改性PP做汽车前端模块与冷却风扇，真正卡人的不是刚性，是耐水解与抗蠕变这两道隐性门槛。这篇把六维工况、短玻纤与长玻纤两条路线、五列选型判据、验证顺序与换料风险一次讲清，并说明哪三种情况这个件不该用改性PP。
"前端模块和冷却风扇，能不能都用同一种玻纤增强料？"
这是展会上被问得最多的一类问题。问的人多半已经知道要上玻纤，只是想确认含量——GF20 还是 GF30，还是直接上长玻纤。但这句话其实问早了。
真正决定这个件成败的，不是玻纤加多少，是它在长期高温水汽和持续旋转载荷下，能不能不水解、不蠕变。 这两项没有写进任何一张常规选型表，却是后期失效的高发区。
下面按工况、路线、判据、验证四层往下拆。
一、工况六维拆解：短时可扛 140℃，长期熬的是冷却液
前端模块和冷却风扇装的位置很特殊——紧贴散热器和发动机舱，既要扛热，又要长期泡在冷却液、水汽、盐雾的环境里。把六个数报齐，方向基本就出来了。
| 维度 | 这个件的真实工况 | 对材料的要求 |
|---|
| 温度 | 短时热负荷可到 140℃（散热器前、发动机舱局部）；长期在热氧+冷热循环下工作 | 短时耐热是门槛，长期热老化才是生死线 |
| 载荷 | 风扇叶离心力随转速上升（动辄每分钟数千转）+ 气流交变疲劳；前端模块集成后承多个附件 | 抗蠕变 + 耐疲劳，不是单纯刚性 |
| 介质 | 乙二醇长效冷却液、水汽、盐雾、机油与制动液飞溅 | 耐水解、耐冷却液是隐性硬线 |
| 寿命 | 整车生命周期（常见按 10 年 / 15 年或 10 万公里级设计） | 长期泡水老化后强度不塌 |
| 外观 | 多数为发动机舱内不可见件，外观可让步 | 表面要求低，重点在尺寸与强度 |
| 合规 | 主机厂材料管控：耐热老化、耐水解、耐冷却液 | 走汽车级基材与稳定体系 |
六个维度里，介质这一维最容易被漏看。很多人选这个件只看刚性和耐热，结果装车跑了一两年，长期泡在冷却液里的件开始老化开裂——根因不在强度，在水解。
一个内行细节：PP 本身吸水率极低（通常低于 0.05%），尺寸不受湿度影响，这本是它在这类件上的天然优势。但"不吸水"不等于"耐水解"——长期高温下，水分子会打断分子链、侵蚀玻纤与基体的界面，让强度悄悄往下掉。所以耐水解是体系的事，不是基材一句话能覆盖的。
二、材料路线对比：短玻纤、长玻纤，各管一段
这个件往下落，材料方向主要收敛到两条玻纤路线，再加一条"什么时候该换材料"的边界。不做"谁更好"的结论，只看分工。
| 路线 | 拿到的能力 | 要付的代价 | 适合哪一段 |
|---|
| 短玻纤 PP-GF20 / GF30 | 刚性、尺寸稳定、降蠕变；因结构设计倾向挠曲的零件用 GF 增强最对症 | 各向异性、熔接线弱、表面浮纤 | 风扇叶、导风罩、结构倾向挠曲的件 |
| 长玻纤 PP-LGF | 拉伸 50–80 MPa、弯曲 80–120 MPa、常温缺口冲击 15–40 kJ/m²、HDT 120–180℃、密度 1.0–1.2 g/cm³、收缩 0.3–0.8%；前端模块集成后可减重约 30% | 对注塑剪切极敏感，保留长度保不住就废了 | 前端模块、脚踏板、尾门板等承力结构件 |
| 金属（钢 / 铝）或其他耐热体系 | 长期 150℃ 以上、极高动平衡、金属级导热 | 成本高、重、工序多 | 超出 PP 边界的工况 |
短玻纤这条线，行业通行做法是 GF20–30 玻纤增强 + 增韧 + 成核，用来降蠕变与收缩；短时热负荷按 140℃ 这一档来校核。它对风扇叶这类"形状要守住、质量分布要匀"的件最贴身。
长玻纤这条线，关键不在玻纤含量，在玻纤保留长度。公开数据里，临界长度是 >3.1 mm——低于它，纤维在受力时会被直接从基体里拔出，强度发挥不出来。对策是用超低熔体粘度 PP 树脂（MFR 约 300 g/10min）降低剪切 + 高结晶 PP 保强度 + 低剪切螺杆，把保留长度留在临界值以上。
这两条路不是"短的好还是长的好"，是件不同、分工不同。 风扇叶怕翘曲和动平衡，短玻纤够用且好控；前端模块要承力和减重，长玻纤才值当。
三、★ 选型判据表：五列，每项都带验证方法
下面这张表是全篇最该收藏的部分。注意第三列"验证方法·标准号"——选这个件最常卡住的不是"看哪个指标"，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 |
|---|
| 短时耐热负荷 | 短时可承受 140℃ 热负荷 | 热变形温度 ISO 75 / GB/T 1634（注明载荷档）+ 短时热态试验 | 热态变形、局部软化 | 玻纤增强 + 热稳定体系 |
