液冷管路选料，有一个反常识的结论要先说：
这里最不能用的，恰好是最常见的 PA6 和 PA66。
原因只有一个词：水解。
这篇把水解这件事讲透——它不是"料不好"，是分子链在水和热一起作用下被剪断。理解了机理，选料就不用猜了。
开篇先讲个现场
去年秋天，一家储能集成商的售后群里发了几张照片：运行一年半的液冷管路，快接头根部渗液，白色的冷却液在柜子底部积了一小滩。供应商起初怀疑是装配扭矩问题，把现场备件换上一批新的，三个月后原样复发。
后来把漏液的接头切开看，内壁出现了细微的龟裂——这不是装配问题，是材料在乙二醇型冷却液里长期服役后的水解。
同一个案子还有个耐人寻味的细节：管路本体用的料没事，出事的只在快接头。因为接头处的冷却液温度更高、流速更快、还有注塑残余应力集中，水解在这个点上被加速了好几倍。
这篇就从水解这个根源讲起。先把“乙二醇加高温如何把尼龙剪断”这个化学过程用大白话说清，再讲长碳链尼龙凭什么能扛住——碳链长了，酰胺基团的密度就稀了，水分子下不去手。然后分两段讲选型：管路本体一段，快接头一段，后者比前者难得多。
最后是五个坑和边界。做储能和液冷热管理的读者，重点看第四节快接头，那是这个赛道里最挑料的位置。
一、水解：把尼龙"剪断"的过程
先说清机理，后面所有结论都从这里推出来。
尼龙的分子链里有一个化学键叫酰胺键（—CO—NH—）。它本身是稳定的，但遇到两样东西会出事：
① 水分子。 高温下水会进攻酰胺键，把链剪断。② 温度。 温度每升高一档，水解速度不是线性增长，而是明显加速。
所以真正的杀手是"高温 + 水分"同时存在。
而液冷管路的工况，恰恰就是这个组合：
冷却液（常见是乙二醇基）- 长期温度 90-120℃- 管路内外都是湿的
在这个环境里，PA6 和 PA66 的分子链会持续断链。 表现先是强度下降、表面发黄发脆，再往后是开裂渗漏。
最麻烦的是：它在件的外观看不出问题时就已经发生了。
为什么乙二醇更麻烦
纯水已经够呛，乙二醇基冷却液还要加一层：
乙二醇本身在高温下会生成酸性物质- 冷却液里的添加剂（防锈、防垢）会进一步影响材料- 冷却液循环时还带着压力脉动
这三条叠加起来，就是液冷管路选料必须"往保守走"的原因。
还有一类介质容易被忽略：去离子水。
去离子水里没有离子，但它反而会从材料里"抽"离子和助剂，长期浸泡同样会影响材料状态。数据中心冷板式液冷用的就是这一类介质。
所以"走水就安全"这个判断并不成立——要看是什么水、多少温度、流多久。
一句话判断：只要介质是"高温水或高温冷却液"，选料第一步就把 PA6 / PA66 划掉。
二、长碳链尼龙：为什么它能扛住
尼龙家族里，链越长，酰胺键的"密度"越低。
酰胺键密度低 = 能被水解的位点少 = 耐水解更好。
同时还带来第二个好处：吸水率低。
| 材料 | 平衡吸水率 | 耐水解 | 相对成本 |
|---|
| PA6 | 8-10% | 差 | 低 |
| PA66 | 8-9% | 差 | 低 |
| PA610 | 约 1.5% | 较好 | 中 |
| PA612 | 约 1.2% | 好 | 中高 |
| PA1010 / PA1012 | 小于 1.5% | 好 | 中高 |
| PA11 | 约 0.8% | 好 | 高 |
| PA12 | 约 0.7% | 最好 | 高 |
（典型量级，具体以牌号 TDS 为准）
吸水率低，在液冷管路上是双重收益：
① 尺寸稳。 管路有接头、有卡箍、有装配位置。吸水涨缩会让密封配合跑掉。② 水解慢。 材料内部含水少，参与水解的"水"就少。
PA12 和 PA11 是这一族里最稳的。 吸水率在 1% 以下，耐水解最好，长期用在水路和油路上。
代价是价格——PA12 大概是 PA6 的数倍量级。它在液冷管路上不是"用了更好"，是"不用不行"。
水解稳定剂能救 PA66 吗
答案是：能改善，不能解决。
加水解稳定剂，确实可以把 PA66 在湿热条件下的寿命拉长，这在行业里是比较成熟的做法。但它改变的是"多久断链"，不是"会不会断链"。
