光伏件选材料，很多人第一眼会看强度、看阻燃。
但光伏件最大的特殊之处，写在"户外 25 年"这五个字里。
不是一年、不是三年，是设计寿命 25 年，还要经历暴晒、雨淋、湿热、温差、盐雾、氨气。
这是一场老化考试，而不是一场强度考试。
这篇讲清光伏连接器和接线盒这两类件，材料的门槛到底在哪里。
开篇先讲个现场
前年夏天跟一个电站运维团队去了趟西北的集中式电站。戈壁滩上，地表温度接近六十度，运维师傅拧开一个接线盒给我们看：里面的尼龙端子座表面已经粉化，指甲一划一道白痕，塑料的表层像酥皮一样掉渣。同一个盒子里，五年前装的另一个牌子的件，只是颜色变深，结构完好。
差异在哪？两个件的配方里，耐候体系的档次差了一个台阶。光伏是所有尼龙应用里太阳最毒、湿热最长、昼夜温差最大的场景，材料的老化在这里被加速到极致——这也是为什么光伏件的失效，多数不是坏在强度上，是老出来的。
这篇就按“老”这条主线讲光伏选料。先看连接器和接线盒各自的考察点，再把双 85 这个湿热老化分水岭讲透，然后是 CTI 在湿热下掉档的问题——这一点和高压连接器那篇呼应，但光伏的老化条件更狠。
逆变器外壳的耐候阻燃双重要求单独一节。最后五个坑加边界。做光伏组件配套的读者，读完记得把文中的老化验证清单对照到自己供应商身上。
一、光伏件的失效，多数是"老"出来的
先分清两条老化路径：
路径一 · 紫外老化（表面）
阳光里的紫外线会让高分子链断裂，表现是：
表面粉化、变色、失去光泽- 表层开裂，形成微裂纹- 力学性能从表层开始下降
路径二 · 湿热老化（内部）
高温 + 高湿的组合，会同时做两件事：
让材料吸湿，尺寸变化、绝缘下降- 在高温下加速水解，断链
对尼龙来说，第二条路径更致命。 因为尼龙天生吸水，而光伏件的工作环境常年是湿热。
两条路径还会互相加速：表面紫外开裂后，水汽更容易进去，内部湿热老化加快。
一句判断：光伏件选料，先把"耐候"和"耐湿热"分开看。它们不是一件事，药也不同。
二、连接器与接线盒：分别看什么
| 件 | 材料方向 | 关键指标 |
|---|
| 光伏连接器外壳 | PA66-GF + 耐候体系 / PPA | UL94 V0、CTI、耐紫外、耐湿热 |
| 连接器胶芯 | PA66-GF / PA6T | CTI、尺寸稳定、耐温 |
| 接线盒本体 | PA66-GF + 耐候 + 阻燃 | V0、耐紫外、耐水解、尺寸稳 |
| 接线盒盖板 | PA66 / PA6T | 耐候、透光率（部分需透明） |
| 灌胶件底座 | PA66-GF / PBT | 与灌封胶相容、耐温 |
| 逆变器外壳 | 阻燃 PA66-GF / PPA | V0、耐候、刚性 |
| 支架 / 安装件 | PA66-GF30 | 刚性、抗蠕变、耐候 |
这里最挑的是连接器外壳。
因为它要同时满足：阻燃 V0、高 CTI、耐紫外、耐湿热、机械强度、户外 25 年。六条要求叠在一起，PA66 加耐候体系能覆盖大部分，但要求更高的场景要往 PPA、PA6T 走。
连接器有一个特殊要求：不能"越老越漏"
光伏系统是直流高压（常见 1000V / 1500V 系统）。
直流下的漏电起痕比交流更严苛，因为直流电弧不容易自熄。
所以光伏连接器的 CTI，要求比一般交流件更高。而且这个 CTI 必须是在老化之后仍然达标，不是出厂时的数据。
三、双 85：湿热老化的分水岭
光伏行业里有一个绕不过去的测试：双 85。
85℃ + 85% 相对湿度，持续一定时间（常见 1000 小时）。
它的意义是：把户外的湿热环境压缩到实验室里，看材料几年后的状态。
为什么要专门说这个？
因为很多"耐候尼龙"的宣传，指的是抗紫外。而双 85 考的是耐湿热。两件事，很多供应商只做了一件。
选料时要问清楚三句：
1. 双 85 做了多少小时？
2. 老化后的力学保持率是多少？（不是"外观无变化"）
3. 老化后的 CTI 是多少？
三句里有任何一句答不上来，说明这个料没打算用在光伏上。
双 85 之后还要看什么？
除了前面说的三项，还有一个常被漏掉的关联：外观变化其实是电性能问题。
表面一旦粉化或出现微裂纹，污渍就更容易附着，而污渍正是 CTI 失效的条件之一。所以"外观变化"在光伏件上不是审美问题。