| 耐水解 / 耐冷却液 | 乙二醇长效冷却液长期浸泡不开裂 | 冷却液浸泡热老化试验（行业通行，按主机厂企标） | 长期浸泡老化开裂 | 共聚 PP 混增韧体系 + 耐水解稳定剂 |
| 收缩率与各向异性 | 短玻纤 0.5–0.9%；长玻纤 0.3–0.8% | GB/T 17037.4 / ISO 294-4 | 翘曲、装配间隙不均 | 成核剂控收缩、对称浇口 |
| 玻纤保留长度（长玻纤） | >3.1 mm（临界长度） | 玻纤长度显微测定（断面/萃取） | 长度不足、纤维被拔出 | 超低粘度树脂 MFR≈300 + 低剪切螺杆 |
| 弯曲模量 / 刚性 | 长玻纤弯曲 80–120 MPa | GB/T 9341 / ISO 178 | 承力变形 | 玻纤增强档位选配 |
| 常温缺口冲击 | 长玻纤 15–40 kJ/m²；短玻纤增韧体系 | GB/T 1043.1（简支梁） | 低温脆裂（风扇叶） | 增韧体系加量 + 基材档位复核 |
| 动平衡 / 尺寸一致性 | 叶片间质量差在整机动平衡等级内 | 动平衡测试（按整机规格定） | 振动、轴承磨损、叶根疲劳 | 收缩各向异性控住 + 对称充填 |
文字版结论：七项里 耐水解与玻纤保留长度是这个件最该先看的两项，它们都不在常规"强度表"里，却偏偏是后期失效的主因。收缩率不是"料自己的事"，它要和客户的模具一起看——长玻纤收缩动 0.1%，大件上的尺寸差就可能吃满公差带。把这张表当体检单，缺一项不判合格，比样件试出来再回头找原因省钱得多。
四、常见失效与根因：四个现象，四条根因
失效一：高速旋转后蠕变翘曲、动平衡失衡。 根因多在玻纤取向带来的各向异性收缩，以及叶片间充填条件不一致。先查浇口对称性和收缩率，再查料——顺序反了会白换几轮。
失效二：长期高温冷却液浸泡老化开裂。 根因是基体耐水解没做够，没走共聚 PP 混增韧体系。这类开裂往往装车一两年后才暴露，返工成本最高。
失效三：风扇叶低温脆裂。 根因多为增韧体系加量不够、基材档位偏低，或转角处壁厚减薄过快导致应力集中。先查壁厚设计，再查料。
失效四（敢否定一个常见做法）：把翘曲全归因于"模具没做好"。 错。玻纤料的翘曲，根子是纤维排列的方向性——顺流动方向收缩小、垂直方向收缩大，这是路线自带的各向异性，不是模具精度问题。治它是靠含量、浇口、成核剂去平衡，抱怨模具只会把真正该调的料参数漏掉。
还有一个更隐蔽的误区：以为耐水解就是多加玻纤。 耐水解是基体与界面体系的事（共聚 PP 混增韧 + 耐水解稳定剂），玻纤本身不解决水解；界面若没处理好，玻纤与基体的缝隙反而成了进水通道，开裂来得更快。
五、验证顺序：先验什么，后验什么
这一段同行几乎没人写，但它是换料能不能省钱的关键。顺序错了，成本会在最后一步集中爆出来。
`
① 小样物理比对 拉伸 / 弯曲 / 缺口冲击 / 收缩率 / MFR / 玻纤保留长度
↓ 七项都在门限内，才往下走
② 耐水解与耐热老化 乙二醇冷却液浸泡 + 热氧老化（按企标时长）
↓ 这一关不过，后面全部不用做（最易一票否决）
③ 短射试模 看充填是否完整、熔接线在哪、浮纤与动平衡预留
↓ 短射走通，才谈批量
④ 装车 / 整机匹配 间隙、动平衡、蠕变跟踪
↓
⑤ 批量试产 + 客户端验证
`
文字版结论：验证顺序是 小样 → 耐水解老化 → 短射 → 装车匹配 → 批量。耐水解这一关必须在试模之前过，因为它是最可能一票否决、也最晚显形的项；过了它再做模具侧的事，才不会白花试模费。
六、反向诚实：这三种情况，这个件不该用改性PP
前面讲"怎么做"，这里讲"什么时候别做"。这一段对选型判断的价值最高。
| 出现的情况 | 为什么改性PP不合适 | 该往哪走 |
|---|
| 要求长期工作温度 150℃ 以上 | 改性PP 的负荷变形温度上限就在那条线附近，玻纤增强往上抬也有边界 | 换更高耐热的工程塑料体系 |
| 要求极高动平衡精度，且不允许任何蠕变（风扇叶类长期高速旋转件） | PP 的蠕变是结构性的，靠改性只能缓解，做不到零蠕变 | 换金属或专用高精度方案 |
| 要求金属级导热 | PP 本身是隔热材料，导热要靠填充体系另做，且会牺牲力学 | 走金属基或导热专用材料 |
| 要求 A 级表面 + 高玻纤含量 同时 | 玻纤外露与表面质量是天生冲突 | 结构件走玻纤，表面件另选 |
规律很清楚：凡是"两个方向相反的要求同时出现"，就说明这个件不该用 PP 硬撑。 遇到这种需求，我们的做法是先把这条讲清楚，再谈有没有折中空间——硬接下来的单子，最后都要用返工和索赔还回去。
七、换料要动什么：一张先看再动的清单
