很多人问"改性尼龙怎么选"，但真正的卡点不是"选"，是"问"。
一个很典型的情形：客户开口就要"耐磨的尼龙"。追问三句之后发现——他要的其实不是耐磨。是那个件在 120℃ 下尺寸不稳，齿轮啮合间隙变了，被现场判断成"磨损"。真正要解决的是热变形和尺寸问题，跟耐磨半点关系没有。
按他原话去选料，试三模也不会对。
这篇不讲材料，只讲流程。五步法，从工况到牌号，每一步都有具体动作。
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① 定工况 → ② 定失效模式 → ③ 定基材 → ④ 定改性体系 → ⑤ 打样验证
`
前三步定方向，第四步排序，第五步验证。九成人卡在第一步，也栽在第二步。
第一步：定工况——六个要素，缺一个都会走偏
工况不是"用在什么地方"，是六个数。少问一个，后面就会返工一次。
要素一 · 温度——必须问三个数，不是问一个
这是最容易含糊的地方。别问"多少度"，要拆成三个问题：
1. 长期连续使用温度是多少？（这个数决定基材等级）
2. 有没有短时峰值？多高、持续多久？（决定要不要往上跳一档）
3. 环境是干热还是湿热？（决定要不要耐水解体系）
判断时看 RTI（相对热指数），不要看 TDS 上的峰值温度。 TDS 写 200℃，说的是"能扛几分钟"；RTI 才告诉你"能扛几年"。
要素二 · 时间——连续、间歇，还是循环
连续 120℃ 和每天开 2 小时的 120℃，材料要求完全不同。前者要热稳定体系，后者可能普通料就够。
要素三 · 载荷——分清是静载还是动载
这一条直接决定选"增强"还是"增韧"，两者在配方里是对冲的：
静载结构件（支架、端板）→ 刚性优先 → 高玻纤
反复冲击（外壳、护罩）→ 韧性优先 → 增韧体系
长期疲劳（齿轮、卡扣、弹簧片）→ 看疲劳强度，不看拉伸强度，这是两个数据
要素四 · 介质——接触什么，多热，多久
光问"接触什么"不够，要问"多热、多久"。
80℃ 的热水对 PA6/PA66 是水解环境；常温的水不是。同一个介质，温度一变，材料就得换。
要素五 · 精度——公差是多少
公差 ±0.5mm 和 ±0.05mm，选料完全是两个逻辑。后者必须把吸水率和收缩率各向异性算进去。
要素六 · 寿命——设计用几年
一年期的件和十年期的件，稳定性体系的投入不是一个量级。户外 25 年的件，必须上完整耐候体系。
六个要素汇总成一张表：
| 要素 | 必问的问题 | 影响什么 |
|---|
| 温度 | 长期连续？短时峰值？干热还是湿热？ | 基材等级（最重要） |
| 时间 | 连续 / 间歇 / 循环？ | 热稳定体系 |
| 载荷 | 静载 / 冲击 / 疲劳？ | 增强还是增韧 |
| 介质 | 接触什么？多热？多久？ | 耐水解、耐化学 |
| 精度 | 公差等级？ | 长碳链、PA9T、收缩率控制 |
| 寿命 | 设计几年？ | 老化体系投入 |
第一步的真正难点：客户自己往往不知道这六个数。他不知道长期温度是多少——因为没测过。
这时候你的价值就出来了：帮他问出来。问出来的过程，也就是他信任你的过程。
第二步：定失效模式——这一步决定了能不能选对
大部分人跳过这步，直接问"我要什么性能"。
这个问法是错的。因为它没有唯一答案。 "强度高一点好还是低一点好"——当然高一点好，但代价你接受吗？
正确问法是反过来：这个件最怕怎么坏？
这个问题有唯一答案。而且答案一旦明确，材料方向基本就定了。
10 类失效模式，倒推材料对策
| 失效模式 | 现场表现 | 根因方向 | 材料对策 |
|---|
| 热变形 | 高温下软化、装配失效 | 耐热等级不够 | 升级基材（PA66→PA46/PA6T）、提高 GF 含量 |
| 常温脆断 | 受冲击直接裂 | 韧性不足 | 弹性体增韧体系 |
| 低温脆断 | -20℃ 以下裂 | 低温韧性不足 | 核壳结构增韧（普通弹性体在低温失效） |
| 尺寸超差 | 装配不上、间隙变化 | 吸水膨胀 / 收缩 | 长碳链或 PA9T、控制模温与后处理 |
| 翘曲变形 | 长条件扭曲 | 玻纤各向异性 | 矿物填充、降 GF 含量、改浇口位置 |
| 磨损失效 | 表面磨损、尺寸变小 | 耐磨不足 或对偶件不匹配 | PTFE/MoS₂ 体系 + 检查对偶件 |
| 老化脆化 | 用一年后变脆 | 热氧老化 / UV | 热稳定体系、抗 UV 体系 |
| 水解降解 | 高温水环境强度跌 | 水解断链 | 耐水解体系，或换长碳链基材 |
| 电气失效 | 漏电起痕、灼热丝不达标 | 绝缘 / 阻燃不足 | 提高 CTI、换无卤体系 |
