74 PA66 与 PC：耐温、透光、抗冲的三个分量怎么权衡
一、为什么这两个料经常被并列
PA66 和 PC 是改性塑料里两个方向完全不同的大料：
PA66：结构件的主力料，半结晶型尼龙。
PC：透明/抗冲主力料，非晶型聚碳酸酯。
在很多项目里，两者是"不重叠但放一起比较"的局面——一个是结构件首选，一个是透明件首选。这一篇就讲清楚在什么场合必须切到 PC，什么场合必须用 PA66。
充电桩上有一对邻居件最能说明 PA66 与 PC 的关系：观察窗与门锁座。观察窗要透明耐候，PC 当仁不让；门锁座要刚性耐温还要过灼热丝，PA66 阻燃体系上。
有个桩企曾经想统一成 PC 阻燃，减少一种料号。验证发现门锁座的螺纹嵌件在 PC 里蠕变保持力不够，锁具间隙冬天变大。
最后维持了双料方案，采购经理的说法是：透明归透明，结实归结实，一个桩上两种料不丢人，装错了才丢人。
分工这件事，在材料上永远成立。
二、化学结构的差异
PA66：脂肪族聚酰胺，含酰胺基，半结晶。
PC：双酚 A 型聚碳酸酯，主链含碳酸酯基，非晶。
结构差异决定了三个根本不同：
① 透明性
PC 非晶无定形区，光通过率高。PC 的透光率 88-92%，可以做光学件、透明件。PA66 半结晶，光通过率不到 10%，只能做白色或不透明件。
② 抗冲击
PC 的冲击强度极高（缺口冲击 70-90 kJ/m²），是 PA66 的 7-10 倍。即使在 -40℃，PC 仍保持高冲击，而 PA66 已经脆化。
③ 耐温
PC 的玻璃化温度 145-150℃，长期工作 120-130℃。PA66 长期 120-150℃（GF 后）。两者在"耐温"档位接近，但PC 不耐沸水——沸水浸泡会让 PC 应力开裂。
所以这三点的差异，决定了 PA66 和 PC 的应用完全不同。
三、关键性能对照
| 指标 | PA66 | PC | 差异方向 |
|---|
| 透明度 | 半透明/不透明 | 透明 88-92% | PC 远远胜 |
| 拉伸强度（未增强，MPa） | 80-90 | 60-70 | PA66 略高 |
| 弯曲模量（未增强，GPa） | 3.0-3.5 | 2.2-2.4 | PA66 高一档 |
| 缺口冲击（kJ/m²） | 5-10 | 70-90 | PC 是 PA66 的 7-10 倍 |
| 玻璃化温度（℃） | 50-65 | 145-150 | PC 高一档 |
| 长期工作温度上限（℃） | 120-150 | 120-130 | 接近 |
| 吸水率（23℃ 饱和，%） | 2.0-2.5 | 0.2-0.3 | PC 极低 |
| 焊接强度 | 中 | 低 | PA66 强 |
| 注塑流动性 | 中 | 良好 | PC 好 |
| 玻纤协同效率 | 高 | 中 | PA66-GF 强 |
| 耐醇 / 耐弱酸 | 中 | 差 | PC 较差 |
| 耐碱 | 差 | 差 | 两者都差 |
| 抗紫外老化 | 中 | 差 | PC 偏弱 |
| 单价（普通级，参考） | 1.0× | 1.4-1.8× | PC 略贵 |
四、PC 胜在何处
① 透明件、透明罩、光学件
这是 PC 的核心位置。车灯罩、玻璃替代件、透明壳体、仪表盘镜片、安全眼镜、食品级透明容器。PA66 完全做不了透明件——这点没商量。
② 高冲击需求
手机外壳、头盔、防护罩、儿童用品、行李箱。PC 的抗冲击是 PA66 的 7-10 倍，低温下也保持。这是 PC 的另一个不可替代位置。
③ 几乎不吸水
PC 0.2-0.3% 的吸水率，对精密尺寸件极友好。长期户外暴露后尺寸不飘移。这是 PC 在精密光学件上稳定的原因。
④ 食品接触级
PC 在食品接触合规上比 PA66 简单——配方简单（无双酚 A 风险外的少数关注点）。但要注意双酚 A 在某些国家的限制——近年 BPA-free 改用其他共聚 PC 或 Tritan。
五、PA66 胜在何处
① 焊接组合件
PC 的焊接强度极差，几乎不能超声波焊。PA66 的焊线强度比 PC 高很多。电子电器、连接器、电池模组组合件，PA66 是正确选择。
② 玻纤增强后的强度
PA66-GF30 vs PC-GF30：GF 后 PA66 强度性能略胜 PC，且 PA66-GF 在长期载荷下尺寸稳定更好。PA66-GF30 在结构件上的"撑得住"比 PC 更稳。