在 90-120℃ 长期泡冷却液的工况里，即使用了水解稳定体系，PA66 的长期表现依然不如长碳链尼龙。因为吸水率就摆在那里——水进去了，水解就有了原料。
所以选料的顺序应该是：先按介质和温度排除掉不合适的树脂，再谈用什么助剂优化。 反过来做，就是拿助剂去补树脂的短板，成本不低，效果有限。
三、管路本体怎么选
| 部位 | 材料方向 | 理由 |
|---|
| 冷却液软管 | PA12 / PA11 / PA612 | 耐水解 + 柔软 + 耐低温 |
| 波纹管护套 | PA612 / PA12 | 弯折疲劳 + 耐水解 |
| 多层阻隔管 | PA/EVOH 复合 | 阻隔渗透（燃油系更常见） |
| 硬质管路段 | PA12-GF / PA612-GF | 耐压 + 耐水解 |
| 快接头本体 | PA12 / PA612（含增强） | 耐水解 + 尺寸稳定 |
| 密封件 / O 圈座 | PA12 / 弹性体 | 配合精度 + 回弹 |
几个选型细节：
① 波纹管看的是"弯折疲劳"，不是强度。 管路要反复弯折、经振动，抗疲劳比拉伸强度重要得多。
② 低温性能要一起看。 长碳链尼龙的低温韧性普遍好于 PA66，但不同碳链长度之间也有差异。寒区车型必须看 -40℃ 数据。
③ 加工方式决定料的状态。 挤出管材和注塑件对料的流动性要求完全不同，不能拿注塑牌号去做挤出。
④ 软管和硬管的过渡位置要单独算应力。 软管（PA12、PA612）和硬管段（PA12-GF）刚性差很多，连接位置的应力集中比管身大得多。很多管路开裂不发生在管身，就发生在软硬过渡处。 设计上要么做渐变，要么在过渡处加固定约束，把应力分散掉。
一句判断：液冷管路上，"耐水解"是入场券，"低吸水带来的尺寸稳定"才是真正的门槛。
四、快接头：比管路更难的地方
管路本体出问题，是慢的；快接头出问题，是快的。
快接头的要求比管路本体多三条：
① 尺寸精度。 密封面靠配合尺寸。吸湿涨 0.1mm，就可能从"不漏"变成"渗"。
② 长期受力。 卡扣、锁止结构长期处于应力状态，看蠕变。
③ 反复插拔。 维修时会被拆装，插拔寿命是硬指标。
这三条里，尺寸精度最容易翻车。
快接头还有一个常见误区：认为"能插上就行"。
密封是靠尺寸和力共同实现的。插拔力太小，密封压不紧；太大，装配时会损伤卡扣。所以快接头的验收要同时看两个数：密封测试结果和插拔力曲线。
只测密封不测插拔力，问题会留到量产阶段才暴露。
所以快接头在长碳链尼龙里，更偏向 PA12、PA612 加增强 的方向——吸水率低换来尺寸稳，增强撑住卡扣强度。
这里有一个非常实用的自检问题：
你这个件，是"长期泡在冷却液里"，还是"偶尔接触冷却液"？
长期泡：必须上长碳链，没有余地- 偶尔接触（比如溅到）：可以放宽到 PA66 + 耐水解体系，但要做验证
很多液冷项目选错料，是因为把"长期浸泡"当成了"偶尔接触"。
长碳链家族怎么挑
决定上长碳链之后，家族内部怎么挑又是一道题。这里给一个简明的分层。PA11、PA12：生物基或单体来源，吸水率最低、耐水解最稳，柔韧性好，是管路和接头的传统主力，价格也最高。PA12 的共聚改性牌号在耐燃油渗透上有专门强化，燃油管路用它压阵。
长碳链共聚尼龙：性能在 PA12 和 PA66 之间找平衡，价格低一截，用在温度和介质要求中等的管路段。选择逻辑一句话：接触乙二醇和燃油的位置，按最高要求选；过渡段和静态段，可以用平衡型降本。
最怕的是反过来——静态段用最好的料，接触口用便宜的，钱花了，漏点还在。把介质接触图谱画出来，按图分配材料档次，长碳链的钱才花在刀刃上。
五、液冷管路的五个坑
坑 1：用 PA66 做冷却液管路。 短期能撑，长期水解断链。这类失效通常在两三年后才暴露，届时已过质保窗口。
坑 2：只看原始强度。 液冷件必须看水解老化后的强度保持率（比如 1000 小时、不同温度下的数据），不是初始拉伸强度。
坑 3：忽略冷却液的具体配方。 不同配方对材料的侵蚀差异很大。选料时要拿实际用的冷却液做浸泡试验，不要用"通用冷却液"代替。
坑 4：管路和快接头用同一个牌号。 管路看柔软和耐水解，快接头看精度和刚性，需求不一样。