| 熔接线开裂 | 熔接处断裂 | 工艺问题 | 提高模温、改浇口——不是换料 |
这张表最值钱的地方在最后一行
10 类失效里，至少有一类根本不是材料问题。
熔接线开裂、浮纤、缩痕、银纹——这些是工艺和模具问题。很多人一看到件坏了就换料，换了三块料问题还在，就是因为找错了方向。
判断口诀很简单：如果是"每一模都坏、坏在同一个位置"，先查工艺和模具；如果是"批次之间时好时坏"，才优先怀疑材料。
行业里的一条实感：大量"材料问题"最后被证明是工艺问题，而大量"工艺问题"的根源是设计时没考虑材料特性。 我们这边被问得最多的问题，答案其实都不在"选哪个料"上。 第一句往往是"这个料多少钱"，而不是"这个件在什么温度下用"。也有客户拿着一个进口牌号来问"能不能替代"，却说不清件受什么力、接触什么介质。他要的是"一个能用的料"，给出的却是"一组不知道重不重要的指标"。
举个最典型的例子。 黑色件表面发白发毛、喷不上漆，客户第一反应是"玻纤加多了，给我换个低玻纤的料"。
把模温表一查——80℃。提到 115℃，同一批料、同一个模具，浮纤基本消失。
原理不复杂：熔体在模腔里是"喷泉式流动"，玻纤被推到流动前沿，一碰到温度低的模壁就被瞬间冻住，树脂来不及把它包回去。玻纤被你加进去，又被你冻在了表面上。
这不是配方的事，是模温的事。 但它会以"材料问题"的身份找上门来。
用失效模式反推：两个实例
实例 A：客户说"要耐磨"
追问 → 件在 120℃ 环境下尺寸变化，齿轮间隙变大，被判断成磨损。
真实失效模式：热变形 + 尺寸超差，不是磨损。
对策：提高基材耐温（PA46）或提高 GF 含量提升热变形温度，加尺寸稳定体系。不是加 PTFE。
实例 B：客户说"要更硬"
追问 → 低温环境下卡扣断裂。
真实失效模式：低温脆断。
对策：核壳结构增韧。而且要注意——"更硬"和"低温不断"是相反的方向，加玻纤只会更脆。
这就是为什么第二步不能跳过。 客户说的性能诉求，往往不是他真实的失效模式。
第三步：定基材——用四把尺子筛出两三个候选
工况和失效模式清楚了，基材范围会很自然地收窄。
先按温度分档（第一道筛子）
| 长期使用温度 | 基材方向 | 说明 |
|---|
| ≤120℃ | PA6、PA66 | 通用主力区间 |
| 120-150℃ | PA66 + 热稳定体系 | 加铜盐或有机热稳定 |
| 150-170℃ | PA46、PA6T、PA9T、PA10T | 高温尼龙区间 |
| 短期峰值 200℃+ / 过回流焊 | PA6T、PA9T、PA4T | SMT 件必选 |
| 长期 >200℃ | 跳出尼龙体系 | PPS / PEEK |
再按工况组合微调（第二道筛子）
| 工况组合 | 首选基材 |
|---|
| 常温 + 一般精度 + 通用结构件 | PA6（性价比最高） |
| 中温 + 结构受力 + 尺寸稳定 | PA66-GF30 |
| 高精度 + 高湿环境 | PA612 / PA12（吸水低） |
| 热水 / 冷却液长期接触 | PA612 / PA1010（耐水解） |
| 耐回流焊 + 薄壁充填 | PA6T / PA9T |
| 高温 + 高精密（公差 ±0.05） | PA9T（高温尼龙里吸水最低） |
| 高温 + 耐磨承载 | PA46（耐磨和流动性最好，但吸水最高） |
| 低翘曲 + 外观件 | PA/ABS 合金 |
| 需要透明 | 透明尼龙 |
| 极端长期高温 | 不选尼龙，换 PPS / PEEK |
这一步的输出应该是 2-3 个候选基材，不是一个。 一个候选意味着你没有比较余地，后面工艺或成本出问题就没退路。
第四步：定改性体系——不是全都要，是排序
基材定了，接下来是把要求落到改性体系上。这一步的核心动作是排序。
动作一：列出全部要求
把客户提的每一条都写下来，包括他自己没说但工况里隐含的：
增强（刚性、耐蠕变）
增韧（冲击、低温）
阻燃（UL94 / GWIT / CTI）
耐热（热稳定体系）
耐磨（自润滑）
耐候（UV）
尺寸稳定（低翘曲）
高流动（薄壁）
导电 / 导热 / 食品级……
通常会列出 5-8 条。这很正常。
动作二：用冲突矩阵找出哪几条打架
改性方向之间不是加法关系。常见的强冲突组合：
| 冲突组合 | 冲突原因 | 出路 |
|---|
| 增强 ✖ 增韧 | 玻纤降韧性，增韧剂降刚性 | 换长玻纤，或改结构减薄加筋 |
| 增强 ✖ 阻燃 | 玻纤要低粘度，阻燃剂拉高粘度，双双压冲击 | 找成熟复合牌号，成本上浮 |