决定试改性PP之前，这张表建议先过一遍。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"。
| 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，长件上尤其敏感 | 尺寸超差，装配间隙对不上 |
| 浇口与排气 | 玻纤料的流动差异是否需要改浇口位置与数量 | 充填不足、熔接线落在受力处 |
| 料温与模温 | 长玻纤料对剪切更敏感，工艺窗口不同 | 玻纤剪断、保留长度不足、浮纤 |
| 干燥 | 玻纤体系按具体牌号定，多数需控水 | 银丝、气泡、界面劣化 |
| 保压与脱模 | 收缩差异带来变形与顶白 | 变形、顶出拉伤 |
| 色差 | 发动机舱内件多不可见，外观可让步 | 可见件批次色差争议 |
| 验证顺序 | 小样 → 耐水解老化 → 短射 → 装车匹配 | 风险全部压到最后一步集中爆发 |
文字版结论：换料要动的是模具、工艺、色差三块，其中最该先谈的是验证顺序。跳过小样直接试模，等于把成本提前花出去；跳过耐水解老化直接批量，一次失败就是整批在客户端暴露。
八、一页纸汇报表（可以直接贴进 PPT）
| 场景 | 推荐路线 | 关键指标 | 验证标准 | 需先确认的条件 |
|---|
| 冷却风扇叶 | 短玻纤 PP-GF20/GF30 + 增韧 + 成核 | 收缩 0.5–0.9%；常温缺口冲击留余量 | GB/T 17037.4、GB/T 1043.1 | 转速区间、最低使用温度、模具现定收缩率 |
| 前端模块 | 长玻纤 PP-LGF（保留长度 >3.1 mm） | 弯曲 80–120 MPa；HDT 120–180℃；收缩 0.3–0.8% | ISO 178、ISO 75、玻纤长度测定 | 集成承力件清单、减重目标 |
| 散热器水室 / 膨胀箱 | 共聚 PP 混增韧体系 | 耐乙二醇冷却液、耐水解、耐热老化 | 冷却液浸泡热老化（企标） | 冷却液型号、工作温度区间 |
| 发动机舱内高温件 | 短玻纤增强 + 热稳定体系 | 短时 140℃ 热负荷 | GB/T 1634（注明载荷档） | 长期温度是否逼近 PP 上限 |
文字版结论：这张表的作用是让技术员能把结论直接往上报，不必重新组织语言。判断标准只有一条——客户拿这张表，能不能在一次会议里把材料方向定下来。
九、这个件上最容易出问题的，往往不是料
行业上这类件最常出的早期失效，集中在两类：一是长期泡在冷却液里老化开裂，二是风扇叶高速旋转后蠕变翘曲、动平衡失衡。公开资料里，空调风道 / 导风罩 / 风扇叶这一行的通行路径是 GF20–30 玻纤增强 + 增韧 + 成核，用来降蠕变与收缩；长玻纤结构件（前端模块 / 脚踏板 / 尾门板）则要求玻纤保留长度 >3.1 mm 临界长度，拉伸 50–80 MPa、弯曲 80–120 MPa、HDT 120–180℃、收缩 0.3–0.8%，前端模块集成后可减重约 30%。散热器水室 / 膨胀箱这一类更强调耐乙二醇长效冷却液、耐水解、耐热老化，走共聚 PP 混增韧体系。
公开的判据写得很清楚：短时热负荷按 140℃ 校核（ISO 75 / GB/T 1634，必须注明载荷档）；耐水解按冷却液浸泡热老化试验判定；长玻纤的强度发挥，取决于玻纤保留长度是否过临界值，对策是超低熔体粘度 PP 树脂（MFR 约 300 g/10min）降低剪切 + 高结晶 PP 保强度 + 低剪切螺杆。
行业通行的做法，是把基材档位、玻纤含量、增韧体系、耐水解稳定剂一起定——单看任何一项都没意义。关键不在"谁的料更强"，在基材、增强、界面、稳定体系四件事能不能同时对上。
宁波市科隆新材料有限公司自产改性聚丙烯（PP）造粒，这个件上常供的是玻纤增强与耐水解方向的粒子，按件的热负荷位置、转速区间和冷却液环境给到对应的基材档位与改性方向，主要用来解决上面说的"长期泡水开裂"和"旋转蠕变翘曲"这两件事；配方按件的工况调，可以配合做小样比对与试模，件级客户多品种小批量的需求也能接。
常见问答
问：短玻纤和长玻纤，这个件该上哪条？
答：看件怕什么。风扇叶怕翘曲和动平衡，短玻纤 GF20–30 够用且好控；前端模块要承力和减重，长玻纤才值当。不是"长的一定好"，是保留长度够不够、件要不要承力。
问：耐水解是不是多加玻纤就行？
答：不是。耐水解是基体与界面体系的事（共聚 PP 混增韧 + 耐水解稳定剂），玻纤本身不解决水解；界面没处理好，反而成了进水通道。这条在选型时最容易被漏看。
| 工况 | 关键判据 | 科隆常规供应 |
|---|
| 冷却风扇叶 | 收缩 0.5–0.9%；常温缺口冲击；动平衡预留 | 短玻纤 PP-GF20/GF30 + 增韧 + 成核方向 |
