ASTM G154 and ASTM G155 Explained

ASTM G154和G155测试评估非金属材料对模拟阳光和湿气暴露的抗性. When rays of sunlight—particularly UV rays—bombard a surface, they degrade smaller pigment particles, changing the surface color and creating a chalky effect. Cracking, peeling, de-glossing, oxidation, and loss of mechanical properties are additional outcomes of exposure; sometimes such deterioration can even occur through glass. Moisture takes its own toll on surfaces, 阳光和水分的结合会放大伤害, costing millions of dollars of depreciation each year. ASTM G154和G155测试帮助制造商设计能够承受阳光和潮湿暴露的产品. 

然而，重要的是要记住，这两个测试都提供了暴露近似. Ultimately, 测试耐候性最现实的方法是让产品实时降解, with outdoor testing panels. 这种实时测试设施通常位于炎热地区, 因为阳光的破坏作用在高温下会被放大. 在美国，黄金标准地点为户外 exposure testing facilities are located in Arizona (for simulating hot, dry climates) and south Florida (for simulating hot, humid climates). Due to time constraints, however, 许多生产商采用G154和G155实验室室测试，以便在较短的时间内获得暴露结果. 

Florescent vs. Xenon Arc Testing

Accelerated testing G154和G155中使用的仪器通过强烈暴露于太阳光中最具破坏性的im体育APP-紫外线来测试近似性能. 紫外线只占阳光的5%，但它们造成了大部分的暴露伤害. 通过将产品暴露在紫外线下，测试仪器可以模拟这些暴露结果. 

在ASTM G154测试中，荧光灯泡在受控测试室内模拟阳光照射. The ASTM G155 test is similar, 但它利用氙气弧光灯来模拟全光谱的阳光风化. 因为氙弧光与自然光最相似, ASTM G155测试主要用于室外耐候性测试. Fluorescent light has a lower correlation to natural sunlight than xenon arc light; therefore, ASTM G154试验方法一般用于模拟室内或室内暴露. 

ASTM G154: Our Most Popular Accelerated Weathering Test

Although an infinite variety of exposure conditions can occur, ASTM G154测试通常包括将样品暴露在紫外线照射的交替周期中，然后是黑暗时期. 水分循环可以分布在整个光照循环中. 

In ASTM G154 testing, UVA-340灯泡与户外照射的相关性最好, 因为它们发出的波长最接近自然光中的破坏性波长(295至365纳米). Different UV bulbs are useful for different testing purposes. 例如，UVA-351灯可以重现透过窗玻璃过滤的那部分紫外线. 因此，这些灯泡是有用的测试室内应用. UV-B light accelerates the brittleness that materials, particularly polymers, may suffer as they age indoors. 相比之下，UV-A灯泡有加速颜色褪色和变黄的倾向. 如果测试的目的是提高色牢度，UV-A灯泡是理想的. 

Exposure Testing Considerations - ASTM G154 and G155

It is impossible to recreate nature in the lab. 世界上的每个地方都有自己独特的破坏因素组合, such as pollution, salt spray, and biological attack. 没有在特定地点进行多年的测试, it is impossible to perfectly predict product response. As such, the ASTM G154 and G155 tests produce comparative, not absolute data, 但这些比较评估对设计师来说仍然是非常有价值的. 例如，配方的轻微改变可能会产生两倍的抗风化能力. Such outcomes cannot be quickly obtained in outdoor settings; therefore, 这些耐候性测试在及时的产品开发中是无价的.  

Recreate specialized conditions with filters. In xenon arc testing, 不同的滤光片可以应用于日光的位移测试条件, window glass, or extended UV spectrum exposure. Similar filters can be used in fluorescent light testing. 

Include a control, to act as a weatherization standard. 美国材料试验协会(ASTM)国际建议，与测试样品同时暴露一种性能确定的可比材料(对照). This allows for an accurate comparison. Additionally, 每种样品材料最好包括至少三个副本, for optimized statistical evaluation. Remember, 这些加速风化试验不能准确地再现室外条件, as they cannot account for altitude, seasonal variations, local geographical features, and other variables. 对照样品和多种材料样品产生最佳的比较数据. 

There is no easy exposure formula. 可以进行计算，估计测试仪器内的等效能量暴露及其与世界各地不同地点的相关性. However, because the actual results can vary with temperature, humidity, altitude, and weather and biological conditions, there is no simple equation for calculating exposure.

Don’t fall for common weathering myths. It may be tempting to assume that shorter wavelengths, continuous exposure, high temperatures, and other variables can result in more intense acceleration. 但是，每一个变量都会带来独特的不同结果. For example, 没有温度循环的持续暴露无法重现材料在室外所面临的膨胀和收缩应力. 

The Element Advantage in ASTM G154 & ASTM G155

Element已经帮助公司确定了超过188年. We can work with you to ascertain the most cost-effective, accurate testing approach for your material. 耐候性测试的费用将根据许多因素而变化, including moisturization, sample size, number of cycles, and more.