题材边界：仅限民用安防器材的塑料壳体（监控设备外壳、门禁机箱、报警器壳体、防护箱体），不涉及武器装备、警用装备与军警专用器材，不写防护等级对应的实体产品细节。
安防壳体材料为什么难选？因为阻燃和抗冲击在 PP 里是互相拉扯的两件事。这篇把安防器材壳体的六维工况、三条材料路线的部位分工、八项判据、验证顺序、反向诚实段与换料风险清单摆清楚，并说明哪几种条件下这个件不该用改性PP。
- 与 PP-A16 的分工：PP-A16 走"档位怎么定"，本篇走"阻燃与抗冲击的不可能三角"，重心在冲击、低温与跌落
有个做安防器材壳体的技术员跟我说过一句话：这批料阻燃做到 V-0 了，客户一摔就碎。
隔了不到两周，另一家问的是反过来的版本：冲击做到了，整机送检阻燃又过不去。
这两句话讲的是同一件事——在 PP 里，阻燃和抗冲击是往两个方向拉的两股力，而这两股力又必须同时满足。
先把范围说明白：本篇讲的安防壳体，指监控设备外壳、门禁机箱、报警器壳体、防护箱体这类民用安防器材的塑料壳体，不涉及武器装备、警用装备与军警专用器材。
为什么这两件事总打架，机理并不复杂：
- PP 本身易燃，要过阻燃就得外加阻燃体系，而PP 的阻燃剂加量普遍落在 25–30% 这一档；
- 加量上去，拉伸、弯曲、冲击、韧性一起往下掉——这是 PP 的结构性问题，不是配方水平问题；
- 补韧性要加增韧剂，增韧剂一多，阻燃效率、刚性和流动性又跟着掉；外加免喷涂外观对填充与阻燃组分也不友好。
所以选型的本质，不是找到一款"样样都好"的料，而是确定这三条里哪一维让位。
一、安防壳体材料怎么选：先问这个件"最怕摔"还是"最怕烧"
结论先说：第一个问题不是"用什么料"，是"这个件最怕的那件事是哪一件"。
装在外墙、杆件上的监控设备外壳，最怕搬运、安装和风载下的撞击；装在机柜里的门禁机箱，最怕内部电源模块长期发热。同一个项目里的两个壳，怕的东西可以完全不同，本来就不该用同一档料。
第二件事要先问清：这个壳体是不是承载带电部件。 它直接决定 UL94 档位与灼热丝要求，也决定后面要不要看 CTI 与电气强度。第三件事才是选料——先定"最怕什么"，再定"哪一维让位"，最后才轮到改性PP 的牌号方向。
一句判读：安防壳体上不存在"阻燃高、冲击高、成本低"三项同时满足的料。 谁把这三项一起写进要求里，谁就还没开始选型。
二、工况六维拆解：安防器材壳体的六个维度，数字先报齐
结论先说：温度与载荷决定选哪条路线，介质与寿命决定料能撑几年，外观与合规是两个否决项。
| 维度 | 安防器材壳体的实际工况 | 对材料的要求 |
|---|
| 温度 | 户外机箱夏季暴晒表面可到 70–80℃；机内电源模块与主控板周边常 40–70℃；寒冷地区冬夜环境温度可到 −20 ~ −30℃ | 低温冲击是硬线；长期耐热按 RTI ≥105℃ 口径 |
| 载荷 | 安装与运输中的跌落、抛掷（常按 1–2 m 级跌落设计）；堆码挤压；安装扭矩与螺柱、卡扣预紧；风载与振动 | 要韧性与抗应力开裂，不是高刚性 |
| 介质 | 雨水与凝露、酒精与清洗剂擦拭、手汗与油脂、户外灰尘与紫外线 | 耐候 + 耐擦拭；户外件还要过 UV 老化 |
| 寿命 | 商用设备常按 3–5 年设计，户外件要求更严 | 老化之后阻燃与冲击都不能塌 |
| 外观 | 多为免喷涂外观件，色泽与耐划伤直接被看见 | 免喷涂体系 + 划痕口径 |
| 合规 | UL94 档位、灼热丝、无卤量化、RTI；壳体若承载带电部件还看 CTI 与电气强度 | 少一条就不算过关 |
无卤量化是最容易被口头带过的一条：溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm，三条都满足才算。
文字版结论：温度和载荷这两维会一票否决——改性PP 在低温下已接近脆化区间，跌落开裂是整机返工级的问题；介质与寿命这两维的问题往往几个月后才暴露，最容易被漏掉。
三、材料路线对比：阻燃抗冲击PP 的三条路线，分的是壳体部位不是好坏
结论先说：三条路线不是"谁更高明"的关系，是"哪一条的短板正好不在你这个部位上"的关系。
| 路线 | 拿到什么 | 代价 | 适配的壳体部位 |
|---|
| ① 阻燃 + 增韧体系（冲击优先） | 冲击与低温韧性表现好；螺柱、卡扣处不容易发白开裂 | 阻燃加量与增韧剂双重占量，刚性与流动性一起掉；成本偏高 | 前面板、上盖、外露易撞击面、薄壁大件 |
| ② 阻燃 + 玻纤/矿物增强体系（刚性优先） | 弯曲模量高、收缩率低、尺寸稳定好 | 各向异性与熔接线强度问题；表面质量下降；冲击尤其低温冲击不占优 | 内部支架、安装板、导轨、需压公差的承力位 |
| ③ 纯阻燃体系（成本优先） | 只解决"烧"的问题，材料成本与加工窗口相对好控 | 冲击余量小、跌落表现差 | 封闭腔体内的非受力件、无跌落风险的内部小件 |
改性PP 的这三条路线里，最容易被搞混的是①和②：外壳薄壁件上了玻纤增强料，冲击与表面两头受损；内部支架上了高增韧料，尺寸稳定和成本又压不住。
一个公开可查的降加量方向：据公开期刊成果（A 级），引入有机无机杂化催化剂后，PP 过 V-0 所需的阻燃剂含量可从 25wt% 降到 15wt%。加量降下来，力学与韧性的损失也跟着降——这是"不可能三角"里少数能同时松两边的着力点。但公开资料只到实验室口径，上机仍要按件逐项验证。
有卤体系只做并列陈述：它效率高、用量低，容易做到 V-0，代价是加工受热释放卤化氢腐蚀设备模具、燃烧时浓烟大，有出口环保要求的项目通常先排除它。