③ 耐醇 / 耐弱酸
PC 在醇、酮、酯类溶剂里会应力开裂。PA66 在这些介质里表现优于 PC。PA66 是耐介质的料。
④ 抗紫外老化
PC 长期 UV 暴露会变黄。PA66 比 PC 略稳。户外透明的 PC 通常要加 UV 涂层或选 ASA / PMMA 替代。
六、两者都不擅长的工况
① 高温 ≥150℃ 长期
两者都不行。PC 150℃ 以上软化，PA66 长期 150℃ 已接近上限——走 PA46 / PA6T / PPA / PPS。
② 食品级透明 + 高温
PC 双酚 A 风险限制 + PC 不耐沸水——这一组合要特殊配方。食品级透明 + 高温是 Tritan / 高温 PC / 共聚酯的主战场。
③ 强碱环境
两者都不耐碱。PA66 胺基水解、PC 碳酸酯基水解。
④ 户外长期透明
PC 户外 5 年以上开始发黄。走 PMMA / 涂层 PC / 玻璃化复合。
⑤ 高刚性 + 高透明
PC 透明但刚性不如 PA66-GF30，PA66-GF 高刚性但不透明。这种工况要做复合（比如双层注塑 PA66-GF + PC），工艺复杂。
七、四条双向应用的判断
很多项目里 PA66 和 PC 不是必须二选一，而是分工：
① 透明外壳 + 内部结构件
外壳 PC（透明好看），内部结构件 PA66-GF30（强度高）。家电、消费电子这种做法很常见。
② 透明面板 + 黑色齿轮
面板 PC（透明），齿轮 PA66-GF30（强度）。办公设备、打印机常用。
③ PC/PA 合金
直接用 PC/PA 合金，得到"部分透明 + 部分强度"的中间性能。这种合金在工具箱、汽车内饰上常见。
④ 双色注塑
硬胶 PC + 软胶 TPU，透明 PC 与黑色 PA66 二次注塑——很多高端厨具、电动工具外壳用这种。
分工选料比二选一更实用。
八、四个延伸判断（结构件 vs 透明件对比）
判断一：透明是 PC 的入场券，不是"装饰"。透明件几乎只能用 PC、PMMA、COC、COP、玻璃。PA66 不在这个列表。透明需求一旦确定，PA66 自动出局。
判断二：抗冲击差距比想象更大。PC 的 70-90 kJ/m² 缺口冲击 vs PA66 的 5-10 kJ/m²，差 7-10 倍。安全件、户外件、儿童用品几乎只能用 PC。
判断三：玻纤增强不是 PC 的强项。PC 加玻纤流动性急剧下降，且 GF/PC 界面结合不如 GF/PA66。所以高刚性 + 透明 = 几乎不可能——要么牺牲透明，要么牺牲刚性。
判断四：透明 + 食品 + 高温是个三角悖论。同时满足这三点要特殊配方。普通 PC 已被 BPA-free 替代，Tritan、高温 PC、共聚酯各有位置。
九、边界声明
| 工况 | 建议 |
|---|
| 透明件（外壳、镜片、罩） | PC |
| 高冲击件（防护、儿童用品） | PC |
| 焊接组合件 | PA66 |
| 耐醇 / 耐弱酸 | PA66 |
| 结构件高刚性 | PA66-GF30 |
| 精密尺寸（不吸水） | PC |
| 食品级透明（双酚 A 限制地区） | Tritan / PA 高透明配方 |
| 高温 ≥150℃ | 走 PPA / PA46 / PPS |
| 户外透明件 + UV 稳定性 | 涂层 PC / PMMA |
附：两个选型实例
实例一：电动工具外壳
工况：高冲击（用户从一米高跌落）；要求外壳不破损；要求有强度。
推演：
高冲击 → PC
强度 → PC 略弱但加 10-20% GF 可补
综合 → PC-GF20
结论：PC-GF20。
实例二：连接器绝缘件
工况：电绝缘；焊接组合件；要求耐温 130℃。
推演：
绝缘 → 两者都可行
焊接 → PC 不可，PA66 可
耐温 → 两者都过 130℃
综合 → PA66-GF30 + 阻燃
结论：PA66-GF30 + 阻燃。透明在这个件上不是需求，所以 PA66 优势明显。
行业感：透明 vs 强度的边界，最容易被"客户想好看"模糊掉。 我们见过一个做电子秤的项目，外壳原本用 PA66-GF30（耐摔 + 强度），但 PM 说"客户喜欢透明"，改成 PC。结果大批量出货后，2 万台中有 800 台因为跌落试验裂纹退机——透明好看，但 PC 在跌落冲击的耐受反而比 PA66-GF30 低很多吗？不一定，但 PA66-GF30 的延展性更好，"砸后变形不裂"，PC 可能裂。 材料选型是工况选型，不是个性偏好。 这次决策中"客户喜欢好看"看似对，但工程角度看"用 PC + 加厚"可能更稳。