验收标准里，最好把表面粉化等级和CTI 保持率绑在一起看，而不是分开各自达标——分开看，很容易出现"外观合格、电气掉档"的组合。
| 老化条件 | 考什么 | 典型时长 |
|---|
| 紫外加速老化 | 表面耐候 | 视标准，常按等效户外年限折算 |
| 双 85（85℃/85%RH） | 湿热 + 水解 | 常见 1000 小时 |
| 温度循环 | 热胀冷缩疲劳 | 视标准 |
| 盐雾 | 沿海环境 | 视标准 |
| 耐氨 | 农业光伏（氨腐蚀） | 视场景 |
注意最后一行：耐氨。 这是农业光伏（尤其养殖场屋顶）的特殊要求，普通耐候体系不一定覆盖。如果项目在农光互补场景，这条必须单独提。
接线盒里还有一个容易漏的件：旁路二极管附近的绝缘件。
这个位置温度比盒体其他位置高，而且长期处在热循环里。绝缘件要同时看耐温和长期热老化后的电气性能。
如果只按盒体本体的温度要求去选料，这个位置往往是最先出问题的地方。
四、CTI 在湿热下会掉档
这是最容易被忽略、后果最严重的一条。
CTI 不是出厂值，它会随吸湿和老化下降。
原因在机理上很清楚：CTI 失效需要"电压 + 湿气 + 污渍"，而吸湿本身就是给失效创造条件。
所以：
出厂测 CTI 600V 的件，在湿热老化后可能掉到 500V 甚至更低- 户外灰尘、鸟粪、盐分附着，会进一步降低表面电阻- 表面紫外粉化之后，更容易积污
这三条叠起来，就是"出厂合格、装机几年后出问题"的典型路径。
正确的做法是：要求供应商提供老化后的 CTI 数据，并按老化后的数据留安全余量。
再补一条：CTI 的验证要按实际件的结构和厚度做。 标准试样的数据与实际件之间会有差异——薄壁、有嵌件、有开孔的位置，表现和标准试样不是一回事。关键件最好做零件级验证，不要直接引用材料数据。
一句话：光伏件选料，"出厂数据"只能当参考，"老化后数据"才是设计依据。
五、逆变器外壳：阻燃和耐候要同时做
逆变器外壳是光伏系统里另一个大件，要求更综合：
阻燃：UL94 V0、无卤趋势、GWIT- 耐候：长期户外，紫外 + 湿热- 刚性：大尺寸件，安装固定- 耐温：内部有功率器件，环境温度高
这里最容易犯的错是"先满足阻燃，再补耐候"。
因为阻燃体系（尤其无卤、大加量）会影响材料的耐候性和韧性，反过来耐候助剂也会影响阻燃效率。这类复合要求，最好是找能同时做阻燃 + 耐候的配方，不要自己拼接需求。
还有一类位置要单独评估：风机和进出风口附近。
这些位置除了耐候，还要耐粉尘与湿气交替。材料在这里的老化节奏和密闭区域完全不同——干湿交替比长期潮湿更伤材料。
如果项目在粉尘大的地区，这类位置的材料要单独看，不能沿用外壳本体的结论。
双 85 的数字背后
光伏行业言必称双 85，但很多招标文件只写了温度湿度，没写时间和判定，这让双 85 的含金量差异巨大。一千小时和两千小时是两回事，湿热后测外观和湿热后测绝缘、测 CTI 是两回事。
我们建议光伏配套企业把双 85 的验收条款自己写细：时长按产品定位定，户内配套一千小时打底，户外暴露件直接两千；测试后加测三项——绝缘电阻、CTI、外观粉化，任何一项掉档都算不通过。
写细的另一个好处是筛选供应商：能按细则出报告的，说明真做过；只能给一张笼统合格证的，多数是抄来的。双 85 不是一句口号，是一组可以核查的数字，把它变成你们采购文件的附件，老化的坑就先避掉一半。
六、五个坑
坑 1：把"抗紫外"当成"耐湿热"。 两条老化路径，两套助剂。双 85 过不了，光伏就用不了。
坑 2：只看出厂 CTI。 CTI 会随老化下降，设计要按老化后留余量。
坑 3：忽略直流高压的特殊性。 直流漏电起痕更严苛，CTI 要求高于交流件。
坑 4：忘了当地环境。 沿海要盐雾，农光要耐氨，高海拔要更严的紫外。光伏项目是"按地点选料"的。
坑 5：接线盒忽略灌封胶相容性。 灌胶件长期接触灌封胶，材料与胶的相容性要一起验，否则会出现界面开裂。
七、边界
| 场景 | 结论 | 说明 |
|---|
| 普通屋顶光伏 | PA66 + 耐候体系 | 主流方案 |
| 沿海 / 高盐雾 | 需加强耐候 | 盐雾试验必须做 |