四、★ 选型判据表：防护外壳材料要看八项指标，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——现场卡住的常常不是不知道看哪一项，而是不知道拿什么测、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 | V-0：单次余焰 ≤10 s、10 次总余焰 ≤50 s、余焰+余灼 ≤30 s、不允许滴落物引燃棉花；V-2：≤30 s / ≤250 s / ≤60 s、允许滴落物引燃棉花 | GB/T 5169.16（idt IEC 60695-11-10）；等级须连厚度标注 | 档位与滴落风险不匹配 | 按部位分档：承载带电件、滴落物可能落到发热件上的走 V-0；无引燃风险的纯外壳可落到 V-2 |
| 无卤量化 | 溴 <900 ppm、氯 <900 ppm、两者总和 <1500 ppm | 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 |
| 灼热丝 GWIT / GWFI | GWIT 750 / 775℃；GWFI 850 / 960℃；850℃ 接触 30 s 不引燃 | GB/T 5169.13、GB/T 5169.12（idt IEC 60695-2-13 / 2-12） | 靠近电源模块处起燃 | 无卤阻燃 + 玻纤或矿物填充 |
| 常温缺口冲击 | 23℃ 缺口冲击 ≥6 kJ/m²（家电壳体公开口径） | GB/T 1043.1（简支梁）、GB/T 1843（悬臂梁） | 常温磕碰、装配应力开裂 | 阻燃 + 增韧体系 |
| 低温缺口冲击 | −20℃ 简支梁缺口冲击 ≥3 kJ/m²；同类硬壳件物性表的 −20℃ 悬臂梁缺口冲击可到 ≥93 J/m | GB/T 1843、GB/T 1043.1；样条与缺口类型、试样放置状态都要写清 | 冬季或冷库环境下跌落碎裂 | 增韧加量 + 基材档位复核 + 件结构圆角 |
| 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 |
| CTI / 电气强度（承载带电部件时） | 材料组别：I 为 ≥600 V，II 为 400–600 V，IIIa 为 175–400 V；电气强度门限按电气间隙与爬电距离倒推 | GB/T 4207-2022（idt IEC 60112:2020）；GB/T 1408.1-2016（idt IEC 60243-1:2013） | 潮湿与污秽下表面漏电起痕 | 无卤阻燃 + 矿物填充，避免助剂大量迁移 |
| 免喷涂外观（耐划伤与色差） | 划痕 dL <1.5（低于 1.0 更理想），至少测 5 点取平均 | VW PV3952：载荷 10 N、划针 φ1 mm、网格间距 2 mm、划速 1000 mm/min、23±5℃；户外件附加 UV + 热老化 500–1000 h | 划痕发白、批次色差 | 外露件不用酰胺类体系，走硅氧烷体系 |
文字版结论：八项里 UL94 那一行的"滴落"二字、低温冲击那一行、免喷涂那一行最容易被忽略。VW PV3952 是行业通行的参照口径，不是安防壳体这个件的强制标准——写进技术协议时要连载荷、划针、温度一起写。
五、常见失效与根因：四个现象，其中两条是行业通行但会出错的做法
结论先说：改性PP 壳体上的这四类失效里，有两条根本不是料的问题，而是判据选错了、或者用错了代偿手段。
失效一：跌落或撞击后壳体开裂、碎裂。 根因通常是三点之一——阻燃剂 25–30% 的加量拉低了冲击与韧性；低温下 PP 接近脆化区间，韧性余量不足；转角与螺柱处壁厚突变形成应力集中。先查壁厚与圆角，再查料。
失效二：螺柱、卡扣、装配孔位发白开裂。 根因多半是收缩率差异加上装配扭矩：阻燃料的收缩率与普通 PP 差别明显，模具若仍按原料的收缩率开，装配尺寸和残余应力都会改。这是换料最典型的连带成本，不是料的缺陷。
失效三（敢否定一个常见做法）：只盯 UL94 等级、不看滴落项，是错的。 V-0 与 V-2 的差别恰恰就在"是否产生引燃棉花的滴落物"上。件内若有带电部件，滴落物会不会落上去，比余焰时间那几秒更关键——把 V-0 当成目标、却不看件内有没有会接着滴落物的东西，等于买了一个不解决实际风险的等级。
失效四（敢否定另一个常见做法）：为了过阻燃把壁厚加厚，是错的。 加厚会延长冷却时间、加剧内应力，反而拉低冲击表现，同时把重量和成本一起加上去；而 UL94 等级本身连厚度标注，靠加厚"蹭"上去的等级，换个更薄的部位就不成立了。正确做法是选对阻燃体系、优化浇口与壁厚均匀度。
六、验证顺序：阻燃是准入，冲击是主战场，装配是终判
结论先说：这个件的顺序不能反——阻燃是准入资格，冲击是真正的主战场，装配与跌落是最终裁判。
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① 阻燃：垂直燃烧 + 滴落物是否引燃棉花
↓ 不过 → 退回换阻燃体系或调加量
② 灼热丝：GWIT / GWFI，850℃ 接触 30 s 不引燃
↓ 不过 → 退回 ① 重配体系
③ 常温冲击：23℃ 缺口冲击 + 螺柱与卡扣装配预验
↓ 不过 → 退回 ② 用增韧补，或改件结构
④ 低温冲击：−20℃ 缺口冲击，试样放置后按同一口径测
↓ 不过 → 退回 ③ 补增韧；补不回来 → 改壁厚均匀度与圆角
⑤ 装配与跌落：整机跌落、安装扭矩、卡扣保持力
↓ 不过 → 退回 ④ 或改件设计；只换料通常解决不了
⑥ 老化后复测：热老化 / UV 之后，阻燃与冲击各复测一遍
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最常见的错是跳过 ① 和 ② 直接进 ③——试模件的成型条件往往是临时的，拿它判断材料性能没有代表性。
文字版结论：阻燃那一关决定这个配方还有没有往下走的资格，低温冲击那一关决定整机跌落的试模费要不要重花。 顺序反了，账都堆在最后一步。
七、反向诚实：这四种情况，安防壳体就不该用改性PP
