Corrosivity Test Methods for Polymeric Materials. Part 5- A Comparison of Four Test Methods

Abstract

This is the fifth in a series of papers published by the Polyolefins Fire Performance Council, a unit of The Society of the Plastics Industry, Inc. In this paper, four test methods are compared for their ability to evaluate smoke corrosivity of polymeric materials: 1) the proposed ASTM E05.21.70 radiant combustion/exposure standard test method, 2) the CNET corrosivity test stan dard being reviewed by ISO (DIS 11907-2), 3) the DIN 57 472 acid gas test stan dard, and 4) the proposed ASTM D09.21.04 cone corrosimeter standard test method. The ASTM E05.21.70, CNET, and ASTM D09.21.04 test methods directly de termine the corrosive effects of combustion gases, as they measure the resis tance changes in copper circuit targets exposed to the gases. The ASTM tests report the resistance change in terms of metal loss and the CNET test reports the resistance change in terms of % corrosivity factor. The DIN test standard determines the conductivity and pH changes of aqueous solutions through which combustion gases are passed. Twenty-four polymeric materials were evaluated for smoke corrosivity by these four test methods, so that the test methods could be reliably compared based on results from many types of polymeric materials. The polymeric materials evaluated are commercially available and they cover a broad range of compositions used for wire and cable insulation and jacketing. The ASTM E05.21.70, CNET, DIN and ASTM D09.21.04 tests are evaluated based on several criteria. Each test is evaluated on the basis of precision, or whether the test is repeatable, and accuracy, or whether the test differentiates corrosive potentials consistent with the expectations based on the known chem istry of the material compositions. To also determine accuracy, the ASTM E05.21.70, CNET, and D09.21.04 test methods are compared to the DIN 57 472 test method, as this test and similar acid gas tests are accepted standards that have been historically used to measure corrosive potential. Recommendations are made for improving the proposed test methods.