| 增强 ✖ 高流动 | 玻纤本身就增粘 | 减壁厚设计或降 GF 含量 |
| 阻燃 ✖ 高流动 | 阻燃剂加量必然增粘 | 问：是料不行还是壁厚太激进 |
| 阻燃 ✖ 增韧 | 两者抢配方空间 | 高成本方案，需评估性价比 |
| 增韧 ✖ 高刚性 | 方向相反 | 明确优先级，不能都要 |
动作三：排序——问一个问题就够
把这句问出来，方案基本就定了：
"这几条里，哪一条是不满足就报废的？哪一条是差一点也能接受的？"
然后按"不能妥协 → 可以妥协"排成一条线。配方永远是在解这道排序题，不是凑齐所有要求。
举个真实的排序逻辑：
客户要"GF30 + V0 + CTI 600V + 高韧性 + 便宜"。
排序结果是：V0 和 CTI 600V 是安规硬要求（不满足直接报废）→ GF30 是结构要求（可微调到 GF25）→ 韧性是"别太脆就行"（可接受保留 60%）→ 便宜排在最后。
这个排序一出来，客户自己就明白"便宜"这条保不住了。 你不用去说服他，是他自己排出来的。
第五步：打样验证——三件事不做，前面全白干
第一件：干燥——最容易废批的一步
尼龙吸水。含水率超标直接上机，熔融时会水解断链，分子量下降、冲击强度断崖式下跌，而且从外观完全看不出来。
常规要求：含水率 < 0.1%-0.2%（具体看牌号）
干燥后要留记录：温度、时长、实测含水率
回料必须单独干燥，不能和 new 料混投
三个典型动作会废掉一整批：干燥机开机就投料、料斗不盖盖、回料不烘干。这三件事废掉的件，比选错料多得多。
第二件：按材料工艺窗口试模
不同改性料的工艺窗口完全不同，不能拿上一块料的参数直接用：
| 材料 | 干燥 | 料温 | 模温 | 关键点 |
|---|
| PA6-GF30 | 80-100℃×4h | 240-260℃ | 80-100℃ | 模温低会浮纤 |
| PA66-GF30 | 80-100℃×4h | 280-300℃ | 80-100℃ | 料温不足充填不良 |
| 增韧 PA66 | 80℃×3-4h | 260-280℃ | 60-80℃ | 模温过高增韧剂析出 |
| 无卤阻燃 PA66 | 100-120℃×4h | 250-270℃ | 70-90℃ | 料温过高分解发黄 |
| PA46-GF30 | 100-120℃×4h | 300-320℃ | 100-140℃ | 模温低不结晶，件脆 |
| PA6T/PA9T | 120-140℃×4h | 310-330℃ | 120-140℃ | 必须高模温 |
（典型参考值，具体以牌号工艺建议为准）
如果只有一个工艺细节要盯，就是高温尼龙的模温。 PA46、PA6T 类必须高模温结晶——模温开到 60℃，出来的是半结晶态，件脆、表面暗、耐热达不到标称值。这是最高频、也最容易被忽略的浪费。
第三件：按测试清单验证
只测一个拉伸强度就下结论，是最常见的偷懒。一份完整的验证清单是这样：
| 测试项 | 常用标准 | 建议判据 |
|---|
| 拉伸强度 | ISO 527 | 干态 + 湿态都测 |
| 缺口冲击 | ISO 179 | 常温 + 低温（-20 或 -40℃） |
| 热变形温度 | ISO 75（1.8MPa） | 要高于使用温度 20℃ 以上 |
| 热老化 | ISO 2578 | 150℃×1000h，拉伸保留率 |
| 阻燃 | UL94 | V0 / V2 |
| 灼热丝 | IEC 60695 | GWIT（家电必测） |
| CTI | IEC 60112 | 分档，高压件要 600V |
| 吸水率 | ISO 62 | 平衡吸水率 |
| 尺寸稳定性 | — | 注塑后 24h / 48h / 吸湿平衡，三个时间点都要测 |
打样阶段三个高频错误：
1. 只测干态——装到南方梅雨天里运行的是湿态，干态数据好看没用
2. 只打一个样——单件合格不代表工艺窗口够宽，量产会翻车
3. 只拍照不比尺寸——尤其玻纤件，纵横收缩率不同，翘曲必须在尺寸上验证
附：改性尼龙选型的 12 个必问参数（可直接复制给客户填）
这套问题我做成了一张表，客户填完发回来，基本就是一份完整询盘：
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1. 长期连续使用温度：____℃ （核心）
2. 短时峰值温度与时长：____℃ / ____分钟
3. 受力类型：静载 / 冲击 / 疲劳 / 振动
4. 载荷大小：____N 或 ____MPa
5. 接触介质：________（温度____℃）
6. 尺寸公差要求：±____mm