结论先说：只要出现"要 PP 拿不到的东西"，就不要硬撑——这几类要求都在 PP 的能力边界之外。
| 出现的情况 | 为什么改性PP不合适 | 该往哪走 |
|---|
| 长期户外暴晒、同时要求外观长期不变色不变形 | 25–30% 档的阻燃加量加填充本就压表面，UV 之后色差与失光更难控 | 外壳换 PC/ABS 类或工程塑料路线；结构件仍可留在 PP |
| 要求高等级防护（防爆、防弹级别） | 这类要求靠结构与复合材料体系吸收能量，材料韧性补不了这个量级 | 回到结构方案，外壳走金属件或纤维复合材料 |
| 长期连续工作温度持续超过 100–110℃ 且同时承载结构载荷 | PP 的热变形与长期耐热上限就在这条线附近，填充与玻纤增强往上抬也有边界 | 换 PA 类、PBT 一类耐热工程塑料或金属件 |
| 要求金属级的屏蔽或散热功能 | 塑料本体的电磁屏蔽与导热能力与金属不在一个量级 | 金属件，或在 PP 结构上用金属屏蔽件与散热结构配合 |
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——加阻燃与保韧性、加填充与保表面、加增韧与保刚性，三组都是两头顶着。
八、换料要动什么：一张先看再动的清单
结论先说：客户真正的顾虑常常不是性能，而是"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 | 阻燃料的收缩率与普通 PP 差别明显（普通抗冲共聚壳体类件公开口径常见 0.8–1.5% 量级），长件与多孔位件尤其敏感 | 尺寸超差，装配与外观一起出问题 |
| 浇口与排气 | 阻燃填充料对浇口位置与排气更敏感，阻燃组分受热会产气 | 充填不足、困气烧焦、熔接线强度不足 |
| 料温与模温 | 阻燃体系热稳定窗口相对窄，熔体停留时间要控 | 分解、表面缺陷、阻燃表现批次波动 |
| 干燥 | 按具体体系确认，不能照搬原工艺 | 银丝、气泡 |
| 保压与脱模 | 收缩差异带来变形与顶白，加量高的体系更明显 | 变形、顶出拉伤、螺柱位开裂 |
| 色差 | 免喷涂件必须先确认色板再上机，阻燃组分自身带色 | 批次色差争议 |
| 验证顺序 | 垂燃与滴落 → 灼热丝 → 常温冲击 → 低温冲击 → 装配与跌落 → 老化复测 | 风险全部压到最后一步集中爆发 |
文字版结论：其中最该先谈的是收缩率与验证顺序。 跳过收缩率重新核模，尺寸问题会在装配线上一次性爆出来；跳过低温冲击直接做整机跌落，失败重来的成本要翻几倍。
九、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 |
|---|
| 户外监控设备外壳（免喷涂外观件） | 无卤阻燃 + 增韧体系 | 按部位定档；−20℃ 缺口冲击留余量；划痕 dL <1.5 | GB/T 5169.16、GB/T 1843、PV3952 | 跌落高度、暴晒温度、是否承载带电件 |
| 门禁机箱 / 报警器壳体（靠近电源模块） | 无卤阻燃 + 增韧，灼热丝走高档 | GWFI ≥850℃、GWIT 775℃；按位置定 V-0 | GB/T 5169.12 / .13 | 与发热件的距离、有无隔离挡板 |
| 内部支架 / 安装板（承力、压公差） | 阻燃 + 玻纤或矿物增强体系 | 弯曲模量与收缩率 | GB/T 9341、GB/T 17037.4 | 装配公差、螺柱扭矩、有无跌落风险 |
| 封闭腔体内非受力件 | 纯阻燃体系（成本优先） | 按位置定 V-2 或 HB40 以上 | GB/T 5169.16 | 件内有无会接着滴落物的部件 |
文字版结论：同一台设备上，外露外壳走"阻燃 + 增韧"、内部支架走"阻燃 + 增强"是正常配置；靠的不是统一用一档料，而是每个部位都对上它自己的那条要求。
十、这个件上最容易出问题的，往往不是阻燃等级
这类件上最常见的偏差有两类。一类是只盯阻燃等级、不看滴落与位置——V-0 与 V-2 的差别就在滴落物是否引燃棉花，而现场常见做法是把"越高越保险"当成选型依据，结果档位买高了，力学与韧性一起付代价。另一类是用增韧单打独斗去救冲击——阻燃剂加量 25–30% 是 PP 的结构性代价，单靠加增韧剂补，往往把刚性与流动性一起补掉了，螺柱和卡扣位反而更容易出问题。
判据层面的通行硬线是：UL94 按部位定档并连厚度标注；无卤按溴 <900 ppm、氯 <900 ppm、总和 <1500 ppm 三条一起判；灼热丝按 GWIT 750 / 775℃、GWFI 850 / 960℃、850℃ 接触 30 s 不引燃；低温冲击按 −20℃ 口径连样条类型一起写；长期耐热按 RTI ≥105℃ 口径。通行解法是把顺序做实：先过阻燃与滴落，再用增韧补冲击，同时用壁厚均匀度、圆角与加强筋分散应力，最后用装配与跌落做终判。
宁波市科隆新材料有限公司在这个件上常供的是改性聚丙烯（PP）粒子里的无卤阻燃方向，按壳体是外露撞击面还是内部承力位给到不同的增韧与填充配平，阻燃档位按部位与滴落风险分档；配方按件的工况调，可陪客户做小样比对、低温冲击与试模跟踪。
常见问答
问：客户直接要 V-0，我又给不了 V-0 又抗冲击，是不是就没戏了？
答：先分清两件事。一，这个件是不是真的需要 V-0——件内若没有会接着滴落物的带电部件或发热件，按部位定档往往有空间。二，冲突单靠配方解不开时，解通常在件结构上：壁厚均匀度、转角圆角、加强筋，比继续加阻燃剂有用。
问：阻燃加多了冲击就掉一半，能不能两头都要？
答：这是 PP 的结构性问题，不是配方水平问题，只能三条路一起走：选效率更高的阻燃体系把加量压下来、用增韧效率更高的体系把加量压下来、用件结构分担冲击能量。三条都不做，只要求"两头都要"，最后通常是两头都不达标。
