracking.
The real first solution lies in stress and structure: increase the root fillet and transition radius, change the self-tapping screw posts to embedded copper nuts, reduce the interference fit to just enough, and make wall thickness changes gradual; on the molding side, adjust holding pressure and mold temperature to a window where internal stress is lower, and anneal if necessary. Only after doing all this should material replacement be considered.
5. How to test detergent tolerance and ESC: first distinguish whether there is 'stress', then discuss which medium to use for foaming
Conclusion first: The point most likely to be tested incorrectly in this case is soaking specimens without stress in the medium — unstressed specimens can be soaked for a long time without issue, while stressed ones will crack in a week; the conclusions are completely different.
The ingredients of the detergent are complex, so verification requires first making a mapping: which types of media this product actually comes into contact with, and which type of accelerated test corresponds to each.
| Medium type | Why is it a typical trigger for ESC | Common verification caliber |
|---|
| Alcohols (ethanol, isopropanol) | Quick penetration, reduces surface energy, induces silver streaks in combination with assembly stress | Constant strain method (ISO 6252 caliber) repeated wiping cycle |
| Chlorine disinfectant | Strongly oxidative combined with polar media erodes the surface and interface of polyolefins | Stress soaking Retest after aging |
| Surfactant Cleaner | Surfactants induce the expansion and cracking of silver streaks under stress synergy (similar mechanism to that inside the washing equipment drum) | Mandrel test ASTM D1693: 10% Igepal CO-630, 50±0.5°C, record the time for 50% of specimens to crack F₅₀ |
| Essential oil / solvent-based care products | Aromatic hydrocarbons and terpenes have strong permeability to polyolefins | Constant tensile stress method ISO 22088-3: Measuring time to break or critical stress in a medium at 40°C |
Text version of the conclusion: Among the four lines, only the third line has a ready-made standard aqueous solution caliber; the other three types need to be determined according to the actual medium on site. When determining the medium, at least ask about three things: brand and model, actual concentration, and wiping frequency. Using just the words 'cleaning agent' to report the test is equivalent to not reporting at all.
The criteria are written as three elements: soaking temperature, soaking duration, result. Do not write 'pass' for the result; write 'cracked / not cracked, appearance changes.' In the same system, the time to not crack in 10% Igepal at 50°C can reach hundreds of hours; this is just a reference point, not a threshold. The threshold should be deduced based on the actual wiping frequency and service life.
Two reminders. First, the results of stress-free and stressed specimens must be reported separately. Second, medium immersion should be retested after aging — thermal aging makes the material brittle, and UV changes the surface system, so the performance of the material after aging in the medium reflects its behavior at the end of service.
6. Verification sequence: First perform soaking with the stress medium, and only then proceed to full machine operation.
Conclusion First: The verification order for this part has only one principle—put the most likely veto, and the easiest to miss, at the very front.
'
(1) Soak in stressed medium: Map the medium according to the on-site cleaning agent; Sample with stress; Record "cracked/not cracked + appearance changes"
↓ However, no further steps are needed; Return to internal stress and structure, then discuss material replacement
(2) Drop and snap impact: normal temperature + −20°C low temperature + machine drop after assembly; Clips and screw posts with local impact
↓ cracked or snapped, return toughening and increased amount, rounded corners and interference weight
(3) Appearance and color difference: color palette comparison, color difference, flow marks/tiger skin pattern/shrink mark + continuous production consistency
↓ However, return to surface system, filling amount, and gate position
↓ (4) Flame retardant UL94 V-0 (including thickness), halogen-free three items, hot wire contact at 850°C for 30 seconds, GWIT/GWFI
↓ However, return to flame-retardant system
(5) Retest after aging: Thermal aging + UV redoing medium soaking and impact, check retention rate
↓ If not up to standard, return to substrate level and stabilization system
(6) Full machine operation verification: Cleaning agent wiping cycle + machine collision and drag + continuous operation
'
Text version Conclusion: (1) and (5) are the most prone to leakage and also the most expensive. Skipping (1) means leaving the crack for three months after installation; Skipping (5) means using the performance of the new part to represent performance three years later. The most common mistakes are (1) not doing it, going straight to (2)—using a trial mold to perform a drop, and the measured numbers are not representative.