7. 是否涉及安规：UL / 3C / IATF / 无
8. 阻燃要求：UL94____ / GWIT____℃ / CTI____V
9. 预期使用寿命：____年
10. 现在用什么料？遇到什么问题？
11. 月用量：____ 吨
12. 成型方式与设备：注塑 / 挤出 / 其他
`
第 10 项是全表最关键的一条。
它一句话就把"现在的失效模式"和"客户的心理锚点"都给你了。而且答得上这一条的客户，才是真有项目的客户——只是随便问问的人，答不出第 10 项。
结语
改性尼龙选型的五步法，说到底是一句话：
先把件问清楚，再谈料。
① 定工况（六要素）→ ② 定失效模式（最怕怎么坏）→ ③ 定基材（2-3 个候选）→ ④ 定改性体系（排序，不是全都要）→ ⑤ 打样验证（干燥、工艺、测试）。
五个步骤里，第一步和第二步决定对错，后面三步决定效率。
而这两步恰恰是大部分人跳过的——上来就问"给我推荐个牌号"，这是改性尼龙选型里最常见的开头。
一个愿意花二十分钟问工况的人，比一个三分钟就报价的人，最后省的钱多得多。
十几年，只做一件事：把尼龙改成能用的样子。
PA6、PA66 是基本盘，PA46、PA6T、PA9T 是耐高温的门槛，PA11、PA12 管水路和油路，尼龙合金补单一树脂给不了的平衡。除了改性尼龙，还有改性 PPO、PPS、热塑性弹性体，以及各大化工巨头的尼龙树脂、副牌料、大包料现货。
同一块料，用错地方就是事故。所以先问件，再问料。
Many people ask 'how to choose modified nylon,' but the real bottleneck is not 'choosing,' it is 'asking.'
A very typical situation: the customer immediately asks for 'wear-resistant nylon.' After asking three more questions, it turns out that what they really want is not wear resistance. The part is unstable in size at 120℃, and the gear meshing clearance changes, which is interpreted on-site as 'wear.' The real problem to solve is thermal deformation and dimensional issues, which have nothing to do with wear resistance.
If you select the materials according to his original words, testing three molds still won't be correct.
This article does not discuss materials, only the process. The five-step method, from working conditions to grade, has specific actions at each step.
`
① Define working conditions → ② Define failure modes → ③ Define base material → ④ Define modification system → ⑤ Sample verification
`
The first three steps set the direction, the fourth step sorts, and the fifth step verifies. Ninety percent of people get stuck at the first step and also fail at the second step.
Step One: Define the operating conditions—six elements, missing any one will lead you astray
'Operating condition' is not used 'in what place'; it is six numbers. If you ask one less, it will have to be redone once afterwards.