| 农光互补（氨环境） | 需专门验证 | 普通耐候体系不够 |
| 长期 >120℃ 件 | PA6T / PPA | 按温度换体系 |
| 高 CTI + 薄壁 + 户外 | 难度最高 | 建议早期做复合配方 |
行业里的一条实感
光伏询盘里，我们最常被问的一句话是："你们的料耐候吗？"
"耐候"这个词听起来很清楚，其实很模糊——它至少包含三层意思：抗紫外、耐湿热、耐盐雾/耐氨。
我们通常会拆开来问四句：
1. 项目在什么地区？（沿海、内陆、农光？）
2. 有没有做过双 85？要求多少小时？
3. 件是连接器还是接线盒，还是在逆变器里？
4. 有没有 CTI 要求，要求多少？
四句问完，很多客户自己就发现：他要的不是"耐候"，是"耐某一类环境下、老化之后的某几项指标"。
光伏件最怕的一句话是"差不多就行"。因为这个行业的验证周期太长——件出问题不是在打样阶段暴露，是在装机三五年之后。那时候返工的成本，是一整片电站的事。
所以在这类项目上，我们宁可前期多问几句，把要求问得比客户自己想的还细。
料有人卖，判断不一定有人给。 光伏件上，这句话特别值钱。
读者追问三则
追问一：屋顶分布式和地面电站的选料差异在哪？ 核心差异是温度和通风。屋顶分布式贴着屋面装，背板通风差，组件接线盒的常年温度比地面电站高一截，湿热老化速度随之加快，材料档次建议整体上移半档，重点看长期耐温和水解稳定性。
地面电站的优势是通风好，但风沙紫外更狠，耐候体系的要求反过来更高。先看安装形态，再定材料档位，这是光伏选料的第一步。
追问二：组件质保二十五年，塑料件怎么表态？ 务实的说法是分件表态：接线盒体、连接器这类结构件，按双 85 加热循环的加速模型给年限证据；密封圈灌封胶这类弹性体，按压缩永久变形曲线推。
二十五年没有人能实测，招标方心里也清楚，他们看的是你的加速验证逻辑是否完整、证据链是否诚实。敢把模型和假设写出来的供应商，反而更容易赢得信任。
最后给光伏配套企业一个展会之外的验厂小技巧：去供应商车间重点看三个角落——留样室有没有按批次归档的实物、老化箱里跑的是不是你同行订单的样品、色粉库房的管理是不是分区标识。这三个角落十分钟看完，比看任何资质墙都真实。
留样室空荡的工厂，出了问题连对比的样品都拿不出来；老化箱排不满的实验室，双 85 报告的水分你自己算。
双 85 验收条款清单
给光伏配套采购一份可直接引用的双 85 细则：测试条件栏写明八十五度、相对湿度百分之八十五、时长分档，户内配套件不少于一千小时，户外暴露件不少于两千小时；测试后加测三项目，绝缘电阻衰减不超过一个数量级、CTI 保持原档或仅降一档、外观无粉化开裂；
样品数量按批次抽取不少于规定值，第三方机构出报告；报告之外附留样，留样保存至质保期满。四条细则加在一起，双 85 就从一句行业黑话变成了一份可核查、可追责的技术条款。第一次执行会淘汰一批供应商，这是正常的，被淘汰的多数不是料不行，是从没真做过。筛完之后的市场会干净很多，你的售后数据会证明这轮筛选的每一分价值。
最后一个提醒关于采购合同的条款衔接：双 85 报告在合同里要绑定批次有效性，不是一证走天下。配方调整、玻纤换供应商、色粉更换，任何一项变更之后，原报告的效力就应该重新评估，合同里写明变更触发复测的义务和费用承担方式。
很多光伏售后纠纷的根子，是供应商三年前换了玻纤供应商，性能悄悄下滑，客户的报告还是老版本。条款写得越清楚，双方合作得越长久，这是光伏供应链用大量学费换来的共识。
结语
光伏连接器和接线盒的选料，抓住三句话就够了：
先分清抗紫外和耐湿热；再用双 85 卡材料；最后按老化后的 CTI 留余量。
户外 25 年，考的不是能扛住多大力，而是能扛住多久不变。
做改性尼龙：PA6、PA66、PA46、PA11、PA12、PA6T、PA9T、尼龙合金。做改性 PPO、PPS、热塑性弹性体。做各大化工巨头的尼龙树脂、副牌料、大包料。
When selecting materials for photovoltaic components, many people first look at strength and flame retardancy.