一个油杯视窗的耐化学课
起点是空压机油杯视窗选了 PC，图它的透明与冲击强度。
潜伏期三个月，透光开始下降。爆发在半年后，视窗内壁出现蛛网状裂纹，油雾长期侵蚀加应力开裂，PC 的短板被工况精准命中。
结算方案：视窗换耐化学透明的其他材质，油路密封圈同步换氟橡胶。PA66 在这个件上也不行——不透明，直接出局。
这个案例常被引用：透明件先问介质，结构件先问温度，选型的次序不能乱。
PA66 与 PC 的对比会，三个追问。
追问一：接触什么介质？ 油与有机溶剂直接淘汰 PC。
追问二：有没有冲击与低温？ PC 低温韧性好，寒冷地区占优。
追问三：灼热丝或阻燃要求多少？ 750℃ 灼热丝这类电气要求，PA66 阻燃体系更顺。
延伸：四步速判（PA66 vs PC 方向）
四步把这场"结构 vs 透明"对比压成可走动作：
第一步：问"是否要透明"。透明 → PC；不透明 → PA66。这一步直接决定大半。
第二步：问"是否要高抗冲"。PC 缺口冲击 70-90 kJ/m²，PA66 仅 5-10 kJ/m²。安全件、户外件、儿童用品 → PC 不可替代。
第三步：问"是否要焊接"。PC 焊接强度极差，PA66 焊接强度远高于 PC。焊接组合件 → PA66。
第四步：算耐温。长期 ≤130℃，两者都过；长期 ≥130℃ → 走 PA46 / PPA / PPS（PA66 也不行）。
这四条之外还有"分工"的方案：透明外壳 PC + 内结构 PA66-GF30，很多高端产品都这样用——这种分工比二选一更实际。
实战：三步走
第一步：透明 vs 不透明二选一。透明 → PC；不透明 → PA66-GF。这一步必须先做。
第二步：抗冲击 vs 焊接单独看。PC 抗冲击高但不能焊，PA66 可焊接但脆。两个方向选一个先。
第三步：高温件二选一走 PPA/PA46。长期 ≥130℃ 时 PA66 也不行，但透明 + 高温件 PC 也做不到——这种工况要么牺牲透明，要么牺牲耐温。
收尾补一张三问三答。
| 高频问题 | 一句话回答 |
|---|
| 谁更耐冲击？ | PC，尤其低温冲击 |
| 谁更耐磨？ | PA66，对磨场合 PC 出局 |
| 能做透明件吗？ | PC 能，PA66 不能 |
| 电气件用谁？ | 看灼热丝与 CTI 要求，多数落 PA66 |
再补一个反向案例。
有个项目把 PC 用在了纺织机的导纱件上，看中它的表面硬度。两周后纱线把导纱槽磨出沟痕，PC 对纤维的耐磨性远不如耐磨 PA66。硬度高不等于耐磨，这是滑动件选型最经典的误读，每一次现场都会再教一遍。
数字的来历：两三个为什么
PC 的应力开裂怎么来的？两个因素叠加：内应力与介质。注塑残余应力是内因，油雾、清洗剂这类介质是外因，介质渗入微裂纹削弱界面，裂纹沿着应力集中处生长，蛛网纹就是这么画出来的。透明件的耐化学评估，本质是在查这两条线的交汇点。
灼热丝 750℃ 为什么 PA66 顺？阻燃 PA66 的分解成炭特性在灼热丝测试里占便宜，配上合适的阻燃体系，电气件的这一关通过率高。PC 也能阻燃，但电气件还叠加 CTI、介电等要求，PA66 阻燃体系的整体匹配度更好。
电气件选 PA 不是习惯，是多项指标交集的结果。
实操清单：电气与透明件六动作
透明件先问介质清单，油与溶剂直接排除 PC
PC 件做退火或降应力设计，防蛛网纹
灼热丝与 CTI 要求先确认，再谈阻燃体系
金属嵌件做蠕变保持力复核，季节温差算进去
寒区项目标注低温冲击，PC 的主场要标出来
耐磨滑动件禁用 PC，红线写进选型手册
透明与结实是两套逻辑，强扭在一起，总有一头吃亏。图纸上一条分区线，省掉的是两个部门的来回扯皮。
速判手册：PA66 与 PC 分工速查
| 工况 | 首选 | 说明 |
|---|
| 透明 + 户外 | PMMA 或 PC | 紫外优先 PMMA，冲击优先 PC |
| 透明 + 接触油 | 特殊透明料 | PC 出局，PA 也不行 |
| 结构件 + 电气要求 | 阻燃 PA66 | 灼热丝与 CTI 匹配 |
