165 LED灯具外壳与散热件
LED 灯具的核心矛盾是散热
LED 的光衰和寿命直接由结温决定，结温每升高 10℃，寿命减半。
灯具外壳承担了 30-50% 的散热任务。塑料的导热系数只有 0.2-0.3 W/(m·K)，铝是 200 W/(m·K)，差距近千倍。用塑料做散热件必须用导热改性。
导热改性的现实边界
导热 PA 加氮化硼或氧化铝填料，导热系数可做到 1.0-3.0 W/(m·K)，
是普通 PA 的 5-10 倍，但仍只有铝的百分之一。
导热 PA 只能用于 20 W 以下的灯具，大功率灯具还是要用铝基板 + 铝外壳。
不要为了减重把大功率灯做成全塑。
现场还原：一年就黄的路灯外壳
2025 年 6 月，中山一家灯具厂的售后翻着照片找到我们：一批户外路灯的外壳，装灯一年，正面晒的那一侧黄得像泡了茶，还有粉化迹象，指甲一刮就掉粉。采购的原话：「供应商说 PA66 本来就耐晒，我们信了。」
PA66 本身不耐晒，这话得说破。未加耐候体系的 PA66 在户外紫外下，分子链断裂加黄变，一年到头就是这个样子。
拿样回来测：氙灯 1000 小时，黄变指数涨了 12，拉伸掉到六成——典型的没做耐候。客户原来的料是通用牌，图便宜，每公斤省两块多。
我们给的是灯具外壳专用耐候 PA66-GF30：UV 吸收剂加受阻胺光稳定剂再加抗氧剂，三件套配齐，3000 小时氙灯黄变指数变化小于 3，拉伸保持 82%。单价贵回去了，但按五年质保算，返修成本降了一个数量级。
这家厂后来把「灯具外壳必须有 3000 小时氙灯报告」写进了采购合同附件。黄变这种失效不致命，但在户外照明上等于直接砸招牌——用户不懂什么分子链断裂，他只看见灯壳黄了。
阻燃是强制项
灯具是长期通电的家电，外壳必须 UL94 V-0，且要通过灯具安规（如 IEC 60598）。
PC 无卤阻燃和 PA66 无卤阻燃都可以，但要注意阻燃剂对透光的影响——
灯罩部分不能用含阻燃剂的料，灯罩和灯体要分开选料。
户外灯具的耐候门槛
路灯、投光灯、景观灯长期户外，紫外、雨水、高低温循环三件套。
未加耐候的 PC 户外 2 年黄变雾度上升，透光率下降 15%。
必须加 UV 吸收剂 + HALS + 抗氧剂三件套，并且要做 1000 h 氙灯老化验证。
户外灯具的塑料件寿命目标 5-10 年。
深一层：导热塑料的真相与边界
LED 灯具绕不开散热，而「导热塑料」这个词被用得太滥了，值得把真相摆出来。
纯 PA66 的导热系数大概 0.2 W/(m·K)，铝是 200 左右，差三个数量级。
加导热填料（氧化铝、氮化硼这类）能提到 1 到 3，已经是配方和成本的极限——再往上，填料占到四成以上，韧性没了、注塑难了、价格逼近压铸铝，失去意义。
所以工程上要看清一件事：塑料外壳的散热贡献是有限的，LED 真正的散热路径是芯片到铝基板、铝基板到散热器这段，这段必须是金属。
塑料壳的价值在别处：防腐（海边、化工厂铝壳活得艰难）、绝缘（省掉一层绝缘处理）、轻（安装和维护都省力）、以及设计自由度（一体成型出铝压铸做不出的造型）。
想明白这个分工，选料就简单了：热流密度高的部位留给金属，塑料壳做结构件和外观件。全塑灯具不是不行，是功率上不去——十几瓦的庭院灯全塑没压力，上百瓦的路灯全塑就是给自己找麻烦。
市场上「导热塑料全面替代铝」的说法，听听就好，先问导热系数多少、什么功率、散热结构怎么设计。
灯罩与灯体分开选料
灯罩要透光——PC 透光率 88-90%，PMMA 92%，PA 不透明，不能做灯罩。
灯体要阻燃和散热，走阻燃 PC 或导热 PA。这是灯具选料最常见的分工：罩走 PC 或 PMMA，体走 PA 或阻燃 PC。
装配与防水的隐性变量
户外灯具要 IP65 以上防水，接缝处用硅胶密封圈。PA 吸湿膨胀会影响密封压缩量——吸水后体积涨 0.3%，密封槽尺寸要预留。