问：低温下摔一跤就裂，是不是料太脆？
答：先别换料。低温开裂要看三件事：最低使用温度有没有报对、壁厚与转角有没有应力集中、测试是不是按同一口径做的——低温冲击对样条类型、缺口类型和试样放置状态都很敏感，口径不一致时同一批料能测出两个结论。
| 工况 | 关键判据 | 常规供应 |
|---|
| 外露外壳（易撞击、免喷涂） | 按部位定档；−20℃ 缺口冲击留余量；划痕 dL <1.5 | 无卤阻燃 + 增韧方向，低填充配平 |
| 靠近电源模块的机箱、壳体 | GWFI ≥850℃、GWIT 775℃；V-0 | 无卤阻燃方向，高灼热丝档配平 |
| 内部支架、安装板（承力、压公差） | 弯曲模量与收缩率 | 无卤阻燃 + 玻纤或矿物增强方向 |
| 封闭腔体内非受力件 | 按位置定 V-2 或 HB40 以上 | 纯阻燃方向，成本优先配平 |
最后说三句。 第一，安防壳体材料的第一句话是"这个件最怕摔还是最怕烧"，不是问哪种料好。第二，阻燃与抗冲击在 PP 里是结构性对拉，选型的本质是确定哪一维让位。第三，验证顺序比验证项更贵：垂燃与滴落 → 灼热丝 → 常温冲击 → 低温冲击 → 装配与跌落 → 老化复测。
下一篇讲通讯设备外壳与灯座支架——那个件的难点落在介电性能与长期户外老化上。
关于我们
我们交付的，不只是一包料。
还有一句用料的判断、一份对得上的物性表、一个出了问题还能找的人。
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。
Subject boundaries: Only plastic casings for civilian security equipment (surveillance device housings, access control cases, alarm casings, protective casings), does not involve weapons, police equipment, or military/police specialized gear, and does not specify physical product details corresponding to protection levels.
Why is it difficult to choose security shell materials? Because flame retardancy and impact resistance are two tug-of-war issues in PP. This article clearly lists the six working conditions of security equipment housings, the division of labor among the three material routes, eight criteria, verification sequence, reverse honesty section, and the risk list of material replacements, and explains under which conditions modified PP should not be used for this component.
- Division of labor with PP-A16: PP-A16 focuses on "how to set the gear," this article follows the "impossible triangle of flame retardancy and impact resistance," focusing on impact, low temperature, and drop
A technician working in security equipment shells once told me: this batch of material is flame-retardant to V-0, and the customer breaks easily with a drop.
Less than two weeks later, another seller asked about the reverse version: impact is achieved, but the whole machine is sent for flame retardant inspection but still can't pass.
These two sentences say the same thing—in PP, flame retardant and impact resistance are two forces pulling in two directions, and both forces must be met simultaneously.
First, clarify the scope: The security enclosures discussed here refer to the plastic casings of civilian security equipment such as surveillance device housings, access control enclosures, alarm housings, and protective enclosures, excluding weapons, police, and military/police specialized equipment.