But the greatest uniqueness of photovoltaic components is written in the five words 'outdoor 25 years'.
Not one year, not three years, it's a design life of 25 years, and it also has to endure exposure to the sun, rain, humidity, temperature differences, salt spray, and ammonia.
This is an aging test, not a strength test.
This article explains the two types of components, photovoltaic connectors and junction boxes, and where the threshold for materials actually lies.
Let's start with a scene.
The summer before last, I went with a power plant maintenance team to a centralized power station in the northwest. On the Gobi Desert, the surface temperature was close to sixty degrees. A maintenance worker opened a junction box to show us: the nylon terminal blocks inside had already turned powdery on the surface, and a scratch from a fingernail left a white mark, with the plastic layer flaking off like puff pastry. In the same box, another brand's component installed five years earlier had only darkened in color, with its structure intact.
Where is the difference? In the formulas of the two parts, the grade of the weather-resistant system differs by one level. Photovoltaics are the harshest scenario for all nylon applications, with the most intense sun, the longest periods of humidity and heat, and the largest day-night temperature differences. Material aging is accelerated to the extreme here — which is why the failure of photovoltaic parts is mostly not due to strength, but due to aging.
This article follows the main thread of 'aging' to discuss material selection for photovoltaics. First, it looks at the evaluation points for connectors and junction boxes separately, then explains the double 85 wet-heat aging watershed thoroughly, and finally addresses the issue of CTI dropping under humidity and heat—this point echoes the one in the high-voltage connector article, but the aging conditions in photovoltaics are harsher.
The inverter casing has separate requirements for weather resistance and flame retardancy. The last five pitfalls are supplemented with boundaries. For readers working on photovoltaic module support, after reading, remember to compare the aging verification checklist in the text with your own suppliers.
1. The failure of photovoltaic components is mostly due to aging.
First, distinguish between the two aging pathways:
Path One · Ultraviolet Aging (Surface)
Ultraviolet rays in sunlight can break polymer chains, which manifests as:
Surface chalking, discoloration, loss of gloss - surface cracking, forming microcracks - mechanical properties begin to decline from the surface
Pathway Two · Damp-Heat Aging (Internal)
The combination of high temperature and high humidity will do two things at the same time:
Causing the material to absorb moisture, resulting in dimensional changes and decreased insulation - Accelerated hydrolysis and chain scission at high temperatures
For nylon, the second path is more deadly. Because nylon naturally absorbs water, while the operating environment of photovoltaic components is damp and hot all year round.
The two pathways accelerate each other: after surface UV cracking, moisture enters more easily, while internal humidity and heat age faster.
A judgment: When selecting photovoltaic components, first consider 'weather resistance' and 'humidity-heat resistance' separately. They are not the same thing, and the remedies are different.
2. Connectors and Junction Boxes: What to Look at Separately
| piece | Material direction | Key indicators |
|---|
| Photovoltaic connector housing | PA66-GF Weather-Resistant System / PPA | UL94 V0, CTI, UV resistant, humidity resistant |
| Connector adhesive core | PA66-GF / PA6T | CTI, dimensional stability, temperature resistance |
| Junction box body | PA66-GF Weather Resistant Flame Retardant | V0, UV-resistant, hydrolysis-resistant, dimensionally stable |
| Junction box cover | PA66 / PA6T | Weather resistance, light transmittance (partially needs to be transparent) |
| Potting base | PA66-GF / PBT | Compatible with potting compounds, temperature-resistant |
| Inverter casing | Flame-retardant PA66-GF / PPA | V0, weather resistance, rigidity |
| Bracket / Mounting Parts | PA66-GF30 | Rigid, creep-resistant, weather-resistant |
The most picky thing here is the connector housing.