另外灯具内部温度高，密封圈要选硅橡胶而不是普通橡胶。
工程实测：4 条强制测试
测试1：导热系数。普通 PA 0.25 W/(m·K)，导热 PA 1.5-3.0 W/(m·K)，铝 200 W/(m·K)——大功率仍需铝。
测试2：氙灯老化 1000 h。加耐候三件套 PC 透光率保持 97%，未加的降至 85%——户外必加。
测试3：阻燃 V-0。PC 无卤阻燃达 V-0（1.6 mm），导热 PA 达 V-0（1.6 mm）——均可。
测试4：结温对比。20 W 球泡灯用导热 PA 外壳结温 78℃，用普通 PA 结温 95℃——导热料降 17℃。
追问三连：采购最常问的三件事
一问：铝壳换塑壳到底省不省钱。 算总账别算单价：塑壳单件便宜、免喷涂、免绝缘处理、注塑一次成型省两道工序；但要做散热复核、可能要加铝基板厚度。中小功率灯具换塑普遍是赚的，大功率要一单一算，没有万能答案。
二问：灯罩选 PMMA 还是 PC。 透光和耐候 PMMA 占优，抗冲击和耐温 PC 占优。户外灯具罩主流是 PMMA 加 UV 稳定，或者 PC 加硬涂层。尼龙跟这个选择关系不大，但灯罩和壳体的连接件（卡扣、螺柱）是 PA66-GF 的地盘，两种罩的膨胀系数不同，连接部位要留公差。
三问：驱动电源壳为什么要单独说。 电源壳是最容易被忽略的阻燃位：驱动是起火风险最高的部件，壳体阻燃必须 V-0 起步，而且要做灼热丝 750℃ 确认。有的灯具厂为了省料把驱动壳和外壳用同一种料，阻燃等级跟着外壳走 V-2，认证直接卡死——分开选料，这是规矩。### 算一笔材料账：灯具外壳的五年总账
灯具外壳的账要按五年质保期算，单价比出来的都是假账。
以一批一万只户外路灯外壳为例：通用 PA66 单价 9 元，耐候专用牌 12 元，差价 3 万元。
五年里的返修概率，通用牌按行业均值 8% 计（黄变粉化不构成安全问题，但按投诉处理），800 只返修，登高作业单只摊 40 元，返修成本 3.2 万元——刚好把差价吃回去还没算品牌口碑。
再把质保条款算进去：很多灯具厂对工程渠道承诺五年质保，返修超一定比例要罚。罚则一旦触发，金额是差价的十倍量级。
这样算下来，耐候牌的 3 万元差价买的是「五年免操心」，这在中标价差动辄几十万的工程市场里，是最便宜的一笔保险。灯具行业里活得好的品牌，普遍在户外件上不打材料价格战——他们算的正是这本五年总账，而且算得比谁都熟。### 边界声明
| 工况 | 推荐材料 |
|---|
| 20 W 以下全塑灯 | 导热 PA 阻燃 |
| 大功率灯具 | 铝壳 + 塑料装饰件 |
| 灯罩 | PC 或 PMMA 透光 |
| 户外路灯 | 阻燃 PC 或 PA + 耐候三件套 |
| IP65 密封 | 硅胶圈 + 预留吸湿膨胀 |
工程备忘
LED 灯具量产前必须做导热 + 氙灯老化 1000 h + 结温测试三项。
大功率不要做全塑，导热 PA 上限 20 W。灯具企业在降本时最容易动塑料件的念头，但散热件降级带来的光衰和售后成本，通常远高于省下的那点材料费。
实战案例：常见踩坑与正解
踩坑一：只看阻燃等级不看 CTI。LED灯具装在带电回路附近，阻燃 V-0 但 CTI 只有 250 V，长期爬电后表面碳化短路。正解：带电件必须 CTI ≥ 400 V（相比漏电起痕指数），V-0 只解决起火，不解决爬电——这是电气件最常被漏掉的一条。踩坑二：用回收料或副牌料做绝缘件，介电强度批次波动大，耐压测试 5% 击穿。正解：绝缘件一律走正牌新料，批次附耐压报告。踩坑三：端子件装完一段时间扭矩衰减，以为是螺丝松了，实际是尼龙蠕变。正解：LED灯具承载螺纹连接时必须玻纤增强到 GF25 以上，并在装配 24 h 后复拧一次。
反向案例：同一家厂，一次失败一次成功
