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DIN Standards Committee Coatings and Coating Materials

Overview

This standard specifies a method of simulating the damaging effect of outdoor weathering with relevance to acidic atmospheric precipitation on polymeric products. In addition to the classical environmental variables of temperature and humidity, acidic atmospheric precipitation can also have a significant effect on the photochemical ageing of polymers, for example, by attacking the stabilizers. The mechanisms differ from those of harmful gases, which essentially constitute the initial products of acidic precipitation. Arising from changing industrial air pollution and additionally diffused by the stochastic wind and cloud distribution, acidic precipitation occurs sporadically. Thus, especially regarding acidic precipitation, outdoor weathering effects vary enormously within different years. Therefore, it is practically impossible to obtain reliable, representative outdoor exposure results from just one season. These fluctuations can be avoided through the use of artificial deposition, where all weathering parameters, including the acidic deposition, can be controlled. The method is based on VDI Guideline VDI 3958-12 "Environmental simulation - Effects of acidic precipitation on polymers - Test methods". This standard specifies the acid dew and fog test (ADF test) as an accelerated laboratory test method for simulating, by the use of artificial acidic precipitation, the damaging effects of acidic atmospheric precipitation in association with UV radiation, neutral condensed precipitation, and changing temperature and humidity. These test methods are intended to be used in evaluating, on the basis of relative performance rankings, the suitability of polymeric materials for use in outdoor environments with acidic precipitation. The ADF test is not intended to generate the same extent of damage or the same damage pattern as in outdoor weathering, but rather to give a ranking which is similar to that which would be obtained in outdoor weathering. The method produces damage which is more homogeneous, allows fewer specimens to be exposed (and hence more rapid testing) and enables evaluation of the exposed specimens to be carried out using methods which are more objective than visual assessment. The committee responsible for this standard is NA 002-00-07 AA "Allgemeine Prüfverfahren für Beschichtungsstoffe und Beschichtungen" ("General test methods for coating materials and coatings") at DIN.

Document: references other documents

Responsible national committee

NA 002-00-07 AA - General test methods for coating materials and coatings  

Responsible european committee

CEN/TC 139 - Paints and varnishes