Allen Zielnik,程舸,马旭东.高性能涂层实验室加速老化改进试验方法的研发[J].表面技术,2017,46(4):101-113.
Allen Zielnik,CHENG Ge,MA Xu-dong.Test Method Development for Improved Laboratory Accelerated Weathering of High Performance Coatings[J].Surface Technology,2017,46(4):101-113 |
| 高性能涂层实验室加速老化改进试验方法的研发 |
| Test Method Development for Improved Laboratory Accelerated Weathering of High Performance Coatings |
| 投稿时间：2016-09-20 修订日期：2017-04-20 |
| DOI：10.16490/j.cnki.issn.1001-3660.2017.04.018 |
| 中文关键词: 耐候试验 加速老化 户外曝晒 汽车涂料 SAE J2527 ASTM D7869 |
| 英文关键词:weathering test accelerated ageing outdoor exposure automotive coating SAE J2527 ASTM D7869 |
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| 中文摘要: |
| 目的 改进实验室加速老化与亚热带自然老化之间的相关性及其预测能力。方法 包括美国福特、波音、巴斯夫和亚太拉斯等在内的多家公司耗时近10年合作研发改进试验方法。在自然和加速老化的条件下，使用各种不同的测试周期，对20多种已知户外老化性能的汽车面漆/清漆涂层系统及几种单涂层系统进行测试。借助光谱技术跟踪分析了样品涂层中作为光氧化降解和水解降解标记的几个关键峰值。将老化后的涂层系统制成5 m厚超薄切片，跟踪研究其化学变化以及紫外吸收剂浓度的变化。结果 加速老化光源与户外地面阳光在质和量上的光谱匹配度，尤其是紫外波长截止点的匹配，是改变涂层降解过程化学反应的关键。研发出一种特殊滤镜，克服了现有光源系统的局限性。对比佛罗里达自然老化实验发现，现有实验室试验方法无论在质还是量上，水分输送均不够充足。对测试周期加以修改，直至其水分吸收与释放和户外昼夜模式相匹配，并对自然条件下的正常波动给予额外补偿，包括长时间浸透让涂层达到水饱和以及随后的干燥和热冲击循环。最后研究了样品温度的影响，包括热机械应力以及昼夜循环对涂层水动力体积的影响，建立了分段式辐照度和温度循环周期，以更好模拟温度对次级涂层降解反应及物理老化的影响。结论 新的测试方法显著改善了所有样品与户外自然降解时所发生化学反应的相关性，忠实再现了涂层系统在佛罗里达自然老化时产生的物理变化（如剥离、附着力损失、开裂和起泡），并且具备更好的加速性，达到佛罗里达自然曝晒2~5年的同等效果，新试验比现行方法快大约40%。新试验方法最终被建标为ASTM D7869-13《交通工具用涂料氙灯老化测试标准-增强光照及水曝露》。 |
| 英文摘要: |
| To improve correlation and predictive ability of a laboratory accelerated weather test to that of outdoor subtropical exposure. A consortium of several companies, including Ford, Boeing, BASF & Atlas etc., cooperated in the methods development over almost 10 years. Over twenty automotive basecoat/clearcoat coating systems of various known outdoor weathering performance, and a number of monocoat systems, were investigated. Samples were subject to natural and accelerated weathering using various test cycles. A variety of spectroscopic techniques were employed to follow several key peaks in the coatings that are markers for photo-oxidation and hydrolysis degradation and could be followed over time. Microtomy was also used to provide 5-micron thick sections through the weathered coating systems to follow both the chemical changes as well as changes to the UV absorber concentration. It was found that both the qualitative and quantitative spectral match to terrestrial outdoor solar radiation, particularly in the UV cut-on wavelength, were critical factors in altering the coating degradation chemistry. A special light source filter was developed to overcome the limitations of the systems that were in use. Next, the effects of moisture delivery in both quality and quantity were compared to Florida exposures and found to be deficient. Laboratory test cycles were modified until both moisture absorption and desorption match the diurnal pattern of outdoor exposure, with additional compensation for the normal excursions of natural conditions. These included periods of long water soaks to allow coating saturation, followed by drying cycles and thermal shock events. Lastly the effects of specimen temperature were investigated for both thermomechanical stress as well as the effect on coating hydrodynamic volume during diurnal cycles, and a stepped irradiance and temperature profile was established to better mimic the thermal effect on secondary coating degradation reactions as well as physical weathering. The new test cycle produced significant improvements in the correlation of the coatings degradation chemistry to outdoor exposures across all coatings systems tested, and reproduced the physical changes to the coating systems including delamination and adhesion loss, cracking, and blistering similar to Florida exposure. The test was approximately 40% faster in producing the same effects as two and five year Florida weathering exposure compared to existing methods. The final test cycle was established as ASTM D7869-13 standard practice for xenon arc exposure test with enhanced light and water exposure for transportation coatings. |
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