中山这家厂其实换了两次料，第一次失败，第二次成功，过程值得细看。
2024 年初第一次：草坪灯外壳从压铸铝换 PA66，全塑设计，驱动和光源的热全压在壳体上，夏天腔内温度 90℃ 以上，三个月批量黄变加光衰超标，整批报废。
第二次换了思路：散热板保留铝合金，壳体和端盖换耐候 PA66-GF30，中间用导热垫衔接。塑料做它擅长的——防腐、绝缘、造型；金属做它必须做的——搬热。换完成本降 18%，通过全部老化测试，这个设计至今还在跑量。
同一家厂、同一种材料、两种结局，差别只在设计分工。材料从来不是拿来「全面替代」的，是拿来「放在对的位置」的。后来他们研发负责人说过一句话我们记到现在：第一次失败不亏，亏的是差点因为一次失败把塑料壳这条路整个关掉。
延伸判断：最容易被漏掉的隐性变量
LED灯具的量产事故里，有一半不是料选错了，是隐性变量没控住。
第一个变量是含水率。PA 系材料出厂含水率、干燥条件、注塑前的存放时间，三者共同决定实际含水率，含水率不对，强度和外观都会变。
第二个变量是模具温度。模温低 20℃，表面浮纤和熔接痕强度可能差一倍。
第三个变量是装配后的时间。装完 24 h 和装完 30 天的扭矩、尺寸、密封压缩量都不一样。
这三个变量都不写在物性表上，但都写在失效报告里。
把这三件事写成一张表发给供应商，比打十通电话有用——LED灯具的选型沟通成本，基本都花在这几项反复确认上。
最后一组问答：三个纠结时刻的裁决
纠结一：客户嫌耐候牌贵，问能不能「少加一点稳定剂」。 不能。耐候体系的配比是按目标寿命反推的，减配省下的钱按月计，粉化的损失按年计——折算下来减配是最贵的方案。要降成本，从结构省（减壁厚、减工序），不从配方省。
纠结二：室内灯具要不要也上耐候牌。 不用。室内无紫外直射，常规阻燃牌够用，耐候牌的溢价在室内是白花的。选材的精细化就体现在这种分档上——一刀切的上档和一刀切的降档，都是偷懒。
纠结三：灯罩发黄是灯罩的事还是壳体的事。 多数是灯罩（PMMA 或 PC 的黄变更显眼），但壳体黄变会被误判给灯罩。售后判断时两件分开测黄变指数，别让灯罩替壳体背锅——也别让壳体的耐候缺失藏在灯罩背后。### 补记：三个现场判断信号
信号一：壳体单面黄变。 朝晒面黄、背阴面还好——耐候体系不足，紫外是单方向打。整批换耐候料，别只换库存。
信号二：粉化加拉伸件松动。 分子链已经断了，黄变是前奏、粉化是进行时，这类件剩余寿命按月算。
信号三：腔内温度超 85℃。 光衰和材料老化双双加速，先改散热结构再谈材料，料治不了结构病。### 验证顺序：三步走完再下单
第一步，拆热路：按功率画热区图，光源热路走金属，塑料件按热区温度定耐温档，不按常温想当然。
第二步，验耐候：3000 小时氙灯黄变和拉伸双指标，户外件没有这份报告一律不进合格供方名录。
第三步，验组合：壳体、灯罩、密封圈、灌封料四样凑一起做老化组合测试——单件都合格、组合出问题的案例，比单件失效还多。三步走完，灯具外壳的选型风险就压到了可接受区间。
结语
这里做塑料的人多——选料这件事，越早问越省事。
这类件的选料与试模，可以一起聊。
165 The core contradiction between LED fixture enclosures and heat sinks
LED the core contradiction of the lighting fixture is that the luminous decay and lifespan of the heat dissipation
LED are directly determined by the junction temperature; for every 10°C increase in junction temperature, the lifespan is halved.