Why do these two things always clash? The mechanism is not complicated:
- PP itself is flammable, so to pass flame retardant standards, an additional flame-retardant system must be added, and the amount of flame retardant for PP generally falls in the 25–30 % range;
- When the amount is increased, tensile, bending, impact, and toughness all decrease — this is a structural issue with PP, not a formulation level;
- To reinforce toughness, toughening agents must be added; the more toughening agents there are, the lower the flame retardancy efficiency, rigidity, and flowability; Additionally, the no-coating appearance is also unfriendly to fillers and flame-retardant components.
Therefore, the essence of choosing a model is not to find a material that is "good in every way," but to determine which of these three factors takes priority.
1. How to choose security housing materials: First, ask whether this piece is "most vulnerable to dropping" or "most afraid of burning."
Conclusion First: the first question is not "what material to use," but "which part is most vulnerable to that issue."
Monitoring equipment casings installed on exterior walls or rods are most vulnerable to impact during handling, installation, and wind loads; Access control cases installed inside cabinets fear long-term internal power module heating. Two shells in the same project can be completely different in fear, so they shouldn't use the same grade material in the first place.
The second thing to ask first: is this enclosure carrying live components? It directly determines the UL94 level and heat filing requirements, and also whether to consider CTI and electrical strength later. The third thing is material selection—first decide "what is most feared," then "which dimension gives way," and finally the grade direction for modified PP.
One sentence: There is no material on the security enclosure that simultaneously meets all three criteria: "high flame retardancy, high impact, low cost." Whoever includes all three requirements together hasn't started selecting the model yet.
2. Six-Dimensional Disassembly of Operating Conditions: The six dimensions of the security equipment housing, the numbers should be reported first
Conclusion: Temperature and load determine which route to choose, medium and lifespan determine how many years the material can last, appearance and compliance are two disadvantaged factors.
| Dimension | Actual working conditions of security equipment housing | Material requirements |
|---|
| Temperature | Outdoor chassis can reach 70–80°C on the surface exposed to summer sunlight; The area around the internal power module and main control board is often 40–70°C; In cold regions, the temperature at night during winter can reach −20~−30°C | Low temperature impact is a hard line; Long-term heat resistance according to RTI ≥105°C diameter |
| load | drop and throwing during installation and transportation (usually designed for 1–2 m drops); stacking and squeezing; installation torque and pre-tightening with studs and snaps; wind load and vibration | must be tough and stress-resistant for cracking, not high rigidity |
| medium | wiping with rainwater and condensation, alcohol and cleaning agents, hand sweat and oils, outdoor dust and UV | weather-resistant + wipe-resistant; Outdoor parts must also withstand UV aging |
| lifespan | commercial equipment is often designed for 3–5 years, outdoor parts have stricter requirements | after aging and must not collapse in flame retardancy or impact |
| appearance | mostly non-spray-coated appearance parts, with color and scratch resistance directly visible | spray-free system + scratch diameter |
| compliant | UL94 levels, hot wire, halogen-free quantification, RTI; If the casing carries live components, CTI and electrical strength | are missing one to avoid passing the standard. |
Halogen-free quantification is the easiest to mention: bromine <900 ppm, chlorine <900 ppm, combined <1500 ppm. All three must be met to count.
Text Version Conclusion: Temperature and load are unanimously vetoed—modified PP is close to the brittleness zone at low temperatures, and drop-cracking is a rework level issue for the whole machine; Issues with medium and lifespan often only surface months later and are most easily overlooked.
3. Material route comparison: The three routes for flame-retardant and impact-resistant PP are divided by the housing part, not the quality of the
Conclusion First: the three routes are not about "who is more skilled," but about "which one's shortcoming happens not to be in your area."
| Route | What do you get ? | Cost | Compatible housing part |
|---|
| (1) Flame retardant + toughening system (impact priority) | Good impact and low-temperature toughness; Studs and buckles are less likely to turn white or crack | Flame retardant and toughening agent both occupy the same amount, causing rigidity and fluidity to drop together; High cost | front panel, top cover, exposed impact surfaces, thin-walled large parts |
| (2) Flame retardant + fiberglass/mineral reinforcement system (rigidity priority) | high bending modulus, low shrinkage, good dimensional stability | anisotropy and weld line strength issues; surface quality deteriorates; Impact, especially low-temperature impact, is not advantageous | internal brackets, mounting plates, guide rails, bearing position for pressure tolerance |
| (3) Pure flame-retardant system (cost priority) | only solves the "burning" problem, material cost and processing window are relatively controllable | small impact margin, poor drop performance | non-load-bearing parts inside the sealed chamber, and small internal parts without drop risk |
modified PP. Among these three routes, the most easily confused are (1) and (2): thin-walled parts of the shell are coated with glass fiber reinforcement, causing damage to both impact and surface ends; internal supports are coated with high-toughening materials, which are dimensionally stable but cost cannot be controlled.
A publicly available direction for reducing and increasing dosage: According to published journal results (Class A), after introducing organic-inorganic hybrid catalysts, the required flame retardant content for PP passing V-0 can be reduced from 25 wt% to 15 wt%. With the dosage reduced, the losses in mechanics and toughness also decrease—this is one of the few points in the "impossible triangle" that can simultaneously relax both sides. However, public data only covers laboratory standards; testing still requires item-by-item verification
The halogen system only makes parallel statements: it is highly efficient, uses a small amount, and easily achieves V-0, but the downside is that processing releases halogenated hydrogen which corrodes equipment molds, and it produces thick smoke when burning. Projects with export environmental requirements usually exclude it first.
4. ★ Selection Criteria Table: The protective enclosure material should be evaluated based on eight indicators, each with a verification method.