7. Reverse honesty: In these three situations, this part should not be modified PP
Conclusion First: As long as there is "two requirements in opposite directions requiring simultaneous demand," it means the part should not be rigidly supported with modified PP.
| Situations Occurring | Why Is Modified PP Unsuitable ? | Where Should It Go ? |
|---|
| Requires Long-Term High-Intensity Collisions (Heavy Load on the Robot Shell, Repeated Impacts) | Toughening and Flame Retardant Additives Set an Upper Limit on Toughness, and Under Repeated High-Energy Impacts, Crack Expansion Easily Occurs | Fiberglass/Long Fiberglass Reinforced Engineering Plastic Housings, or 'Metal Frame + Plastic Skin' Split Structure |
| Requires High-Gloss Spray-Free + Long-Term Cleaning with Solvent-based Cleaners | Spray-Resistant: High-gloss and minimal filler; Long-term wiping can remove the surface structure and trigger stress marks. The two directions are pulled together | to separate the appearance parts from the wiped surface; Or the entire piece can be changed to ABS/PC-ABS system |
| requiring load-bearing structural parts (joints, arms, reducer mounting positions) | to bear loads depending on rigidity, fatigue, and creep. These three are not the main domain for modified PP | Returning to the structural solution: metal parts, long fiberglass PP structural parts, or PA/PBT load-bearing components |
| require the same piece to simultaneously meet four requirements: V-0 + high gloss and spray-free coating + high impact resistance + long-term rub-resistant solvent | , but the formula does not have room to accommodate them all at once | to assign the requirements to different parts; Or the whole piece material replacement system |
Consistency: It's not that modified PP can't do one thing, but that 'two items in opposite directions are fully matched at the same time.' In such cases, we first clarify this point, then discuss whether there is a compromise structure—for the next order, all will be returned through rework and claims.
Eighth, Material Change Risk Checklist: Seven Things to Confirm Before Replacing Toughened Flame-Retardant PP
Conclusion: First: The customer's real concern is often not performance, but 'Should I change my current mold and process'—this chart is recommended to be reviewed before deciding on the sample.
| Items to be moved | What needs to be confirmed | What happens if not done |
|---|
| Mold shrinkage rate | Differences between toughening and filling and original plan; Assembly gap parts are especially sensitive | Size deviations, assembly mismatches |
| Gate and venting | Flame-retardant filling system flow and gas production are different; Appearance parts are extremely sensitive to gate position | Insufficient filling, flow marks, weak welding lines |
| Material temperature and mold temperature | Halogen-free systems have narrow thermal stability windows, residence time must be controlled; Mold temperature affects surface | decomposition, surface defects, flame retardancy fluctuations |
| drying | according to the specific system, cannot be directly copied from the original process | silver wire, bubbles |
| holding pressure and demolding | holding pressure determines internal stress, demolding determines whitening and strain | excessive internal stress, directly increasing ESC risk |
| color difference | light-colored and white parts must first set the color plate; Toughening and filling make color difference more difficult to control | batch color difference dispute |
| verification sequence | soaking in stressed medium → drop and snap impact → appearance and color difference → flame retardant → post-aging retesting → whole machine | all risks concentrated at the last step |
text version conclusion: material change involves mold, process, and appearance. The most important thing to discuss is the verification sequence, followed by holding pressure. Holding pressure is the easiest to overlook—it is not written in the physical property table, but directly determines how much internal stress remains in the part, and internal stress is the seed for cracking later.
9. One-Page Report Comparison Table: Robot Enclosure / Vacuum Cleaner Structural Parts Divided into Two Columns
Conclusion First: There is only one way to judge whether this form is qualified—the customer can use it and determine the material directions for both parts together in a single meeting.
| Scenario | Recommended Route | Key Indicators | Verification Standards | Conditions to Be Confirmed First |
|---|
| [Robot] Indoor Non-Load-bearing Enclosure (with Flame Retardancy) | Toughened and Flame-Retardant Modified PP | Soaked in stressed media; UL94 V-0 continuous thickness; −20°C Impact | ASTM D1693 / ISO 22088-3; GB/T 5169.16; GB/T 1843 | Which types of cleaning agents to contact, wiping frequency |
| 【Robot】Light-colored high-gloss appearance parts | Toughening PP + mineral filling, plus surface system | Color difference, flow marks, tiger skin texture, shrinkage marks; Shrinkage rate | GB/T 17037.4; color swatch comparison | color swatch, spray-free |
| 【Robot】heavy-duty casing | PP for long-term high-intensity collisions Not preferred: glass fiber/long glass fiber reinforced engineering plastic, or metal frame + plastic skin | no cracking after repeated impact | by unit stand and machine diameter | impact energy, collision frequency |
| [Sweeping Robot] Structural Components, Collision Buffer Components | Toughened modified PP (add halogen-free system when flame-retardant) | −20℃ low-temperature drop; local impact on the buckle and screw post | GB/T 1843; Overall Machine Drop Caliber | Transport temperature, drop height, latch design |
| [Sweeping Robot] Load-bearing Position (such as the roller brush motor mount) | PP not preferred: PC series or PA/PBT metal inserts | Rigidity, creep, assembly accuracy | According to the part drawing and the overall machine caliber | Load, number of assemblies and disassemblies, accuracy requirements |
| [Sweeping Robot / Window Cleaning Robot] Requires outdoor or semi-outdoor environment | Toughened weather-resistant modified PP (add halogen-free system when flame retardant is included) | Xenon lamp aging ΔE ≤ 3.0 | GB/T 16422.2 | Duration of exposure to the sun, whether coastal |
Text version of the conclusion: On the same machine, it is normal to have 'the casing made of PP, the panel made of ABS, and the load-bearing parts made of PC with inserts.' It does not rely on a higher grade; rather, each position meets its own primary constraint.