| 低温冲击件 | PC | 寒区优势明显 |
这张表能解决八成的初始争论，剩下两成靠测试。分工表的用法是先定性再定量：先把件放进某一格，再去核那一格里的具体牌号与数据，比把所有参数摊在一张大表上快得多。
有个关于应力开裂的现场识别技巧值得记录：蛛网纹从应力集中处开始，看裂纹走向就能反推内应力的来源。裂纹围着螺丝孔放射，多半是装配过扭；裂纹沿着流纹分布，多半是注塑残余应力加介质。两种解法不同，前者改装配工艺，后者退火或改设计。
把看裂纹的本事教给现场，比往返寄样快一周。
最后一句给采购：PA66 与 PC 的价格周期不同步，一个跟己二腈走，一个跟光气与双酚走。年度框架协议里留一点切换弹性，行情大年能省出真金白银。这是双料方案的隐藏福利，用的人不多，用过都说好。
双料方案的仓储也有讲究：PA66 阻燃料与 PC 的干燥要求不同，吸湿率、烘料温度、烘料时间三组参数不同，混用烘料斗会造成两边都不达标。产线上最省事的办法是烘料斗分区并标注颜色，料斗管理跟着料号走。
这个细节小，但它决定的是批次的稳定性，出问题时的表现又很隐蔽——水分超标的两批件，做出来都能过出厂检验，一个月后才在客户端慢慢冒头。把干燥纪律当制度建，是电气件与透明件共用的功课。
结语
PA66 和 PC 的分工，是"结构件"与"透明件"的完全分离。
PA66 是结构件主场：强度、焊接、耐介质、玻纤增强——电子电气、汽车、结构件。
PC 是透明件主场：透光、高抗冲、精密尺寸——透明罩、光学件、安全件。
选型的起点不是"哪个更贵更好"，而是"我这个件需要透明吗"。 需要透明，PC 是答案之一；不需透明，PA66 是更稳的选择。
74 PA66 and PC: How to balance the three components of heat resistance, light transmittance, and impact resistance
1. Why are these two materials often listed together?
PA66 and PC are two completely different types of base materials in modified plastics:
PA66: The main material for structural parts, semi-crystalline nylon.
PC: Transparent/impact-resistant main material, amorphous polycarbonate.
In many projects, the two are in a situation of 'non-overlapping but compared together' — one is preferred for structural parts, and the other is preferred for transparent parts. This article will clearly explain in which situations you must switch to PC and in which situations you must use PA66.
There is a pair of neighboring components on the charging pile that best illustrate the relationship between PA66 and PC: the inspection window and the door lock base. The inspection window needs to be transparent and weather-resistant, and PC is naturally the choice; the door lock base needs rigidity, heat resistance, and must pass the glow wire test, which is where the flame-retardant PA66 system comes in.