坑 5：忘了低温。 长碳链尼龙耐低温不错，但加玻纤之后低温韧性会下降。寒区件必须验证。
六、边界
| 场景 | 结论 | 说明 |
|---|
| 长期 90-120℃ 冷却液 | 长碳链尼龙 | PA12 / PA11 / PA612 |
| 长期 >120℃ 高温水路 | 需谨慎 | 换 PA1010 或改金属/复合方案 |
| 强酸碱介质 | 不适合 | 需专门耐化学体系 |
| 高压燃油系统 | PA11 / PA12 | 耐油 + 阻隔（多层结构） |
| 极低温 -40℃ 以下 | 需谨慎 | 增韧体系或弹性体 |
行业里的一条实感
有一类询盘，我们每次看到都会多问几句：
客户拿一段裂开的波纹管过来，说"这是尼龙的，裂了，你们有没有更结实的尼龙"。
问下去，十有八九是 PA66 或 PA6 做的冷却液管路。
这时候我们的回答通常是：不是要换更结实的料，是要换"不怕水的"料。
因为客户问的是"结实"，但问题根本不在强度上——它是被水解掉的，断链断出来的裂纹，跟强度没半点关系。 你换一个强度更高的 PA66，照样会裂；只是裂得晚一点。
我们的追问一般是三句：管子里走的是水还是乙二醇？长期温度多少？用多久裂的？
走水、温度不高、几年才裂 → 是选料偏保守，可以调- 走乙二醇、温度 90℃ 以上、一两年就裂 → 必须换长碳链，没有中间方案
同一个"裂"字，两种答案。问错一句，换十次料也没用。
读者追问两则
追问一：现有 PA66 系统能不能靠加抗水解剂续命？ 能缓解，但有上限。抗水解剂能明显拉长 PA66 在乙二醇里的寿命，常规工况从两三年拉到五年以上，这是很多冷却系统一直在用的成熟路线。
但要清醒：抗水解剂改变不了酰胺基团密度，在快接头这种高温高流速高应力的位置，它只是把翻车时间推后，不是取消。所以判据是看位置：本体和静态段，抗水解 PA66 够用；接触口和运动密封位，直接上长碳链，别省。
追问二：渗液的判定标准怎么定？ 建议分三级：一级是表面潮痕，擦掉不复发，观察记录；二级是滴渗，二十四小时内成滴，进入整改流程；三级是连续渗漏，立即停机更换。判据写进运维手册后，最重要的动作是每级都要留样送检，渗液件的解剖结论是下一代产品选型最值钱的输入，比任何实验数据都真实。
顺手把液冷管路的验收动作也说全：到货验收除了常规的尺寸外观，建议加两项针对性检查——一是溶胀率抽检，把样品在工况冷却液里泡七十二小时量尺寸，超标的直接退；二是密封面状态检查，用放大镜看密封带上有没有流痕和缺料，这个位置的缺陷用卡尺量不出来。两个动作各花十分钟，能拦住绝大多数批次问题。验收严一分，售后的电话就少十分。
渗液三级响应卡
运维现场配一张渗液三级响应卡。一级，潮痕级：表面湿润不成滴，动作是标记位置拍照、擦拭观察四十八小时、录入台账跟踪，不用停机。二级，滴渗级：二十四小时内成滴，动作是拍照取样、安排备件更换窗口、把失效件密封寄回分析，系统可以带病运行但限期整改。
三级，连续渗级：正压渗出或滴速加快，动作是立即隔离该柜、断电排液、启动应急预案，这一级没有讨论空间。每级响应的末尾都是同一个动作：失效件寄回做解剖分析，渗液件是液冷系统最诚实的老师，它的断口和龟裂形态会告诉你下一次选料该往哪走。响应卡贴在运维值班室，写清楚责任人，比任何微信群通知都管用。
顺便回答一个经常被问到的问题：液冷管路要不要也上长碳链，一步到位？我们的建议是分开看。管路本体的工况比接头温和，流量低、无装配应力、温度均匀，抗水解 PA66 或平衡型共聚尼龙在这个位置有成熟的表现记录，全上长碳链的成本增加相当可观，省下来用在该用的位置更划算。
判断的标准不是料越贵越安心，是每个位置配它该配的料，然后对每个位置的验证都一视同仁。浪费和省错地方，都是选料的大忌。
结语
液冷管路选料，逻辑其实非常干净：
介质是水或冷却液 → 划掉 PA6 / PA66 → 往长碳链走 → 按温度和精度定具体牌号。
四步走完，剩下的就是价格和验证。
唯一要警惕的，是"先凑合用 PA66，坏了再换"。 在液冷件上，这条路的代价不是返工，是质保期内批量渗漏。