Because it needs to simultaneously meet: flame retardant V0, high CTI, UV resistance, moisture and heat resistance, mechanical strength, and 25 years outdoors. When these six requirements are combined, PA66 with a weather-resistant system can cover most cases, but for higher-demand scenarios, one has to turn to PPA or PA6T.
The connector has a special requirement: it cannot 'leak more as it gets older'
A photovoltaic system is a high-voltage direct current (commonly 1000V / 1500V system).
Leakage tracking under DC is more severe than under AC, because DC arcs are not easily extinguished.
Therefore, the CTI of photovoltaic connectors is required to be higher than that of general AC components. Moreover, this CTI must still meet the standard after aging, not just the data at the time of manufacture.
3. Double 85: The Watershed of Humid Heat Aging
In the photovoltaic industry, there is an unavoidable test: the Double 85.
85℃ 85% relative humidity, maintained for a certain period of time (commonly 1000 hours).
Its meaning is: to compress the humid and hot outdoor environment into the laboratory, to see the state of the materials after several years.
Why specifically mention this?
Because much of the promotion of 'weather-resistant nylon' refers to UV resistance, while the DuPont 85 test is about moisture-heat resistance. These are two different things, but many suppliers only address one.
When selecting materials, you need to ask three questions clearly:
1. How many hours did Double 85 work?
2. What is the mechanical retention rate after aging? (Not 'no change in appearance')
3. What is the CTI after aging?
If you can't answer any of the three sentences, it means this material wasn't intended for use in photovoltaics.
What else should be looked at after Double 85?
In addition to the three items mentioned earlier, there is another often overlooked correlation: appearance changes are actually an electrical performance issue.
Once the surface starts to chalk or develop microcracks, stains adhere more easily, and stains are one of the conditions for CTI failure. Therefore, 'appearance changes' on photovoltaic components are not an aesthetic issue.
In the acceptance criteria, it is best to consider the surface chalking level and CTI retention rate together, rather than evaluating them separately—looking at them separately can easily result in a combination of 'appearance qualified, electrical performance downgraded'.
| Aging conditions | What exam | Typical duration |
|---|
| Ultraviolet accelerated aging | Surface weather resistance | According to standards, it is often converted based on the equivalent outdoor annual life. |
| Dual 85 (85°C/85% RH) | Damp-heat Hydrolysis | Common 1000 hours |
| Temperature cycling | Thermal expansion and contraction fatigue | according to the standard |
| Salt spray | Coastal environment | according to the standard |
| Ammonia-resistant | Agricultural Photovoltaics (Ammonia Corrosion) | Depends on the situation |
Pay attention to the last line: ammonia resistance. This is a special requirement for agricultural photovoltaics (especially the rooftops of livestock farms), which ordinary weather-resistant systems may not cover. If the project is in an agri-PV complementary scenario, this point must be mentioned separately.
There is another part in the junction box that is prone to leaking: the insulation near the bypass diode.
This position has a higher temperature than other parts of the enclosure and is subjected to long-term thermal cycling. The insulating components need to be considered for both temperature resistance and electrical performance after long-term thermal aging.
If materials are selected based solely on the temperature requirements of the box body itself, this position is often the first place to encounter problems.
4. CTI will lose performance under hot and humid conditions
This is the one that is easiest to be overlooked and has the most serious consequences.
CTI is not a factory value; it will decrease with moisture absorption and aging.
The reason is clear in terms of the mechanism: CTI failure requires 'voltage, moisture, and contamination,' and moisture absorption itself creates conditions for the failure.
So:
For components tested with a CTI of 600V at the factory, after damp-heat aging, the value may drop to 500V or even lower. Outdoor dust, bird droppings, and salt deposits can further reduce surface resistance. After surface ultraviolet chalking, it is easier for dirt to accumulate.
Stacked together, these three points represent the typical path of 'passing factory inspection but developing problems a few years after installation'.
The correct approach is: require suppliers to provide aged CTI data and maintain a safety margin based on the aged data.
One more thing: CTI validation should be done according to the structure and thickness of the actual part. There will be differences between the data of standard samples and the actual parts—thin walls, inserts, and locations with holes behave differently from standard samples. For critical parts, it is best to perform part-level validation and not directly refer to material data.