A certain piling company once wanted to standardize to PC flame retardant to reduce one type of material number. Verification found that the threaded inserts of the door lock base did not have enough creep retention strength in PC, causing the lock gap to increase in winter.
In the end, we stuck with the dual-material solution. The procurement manager said: 'Transparency is transparency, sturdiness is sturdiness; it's not shameful to have two types of materials on one pile, only installing them incorrectly is shameful.'
The matter of division of labor is always valid in theory.
2. Differences in Chemical Structure
PA66: Aliphatic polyamide, contains amide groups, semi-crystalline.
PC: Bisphenol A type polycarbonate, the main chain contains carbonate groups, amorphous.
Structural differences determine three fundamental distinctions:
① Transparency
PC is an amorphous region with high light transmittance. The light transmittance of PC is 88-92%, and it can be used for optical parts or transparent parts. PA66 is semi-crystalline, with a light transmittance of less than 10%, and can only be used for white or opaque parts.
② Impact Resistance
PC has extremely high impact strength (notched impact 70-90 kJ/m²), which is 7-10 times that of PA66. Even at -40°C, PC still maintains high impact resistance, while PA66 has already become brittle.
③ Temperature Resistance
The glass transition temperature of PC is 145-150℃, and its long-term operating temperature is 120-130℃. PA66 has a long-term temperature range of 120-150℃ (after GF). Both are close in the "temperature resistance" category, but PC is not resistant to boiling water—immersion in boiling water can cause stress cracking in PC.
So these three differences determine that the applications of PA66 and PC are completely different.
3. Key Performance Comparison
| Indicator | PA66 | PC | Direction of difference |
|---|
| Transparency | Translucent/Opaque | Transparent 88-92% | PC far superior |
| Tensile Strength (Unreinforced, MPa) | 80-90 | 60-70 | PA66 slightly higher |
| Bending modulus (unreinforced, GPa) | 3.0-3.5 | 2.2-2.4 | PA66 High Grade |
| Notch Impact (kJ/m²) | 5-10 | 70-90 | PC is 7-10 times that of PA66 |
| Glass transition temperature (°C) | 50-65 | 145-150 | PC high-end |
| Maximum long-term operating temperature (°C) | 120-150 | 120-130 | approach |
| Water absorption rate (23℃ saturated, %) | 2.0-2.5 | 0.2-0.3 | PC extremely low |
| Welding strength | middle | Low | PA66 Strong |
| Injection molding fluidity | middle | Good | PC is good |
| Glass Fiber Synergy Efficiency | Tall | middle | PA66-GF Strong |
| Alcohol-resistant / Weak acid-resistant | middle | poor | PC is poor |
| Alkali-resistant | poor | poor | Both are bad |
| UV aging resistance | middle | poor | PC is weak |
| Unit price (standard grade, reference) | 1.0× | 1.4-1.8× | PC is slightly expensive |
4. Where the PC Wins
① Transparent parts, transparent covers, optical components
This is the core position for PCs. Headlamp covers, glass replacements, transparent housings, dashboard lenses, safety goggles, food-grade transparent containers. PA66 cannot make transparent parts at all — there is no negotiation on this point.
② High-impact demand
Mobile phone cases, helmets, protective covers, children's products, luggage. The impact resistance of PC is 7-10 times that of PA66, and it is maintained at low temperatures. This is another irreplaceable position for PC.
③ Almost does not absorb water
PC has a water absorption rate of 0.2-0.3%, which is very friendly to precision dimension parts. After long-term outdoor exposure, the dimensions do not drift. This is the reason why PC is stable in precision optical components.
④ Food contact grade
PC is simpler than PA66 in terms of food contact compliance—its formulation is simple (with only a few concerns aside from the risk of Bisphenol A). However, attention should be paid to Bisphenol A restrictions in some countries—in recent years, BPA-free versions have switched to other copolymer PCs or Tritan.
5. Where PA66 Excels
① Welded assembly
The welding strength of PC is extremely poor, and it can hardly be ultrasonic welded. The weld line strength of PA66 is much higher than that of PC. For electronic and electrical appliances, connectors, and battery module assemblies, PA66 is the correct choice.
② Strength after glass fiber reinforcement
PA66-GF30 vs PC-GF30: After adding GF, PA66 has slightly better strength performance than PC, and PA66-GF has better dimensional stability under long-term load. PA66-GF30 is more reliable than PC in supporting structural components.