最后提醒一句：液冷件选料，可以被"价格"说服，不能被"经验"说服。别人用 PA66 没出问题，不代表你的介质和温度下也不出问题。
Regarding the selection of materials for liquid cooling pipelines, there is a counterintuitive conclusion that needs to be mentioned first:
The ones that should not be used here the most are exactly the most common PA6 and PA66.
There is only one word for the reason: hydrolysis.
This article explains hydrolysis thoroughly—it’s not that the material is 'bad,' it’s that the molecular chains are being broken down under the combined action of water and heat. Once you understand the mechanism, choosing materials no longer requires guessing.
Let's start with a live scene
Last fall, a few photos were posted in an after-sales group of an energy storage integrator: the liquid-cooled piping, which had been in operation for a year and a half, was leaking at the base of the quick connector, and a small puddle of white coolant had accumulated at the bottom of the cabinet. The supplier initially suspected it was an assembly torque issue and replaced the on-site spare parts with a new batch, but the problem recurred in the same way three months later.
Later, when the leaking joint was cut open for inspection, fine cracks appeared on the inner wall — this was not an assembly problem, but hydrolysis of the material after long-term service in ethylene glycol-based coolant.
There is another intriguing detail about the same case: the material used for the main body of the pipeline was fine, and the problem only occurred at the quick connector. This is because the coolant temperature at the connector is higher, the flow rate is faster, and the residual stress from injection molding is concentrated there, causing hydrolysis at this point to be accelerated several times.