| 前端模块 | 玻纤保留长度 >3.1 mm；弯曲 80–120 MPa | 长玻纤 PP-LGF 方向 |
| 散热器水室 / 膨胀箱 | 耐乙二醇冷却液、耐水解、耐热老化 | 共聚 PP 混增韧耐水解方向 |
想提醒一句：件出问题，最常见的错法是先换料。蠕变、开裂、动平衡失衡——每一条的原因都不止一个。先定位，再换料；顺序反了，往往换了几轮还在原地。
十、最后说三句
第一，这个件真正卡人的是耐水解与抗蠕变，不是刚性。 六维工况里介质这一维最容易被漏看，而它偏偏是后期失效的高发区。
第二，长玻纤的强度不是加出来的，是留出来的。 保留长度过不了 3.1 mm 临界值，纤维就被拔出，含量再加也没用；短玻纤和长玻纤是分工，不是高低。
第三，验证顺序比验证项更重要。 小样 → 耐水解老化 → 短射 → 装车匹配，耐水解那一关必须放在试模之前。
下一篇讲仪表板骨架——那个件最怕的不是刚性不够，是气味和尺寸同时卡你。
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最麻烦的询盘是这一句：料没变，件出问题了。
料确实没变，变的是批次、干燥、模温、模具磨损，或者为了省钱动的某一项。参数是慢慢飘的，问题是一夜之间出来的。
宁波市科隆新材料有限公司，改性聚丙烯（PP）粒子与 PP 树脂现货，覆盖填充、增强、增韧、阻燃、低气味、耐候、免喷涂等方向。
Modified PP is used for automotive front-end modules and cooling fans. The real challenge is not rigidity, but hydrolysis resistance and creep resistance, these two hidden thresholds. This article explains the six-dimensional operating conditions, the two paths of short glass fiber and long glass fiber, the five sets of selection criteria, the verification sequence, and the risks of material substitution all at once, and also highlights the three situations where this part should not use modified PP.
Can the front-end module and the cooling fan both use the same type of glass fiber reinforced material?
This is the most frequently asked type of question at the exhibition. Most of the people asking already know they want to use glass fiber, they just want to confirm the content — GF20 or GF30, or to go straight to long glass fiber. But in fact, this question is asked too early.
What truly determines the success or failure of this component is not how much fiberglass is added, but whether it can resist hydrolysis and creep under long-term high-temperature moisture and continuous rotational load. These two factors are not listed on any standard selection tables, yet they are the areas where failures frequently occur later.
Below, break it down layer by layer according to operating conditions, routes, criteria, and verification.
