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发表于 2022-9-27 16:39:35
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哦,上面的说法有问题,刚看了ASTM F1980-21附录X3,这个里面说的比较清楚,在老化温度下设置成45%~55%就可以了。
X3.3 When controlling humidity during an accelerated aging study, 45–55 % RH should be targeted unless there is specific warrant for using other humidity conditions (based on material knowledge). If other conditions are used, a rationaleshould be documented.
X3.4 To achieve an equivalent moisture concentration in a material at elevated temperatures (compared to ambient temperature), comparable relative humidity conditions must be maintained: not absolute humidity conditions. Using absolute moisture contents of air (as opposed to equivalent relative humidity) at elevated temperatures can result in lower absorbed moisture in materials than at ambient temperatures and the possibility of significant deviation from real time behavior (that is, artificially reduced degradation rates). At elevated aging temperatures (for example, 50–60°C), low relative humidity levels (for example, <30 % RH) will typically result in lower moisture contents in the material, which can retard hydrolytic degradation that may be inherent in a real-time system. Conversely, exceeding 55 % relative humidity at temperatures above 50°C may result in unnatural physical changes to materials (for example, delamination of laminates and coextrusions that incorporate water-based or water-soluble primers or adhesives), particularly hygroscopic polymers. As such, care
should be exercised in using humidity levels (either higher or lower) that, when combined with temperature, produce moisture levels that may cause these unnatural physical changes.
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