The lamp enclosure handles 30-50% of the heat dissipation task. The thermal conductivity of plastic is only 0.2-0.3 W/(m·K), while aluminum is 200 W/(m·K), a difference of nearly a thousandfold. Using plastic for heat dissipation components requires thermal conductivity modification.
Practical Limits of Thermal Conductivity Modification
Thermal PA with boron nitride or alumina filler can achieve a thermal conductivity of 1.0-3.0 W/(m·K).
is 5-10 times that of ordinary PA, but still only about 1% of aluminum.
Thermal conductive PA can only be used for lamps under 20 W; high-power fixtures should still use aluminum substrate + aluminum housing.
Do not make high-power lamps entirely plastic just to reduce weight.
On-site reconstruction: Street lamp casings that turn yellow after just one year
In June 2025, an after-sales service representative from a lighting factory in Zhongshan flipped through photos and found us: a batch of outdoor streetlight housings, after a year of installation, the side exposed to sunlight turned yellow like tea brewed and showed signs of powdering, and the powder fell off with just a scratch from the nails. The buyer's exact words: "The supplier said PA66 is naturally sun-resistant, and we believed it."
PA66 is not sun-resistant, so this must be clarified. Without a weather-resistant system, PA66 undergoes outdoor UV rays, causing molecular chain breakage and yellowing, and it remains like this all year round.
Brought back samples for testing: xenon lamp yellowing index increased by 12 after 1000 hours, stretch dropped to 60%—typical case of not doing weather resistance. The customer's original material was a generic brand, cheap price, saving over two yuan per kilogram.
We provided the lamp housing-specific weather-resistant PA66-GF30: UV absorber, blocked amine light stabilizer, and antioxidant, three-piece set, xenon lamp yellowing index changes less than 3 times after 3000 hours, tensile strength maintained at 82%. The unit price was expensive, but with a five-year warranty, the repair cost dropped by an order of magnitude.
This factory later included the "xenon lamp shell must have a 3000-hour xenon lamp report" in the procurement contract attachment. Yellowing is not fatal, but in outdoor lighting, it's like ruining the brand—users don't understand what molecular chain breaks mean; they only see the lamp casing turning yellow.
Flame retardant is mandatory .
Lighting fixtures are household appliances that are powered on long-term; the casing must meet UL94 V-0 and meet safety standards (such as IEC 60598).
PC Both halogen-free and PA66 halogen-free flame retardants are acceptable, but attention must be paid to the effect of flame retardants on light transmission—
The lampshade must not use materials containing flame retardants; the lampshade and lamp body should be selected separately.
Weathering threshold for outdoor lighting fixtures
Street lights, floodlights, landscape lights, long-term outdoor lighting, ultraviolet, rainwater, and high/low temperature cycling three-piece set.
PC without weather-resistant outdoor conditions shows yellowing and fog increase after 2 years, with light transmittance dropping by 15%.
Must include UV absorber + HALS + antioxidant three-piece set, and undergo 1000 hours xenon lamp aging verification.
Outdoor lighting plastic parts target 5-10 years.