③ Alcohol-resistant / Weak acid-resistant
PC will experience stress cracking in alcohol, ketone, and ester solvents. PA66 performs better than PC in these media. PA66 is a material resistant to these media.
④ Anti-ultraviolet aging
PC will yellow after long-term UV exposure. PA66 is slightly more stable than PC. Outdoor transparent PC usually needs a UV coating or an alternative like ASA/PMMA.
6. Operating conditions that neither of them is good at
① High temperature ≥150℃ long-term
Neither of them is feasible. PC softens above 150°C, and PA66 is already near its long-term limit at 150°C — go with PA46 / PA6T / PPA / PPS.
② Food-grade transparent high temperature
PC Bisphenol A risk restriction PC is not resistant to boiling water—this combination requires a special formula. Food-grade transparent High temperature is the main battlefield of Tritan / high-temperature PC / copolyester.
③ Strong alkaline environment
Both are not alkali-resistant. PA66 amine hydrolysis, PC carbonate hydrolysis.
④ Long-term outdoor transparency
PC starts to yellow after more than 5 years outdoors. Use PMMA / coated PC / glass composite.
⑤ High rigidity High transparency
PC is transparent but not as rigid as PA66-GF30, while PA66-GF is highly rigid but not transparent. For this working condition, a composite (such as double-layer injection molding with PA66-GF and PC) is needed, which involves a complex process.
7. Judgment of the Four Two-Way Applications
In many projects, PA66 and PC are not necessarily a choice between the two, but rather have divided roles:
① Transparent casing Internal structural components
The outer shell is made of PC (transparent and attractive), and the internal structural parts are made of PA66-GF30 (high strength). This approach is very common in home appliances and consumer electronics.
② Transparent panel Black gear
Panel PC (transparent), gear PA66-GF30 (strength). Commonly used in office equipment and printers.
③ PC/PA Alloy
Directly use PC/PA alloy to obtain intermediate properties of 'partially transparent and partially strong.' This kind of alloy is commonly seen in toolboxes and car interiors.
④ Two-color injection molding
Hard plastic PC, soft plastic TPU, transparent PC and black PA66 double injection molding — this is used for many high-end kitchenware and power tool housings.
Dividing labor and selecting materials is more practical than choosing between two options.
8. Four Extended Judgments (Structural Parts vs Transparent Parts Comparison)
Judgment 1: Transparency is the entry ticket for PC, not a 'decoration.' Transparent parts can almost only use PC, PMMA, COC, COP, or glass. PA66 is not on this list. Once the transparency requirement is determined, PA66 is automatically ruled out.
Judgment Two: The impact resistance gap is larger than imagined. PC's 70-90 kJ/m² high-impact vs PA66's 5-10 kJ/m², a difference of 7-10 times. Safety components, outdoor parts, and children's products can almost only use PC.
Judgment Three: Glass fiber reinforcement is not PC's strength. When PC is reinforced with glass fiber, its flowability drops sharply, and the GF/PC interface bonding is not as good as GF/PA66. Therefore, high rigidity + transparency = almost impossible—either transparency is sacrificed, or rigidity is sacrificed.
Judgment Four: Transparency, Food, High Temperature is a triangular paradox. Meeting all three at the same time requires a special formula. Ordinary PC has been replaced by BPA-free alternatives, while Tritan, high-temperature PC, and copolyesters each have their own place.
9. Boundary Statement
| Operating condition | Suggestion |
|---|
| Transparent parts (housing, lens, cover) | PC |
| High-impact parts (protective, children's products) | PC |
| Welded assembly | PA66 |
| Alcohol-resistant / Weak acid-resistant | PA66 |
| High rigidity of structural components | PA66-GF30 |
| Precision dimensions (non-absorbent) | PC |
| Food-grade transparent (BPA-restricted area) | Tritan / PA High Transparency Formula |
| High temperature ≥150℃ | Walk PPA / PA46 / PPS |
| Outdoor transparent parts UV stability | Coated PC / PMMA |
Appendix: Two selection examples
Example 1: Electric Tool Housing
Working conditions: high impact (user drops from a height of one meter); the requirement is that the shell must not be damaged; strength is required.