Element One · Temperature — You must ask for three numbers, not just one
This is the easiest place to be vague. Don't ask 'how many degrees,' break it down into three questions:
1. What is the long-term continuous use temperature? (This number determines the base material grade)
2. Are there any short-term peaks? How high are they and how long do they last? (This determines whether to move up a level)
3. Is the environment dry heat or humid heat? (Determines whether a hydrolysis-resistant system is needed)
When judging, look at the RTI (Relative Thermal Index), not the peak temperature on the TDS. The TDS says 200°C, which refers to 'how many minutes it can withstand'; the RTI tells you 'how many years it can withstand'.
Element Two · Time — Continuous, Intermittent, or Cyclical
Continuous 120℃ and 120℃ for 2 hours per day require completely different materials. The former needs a heat-stable system, while the latter might be fine with ordinary materials.
Element Three · Load — Distinguish Between Static Load and Dynamic Load
This directly determines whether to choose 'enhance' or 'toughen'; the two are counterbalanced in the formulation:
Static load structural parts (brackets, end plates) → Rigidity first → High fiberglass
Repeated impact (shell, cover) → Toughness priority → Toughening system
Long-term fatigue (gears, clips, spring pieces) → Look at fatigue strength, not tensile strength; these are two separate sets of data
Element Four · Medium — What to contact, how hot, for how long
It's not enough to just ask about 'what' contact occurs; you also need to ask 'how intense' and 'for how long'.
Hot water at 80℃ is a hydrolytic environment for PA6/PA66; water at room temperature is not. For the same medium, if the temperature changes, the material must be replaced.
Element Five · Precision — What is the tolerance
Tolerances of ±0.5mm and ±0.05mm involve completely different selection logic. The latter must take into account both water absorption and anisotropic shrinkage.
Element Six · Lifespan — Designed for How Many Years
For one-year components and ten-year components, the investment in a stability system is not on the same scale. For outdoor components with a 25-year lifespan, a complete weather-resistant system must be applied.
The six elements are summarized in a table:
| Element | Essential questions | Affect what |
|---|
| Temperature | Long-term continuous? Short-term peak? Dry heat or wet heat? | Substrate Grade (Most Important) |
| Time | Continuous / Intermittent / Cyclical? | Thermally stable system |
| Load | Static load / Impact / Fatigue? | Reinforcement or toughening |
| Medium | Touch what? How hot? For how long? | Hydrolysis-resistant, chemical-resistant |
| Accuracy | Tolerance grade? | Long carbon chain, PA9T, shrinkage control |
| Lifespan | Designed for how many years? | Aging system investment |
The real difficulty of the first step: the customer often doesn’t know these six numbers themselves. They don’t know the long-term temperature—because it hasn’t been measured.
This is when your value comes out: helping him ask. The process of asking is also the process of him trusting you.
Step 2: Determine the failure mode — this step decides whether you can make the right choice
Most people skip this step and directly ask 'What performance do I want?'
This question is asked incorrectly. Because it does not have a single answer. 'Is it better to have higher intensity or lower?' — of course higher is better, but are you willing to accept the cost?
The correct way to ask is the other way around: what failure mode is this part most susceptible to?
This question has a single answer. Moreover, once the answer is clear, the direction of the materials is basically determined.
10 Types of Failure Modes, Reverse-Engineer Material Countermeasures
| Failure mode | On-site performance | Root cause direction | Material Strategy |
|---|
| Thermal deformation | Softening and assembly failure at high temperatures | Insufficient heat resistance rating | Upgrade base material (PA66 → PA46/PA6T), increase GF content |
| Brittle fracture at room temperature | Cracks directly from impact | Insufficient resilience | Elastomer toughening system |
| Brittle fracture at low temperature | Cracks below -20℃ | Insufficient low-temperature toughness | Core-shell structure toughening (ordinary elastomers fail at low temperatures) |
| Size out of tolerance | Cannot assemble, gap variation | Water absorption expansion / contraction | Long carbon chain or PA9T, controlling mold temperature and post-processing |
| Warping deformation | Long condition distortion | Glass fiber anisotropy | Mineral filling, reducing GF content, changing gate position |
| Wear failure | Surface wear, reduced size | Insufficient wear resistance or mismatched mating parts | PTFE/MoS₂ system Check the mating parts |
| Aging and brittleness | Becomes brittle after one year | Thermo-oxidative aging / UV | Heat-stable system, UV-resistant system |
| Hydrolytic degradation | High-temperature water environment strength drop | Hydrolytic cleavage | Hydrolysis-resistant system, or switch to long carbon chain substrate |
| Electrical failure | Electrical leakage tracking, hot wire not up to standard | Insulation / Flame Retardancy Insufficient | Improve CTI and switch to a halogen-free system |
| Weld line cracking | Fracture at the weld | Process issue | Increase mold temperature, change gating—not replace material |
The most valuable part of this table is in the last row.