10. On the robot's casing and the structural parts of the vacuum cleaner, the parts that are most prone to problems are often not about 'how strong they are'.
There are two most common types of deviations in this industry for such parts. One is selecting the wrong verification entry: using stress-free samples to soak in a cleaner, or only performing tensile impact without doing media immersion—ESC is created by overlapping two conditions, testing only half is equivalent to not testing at all. The public accelerated test standards are clear: ASTM D1693, ISO 22088-3, and ISO 6252, which correspond to the bent strip method, the constant tensile stress method, and the constant strain method, respectively.
Another category is misattribution: attributing all cracking to the material. The publicly stated mechanism is that detergents induce silver streak propagation and cracking under stress cooperation, which is precisely the common failure path of washing machine inner tubs; the other half of the cause is often assembly stress and residual stress. The threshold on the flame-retardant side is equally clear: UL94 V-0 across thickness, halogen-free in all three aspects, and no ignition when a 850℃ glowing wire is applied for 30 seconds.
There are two common solutions: structurally, make the stress concentration areas smooth (fillets, transitions, embedded brass nuts, controlled interference), and in forming, reduce internal stress (holding pressure, mold temperature, annealing if necessary).
Ningbo Kolon New Materials Co., Ltd. commonly supplies self-produced modified polypropylene (PP) granules for these two types of parts, focusing on toughening and halogen-free flame retardancy: the solvent resistance is based on the list of cleaners the parts come into contact with, the toughening additive amount is adjusted according to drop height and transport temperature, and the V-0 rating and halogen-free system are determined according to wall thickness. The key issues addressed are 'cracking at assembly edges,' 'drop cracks and clip breakage,' and 'difficulty in processing the surface of light-colored parts.' Formulations are adjusted according to the part's operating conditions, and small sample comparisons and medium soaking tests with customers can be provided. Parts-level clients with many varieties in small batches can also be accommodated.
In the inquiries we come across, seven or eight times out of ten, the first question is 'Does it need to be flame-retardant V-0?' Very few people ask 'Which cleaning agents is it compatible with?' as their first question. Yet the latter often determines earlier whether this material can be used.
Frequently Asked Questions
Question: The casing has cracked. If we switch to a material that is more chemically resistant, will that solve the problem?
Answer: Not necessarily, and often not. ESC is a combination of the medium and stress, and the material only improves the medium part. First, check whether the crack initiation point is on the buckle, screw post, or sharp corner; then check the pressure holding and internal stress; only then talk about changing the material.
Q: For detergent validation, is it okay to soak a stress-free spline for a while?
Answer: No. A stress-free sample may soak for a long time without cracking, while a sample under stress can crack in a week. The criterion should be based on the sample under stress.
Q: If we add a little more toughening agent, wouldn't it be safer against drops and collisions?
Answer: You need to calculate the exchange relationship. As the amount of toughening agent (such as POE, EPDM) increases, rigidity, dimensional stability, and surface quality will decrease, which is especially noticeable on light-colored high-gloss parts. The amount is determined together by the 'low-temperature impact lower limit, rigidity lower limit, and appearance upper limit.'
| Operating condition | Key criterion | Self-produced regular supply |
|---|
| Interior non-load-bearing shell (including flame retardant) | Soaked in a stressed medium; V-0 across thickness; −20°C impact | Toughening Halogen-Free Flame Retardant Modified PP Direction |
| Light-colored highlighted exterior parts | Color difference, flow marks, tiger stripes, shrinkage marks | Toughened PP Mineral-filled Surface system orientation |
| Sweeping machine structural parts, cushioning parts | Low-temperature drop; local impact on the clip and screw post | Direction of toughened modified PP (including halogen-free flame retardant grade) |
| For outdoor or semi-outdoor use | Xenon lamp aging ΔE ≤ 3.0 | Toughened and weather-resistant (including halogen-free flame-retardant grade) modified PP direction |
Lastly, say three sentences.
First, the primary working condition for this part is the cleaning agent, not strength. The first sentence should ask, 'Which cleaning agents does it come into contact with, and how many times is it wiped?'
Second, cracks first start from the clips, screw posts, and sharp corners. The first solution for ESC is to reduce internal stress and modify the structure; materials are only the second solution.
Third, the verification sequence is more expensive than the verification items: soak with stress medium → drop and snap-fit impact → appearance and color difference → flame retardant → retest after aging → whole device. ①② cannot be skipped.
About Us
There are three things we never guess: temperature tolerance, lifespan, and dosage.
If the operating temperature is not given, don’t guess; if the service life is not given, don’t guess; if the monthly usage is not mentioned, don’t guess either. Any plan guessed will eventually need to be reworked and returned for claims.
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.