Deeper Layer: The Truth and Boundaries of Thermal Conductive Plastics
LED Lighting fixtures cannot avoid heat dissipation, and the term "thermal conductive plastic" is used too overly often; it's worth exposing the truth.
pure PA66 has a thermal conductivity of about 0.2 W/(m·K), while aluminum is around 200—three orders of magnitude difference.
Adding thermal conductive fillers (like alumina or boron nitride) can reach 1 to 3, which is already the limit of formulation and cost—above that, fillers account for more than 40%, toughness is lost, injection molding becomes difficult, and prices approach die-cast aluminum, losing meaning.
So engineering requires clear understanding: the heat dissipation contribution of plastic casings is limited. The real heat dissipation path for LEDs is from chip to aluminum substrate, and from aluminum substrate to heat sink, which must be metal.
The value of plastic shells lies elsewhere: corrosion resistance (aluminum shells struggle to survive by the sea and chemical plants), insulation (eliminating a layer of insulation), lightness (easier installation and maintenance), and design freedom (one-piece molding for shapes that aluminum die-casting can't achieve).
Once you understand this division of labor, material selection becomes simple: leave the areas with high heat flux density for metal, and plastic shells for structural and exterior parts. All-plastic lighting fixtures aren't impossible, but their power isn't high—all-plastic courtyard lights with over ten watts are no problem, but streetlights with over a hundred watts are just asking for trouble.
The market claims that "thermal conductive plastics completely replace aluminum" are just worth listening to. First, ask about the thermal conductivity, power, and how the heat dissipation structure is designed.
Lampshade and lamp body should be selected separately
Lampshade must transmit light—PC has 88-90% light transmittance, PMMA 92%, PA is opaque, so it cannot be used for lampshades.
Lamp bodies must be flame-retardant and heat dissipating, using flame-retardant PC or thermal conductive PA. This is the most common division of materials in lighting fixture selection: shades use PC or PMMA, body uses PA or flame-retardant PC.
Hidden variables in assembly and waterproofing
Outdoor lighting fixtures must be waterproof above IP65, with silicone sealing rings at seams. PA moisture absorption and expansion affect sealing compression—after absorbing water, volume increases by 0.3%, so the sealing groove size should be reserved.
Also, the internal temperature of the lamp is high, so the sealing ring should be silicone rubber instead of ordinary rubber.
Engineering Testing: 4 mandatory tests
Test 1: Thermal conductivity. Ordinary PA 0.25 W/(m·K), thermal conductivity PA 1.5-3.0 W/(m·K), aluminum 200 W/(m·K)—high power still requires aluminum.
Test 2: Xenon lamp aging for 1000 hours. With the weather-resistant three-piece PC, light transmittance remains at 97%; without it, it drops to 85%—outdoor testing is mandatory.
Test 3: Flame retardant V-0. PC halogen-free flame retardant reaches V-0 (1.6 mm), thermal conductivity PA reaches V-0 (1.6 mm)—both are acceptable.
Test 4: Junction temperature comparison. For 20 W bulb lamps, the thermal conductive PA shell junction temperature is 78°C; for ordinary PA, the junction temperature is 95°C—the thermal conductive material drops by 17°C.
Follow-up questions: The three most frequently asked questions in procurement
One question: Is replacing aluminum shells with plastic cases really cost-effective? Don't calculate unit price when calculating the total bill: plastic shells are cheap per piece, no need for spraying, no insulation treatment, injection molding saves two processes in one step; However, heat dissipation checks are needed, and aluminum substrate thickness may be added. Replacing plastic for medium and small power lamps is generally profitable, but for high power, you have to calculate individually—there's no one-size-fits-all answer.
Question 2: Should you choose PMMA or PC for lampshades? PMMA is better for light transmission and weather resistance, while PC is better for impact resistance and temperature resistance. The mainstream for outdoor lamp covers is PMMA plus UV stabilization, or PC with a hard coating. Nylon isn't much to do with this choice, but the connectors between the lampshade and the housing (clips, studs) are the PA66-GF mold. The two shades have different expansion coefficients, so tolerances should be left at the connection points.