1. Six-Dimensional Breakdown of Working Conditions: Can withstand 140℃ for a short time, but for the long term, it’s the coolant that bears the load
The placement of the front module and cooling fan is very special—they are right next to the radiator and engine compartment, needing to withstand heat while being constantly exposed to coolant, moisture, and salt spray. Once the six figures are aligned, the direction basically becomes clear.
| Dimension | The real working condition of this part | Requirements for the materials |
|---|
| Temperature | Short-term heat load can reach 140°C (in front of the radiator, local areas of the engine compartment); long-term operation under hot oxygen and thermal cycling | Short-term heat resistance is the threshold, while long-term thermal aging is the line between life and death. |
| Load | The centrifugal force on the fan blades increases with the rotational speed (often several thousand revolutions per minute), causing alternating fatigue on the airflow; after the front-end module is integrated, it bears multiple attachments. | Creep-resistant and fatigue-resistant, not simply rigid |
| Medium | Long-life ethylene glycol coolant, water vapor, salt spray, motor oil, and brake fluid splashes | Hydrolysis-resistant and coolant-resistant are hidden hard lines |
| Lifespan | The entire vehicle lifecycle (commonly designed for 10 years / 15 years or 100,000 kilometers) | After long-term soaking in water, the strength does not collapse. |
| Appearance | Mostly parts that are not visible in the engine compartment, appearance can be compromised | Low surface requirements, focus on size and strength |
| Compliance | OEM Material Control: Heat Aging Resistance, Hydrolysis Resistance, Coolant Resistance | Automotive-grade substrates and stable systems |
Among the six dimensions, the medium dimension is the easiest to overlook. Many people choose this part only based on rigidity and heat resistance, but after one or two years of running in a vehicle, the parts that have been soaked in coolant for a long time start to age and crack—the root cause is not strength, but hydrolysis.
An insider detail: PP itself has an extremely low water absorption rate (usually below 0.05%), and its dimensions are not affected by humidity, which is naturally an advantage for this type of part. But 'does not absorb water' does not mean 'resistant to hydrolysis'—under prolonged high temperatures, water molecules can break molecular chains and erode the interface between glass fibers and the matrix, quietly reducing strength. Therefore, hydrolysis resistance is a matter of the system, not something that can be covered by a single statement about the base material.
2. Comparison of material routes: short glass fiber, long glass fiber, one section for each tube
As this piece falls down, the material direction mainly converges to two fiberglass routes, plus a boundary of 'when to change the material.' We don't make any conclusions about 'which is better,' only looking at the division of labor.
| Route | Acquired ability | The price to pay | Suitable for which section |
|---|
| Short Glass Fiber PP-GF20 / GF30 | Rigid, dimensionally stable, reduced creep; for parts that tend to flex due to structural design, GF reinforcement is most appropriate. | Anisotropy, weld line weakness, surface floating fibers | Fan blades, air guide shrouds, components prone to structural deflection |
| Long Glass Fiber PP-LGF | Tensile strength 50–80 MPa, bending strength 80–120 MPa, notch impact at room temperature 15–40 kJ/m², HDT 120–180℃, density 1.0–1.2 g/cm³, shrinkage 0.3–0.8%; the front-end module can reduce weight by about 30% after integration | Extremely sensitive to injection molding shear; if the retained length cannot be maintained, it will be wasted. | Load-bearing structural components such as the front module, pedal board, and tailgate panel |
| Metal (steel / aluminum) or other heat-resistant systems | Long-term above 150℃, extremely high dynamic balance, metal-grade thermal conductivity | High cost, heavy, many processes | Operating conditions beyond the PP boundary |
For the short glass fiber line, the industry practice is to use GF20–30 glass fiber reinforcement, toughening, and nucleation to reduce creep and shrinkage; the short-term thermal load is checked at the 140°C level. It is most suitable for parts like fan blades, where the shape must be maintained and the mass distribution must be uniform.
For the long glass fiber line, the key is not the glass fiber content, but the retained length of the glass fiber. According to published data, the critical length is >3.1 mm—below this, the fibers will be pulled directly out of the matrix when stressed, and the strength cannot be realized. The solution is to use ultra-low melt viscosity PP resin (MFR about 300 g/10min) to reduce shear, high-crystallinity PP to maintain strength, and a low-shear screw to keep the retained length above the critical value.
These two paths are not about 'is short better or long better'; they are different things with different roles. Fan blades are concerned with warping and dynamic balance, and short fiberglass is sufficient and easier to control; the front-end module needs to bear load and reduce weight, so long fiberglass is worthwhile.
3. ★ Selection Criteria Table: five columns, each item comes with a verification method
The table below is the part of the whole article most worth saving. Pay attention to the third column "Verification Method · Standard Number" — what usually gets stuck when choosing this item is not "which indicator to check," but "what to measure with and how much counts as passing."