Let's start this article from the root cause: hydrolysis. First, explain the chemical process of 'how ethylene glycol at high temperatures cuts nylon apart' in plain language, and then talk about why long carbon chain nylon can withstand this—when the carbon chain is long, the density of amide groups becomes sparse, so water molecules can't get in. Then split the discussion on selection into two parts: one for the main body of the piping, and one for the quick connectors, the latter being much more difficult than the former.
Finally, there are five pitfalls and boundaries. For readers involved in energy storage and liquid-thermal management, pay special attention to Section 4 on quick connectors, as that is the most demanding area in this field.
1. Hydrolysis: The process of 'cutting' nylon
First clarify the mechanism, then all subsequent conclusions will be derived from it.
There is a chemical bond called an amide bond (—CO—NH—) in the molecular chain of nylon. It is stable by itself, but it will react when it encounters two things:
① Water molecules. At high temperatures, water will attack amide bonds, breaking the chain. ② Temperature. Each increase in temperature level does not cause a linear increase in the hydrolysis rate, but a significant acceleration.
So the real killers are the simultaneous presence of 'high temperature and moisture'.
And the operating condition of the liquid cooling pipeline is precisely this combination:
Coolant (commonly ethylene glycol-based) - long-term temperature 90-120°C - both inside and outside of the pipes are wet
In this environment, the molecular chains of PA6 and PA66 will continue to break. The manifestations are first a decrease in strength, yellowing and brittleness on the surface, and later cracking and leakage.
The most troublesome part is: it has already occurred when there is no visible problem with the exterior of the item.
Why is ethylene glycol more troublesome?
Pure water is already tough enough, and ethylene glycol-based coolant adds another layer:
Ethylene glycol itself can generate acidic substances at high temperatures - the additives in the coolant (anti-rust, anti-scale) will further affect the materials - the coolant also carries pressure pulsations during circulation
These three combined are the reason why the selection of materials for liquid cooling pipelines must 'take a conservative approach'.
There is another type of medium that is easily overlooked: deionized water.
Deionized water has no ions, but it can 'pull' ions and additives from materials, and long-term soaking will also affect the material's condition. This type of medium is used in cold-plate liquid cooling in data centers.
So the judgment that 'crossing water is safe' is not valid—it depends on what kind of water it is, the temperature, and how long it flows.
In one sentence: As long as the medium is 'high-temperature water or high-temperature coolant,' the first step in material selection is to rule out PA6 / PA66.
2. Long-chain nylon: Why it can withstand
In the nylon family, the longer the chain, the lower the 'density' of amide bonds.
Low amide bond density = fewer sites that can be hydrolyzed = better hydrolysis resistance.
At the same time, it also brings a second benefit: low water absorption.
| Material | Balanced water absorption | Hydrolysis-resistant | Relative cost |
|---|
| PA6 | 8-10% | poor | Low |
| PA66 | 8-9% | poor | Low |
| PA610 | About 1.5% | Better | middle |
| PA612 | About 1.2% | Good | Medium-high |
| PA1010 / PA1012 | Less than 1.5% | Good | Medium-high |
| PA11 | About 0.8% | Good | Tall |
| PA12 | About 0.7% | Best | Tall |
(Typical magnitude, subject to the TDS of the specific grade)
Low water absorption rate provides a double benefit in liquid cooling pipelines:
① Size is stable. The piping has joints, clamps, and assembly positions. Water absorption and expansion/contraction can cause the sealing fit to fail. ② Slow hydrolysis. The material contains little water internally, so there is little 'water' involved in hydrolysis.
PA12 and PA11 are the most stable in this family. Their water absorption is below 1%, hydrolysis resistance is the best, and they can be used long-term in water and oil pipelines.
The cost is the price—PA12 is roughly several times the magnitude of PA6. In liquid cooling pipelines, it's not 'better to use,' it's 'you have to use it.'
Can hydrolysis stabilizers save PA66?
The answer is: it can improve, but it cannot solve the problem.