Conclusion first: The biggest difference between this table and ordinary physical property tables is the fourth column 'Verification Method · Standard Number'—what commonly gets people stuck on-site is often not that they don't know which item to look at, but that they don't know what to measure or how much counts as passing.
| Indicator | Threshold Value (Typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| UL94 Vertical Burning Rating | V-0: Single afterglow ≤10 s, total afterglow for 10 times ≤50 s, afterglow and afterburn ≤30 s, no dripping allowed to ignite cotton; V-2: ≤30 s / ≤250 s / ≤60 s, dripping allowed to ignite cotton | GB/T 5169.16 (idt IEC 60695-11-10); the grade must be marked along with the thickness | Gear level does not match the dripping risk | Classified by part: load-bearing live parts and falling objects that may fall onto heating parts are rated V-0; pure enclosures with no ignition risk can be rated V-2 |
| halogen-free quantification | Bromine <900 ppm, Chlorine <900 ppm, Total of both <1500 ppm | XRF / IC, refer to IEC 61249-2-21 | Environmental compliance not up to standard | Halogen-free flame retardant system, does not use halogen-containing synergists |
| Scorching Wire GWIT / GWFI | GWIT 750 / 775℃; GWFI 850 / 960℃; 850℃ contact for 30 s does not ignite | GB/T 5169.13, GB/T 5169.12 (idt IEC 60695-2-13 / 2-12) | Ignited near the power module | Halogen-free flame retardant, glass fiber or mineral filled |
| Room temperature notch impact | 23℃ notch impact ≥6 kJ/m² (appliance housing open mouth caliber) | GB/T 1043.1 (simply supported beam), GB/T 1843 (cantilever beam) | Cold cracking from impact or assembly stress | Flame retardant toughening system |
| Low temperature gap shock | −20℃ simply supported beam notched impact ≥3 kJ/m²; for the same type of hard-shell material property table, the −20℃ cantilever beam notched impact can reach ≥93 J/m | GB/T 1843, GB/T 1043.1; the type of spline and notch, as well as the placement state of the specimen, must all be clearly specified | Breakage from dropping in winter or cold storage environments | Toughening and adding quantity Substrate grade review Component structure fillet |
| 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 |
| CTI / Electrical Strength (when carrying live parts) | Material group: I is ≥600 V, II is 400–600 V, IIIa is 175–400 V; the electrical strength threshold is deduced based on the electrical clearance and creepage distance | GB/T 4207-2022 (idt IEC 60112:2020); GB/T 1408.1-2016 (idt IEC 60243-1:2013) | Surface electrical leakage marks under dampness and dirt | Halogen-free flame retardant, mineral-filled to prevent large-scale migration of additives |
| Spray-free appearance (scratch-resistant and color-consistent) | Scratch dL <1.5 (preferably below 1.0), measure at least 5 points and take the average | VW PV3952: Load 10 N, scribe needle φ1 mm, grid spacing 2 mm, scribing speed 1000 mm/min, 23±5℃; additional UV heat aging for outdoor parts 500–1000 h | Scratches appear white, batch color differences | Exposed parts should not use amide-based systems, use siloxane-based systems instead. |
Text version conclusion: Among the eight items, the words 'droplet' in the UL94 row, the low-temperature impact row, and the no-spray coating row are the easiest to overlook. VW PV3952 is a commonly used industry reference, not a mandatory standard for the security enclosure part — when writing it into the technical agreement, the load, scribe test, and temperature should also be included.
5. Common Failures and Root Causes: Four phenomena, two of which are industry practices but can lead to errors
Conclusion first: Among these four types of failures on the modified PP housing, two are not material issues at all, but are due to using the wrong criteria or the wrong compensatory methods.
Failure 1: Cracking or shattering of the casing after dropping or impact. The root cause is usually one of three—an increase of 25–30% in flame retardant reduces impact resistance and toughness; PP approaches the brittle zone at low temperatures, leaving insufficient toughness margin; sudden changes in wall thickness at corners and studs create stress concentrations. First, check the wall thickness and fillets, then check the material.
Failure 2: Studs, clips, and assembly holes turn white and crack. The root cause is mostly the difference in shrinkage rate combined with assembly torque: the shrinkage rate of flame-retardant material differs significantly from that of regular PP. If the mold is still set according to the original material’s shrinkage rate, the assembly dimensions and residual stress will change. This is the most typical collateral cost when changing materials, and it is not a material defect.
Invalid Three (Dare to deny a common practice): Only focusing on the UL94 rating without considering the dripping item is wrong. The difference between V-0 and V-2 lies precisely in whether the dripping material ignites the cotton. If there are live components inside the device, whether the drips fall onto them is more critical than the few seconds of afterflame—aiming for V-0 but not checking if there is anything inside that could be affected by the drips is equivalent to purchasing a rating that does not address the actual risk.
Invalid point four (daring to deny another common practice): Increasing wall thickness to pass flame retardancy tests is wrong. Thicker walls will extend cooling time, increase internal stress, and actually reduce impact performance, while also adding weight and cost; moreover, UL94 ratings specify thickness, so trying to 'bump up' the rating by increasing thickness won't hold for thinner sections. The correct approach is to choose the right flame-retardant system and optimize the gate location and wall thickness uniformity.
6. Verification sequence: flame retardancy is the access requirement, impact is the main battlefield, and assembly is the final judgment.
Conclusion first: The order of this process cannot be reversed—flammability is the eligibility criterion, impact is the real main battlefield, and assembly and drop tests are the final judge.