| Indicator | Threshold (typical) | Verification Method · Standard Number | Common Failures | Common solution |
|---|
| Short-term heat-resistant load | Can withstand a short-term thermal load of 140℃ | Heat deflection temperature ISO 75 / GB/T 1634 (specify load level) Short-term heat test | Hot deformation, local softening | Glass fiber reinforced thermal stable system |
| Hydrolysis resistant / Coolant resistant | Ethylene glycol long-life coolant does not crack after long-term soaking | Coolant Soak Thermal Aging Test (industry standard, according to OEM company standard) | Long-term soaking, aging, and cracking | Compatibilized PP Toughened System Hydrolysis Stabilizer |
| Shrinkage Rate and Anisotropy | Short glass fiber 0.5–0.9%; long glass fiber 0.3–0.8% | GB/T 17037.4 / ISO 294-4 | Warping and uneven assembly clearance | Nucleating agent controlled shrinkage, symmetrical gate |
| Glass fiber retained length (long glass fiber) | >3.1 mm (critical length) | Microscopic measurement of fiberglass length (cross-section/extraction) | Insufficient length, fibers pulled out | Ultra-low viscosity resin MFR≈300 Low-shear screw |
| Bending modulus / Rigidity | Long glass fiber bending 80–120 MPa | GB/T 9341 / ISO 178 | Stress deformation | Glass fiber reinforced gear selection |
| Room temperature notch impact | Long glass fiber 15–40 kJ/m²; short glass fiber toughened system | GB/T 1043.1 (Simply Supported Beam) | Low-temperature cracking (fan blade) | Increase toughening system dosage Substrate grade verification |
| Dynamic Balance / Dimensional Consistency | The mass difference between the blades is within the overall dynamic balance grade | Dynamic balance test (according to the complete machine specifications) | Vibration, bearing wear, root fatigue | Shrinkage anisotropy control Symmetrical filling |
Textual Conclusion: Among the seven items, hydrolysis resistance and glass fiber retention length are the two that should be checked first for this part. They are not included in the standard 'strength table,' yet they are the main causes of later failures. Shrinkage rate is not 'just the material's business'; it needs to be considered together with the customer's mold — a 0.1% change in long glass fiber shrinkage can consume the full tolerance on large parts. Treat this table like a medical check-up form; missing an item should result in a failing judgment. It's much more cost-effective than testing a sample first and then going back to find the reason.
4. Common Failures and Root Causes: Four Phenomena, Four Root Causes
Failure 1: Creep warping and dynamic imbalance after high-speed rotation. The root cause is mostly the anisotropic shrinkage caused by the orientation of the glass fiber, as well as inconsistent filling conditions between the blades. First, check the symmetry of the gate and the shrinkage rate, then check the material—if the order is reversed, you'll go through several rounds for nothing.
Failure 2: Long-term soaking in high-temperature coolant causes aging and cracking. The root cause is that the matrix hydrolysis resistance was insufficient, and it did not use a copolymerized PP blend toughening system. This type of cracking often only becomes apparent one to two years after the vehicle is put into use, and the rework cost is the highest.
Failure 3: Fan blades become brittle and crack at low temperatures. The root cause is mostly insufficient toughening system, the base material grade being too low, or stress concentration caused by wall thickness thinning too quickly at corners. First, check the wall thickness design, then check the material.
Myth 4 (dare to deny a common practice): Attributing all warpage to 'the mold wasn't made well.' Wrong. The root of warpage in fiberglass materials is the directional arrangement of the fibers—shrinkage is small in the flow direction and large in the perpendicular direction. This is the inherent anisotropy of the material, not a mold precision issue. The solution lies in balancing it with content, gates, and nucleating agents; blaming the mold will only overlook the material parameters that truly need adjustment.
There is also a more subtle misconception: thinking that hydrolysis resistance just means adding more fiberglass. Hydrolysis resistance is related to the matrix and interface system (copolymerized PP mixed toughening and hydrolysis stabilizers); fiberglass itself does not solve hydrolysis. If the interface is not properly treated, the gaps between the fiberglass and the matrix can actually become water channels, causing cracks to appear faster.
5. Verification sequence: what is a priori, what is a posteriori
Almost no one in the industry writes this part, but it is the key to whether material changes can save money. If the order is wrong, the costs will concentrate and explode at the final step.
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① Sample physical comparison: tensile / bending / notched impact / shrinkage / MFR / glass fiber retention length
↓ Only if all seven items are within the threshold, proceed further
② Hydrolysis resistance and heat aging resistance Soaked in ethylene glycol coolant Hot oxygen aging (according to enterprise standard duration)
↓ If you don't pass this level, you don't need to do the rest (the easiest to veto)
③ Short shot mold trial Check if the filling is complete, where the weld lines are, floating fibers, and reserve for dynamic balance
↓ Only after the short-range shot works can we talk about mass production
④ Loading / Complete machine matching Clearance, dynamic balance, creep tracking
↓
⑤ Batch trial production Client-side verification
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Text version conclusion: The verification sequence is: sample → hydrolysis aging resistance → short shot → molding matching → mass production. The hydrolysis resistance step must be completed before mold trials, because it is the most likely to result in a total rejection and also the latest to show issues; once it is passed, then tasks on the mold side can be done, so the mold trial costs are not wasted.