In one sentence: When selecting photovoltaic components, 'factory data' can only be used as a reference, while 'post-aging data' is the basis for design.
5. Inverter housing: Flame retardant and weather resistance must be addressed simultaneously
The inverter casing is another major component in the photovoltaic system and requires a more comprehensive approach:
Flame retardant: UL94 V0, halogen-free trend, GWIT- Weather resistance: long-term outdoor, ultraviolet, humidity and heat- Rigidity: large-size parts, installation and fixation- Temperature resistance: internal power devices, high ambient temperature
The most common mistake here is 'satisfy fire resistance first, then add weather resistance'.
Because flame retardant systems (especially halogen-free ones with high loading) can affect the weather resistance and toughness of materials, conversely, weathering additives can also affect flame retardant efficiency. For such composite requirements, it is best to find formulations that can handle both flame retardancy and weather resistance, rather than trying to piece together the requirements yourself.
There is another type of location that needs to be evaluated separately: near the fans and air inlets and outlets.
These locations, in addition to being weather-resistant, also need to withstand alternating dust and moisture. The aging pace of materials here is completely different from sealed areas—alternating dry and wet conditions damage the materials more than prolonged dampness.
If the project is in an area with heavy dust, the materials in such locations need to be considered separately and cannot follow the conclusions for the main body of the enclosure.
Behind the number 85 twice
In the photovoltaic industry, people always mention 'Double 85', but many tender documents only specify temperature and humidity, without specifying time and criteria. This makes the value of 'Double 85' vary greatly. One thousand hours and two thousand hours are two different things; measuring appearance after damp heat and measuring insulation or CTI after damp heat are two different things.
We recommend that photovoltaic supporting companies write the 'double 85' acceptance clauses in detail themselves: duration should be set according to product positioning, with indoor supporting parts tested for a baseline of 1,000 hours and outdoor exposed parts for 2,000 directly; after testing, add three more tests—insulation resistance, CTI, and appearance chalking, and failing any one of them counts as not passing.
Another advantage of writing detailed specifications is screening suppliers: those who can provide reports according to the detailed rules indicate they have actually done the work; those who can only give a general certificate of conformity are mostly copied. 'Double 85' is not just a slogan; it is a set of verifiable numbers. Turn it into an attachment to your procurement documents, and you will avoid half of the pitfalls caused by aging.
6. Five Pits
Pitfall 1: Treating 'UV resistance' as 'humidity and heat resistance.' Two aging paths, two sets of additives. If it can't pass Double 85, it can't be used in photovoltaics.
Pitfall 2: Only look at the factory CTI. CTI declines with aging, so the design should reserve margin according to the aged value.
Pitfall 3: Ignoring the particularities of high-voltage DC. DC leakage tracking is more severe, and the CTI requirements are higher than those for AC components.
Pitfall 4: Forgetting the local environment. Coastal areas require salt mist resistance, agricultural areas need ammonia resistance, and high altitudes require stronger UV protection. Photovoltaic projects are 'material selection based on location.'
Pitfall 5: Ignoring the compatibility of potting compound with the junction box. When potting parts are in long-term contact with the potting compound, the compatibility of the material with the compound must be tested together, otherwise interface cracking may occur.
7. Borders
| Scene | Conclusion | Explanation |
|---|
| Ordinary roof photovoltaic | PA66 Weather-Resistant System | Mainstream solution |
| Coastal / High Salt Fog | Needs improved weather resistance | Salt spray test must be done |
| Agrivoltaics (Ammonia Environment) | Requires special verification | The ordinary weather-resistant system is not enough |
| Long-term >120℃ parts | PA6T / PPA | Change the system according to temperature |
| High CTI, thin-walled, outdoor | The most difficult | It is recommended to start with a compound formula early. |
A real feeling in the industry
In photovoltaic inquiries, the question we are most frequently asked is: 'Is your material weather-resistant?'
The term 'weather-resistant' sounds very clear, but it is actually quite vague — it contains at least three meanings: UV resistance, resistance to damp heat, and resistance to salt spray/ammonia.
We usually break it down into four questions:
1. In which region is the project located? (Coastal, inland, agricultural/solar?)
2. Have you ever done double 85? How many hours does it require?
3. Is the item a connector, a junction box, or is it inside the inverter?
4. Is there a CTI requirement, and if so, how much?
After asking four questions, many clients realize on their own: what they want is not 'weather resistance,' but 'resistance in certain environments and specific indicators after aging.'