`
① Flame retardant: vertical burning Whether the dripping material ignites the cotton
↓ However → revert to changing the flame-retardant system or adjust the dosage
② Glowing wire: GWIT / GWFI, does not ignite when contacted at 850℃ for 30 s
↓ However → Return ① Reconfigure System
③ Room Temperature Impact: 23℃ Notched Impact Preliminary Inspection of Stud and Clip Assembly
↓ However → Return ② Use toughening filler, or modify the part structure
④ Low-temperature impact: −20℃ notched impact, the specimen is measured after placement using the same caliber
↓ However → Return ③ Increase toughness; if it cannot be restored → Modify wall thickness uniformity and fillet radius
⑤ Assembly and drop testing: complete machine drop, installation torque, clasp retention force
↓ However → Return ④ or modify the design; just replacing the material usually doesn’t solve the problem
⑥ Retesting after aging: After thermal aging / UV, retest both flame retardancy and impact.
`
The most common mistake is skipping ① and ② and going straight to ③—the molding conditions of the trial piece are often temporary, and using it to judge material performance is not representative.
Text version of the conclusion: The flame retardancy checkpoint determines whether this formula has the qualification to move forward, and the low-temperature impact checkpoint determines whether the mold cost for full machine drop tests needs to be spent again. If the order is reversed, all the costs pile up at the last step.
7. Reverse Honesty: In these four situations, security housings should not use modified PP.
Conclusion first: As long as there is something 'PP cannot get,' don't force it—these types of requests are all beyond PP's capabilities.
| The situation that occurred | Why is modified PP not suitable? | Which way should I go? |
|---|
| Prolonged outdoor exposure and the appearance must remain undiscolored and deformed for extended periods | Adding flame retardant in the 25–30% range along with fillers already compresses the surface, making color difference and loss of gloss after UV even harder to control. | Change the casing to PC/ABS type or engineering plastic route; structural components can still remain in PP |
| Requires high-level protection (explosion-proof, bulletproof level) | This kind of requirement relies on the structure and composite material system to absorb energy; the toughness of the material alone cannot make up for this magnitude. | Back to the structural scheme, the shell uses metal parts or fiber composite materials. |
| Long-term continuous working temperature continuously exceeds 100–110°C while simultaneously bearing structural load | The hot distortion and long-term heat resistance limit of PP are around this line, and the increase from fillers and glass fiber reinforcement also has boundaries. | Replace with PA type, PBT type heat-resistant engineering plastics, or metal parts |
| Requires metal-grade shielding or heat dissipation functionality | The electromagnetic shielding and thermal conductivity of plastic itself are not on the same level as metals. | Metal parts, or use metal shielding parts in the PP structure in conjunction with the heat dissipation structure |
The pattern is consistent: whenever there is a 'simultaneous requirement for two opposite directions,' it indicates that this part should not be forcibly made with PP—adding flame retardancy while maintaining toughness, adding fillers while preserving surface quality, adding toughening while keeping rigidity, all three sets are conflicting at both ends.
8. What to Move When Changing Materials: A Checklist to Review Before Taking Action
Conclusion first: The client'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 materials.
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The shrinkage rate of flame-retardant materials is significantly different from that of ordinary PP (the open specification of common impact-resistant copolymer shell parts is usually in the range of 0.8–1.5%), and long parts and multi-hole parts are particularly sensitive. | The dimensions are out of tolerance, causing problems with both assembly and appearance |
| Gate and Venting | Flame retardant fillers are more sensitive to gate location and venting, and the flame retardant components generate gas when heated. | Insufficient filling, gas burning, insufficient weld line strength |
| Material Temperature and Mold Temperature | The thermal stability window of the flame-retardant system is relatively narrow, and the melt residence time needs to be controlled. | Decomposition, surface defects, batch-to-batch variation in flame retardant performance |
| Dry | Confirm according to the specific system, it cannot be copied directly from the original process | Silver threads, bubbles |
| Pressure Holding and Demolding | Shrinkage differences cause deformation and whitening at the peak, which is more pronounced in systems with higher additive amounts. | Deformation, ejection tear, stud location cracking |
| Color difference | Parts that do not require spraying must have their color samples confirmed before going on the machine, and the flame-retardant components are colored themselves. | Batch color difference controversy |
| Verification order | Drip and burn → Hot wire → Room temperature impact → Low temperature impact → Assembly and drop → Aging retest | All the risks are concentrated to explode at the final step |
Text version conclusion: The topics that should be discussed first are shrinkage rate and verification sequence. Skipping shrinkage rate and rechecking the mold will cause all size issues to suddenly appear on the assembly line; skipping low-temperature impact and going straight to full machine drop tests will multiply the cost of failures several times.
9. One-page report comparison table (can be directly pasted into PPT)
Conclusion first: There is only one criterion for judgment—whether the client can use this sheet to finalize the material direction in a single meeting.