6. Reverse Honesty: In these three situations, this part should not use modified PP
Earlier we talked about 'how to do it'; here we talk about 'when not to do it.' This section has the highest value for selection and judgment.
| The situation that occurred | Why is modified PP not suitable | Which way should I go? |
|---|
| Requires a long-term operating temperature above 150℃ | The upper limit of the heat deflection temperature of modified PP is around that line, and even glass fiber reinforcement has its boundary when raised. | Switch to a higher heat-resistant engineering plastic system |
| Requires extremely high dynamic balance accuracy and does not allow any creep (such as long-term high-speed rotating parts like fan blades) | The creep of PP is structural, and can only be alleviated through modification; zero creep cannot be achieved. | Change to metal or specialized high-precision solution |
| Requires metal-grade thermal conductivity | PP itself is an insulating material; thermal conductivity relies on an additional filler system, which will also compromise the mechanical properties. | Use metal-based or thermal-conductive special materials |
| Require A-grade surface and high glass fiber content at the same time | Exposed fiberglass and surface quality are inherently in conflict | Structural parts use fiberglass, surface parts choose separately |
The pattern is very clear: whenever 'requirements in two opposite directions appear at the same time,' it indicates that this part should not be forced with PP. When faced with such a demand, our approach is to first clarify this point, and then discuss whether there is room for compromise—orders that are forcibly accepted in the end all have to be returned through rework and claims.
7. What to touch when changing materials: a checklist to look at before you act
Before deciding to try modifying PP, it is recommended to go through this table first. The customer's real concern is often not performance, but 'whether I need to change my current mold and process'.
| Items to move | What needs to be confirmed | What will happen if I don't do it? |
|---|
| Mold shrinkage rate | The difference in shrinkage rate of the new material compared to the original plan is particularly sensitive in long parts | The dimensions are out of tolerance, and the assembly gaps do not align. |
| Gate and Venting | Does the difference in the flow of fiberglass material require changing the gate position and number? | Insufficient filling, weld line located at the stress area |
| Material Temperature and Mold Temperature | Long glass fiber materials are more sensitive to shear, and the process window is different. | Glass fiber cut off, insufficient retained length, floating fibers |
| Dry | The fiberglass system is determined according to the specific grade, and most require water control. | Silver threads, bubbles, interface degradation |
| Pressure Holding and Demolding | Shrinkage differences cause deformation and whitening on the surface | Deformation, extrusion strain |
| Color difference | Many components inside the engine compartment are not visible, so the appearance can be compromised. | Dispute over batch color differences in visible parts |
| Verification sequence | Sample → Hydrolysis aging resistance → Short shot → Vehicle loading match | All the risks are concentrated to explode at the final step |
Text version of the conclusion: Changing materials involves three aspects: mold, process, and color difference, among which the verification sequence should be discussed first. Skipping small samples and directly trying the mold is equivalent to spending the cost in advance; skipping hydrolysis aging tests and going directly to mass production means that a single failure will expose the entire batch to the client.
8. One-page report sheet (can be directly pasted into PPT)
| Scene | Recommended Route | Key indicators | Verification Standard | Conditions that need to be confirmed first |
|---|
| Cooling fan blade | Short glass fiber PP-GF20/GF30 Toughening Nucleation | Shrinkage 0.5–0.9%; leave allowance for notch impact at room temperature | GB/T 17037.4, GB/T 1043.1 | Speed range, minimum operating temperature, current mold shrinkage rate |
| Frontend module | Long glass fiber PP-LGF (retained length >3.1 mm) | Bending 80–120 MPa; HDT 120–180℃; Shrinkage 0.3–0.8% | ISO 178, ISO 75, Glass Fiber Length Determination | List of integrated load-bearing components, weight reduction target |
| Radiator Water Chamber / Expansion Tank | Co-polymerized PP toughened blend system | Ethylene glycol-resistant coolant, hydrolysis-resistant, heat aging-resistant | Coolant Soak Thermal Aging (Enterprise Standard) | Coolant model, operating temperature range |
| High-temperature components in the engine compartment | Short glass fiber reinforced thermal stable system | Short-term 140℃ thermal load | GB/T 1634 (Specify Load Range) | Is the long-term temperature approaching the PP limit |
Text version conclusion: The purpose of this table is to allow technicians to report conclusions directly without having to reorganize their wording. There is only one criterion for judgment—whether the client can use this table to finalize the direction of the materials in one meeting.