The thing photovoltaic components fear most is the phrase 'close enough is fine.' Because the verification cycle in this industry is too long—problems with the components don’t show up during the prototyping stage, but three to five years after installation. At that time, the cost of rework can affect an entire solar power plant.
So for this type of project, we would rather ask a few more questions in the early stages, making the requirements even more detailed than the client themselves have imagined.
Some people have materials to sell, but it’s not certain you can get a judgment. In photovoltaic parts, this sentence is especially valuable.
Three Reader Inquiries
Follow-up Question 1: What are the material selection differences between rooftop distributed systems and ground power stations? The core difference is temperature and ventilation. Rooftop distributed systems are installed close to the roof, with poor backsheet ventilation. The junction box of the modules has a consistently higher temperature than that of ground power stations, which accelerates the rate of moisture-heat aging. Therefore, it is recommended to upgrade the material grade by half a level overall, focusing on long-term temperature resistance and hydrolysis stability.
The advantage of ground-mounted power plants is good ventilation, but the wind, sand, and ultraviolet are harsher, which in turn requires a more durable weather-resistant system. First, look at the installation form, then decide on the material grade; this is the first step in photovoltaic material selection.
Follow-up Question 2: The component warranty is 25 years. How do plastic parts stand on this? A practical approach is to separate the assessment by part: structural components like junction box bodies and connectors are justified with accelerated aging models using double 85 heating cycles; elastomers like sealing rings and potting adhesives are evaluated using compression set curves.
No one can realistically test 25 years, and the bidders are aware of this. What they are looking for is whether your accelerated verification logic is complete and the evidence chain is honest. Suppliers who dare to write out their models and assumptions are actually more likely to earn trust.
Finally, a small factory audit tip for photovoltaic accessory companies outside of trade shows: focus on three corners in the supplier's workshop—whether the sample room has physical samples archived by batch, whether the aging chamber runs samples from your industry peers' orders, and whether the pigment storage is managed with zone labeling. Spending ten minutes in these three corners is more revealing than looking at any certificate wall.
Empty sample rooms mean that if problems arise, there are no comparison samples available; underfilled aging chambers mean you have to calculate the reliability of the double 85 report yourself.
Double 85 Acceptance Clause Checklist
Provide photovoltaic accessory procurement with a directly usable double 85 specification: test conditions should specify 85 degrees Celsius, 85% relative humidity, and staged durations, with indoor components at no less than 1,000 hours and outdoor exposed components at no less than 2,000 hours; after the test, measure three additional items: insulation resistance decay must not exceed one order of magnitude, CTI should remain at its original level or drop only one level, and there should be no powdering or cracking on the surface;
Sample quantities should be drawn per batch and meet minimum specified amounts, with reports issued by third-party agencies; attach retained samples beyond the report, kept until the warranty period ends. Combining these four detailed rules turns 'double 85' from an industry buzzword into a verifiable, accountable technical clause. The first time this is implemented, a batch of suppliers will be eliminated, which is normal. Most eliminated suppliers are not incapable, just never truly qualified. After screening, the market will be much cleaner, and your after-sales data will prove the value of each selection.
Final reminder regarding contract clause alignment: double 85 reports must be linked to batch validity in contracts; a single report does not cover everything. Any changes, such as formula adjustments, switching fiberglass suppliers, or changing pigments, should prompt re-evaluation of the original report's effectiveness. The contract should clearly state obligations and cost responsibility for retesting triggered by changes.
Many photovoltaic after-sales disputes stem from suppliers switching fiberglass providers three years ago, causing performance to quietly decline while the customer still relies on outdated reports. The clearer the terms, the longer the cooperation, which is a consensus gained at the cost of experience in the photovoltaic supply chain.
Conclusion
When selecting materials for photovoltaic connectors and junction boxes, three sentences are enough:
First distinguish between UV resistance and heat-moisture resistance; then use double 85 to screen materials; finally, leave a CTI margin after aging.
For outdoor 25-year service, what matters is not how strong it can endure, but how long it remains unchanged.
For modified nylon: PA6, PA66, PA46, PA11, PA12, PA6T, PA9T, nylon alloys. For modified PPO, PPS, thermoplastic elastomers. Work with major chemical giants' nylon resins, secondary-brand materials, and bulk materials.