Among the 10 types of failures, at least one type is not a material problem at all.
Weld line cracking, floating fibers, sink marks, silver streaks—these are process and mold issues. Many people, upon seeing a defective part, just change the material. Even after changing three batches of material, the problem persists, simply because they are looking in the wrong direction.
The rule of thumb is very simple: if it is 'every mold is bad, bad in the same position,' first check the process and the mold; if it is 'sometimes good, sometimes bad between batches,' then prioritize suspecting the material.
A real feeling in the industry: a large number of 'material problems' are ultimately proven to be process problems, and the root of many 'process problems' is that the material characteristics were not considered during design. The questions we are asked the most don't actually have answers related to 'which material to choose.' The first question is often 'how much does this material cost,' rather than 'at what temperature will this part be used.' Some clients even come with an imported grade asking 'can it be substituted,' yet cannot explain what forces the part will experience or what media it will contact. What they want is 'a usable material,' but what they provide is 'a set of specifications without knowing whether they are important.'
Let me give the most typical example. The surface of the black part turns white and fuzzy and cannot be painted. The customer's first reaction is, 'Too much fiberglass was added, give me a material with lower fiberglass content.'
Checking the mold temperature gauge—it shows 80°C. When raised to 115°C, with the same batch of material and the same mold, the floating fibers basically disappear.
The principle is not complicated: the melt flows in the mold cavity in a 'fountain flow' pattern, and the glass fibers are pushed to the flow front. Once they touch the colder mold wall, they freeze instantly, and the resin doesn’t have time to cover them again. The glass fibers you added are frozen on the surface.
This is not a matter of the formula, it's a matter of mold temperature. But it will come knocking under the guise of a 'material problem'.
Failure mode analysis in reverse: Two examples
Example A: The customer said 'needs to be wear-resistant'
Follow-up → The part's dimensions change in a 120°C environment, the gear clearance increases, and it is judged as wear.
Actual failure mode: thermal deformation. Dimensional deviation, not wear.
Countermeasure: Increase the temperature resistance of the base material (PA46) or increase the GF content to improve the heat deflection temperature, and add a dimensionally stable system. Do not add PTFE.
Example B: The customer said 'Make it harder.'
Follow-up → The buckle breaks in a low-temperature environment.
Actual failure mode: low-temperature brittle fracture.
Countermeasure: Toughen the core-shell structure. Also, note that 'harder' and 'continuous at low temperature' are opposite directions; adding fiberglass will only make it more brittle.
This is why the second step cannot be skipped. The performance requirements mentioned by the customer are often not their actual failure modes.
Step 3: Determine the substrate — use four rulers to filter out two or three candidates
Once the operating conditions and failure modes are clear, the range of base materials will naturally narrow.
First, sort by temperature (the first sieve)
| Long-term operating temperature | Substrate direction | Explanation |
|---|
| ≤120°C | PA6, PA66 | General Main Range |
| 120-150℃ | PA66 Thermally Stable System | Add copper salt or organic heat stabilizer |
| 150-170℃ | PA46, PA6T, PA9T, PA10T | High-temperature nylon interval |
| Short-term peak 200℃ / over reflow soldering | PA6T, PA9T, PA4T | SMT parts must be selected |
| Long-term >200℃ | Break out of the nylon system | PPS / PEEK |
Then fine-tune according to the operating conditions (second sieve)
| Operating condition combination | Preferred base material |
|---|
| Normal temperature General precision General-purpose structural parts | PA6 (Best value for money) |
| Medium temperature Structural stress Dimensional stability | PA66-GF30 |
| High precision High humidity environment | PA612 / PA12 (low water absorption) |
| Hot water / coolant long-term contact | PA612 / PA1010 (Hydrolysis Resistant) |
| Reflow solder-resistant Thin-wall filling | PA6T / PA9T |
| High temperature High precision (tolerance ±0.05) | PA9T (lowest water absorption among high-temperature nylons) |
| High temperature wear-resistant bearing | PA46 (best in wear resistance and flowability, but highest in water absorption) |
| Low warping exterior parts | PA/ABS Alloy |
| Needs to be transparent | transparent nylon |
| Extreme long-term high temperatures | Do not choose nylon; switch to PPS/PEEK |
The output of this step should be 2-3 candidate substrates, not just one. Having only one candidate means you have no room for comparison, and if there are problems with the subsequent process or costs, there's no way to turn back.
