Verein Deutscher Ingenieure

Environmental simulation - Effects of acidic precipitation on polymers - Test methods
 N VDI 3958 BLATT 12

Annotation

Introduction

The subject of this guideline is the simulation of the damaging effect of environmental conditions during the transport, operation and storage of materials and products (referred to in the following as "objects"). Its scope is confined to objects made of polymers or containing a quality-relevant quantity of polymers and used outdoors. 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. The mechanisms differ from those of harmful gases, which essentially constitute the initial products of acidic precipitation. This guideline describes time-lapse laboratory test methods for simulating the damaging effects of acidic atmospheric precipitation in interaction with UV radiation, neutral condensed precipitation and changing temperature and humidity with the use of artificial acidic precipitation. With these test methods it is possible to make comparisons permitting the formulation of recommendations for the selection of polymers for use in environments subject to acidic precipitation.

On the basis of the methods of environmental simulation described in VDI 3958 Part 1, the time-lapse effect is achieved by the serial arrangement of the worst conceivable combinations of environmental conditions for the object (referred to in the following as the "worst case scenario"). To this end these environmental conditions are replicated in a more compressed sequence than outdoors, with the application of artificial acidic precipitation and using a commercially available weatherometer. At the same time, the extreme values of these environmental parameters do not significantly exceed those encountered in practice.