Deduction:
High Impact → PC
Strength → Slightly weaker than PC but can be compensated by adding 10-20% GF
Comprehensive → PC-GF20
Conclusion: PC-GF20.
Example 2: Connector Insulation Part
Working conditions: electrical insulation; welded assemblies; requires temperature resistance of 130℃.
Deduction:
Insulation → Both are feasible
Welding → Not possible with PC, possible with PA66
Temperature resistance → Both exceed 130℃
Comprehensive → PA66-GF30 Flame Retardant
Conclusion: PA66-GF30 is flame retardant. Transparency is not a requirement for this part, so the advantage of PA66 is obvious.
Industry sense: the boundary between transparency and strength is most easily blurred by 'customers want it to look good.' We once saw a project making electronic scales where the casing was originally PA66-GF30 (impact-resistant, strong), but the PM said 'customers like transparency,' so it was changed to PC. As a result, after mass shipments, 800 out of 20,000 units were returned due to cracks from drop tests—transparent looks nice, but is PC really much less impact-resistant than PA66-GF30? Not necessarily, but PA66-GF30 has better ductility, 'deforms without cracking when dropped,' while PC may crack. Material selection is based on working conditions, not personal preference. In this decision, 'customers want it to look good' may seem right, but from an engineering perspective, 'using thicker PC' might be more reliable.
A chemical resistance course for an oil cup window
The starting point was choosing PC for the air compressor oil cup sight glass, because of its transparency and impact strength.
The incubation period is three months, and light transmission begins to decrease. An outbreak occurs after half a year, with spiderweb-like cracks appearing on the inner walls of the window. Long-term corrosion by oil mist combined with stress-induced cracking has precisely hit the weak spot of PC under operating conditions.
Settlement plan: Replace the window with chemically resistant transparent material, and simultaneously replace the oil circuit sealing ring with fluororubber. PA66 also doesn't work on this part—it’s opaque, so it’s immediately out.
This case is often cited: for transparent parts, ask about the medium first; for structural parts, ask about the temperature first. The order of selection should not be mixed up.
PA66 Comparison with PC, three follow-up questions.
Follow-up Question 1: What medium does it come into contact with? Oil and organic solvents directly eliminate PC.
Follow-up Question 2: Is there impact and low temperature? PC has good low-temperature toughness and is advantageous in cold regions.
Follow-up Question 3: What are the requirements for hot wire or flame retardant? For electrical requirements like 750°C hot wire, PA66 flame-retardant systems are more efficient.
Extension: Four-step quick judgment (PA66 vs PC direction)
Four steps: Compare this "structure vs transparent" match into a walkable action:
Step one: Ask "Do you want to be transparent?" Transparent → PC; Opaque → PA66. This step directly decides most of the difference.
Step two: Ask "Do you want high impact resistance?" PC notch impact is 70-90 kJ/m², PA66 only 5-10 kJ/m². Safety parts, outdoor items, children's products→ PC is irreplaceable.
Step 3: Ask "Do you want to solder?" PC has very poor soldering strength, PA66 is much stronger than PC. Welded assembly → PA66.
Step four: Calculate temperature resistance. Long-term ≤ 130°C, both pass; Long-term ≥ 130°C→ use PA46 / PPA / PPS (PA66 doesn't work).
Besides these four, there's another 'division of labor' solution: transparent shell PC + internal structure PA66-GF30. Many high-end products use this method—this division of labor is more practical than choosing one or the other.
Practical: Three steps
Step one: choose transparent versus opaque. Transparent → PC; Opaque → PA66-GF. This step must be done first.
Step two: Look at impact resistance vs. welding separately. PC has high impact resistance but can't be welded; PA66 can be welded but is brittle. Choose one of the two directions first.
Step three: For high-temperature parts, choose between PPA/PA46. For long-term ≥ at 130°C, PA66 is also not possible, but transparent + high-temperature parts can't be achieved either by PC — this condition either sacrifices transparency or temperature resistance.
Adding a three-question, three-answer post at the end.
| High-frequency questions | One-sentence answer |
|---|
| Which is more impact-resistant? | PC, especially low-temperature impact |
| Which is more wear-resistant? | PA66, PC is out of the field for grinding |
| Can it be made for transparent parts? | PC Yes, PA66 can't |
| Who uses for electrical parts? | Depends on the requirements for hot threads and CTI, most are PA66 |
adding a reverse case.