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Outdoor surveillance equipment casing (paint-free exterior parts) | Halogen-free flame retardant Toughening system | Set schedule according to parts; -20℃ notch impact reserve margin; scratch dL <1.5 | GB/T 5169.16, GB/T 1843, PV3952 | Drop height, exposure temperature, whether carrying live components |
| Access control machine casing / Alarm casing (near the power module) | Halogen-free flame retardant, toughened, hot wire goes high-end | GWFI ≥850℃, GWIT 775℃; V-0 by position | GB/T 5169.12 / .13 | Distance from the heating element, presence or absence of isolation baffles |
| Internal bracket / mounting plate (load-bearing, compression tolerance) | Flame-retardant glass fiber or mineral-reinforced system | Bending modulus and shrinkage rate | GB/T 9341, GB/T 17037.4 | Assembly tolerances, stud torque, presence or absence of drop risk |
| Non-load-bearing parts inside a sealed cavity | Pure flame-retardant system (cost-priority) | Set to V-2 or above HB40 according to position | GB/T 5169.16 | Whether there are components inside that will continue to drip |
Text version conclusion: On the same device, it is normal for the exposed casing to follow 'flame retardant and toughened,' and the internal brackets to follow 'flame retardant and reinforced'; it's not about using the same grade of material uniformly, but that each part meets its own specific requirements.
10. The part that is most likely to have problems is often not the flame-retardant rating.
There are two common types of deviations in these types of parts. One is focusing only on flame retardant rating, ignoring drips and position—the difference between V-0 and V-2 lies in whether the drips ignite cotton. The common practice on site is to use 'the higher the safer' as the basis for selection, resulting in higher grades and paying the price for both mechanics and toughness. The other is to rely solely on toughening to rescue the impact—adding 25–30% of flame retardant is a structural cost for PP. Relying solely on toughening agents often compensates for rigidity and fluidity, making studs and snap positions more prone to problems.
The standard standard at the criterion level is: UL94 is set by location and labeled with thickness; Halogen-free is judged as bromine < 900 ppm, chlorine < 900 ppm, total < 1500 ppm; Glow-hot wire is classified as GWIT 750/775°C, GWFI 850/960°C, 850°C and 850°C for 30 seconds without ignition; Low-temperature shock is labeled as −20°C caliber along with the spline type; Long-term heat resistance is rated as RTI ≥105°C caliber. The common solution is to solidify the sequence: first pass through flame retardant and drip test, then use toughening to compensate for impact, and at the same time use wall thickness uniformity, fillet corners, and reinforcing ribs to distribute stress, and finally use assembly and drop as the final judgment.
Ningbo Kelong New Materials Co., Ltd. commonly supplies halogen-free flame-retardant directions for modified polypropylene (PP) particles in this part. Different toughening and filling trims are applied according to whether the shell is exposed on the impact surface or at the internal bearing position, with flame retardant levels classified by location and drip risk; The formula can be adjusted according to the working conditions of the part, and can assist customers in sample comparison, low-temperature impact, and mold trial tracking.
FAQ
Question: If the customer directly wants V-0 and I can't provide V-0 and am impact-resistant, does that mean it's out of the question?
Answer: First, clarify two things. First, does this part really need V-0 — if there are no live or heating components inside the part that will attract dripping material, there is often room to set the settings by location. Second, when the conflict cannot be resolved by the formula alone, the solution usually lies in the component structure: wall thickness uniformity, corner rounds, reinforcing ribs, which are more useful than continuing to add flame retardants.
Question: If too much flame retardant is added, the impact will be halved. Can both ends be used?
Answer: This is a structural issue with PP, not a formulation issue. There can only be three paths together: choose a more efficient flame-retardant system to suppress the increase, use a system with higher toughening efficiency to reduce the loading, and use the component structure to share the impact energy. If none of these are done, only "both ends must be needed," and in the end, neither end meets the standard.
Question: If it cracks after a drop at low temperatures, is the material too brittle?
A: Don't change the material yet. Low-temperature cracking depends on three things: whether the minimum operating temperature is correct, whether the wall thickness and corners have stress concentration, and whether the test is done with the same diameter—low-temperature impact is sensitive to spline type, notch type, and sample placement state. If the diameters are inconsistent, the same batch can yield two conclusions.
| Operating Conditions | Key Criteria | Conventional Supply |
|---|
| Exposed Shell (Prone to Impact, No Spray Needed) | Set by Location; −20°C Notch Impact Leave Margin; Scratch dL <1.5 | halogen-free flame retardant + toughening direction, low-fill trim |
| chassis and housing near power module | GWFI ≥850°C, GWIT 775°C; V-0 | halogen-free flame-retardant direction, high-heat wire trimming |
| internal bracket, mounting plate (load-bearing and compression tolerance) | bending modulus and shrinkage rate | halogen-free flame retardant + glass fiber or mineral reinforcement direction |
| non-load-bearing components inside the sealed chamber | positioned V-2 or above HB40 | pure flame-retardant direction, cost prioritized trimming |
Finally, three words. First, the first question about security housing materials is, "Is this part most afraid of dropping or burning?" It's not about which material is best. Second, flame retardancy and impact resistance in PP are structural tensions; the essence of selection is determining which dimension to give way. Third, the verification sequence is more expensive than the verification items: flame-retardant and dripping → hot wire → room temperature shock → low-temperature shock → assembly and drop → aging retesting.
Next article will discuss communication equipment casings and lamp holder brackets—the challenge lies in dielectric performance and long-term outdoor aging.
About Us
What we deliver is not just a package of materials.
There is also a judgment about materials, a matching physical property table, and a person who can still be found when problems arise.
Ningbo Kelong New Materials Co., Ltd. produces self-produced modified polypropylene (PP) pelletizing, covering three grades of substrates: homopolymer, random copolymer, and impact-resistant copolymer, as well as modification directions such as filling, glass fiber reinforcement, toughening, flame retardancy, low odor and low VOC, weather resistance, and no spraying or scratch resistance; Also engaged in PP resin, sub-brand materials, and large package materials for major petrochemical plants