Adding hydrolysis stabilizers can indeed extend the lifespan of PA66 under humid and hot conditions, which is a relatively mature practice in the industry. But what it changes is 'how long before chain breakage occurs,' not 'whether chain breakage will occur.'
Under the operating conditions of long-term immersion in coolant at 90-120°C, even with a hydrolysis-stabilized system, the long-term performance of PA66 is still inferior to that of long-chain nylon. This is because the water absorption rate is what it is—once water enters, the raw materials for hydrolysis are present.
So the order of selecting materials should be: first eliminate unsuitable resins based on the medium and temperature, and then discuss which additives to use for optimization. Doing it the other way around means using additives to compensate for the shortcomings of the resin, which is costly and has limited effectiveness.
3. How to choose the main pipeline body
| Body part | Material direction | Reason |
|---|
| coolant hose | PA12 / PA11 / PA612 | Hydrolysis-resistant Soft Low-temperature resistant |
| corrugated tube sheath | PA612 / PA12 | Bending fatigue Hydrolysis resistance |
| Multi-layer barrier pipe | PA/EVOH composite | Barrier penetration (more common in fuel systems) |
| Rigid pipeline section | PA12-GF / PA612-GF | Pressure-resistant Hydrolysis-resistant |
| Quick coupler body | PA12 / PA612 (including reinforced) | Hydrolysis resistant Dimensionally stable |
| Sealing / O-ring seat | PA12 / Elastomer | Fit precision Rebound |
A few selection details:
① For bellows, what matters is 'bending fatigue,' not strength. For pipelines that need to be bent repeatedly and subjected to vibration, fatigue resistance is much more important than tensile strength.
② Low-temperature performance should be considered together. Long-chain nylon generally has better low-temperature toughness than PA66, but there are also differences between different chain lengths. Vehicles for cold regions must look at the -40℃ data.
③ The processing method determines the state of the material. Extruded pipes and injection-molded parts have completely different requirements for material flowability, and injection molding grades cannot be used for extrusion.
④ The transition position between the hose and the hard pipe should be calculated for stress separately. The rigidity of the hose (PA12, PA612) and the hard pipe section (PA12-GF) differs significantly, and the stress concentration at the connection is much greater than in the pipe body. Many pipe cracks do not occur in the pipe body but at the soft-hard transition. In terms of design, either make a gradient or add a fixed constraint at the transition to disperse the stress.
A judgment: On the liquid cooling pipeline, 'hydrolysis resistance' is the entry ticket, while 'dimensional stability brought by low water absorption' is the real threshold.
4. Quick Connectors: A More Difficult Area Than Pipelines
If the main pipeline has a problem, it’s slow; if the quick connector has a problem, it’s fast.
The coupler has three more requirements than the pipeline itself:
① Dimensional accuracy. The sealing surface depends on the fitting dimensions. If it absorbs moisture and expands by 0.1mm, it may change from 'no leakage' to 'seepage'.
② Long-term stress. The buckle and locking structure are in a stress state for a long time, observing creep.
③ Repeated plugging and unplugging. During maintenance, it will be disassembled and reassembled, and the plugging and unplugging lifespan is a hard specification.
Among these three, dimensional accuracy is the most prone to failure.
There is another common misconception about quick connectors: thinking 'as long as it can be plugged in, it's fine.'
Sealing is achieved through a combination of size and force. If the plug-in force is too small, the seal will not be tight; if it is too large, it can damage the clip during assembly. Therefore, the acceptance of quick connectors must consider two numbers simultaneously: the results of the seal test and the plug-in force curve.
Only testing the sealing and not the insertion and extraction force will result in problems only being exposed at the mass production stage.
So quick connectors in long-chain nylon tend more towards PA12 or PA612 with reinforcement—the low water absorption ensures dimensional stability, while the reinforcement supports the strength of the clips.
Here is a very practical self-check question:
Is this part of yours 'soaked in coolant for a long time,' or 'occasionally in contact with coolant'?