One project used PC for the yarn guide parts of textile machines, focusing on its surface hardness. After two weeks, the yarn would grind the guide slot into grooves, and PC's fiber wear resistance would be far inferior to PA66. High hardness does not mean wear resistance—this is the classic misconception in sliding part selection, and it's taught again every time.
Origin of the Number: How do the stress cracks of two or three
PC come about? Two factors combined: internal stress and medium. Residual stress in injection molding is the internal factor; media like oil mist and cleaning agent are external. The medium seeps into microcracks weakening the interface, and cracks grow along the stress concentration—that's how spiderweb patterns are drawn. The chemical resistance assessment of transparent parts essentially involves checking the intersection of these two lines.
Why is PA66 smooth for 750°C hot wire? The decomposition to carbon characteristic of flame-retardant PA66 is advantageous in hot wire tests. Paired with a suitable flame-retardant system, electrical components have a high pass rate at this stage. PC can also be flame-retardant, but electrical components also have CTI, dielectric requirements, and other requirements, so the overall compatibility of PA66 flame-retardant systems is better.
Choosing PA for electrical components is not a habit; it is the result of multiple intersecting indicators.
Practical Checklist: Electrical and transparent parts six actions
Transparent parts first ask about the medium list, oil and solvent directly exclude PC
PC parts should be annealed or stress reduction design, anti-spider-weaving
Scorching wire and CTI must be confirmed first, then discuss flame-retardant system
Metal inserts should be checked for creep retention, seasonal temperature differences should be included
Cold region projects should be marked with low-temperature shock, PC's home field must be marked
Wear-resistant sliding parts prohibited from PC, red line written in the selection manual
Transparent and sturdy are two different logics; if you force them together, one end will lose out. The zoning line on the blueprint saves the back-and-forth between the two departments.
Quick Judgment Manual: PA66 and PC Division Quick Check
| Operating Conditions | Preferred | Explanation |
|---|
| Transparent + Outdoor | PMMA or PC | UV Priority PMMA, Impact Priority PC |
| Transparent + Contact Oil | Special transparent material | PC is out, PA is also not good |
| Structural parts + electrical requirements | Flame-retardant PA66 | Glow-hot wire and CTI matching |
| Low-temperature impact parts | PC | Clear cold region advantage |
This table can resolve 80% of the initial debate, the remaining 20% depends on testing. The usage of the division of labor sheet is to qualify and then quantify: first put the piece into a certain compartment, then check the specific grade and data in that compartment, which is much faster than spreading all parameters on a large table.
has an on-site identification tip for stress cracking worth recording: Spider web patterns start from the stress concentration point, and by observing the crack direction, you can deduce the source of internal stress. Cracks radiating around screw holes are mostly due to assembly twisting; Cracks distributed along flow lines are mostly injection molding residual stress plus media. The two methods differ: the former changes the assembly process, the latter anneals or changes the design.
taught the field the ability to spot cracks, which is a week faster than sending samples back and forth.
One last thing for procurement: PA66 and PC have different price cycles—one follows nitrile adipinotrile, the other follows phosgene and bisphenol. Leave some flexibility in the annual framework agreement, so in big market years, you can save real money. This is a hidden benefit of the dual-material solution—few people use it, but those who have used it say it's good.
The storage of the dual-material solution also has its own considerations: PA66 blocks fuel and PC have different drying requirements, with different parameters for moisture absorption, temperature, and drying time. Mixing hoppers will result in both sides failing to meet standards. The easiest way on the production line is to zone the hopper and label it color, with hopper management following the material number.
This detail is small, but it determines batch stability. When problems occur, they are very subtle—two batches with excessive moisture can pass factory inspection and only slowly emerge at the client side a month later. Treating drying discipline as a system is a shared task for electrical and transparent parts.
Conclusion
PA66 The division of labor between PC is a complete separation of "structural parts" and "transparent parts."
PA66 is the main domain of structural parts: strength, welding, dielectric resistance, glass fiber reinforcement—electronics, automotive, structural parts.
PC is the main domain of transparent parts: light transmission, high impact resistance, precise dimensions—transparent covers, optical parts, safety parts
The starting point of selection is not 'which is more expensive and better', but 'does this part need to be transparent?' If transparency is needed, PC is one of the answers; if not, PA66 is a more stable choice.