Step 4: Determine the modification system—not everything is needed, just prioritize
The base material has been decided, and next is to apply the requirements to the modified system. The core action of this step is sequencing.
Action 1: List all requirements
Write down every point the customer raises, including those he didn't mention but are implied in the working conditions:
Reinforced (rigid, creep-resistant)
Toughening (impact, low temperature)
Flame Retardant (UL94 / GWIT / CTI)
Heat-resistant (thermally stable system)
Wear-resistant (self-lubricating)
Weather-resistant (UV)
Dimensional stability (low warping)
High flow (thin-walled)
Conductive / Thermal conductive / Food grade…
It usually lists 5-8 items. This is normal.
Action 2: Use the conflict matrix to find out which ones are fighting
The directions of modification are not additive. Common strong conflict combinations:
| Conflict combination | Cause of conflict | Way out |
|---|
| Reinforce ✖ Toughen | Glass fiber reduces toughness, toughening agents reduce rigidity | Replace with long glass fiber, or modify the structure to make it thinner and add reinforcement |
| Reinforced ✖ Flame Retardant | Glass fiber requires low viscosity, flame retardants increase viscosity, both compromise impact strength. | Looking for mature composite grades, with increased cost |
| Reinforced ✖ High Flow | Fiberglass itself increases viscosity | Reduce wall thickness design or lower GF content |
| Flame Retardant ✖ High Flow | Increasing the amount of flame retardant will inevitably increase viscosity | Question: Is it the material that's not suitable, or is the wall thickness too aggressive? |
| Flame Retardant ✖ Toughened | Both compete for formulation space | High-cost solution, cost-effectiveness needs to be evaluated |
| Toughening ✖ High Rigidity | Opposite direction | Clarify priorities; you can't have everything |
Action Three: Sorting — Asking One Question is Enough
Once this question is asked, the plan is basically set:
Among these items, which one will be discarded if not met? Which one can be accepted even if it falls slightly short?
Then arrange them in a line according to 'non-negotiable → negotiable.' The formula is always about solving this sorting problem, not about meeting all the requirements.
Here's a real sorting logic:
The customer wants GF30 V0 CTI 600V high toughness and cheap.
The ranking results are: V0 and CTI 600V are mandatory safety standards (non-compliance leads to direct scrapping) → GF30 is a structural requirement (can be slightly adjusted to GF25) → Toughness is 'just not too brittle' (keeping 60% is acceptable) → Cheapness is ranked last.
Once this ranking comes out, the customer will understand on their own that the 'cheap' option is no longer guaranteed. You don't need to persuade them; they are the ones who created the ranking themselves.
Step 5: Proofing Verification — If these three things are not done, all previous efforts are wasted
Step 1: Drying — The easiest step to ruin a batch
Nylon absorbs water. If the moisture content exceeds the standard and it is directly put into the machine, it will hydrolyze and break chains during melting, leading to a decrease in molecular weight and a sharp drop in impact strength, and this cannot be seen from the appearance at all.
General requirements: moisture content < 0.1%-0.2% (depending on the grade)
After drying, records must be kept: temperature, duration, and measured moisture content
The return material must be dried separately and must not be mixed with new material
Three typical actions can ruin an entire batch: starting the dryer with materials already added, not covering the hopper, and not drying the return material. These three things ruin more items than choosing the wrong material.
Second item: Trial molding according to material process window
The processing windows of different modified materials are completely different and you cannot directly use the parameters from the previous batch of material.