Long-term immersion: must use long-chain carbon, no exceptions - Occasional contact (for example, splashing): can relax to PA66 hydrolysis-resistant system, but testing is required
Many liquid cooling projects choose the wrong materials because they mistake 'long-term immersion' for 'occasional contact'.
How to choose a long carbon chain family
After deciding to go with longer carbon chains, choosing within the family becomes another issue. Here’s a concise hierarchy. PA11, PA12: they are bio-based or monomer-derived, have the lowest water absorption, the most stable hydrolysis resistance, and good flexibility. They are the traditional mainstays for pipelines and fittings, and also the most expensive. The copolymer-modified grades of PA12 are specially enhanced for fuel permeability resistance, making them the go-to for fuel pipelines.
Long carbon chain copolyamide: performance balances between PA12 and PA66, with a lower price, used in pipeline sections with moderate temperature and medium requirements. Selection logic in one sentence: for areas contacting ethylene glycol and fuel, choose according to the highest requirements; for transition sections and static sections, the balanced cost-reducing type can be used.
The scariest thing is the reverse—using the best material for the static section, but the contact point uses cheap material. The money is spent, yet the leakage points remain. Draw a contact map for the medium and allocate material grades according to the map, so that the money for long carbon chains is spent where it really matters.
5. Five Pitfalls of Liquid Cooling Pipelines
Pitfall 1: Using PA66 for coolant pipes. It can hold up in the short term, but over time it undergoes hydrolysis and chain scission. This type of failure usually only becomes apparent after two or three years, by which time the warranty period has passed.
Pitfall 2: Only looking at the original strength. For liquid-cooled components, you must consider the strength retention after hydrolytic aging (for example, data after 1000 hours at different temperatures), not the initial tensile strength.
Pitfall 3: Ignoring the specific formulation of the coolant. Different formulations have significantly different corrosion effects on materials. When selecting materials, you should perform soaking tests with the actual coolant to be used, and not substitute it with a 'universal coolant'.
Pitfall 4: Using the same grade for both pipelines and quick connectors. Pipelines require flexibility and hydrolysis resistance, while quick connectors need precision and rigidity; their requirements are different.
Pitfall 5: Forgetting about low temperature. Long-chain nylon has good low-temperature resistance, but after adding glass fiber, its low-temperature toughness decreases. Components for cold regions must be verified.
6. Borders
| Scene | Conclusion | Explanation |
|---|
| Long-term 90-120℃ coolant | long-chain nylon | PA12 / PA11 / PA612 |
| Long-term >120℃ high-temperature water circuit | Need to be cautious | Replace PA1010 or switch to a metal/composite solution |
| Strong acid and alkaline medium | Not suitable | Requires special resistance to chemical systems |
| High-pressure fuel system | PA11 / PA12 | Oil-resistant Barrier (multilayer structure) |
| Extremely low temperature below -40℃ | Need to be cautious | Toughening system or elastomer |
A real feeling in the industry
There is a type of inquiry that makes us ask a few more questions every time we see it:
The customer brought over a cracked corrugated tube and said, 'This is nylon, it's cracked. Do you have a stronger nylon one?'
If you ask, nine times out of ten it is a coolant pipe made of PA66 or PA6.
At this time, our usual response is: it's not about using stronger materials, it's about using 'waterproof' materials.
Because the customer asked about 'sturdiness,' but the problem has nothing to do with strength—it is hydrolyzed, with cracks caused by chain breakage, which has nothing to do with strength. If you switch to a higher-strength PA66, it will still crack; it will just crack a little later.
Our follow-up questions are generally three: Is it water or ethylene glycol running through the pipe? What is the long-term temperature? How long did it take to crack?
Leaks, low temperature, cracks appear after several years → The material selection is on the conservative side and can be adjusted. Leaks with ethylene glycol, temperature above 90℃, cracks appear in a year or two → Must switch to long-chain materials, there is no intermediate solution.
The same character '裂' has two different answers. If you get one question wrong, changing the material ten times won't help.