Question 3: Why do you need to talk about the driver power supply casing separately? The flame-retardant aspect of the power supply case is the most easily overlooked: the driver is the component with the highest risk of fire, so the shell's flame retardant must start at V-0, and a scorching wire must be tested at 750°C to confirm. Some lighting manufacturers, to save materials, use the same material for the driver and casing, with the flame retardant rating following the V-2 rating, which directly locks the certification — separate material selection, which is the rule. ### Calculate the material accounts: The five-year general account for the lighting enclosure
should be calculated based on the five-year warranty period; the unit price comparison is all false
Taking a batch of 10,000 outdoor streetlight housings as an example: the unit price of general PA66 is 9 yuan, and the weather-resistant special type is 12 yuan, with a price difference of 30,000 yuan.
The repair probability over five years, for general brands counted according to the industry average of 8% (yellowing and powdering do not pose safety issues, but are handled as complaints), 800 units need repair. Each height work order costs 40 yuan, with a repair cost of 32,000 yuan—just enough to eat back the price difference, not to mention the brand reputation.
Then take the warranty terms into account: Many lighting manufacturers promise a five-year warranty to project channels, and if the repair rate exceeds a certain percentage, there is a penalty. Once the penalty is triggered, the amount is on the order of ten times the price difference.
Calculated this way, the 30,000 yuan price difference for the Weather-Resistant brand buys a 'five years of worry-free' service, which is the cheapest sort of insurance in a construction market where bid price differences can easily be tens of thousands. Successful brands in the lighting industry generally do not compete on material prices for outdoor components—they are calculating based on this five-year total account, and they know it better than anyone.### Disclaimer
| Operating condition | Recommended materials |
|---|
| All-plastic lamp under 20 W | Thermally conductive flame-retardant PA |
| High-power lighting fixtures | Aluminum shell Plastic trim |
| Lampshade | PC or PMMA light-transmitting |
| Outdoor street lamp | Flame-retardant PC or PA weather-resistant three-piece set |
| IP65 Sealed | Silicone ring Reserved for moisture absorption expansion |
Engineering Memo
Before mass production, LED lamps must undergo three tests: thermal conductivity, 1000-hour xenon lamp aging, and junction temperature testing.
For high power, do not make it entirely plastic; the thermal conductivity limit for PA is 20 W. When reducing costs, lighting companies are most tempted to modify plastic parts, but the light decay and after-sales costs caused by downgrading heat dissipation components are usually far higher than the small amount saved on material costs.
Practical Case Study: Common Pitfalls and Correct Solutions
Pitfall 1: Only look at the flame retardant rating and ignore the CTI. LED fixtures installed near live circuits may have V-0 flame retardant rating but a CTI of only 250 V, leading to surface carbonization and short circuits after long-term tracking. Correct approach: Live components must have CTI ≥ 400 V (compared to the tracking index), V-0 only prevents fire but does not prevent tracking — this is the most commonly overlooked point in electrical components. Pitfall 2: Using recycled or substandard materials for insulation parts, resulting in large batch-to-batch fluctuations in dielectric strength, with 5% failing the pressure test. Correct approach: All insulation parts must use authentic new materials, with dielectric test reports for each batch. Pitfall 3: Torque of terminal parts decreases after a period of installation; it's often thought that the screw is loose, but the real reason is nylon creep. Correct approach: When LED fixtures rely on threaded connections, the material must be glass fiber reinforced to GF25 or above, and retightened after 24 hours of assembly.
Reverse case: The same factory, one failure and one success
This factory in Zhongshan actually changed materials twice; the first time failed, the second time succeeded, and the process is worth examining closely.
For the first time at the beginning of 2024: the lawn lamp housing was changed from die-cast aluminum to PA66, an all-plastic design, with the heat from the driver and light source fully pressing on the housing. In summer, the internal temperature exceeds 90°C, and after three months, the batch experiences yellowing and excessive light decay, resulting in the entire batch being scrapped.