| Material | Dry | Material temperature | Mold temperature | Key point |
|---|
| PA6-GF30 | 80-100℃ × 4h | 240-260℃ | 80-100℃ | Low mold temperature will cause floating fibers |
| PA66-GF30 | 80-100℃ × 4 hours | 280-300℃ | 80-100℃ | Insufficient material temperature leading to poor filling |
| Toughened PA66 | 80℃ × 3-4 hours | 260-280℃ | 60-80℃ | Excessive mold temperature causes toughening agent to precipitate |
| Halogen-free flame-retardant PA66 | 100-120℃ × 4h | 250-270℃ | 70-90℃ | Material temperature too high, decomposes and turns yellow |
| PA46-GF30 | 100-120℃ × 4h | 300-320℃ | 100-140℃ | If the mold temperature is low, it won't crystallize, and the part will be brittle. |
| PA6T/PA9T | 120-140℃ × 4h | 310-330℃ | 120-140℃ | High mold temperature is required |
(Typical reference values, subject to the recommendations of the specific grade and process)
If there is only one process detail to pay attention to, it is the mold temperature for high-temperature nylon. PA46 and PA6T types must crystallize at a high mold temperature—if the mold temperature is set to 60℃, the result is a semi-crystalline state, making the parts brittle, with a dull surface, and the heat resistance not reaching the rated value. This is the most frequent and also the easiest waste to overlook.
Third item: Verify according to the test checklist
Drawing a conclusion based on testing only one tensile strength is the most common form of laziness. A complete verification checklist is like this:
| Test item | Common Standards | Recommended criteria |
|---|
| Tensile strength | ISO 527 | Test both dry and wet states |
| Gap impact | ISO 179 | Room temperature Low temperature (-20 or -40℃) |
| Heat deflection temperature | ISO 75 (1.8 MPa) | Must be above the use temperature by more than 20℃ |
| Thermal aging | ISO 2578 | 150℃ × 1000h, tensile retention |
| Flame retardant | UL94 | V0 / V2 |
| Scorching thread | AIXI 60695 | GWIT (Must-Test for Home Appliances) |
| CTI | IEC 60112 | Grading, high-voltage components require 600V |
| Water absorption rate | ISO 62 | Balanced water absorption rate |
| Dimensional stability | — | Measure at three time points: 24h after injection molding, 48h after injection molding, and after moisture equilibrium. |
Three common mistakes in the proofing stage:
1. Only test the dry state — what runs during the rainy season in the south is the wet state, dry state data looks good but is useless
2. Only making one sample — a single piece passing quality control doesn’t mean the process window is wide enough; mass production could fail.
3. Only taking photos is not enough to compare dimensions—especially for fiberglass parts, as the shrinkage rate varies in length and width, warping must be verified by measurements.
Attachment: 12 Must-Ask Parameters for Selecting Modified Nylon (can be directly copied for the customer to fill in)
I compiled this set of questions into a table. After the client fills it out and sends it back, it basically serves as a complete inquiry:
`
1. Long-term continuous operating temperature: _____°C (core)
2. Short-term peak temperature and duration: ____°C / ____ minutes
3. Force type: static load / impact / fatigue / vibration
4. Load size: ____N or ____MPa
5. Contact medium: ________ (temperature ____°C)
6. Dimensional tolerance requirements: ±____mm
7. Safety standards involved: UL / 3C / IATF / No
8. Flame retardant requirements: UL94____ / GWIT____°C / CTI____V
9. Expected service life: ____ years
10. What materials are currently used? What problems did you encounter?
11. Monthly usage: ____ tons
12. Molding methods and equipment: injection molding / extrusion / others
'
Item 10 is the most critical item in the entire table.
It gives you both the "current failure mode" and the "customer's psychological anchor point" in one sentence. And only customers who can answer this item are real clients with projects—just casual inquiries won't answer item 10.
Conclusion
The five-step method for selecting modified nylon ultimately boils down to one sentence:
Ask about the item clearly, then discuss the material.
(1) Determine the operating conditions (six elements)→ (2) Determine the failure mode (the biggest fear is how it fails)→ (3) Determine the substrate (2-3 candidates)→ (4) Determine the modification system (sort, not all candidates)→ (5) Sample verification (drying, process, testing).
Of the five steps, the first and second steps determine right or wrong, while the last three determine efficiency.
And these two steps are exactly what most people skip—immediately asking, "Recommend a grade," which is the most common opening in modified nylon selection.
Someone willing to spend twenty minutes asking about working conditions saves much more money than someone who quotes in three minutes.
For over a decade, I've done only one thing: to make nylon usable.
PA6. PA66 is the foundation; PA46, PA6T, PA9T are the threshold for high-temperature resistance; PA11 and PA12 pipe water and oil lines, and nylon alloys are a balance that a single resin can't provide. Besides modified nylon, there are also modified PPO, PPS, thermoplastic elastomers, and nylon resin, sub-brand materials, and large bulk materials from major chemical giants in stock.
The same piece of material can be used in the wrong place and cause an accident. So ask about the parts first, then the materials