Two Reader Inquiries
Follow-up question one: Can existing PA66 systems survive by adding antihydrolytic agents? It can alleviate this, but there is a limit. Antihydrolytic agents can significantly extend the lifespan of PA66 in ethylene glycol, extending the standard operating cycle from two to three years to over five years. This is a mature route used by many cooling systems.
But be clear: antihydrolytic agents cannot change the density of amide groups. In fast-contact joints with high temperature, high flow rate, and high stress, they only delay the failure time, not cancel it. So the criterion is based on position: the body and static section, PA66 is sufficient for hydrolysis resistance; For contact ports and moving sealing areas, directly apply long carbon chains—don't skimp.
Follow-up question 2: How do you determine the criteria for liquid leakage? It is recommended to divide the data into three levels: Level 1 is surface moisture marks, which should be wiped off without recurrence and recorded for observation; Level 2 is drip seepage, which forms drops within 24 hours and is in the rectification process; Level 3 is continuous leakage, which requires immediate shutdown and replacement. After the criteria are written into the operation and maintenance manual, the most important action is to keep samples for each stage for inspection. The anatomical conclusions of the seepage parts are the most valuable input for next-generation product selection, more accurate than any experimental data.
Casually explained the acceptance procedures for liquid cooling pipelines: besides the standard dimensions and appearance, it is recommended to add two targeted inspections upon arrival—first, sampling swelling rate to measure the sample in coolant for 72 hours; if it exceeds the standard, it is immediately returned; Second, check the sealing surface condition, using a magnifying glass to check for flow marks and material shortages on the sealing belt, which cannot be detected with a caliper. Each of these two actions takes ten minutes, which can block the vast majority of batch issues. The stricter the acceptance inspection, the fewer calls after-sales there are.
Liquid Leakage Level 3 Response Card
Operation and Maintenance On-site Equip a Level 3 Liquid Leakage Response Card. Level 1, Moisture Mark: Surface is moist and does not drip; actions include marking the location, taking photos, wiping and observing for 48 hours, entering into the ledger for tracking, no need to shut down. Level 2, Drip Level: Dripping within 24 hours; actions include taking photos and sampling, arranging spare parts replacement windows, sealing and sending failed parts back for analysis. The system can operate with defects but is required to rectify within a specified period.
Level 3, Continuous Leakage Level: Positive pressure seepage or increased dripping speed; actions include immediately isolating the cabinet, cutting off power to drain liquid, and activating emergency plans. This level has no room for discussion. At the end of each level of response, it's the same action: send the failed parts back for dissection analysis, and the seepage parts are the most honest teachers of liquid cooling systems. Their fractures and cracks will tell you where to go for the next selection process. Stick the response card in the maintenance duty room, clearly write the responsible person, and it's more effective than any WeChat group notification.
By the way, to answer a frequently asked question: Should the liquid cooling piping also be fitted with a long carbon chain to get it done in one step? Our suggestion is to look at them separately. The pipeline itself operates under milder conditions than joints, with low flow rate, no assembly stress, uniform temperature, and mature performance records in this area. The cost of fully long carbon chains increases significantly, so saving money is more cost-effective for the necessary location.
's standard for judgment isn't that expensive material is always safer, but that every location should be matched with the right material, and every location is validated equally. Waste and saving the wrong places are major taboos in material selection.
Conclusion
Liquid cooling pipeline material selection—the logic is actually very clean:
The medium is water or coolant→ cross out PA6/PA66→ go for the long carbon chain→ and specify the exact grade based on temperature and precision.
After four steps, the only thing left is price and verification.
The only thing to watch out for is "just make do with PA66 first, replace it when it breaks." For liquid cooling parts, the cost of this process isn't rework, but batch leakage within the warranty period.
One last reminder: When selecting liquid cooling parts, you can be convinced by "price," not by "experience." Just because others don't have problems with PA66 doesn't mean your medium and temperature won't have issues