9. The part of this piece that is most prone to problems is often not the material.
In the industry, the most common early failures for this type of part fall into two categories: first, long-term immersion in coolant leading to aging and cracking; second, fan blades experiencing creep warping and imbalance after high-speed rotation. According to publicly available information, the standard process for air conditioning ducts / air guides / fan blades is GF20–30 glass fiber reinforcement, toughening, and nucleation, aimed at reducing creep and shrinkage. Long glass fiber structural parts (front modules / pedal panels / tailgate panels) require the glass fiber to retain a length >3.1 mm (critical length), with tensile strength of 50–80 MPa, flexural strength of 80–120 MPa, HDT of 120–180°C, and shrinkage of 0.3–0.8%. After integration, the front module can reduce weight by about 30%. For radiator water tanks / expansion tanks, more emphasis is placed on long-term resistance to ethylene glycol coolant, hydrolytic stability, and heat aging resistance, using a copolymer PP toughened system.
The public criteria are clearly written: short-term heat load is checked at 140°C (ISO 75 / GB/T 1634, the load range must be specified); hydrolysis resistance is determined by a coolant immersion thermal aging test; the strength performance of long glass fibers depends on whether the retained fiber length exceeds the critical value. The countermeasures are ultra-low melt viscosity PP resin (MFR about 300 g/10min) to reduce shear, high-crystallinity PP to maintain strength, and low-shear screws.
The common practice in the industry is to determine the grade of the substrate, the glass fiber content, the toughening system, and the hydrolysis stabilizer together—looking at any single one alone is meaningless. The key is not 'whose material is stronger,' but whether the four aspects of substrate, reinforcement, interface, and stabilizing system can all align simultaneously.
Ningbo Cologne New Materials Co., Ltd. produces modified polypropylene (PP) pellets. The products commonly supplied for this part are glass fiber reinforced and hydrolysis-resistant pellets. The corresponding base material grades and modification directions are given according to the part's thermal load, speed range, and coolant environment. These pellets are mainly used to address the aforementioned issues of 'long-term water soaking cracking' and 'rotational creep warping.' The formulation can be adjusted according to the part's operating conditions, and small sample comparisons and mold testing can be performed. It can also meet the demands of customers for small batches of multiple varieties at the part level.
Frequently Asked Questions
Q: Short glass fiber and long glass fiber, which one should this part go on?
Answer: What’s there to be afraid of? Fan blades are afraid of warping and dynamic imbalance; short glass fiber GF20–30 is enough and easy to control. The front-end module needs to bear load and reduce weight, so long glass fiber is worthwhile. It’s not that 'long is necessarily better'; it’s about whether the retained length is sufficient and whether the part needs to bear load.
Question: For hydrolysis resistance, is it just a matter of adding more glass fiber?
Answer: No. Hydrolysis resistance is a matter of the matrix and the interface system (copolymerized PP with enhanced toughening and hydrolysis stabilizer); the glass fiber itself does not solve hydrolysis. If the interface is not properly treated, it can actually become a water entry channel. This is the easiest aspect to be overlooked during selection.
| Operating condition | Key criterion | Cologne regular supply |
|---|
| Cooling fan blade | Shrinkage 0.5–0.9%; notch impact at room temperature; balancing allowance | Short glass fiber PP-GF20/GF30 Toughened Nucleation direction |
| Frontend module | Glass fiber retention length >3.1 mm; bending 80–120 MPa | Long glass fiber PP-LGF orientation |
| Radiator Water Chamber / Expansion Tank | Ethylene glycol-resistant coolant, hydrolysis-resistant, heat aging-resistant | Copolymer PP toughened and hydrolysis-resistant direction |
I want to give a reminder: when there is a problem with a part, the most common mistake is to replace the material first. Creep, cracking, imbalance in dynamic balance—each of these issues has more than one cause. First identify the cause, then replace the material; if you reverse the order, you often end up replacing materials several times without solving the problem.
Ten, Lastly, Say Three Sentences
First, what really traps people about this part is hydrolysis resistance and creep resistance, not rigidity. In the six-dimensional working conditions, the medium dimension is the easiest to be overlooked, yet it happens to be the high-risk area for later failures.
Second, the strength of long glass fibers is not added on, it is preserved. If the retained length does not exceed the critical value of 3.1 mm, the fibers will be pulled out, and increasing the content will be useless; short glass fibers and long glass fibers have different roles, not higher or lower status.
Third, the verification sequence is more important than the verification items. Sample → Hydrolysis aging resistance → Short shot → Loading match, the hydrolysis resistance step must be placed before mold testing.
The next one talks about the dashboard skeleton—the thing that's most feared is not lack of rigidity, but being constrained by both smell and size at the same time.
About Us
The most troublesome inquiry is this one: the material hasn't changed, but the part has a problem.
The material really hasn't changed; what has changed are the batch, drying, mold temperature, mold wear, or one specific thing altered to save money. The parameters drift slowly, but the problem appears overnight.
Ningbo Kolon New Materials Co., Ltd. offers modified polypropylene (PP) pellets and PP resin in stock, covering directions such as filling, reinforcement, toughening, flame retardant, low odor, weather resistance, and paint-free.
