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This test sheet describes a procedure for testing the compatibility of plastic materials made of PVC, PUR or TPE with nitrogen oxides. The method simulates a colour change due to the influence of nitrogen oxides, which can be released from other emission sources during storage or processing of the material and can thus lead to its discolouration. This colour change caused by “gas fading” is known to occur between phenolic antioxidants present in materials’ formulation and nitrogen dioxide.(1) The gas used in this test method is nitrogen monoxide (nitric oxide) because of safety issues. Nitric oxide (colourless) reacts with oxygen from the air producing nitrogen dioxide (brown).
(1) Kuhn, Tino; “Discoloration of White Plastics”, Kronos International, Leverkusen, Germany, 2010.
This evaluation is recommended for light colour materials (L* ≥ 60, measurement acc. ISO 105- A05), although it can be used in all colours.