Changed the approach the second time: keep the heatsink made of aluminum alloy, but switch the casing and end caps to weather-resistant PA66-GF30, connected in the middle with a thermal pad. Let the plastic do what it’s good at—corrosion resistance, insulation, and shaping; let the metal do what it has to do—conduct heat. After the change, the cost dropped by 18%, passed all aging tests, and this design is still in production today.
The same factory, the same material, two different outcomes—the difference was only in design division. Materials are never meant to be 'completely replaced'; they are meant to be 'placed in the right position.' Later, their R&D head said something we've remembered until now: the first failure is not a loss; the real loss would have been almost shutting down the entire path of plastic casing because of one failure.
Extended Judgment: The Hidden Variable Most Likely to Be Overlooked
In mass production accidents of LED lamps, half are not due to wrong material selection, but because hidden variables were not controlled.
The first variable is moisture content. The factory moisture content of PA series materials, drying conditions, and storage time before injection molding together determine the actual moisture content. If the moisture content is incorrect, both strength and appearance will be affected.
The second variable is the mold temperature. When the mold temperature is 20°C lower, the surface fiber floating and weld line strength may differ by a factor of two.
The third variable is the time after assembly. The torque, dimensions, and seal compression amount are all different after 24 hours and 30 days of assembly.
These three variables are not listed on the material properties table, but they are all included in the failure report.
Write these three things in a table and send it to the supplier; it's more useful than making ten phone calls — the communication cost of selecting LED fixtures mainly comes from repeatedly confirming these items.
The final Q&A: The verdict on three moments of dilemma
Dilemma 1: The client complains that the weather-resistant coating is expensive and asks if we can 'add a little less stabilizer.' We can't. The formulation of the weather-resistant system is calculated based on the target lifespan; the money saved by reducing the dosage is calculated monthly, while the cost of chalking is counted annually — in the end, reducing the dosage is the most expensive option. To reduce costs, save from the structure (reduce wall thickness, reduce processes), not from the formulation.
Entanglement 2: Should indoor lighting also use weather-resistant brands? No. There is no direct UV exposure indoors, and a conventional flame-retardant brand is sufficient. The premium for weather-resistant brands is wasted indoors. The refinement in material selection lies in this kind of tiered differentiation—uniformly upgrading or uniformly downgrading is just laziness.
Dilemma Three: Is a yellowed lampshade due to the lampshade itself or the housing? Most cases are the lampshade (yellowing is more noticeable in PMMA or PC), but yellowing of the housing is often misattributed to the lampshade. When making after-sales assessments, measure the yellowing index of both parts separately; don’t let the lampshade take the blame for the housing — and don’t let the housing's lack of weather resistance hide behind the lampshade. ### Additional note: Three signals for on-site judgment
Signal 1: One side of the casing has yellowing. The side facing the sun is yellow, while the side in the shade is still fine — the weathering system is insufficient, ultraviolet light hits from a single direction. Replace the entire batch with weather-resistant material, not just the stock.
Signal 2: The powdered and stretched parts are loose. The molecular chains have already broken. Yellowing is the prelude, powdering is the process, and the remaining lifespan of such parts is measured in months.
Signal Three: Intracavity temperature exceeds 85°C. Both light decay and material aging accelerate; first modify the cooling structure before talking about the material, as the material cannot fix structural problems. ### Verification sequence: complete the three steps before placing an order
Step one, separate the thermal paths: Draw a thermal zone map according to power, let the heat path of the light source go through metal, and set the temperature rating of plastic parts based on the thermal zone temperature, not just assuming based on room temperature.
Step two, weather resistance test: 3000 hours of xenon lamp yellowing and tensile strength dual indicators. Outdoor components without this report will not be included in the qualified supplier list under any circumstances.
Step three, combination testing: Combine the four items—housing, lampshade, sealing ring, and potting material—for an aging combination test. Cases where individual items pass but the combination has problems are more common than single-item failures. After completing these three steps, the selection risk for the lamp housing is reduced to an acceptable range.
Conclusion
There are many people here who work with plastics — when it comes to choosing materials, the earlier you ask, the less trouble it is.
The material selection and mold trial for this type of part can be discussed together.
