Corrosivity Test Methods for Polymeric Materials. Part 3- Modified DIN Test Method

Abstract

This is the third in a series of papers to investigate corrosivity test methods published by the Polyolefins Fire Performance Council, an operating unit of The Society of the Plastics Industry, Inc. In the first paper, 24 polymeric materials were evaluated for smoke corrosivity following the "Stan dard Test Method for Measuring the Corrosive Effect of Smoke from the Burn ing or Decomposition of Materials and Products" proposed by ASTM E05.21.70 which uses a radiant combustion/exposure apparatus. The second paper dis cussed the evaluation of the same 24 materials using the CNET corrosion test method "Plastics-Smoke Generation-Determination of the Corrosivity of Fire Effluents (Static Method)" under consideration by ISO TC61/SC4/WG2 and IEC TC89/WG3 and compared the CNET combustion results with the ASTM E05.21.70 results. In this paper, the 24 polymeric materials were evaluated us ing a modified "Testing of Cables, Wires and Flexible Cords; Corrosivity of Combustion Gases DIN 57 472 Part 813 Standard" acid gas test method and the results are compared to the previous ASTM E05.21.70 and CNET results. These commercially available polymeric materials cover a broad range of com positions used for wire and cable insulation and jacketing.

The samples were decomposed in a modified DIN apparatus under dynamic conditions and the combustion gases were absorbed in a water trap where the pH and the conductivity were measured. The DIN apparatus was modified by the addition of gas dispersion frits for improved absorption of the combustion gases in the aqueous solution. The acid content of the aqueous solutions was determined using a silver nitrate/ammonium thiocyanate Volhard titration. The data demonstrate that the modified DIN test method using these indirect determinations of corrosive potential does differentiate polymeric materials, ranking them in a similar order to the ASTM E05.21.70 test method. Little cor relation with the CNET % Corrosivity Factor "COR" was found. Reasons for these differences are discussed.

To complete the review of corrosion test methods, studies are under way to evaluate these same 24 materials with the "Fire Response Standard for Deter mining the Corrosive Effect of Combustion Products Using a Cone Corro simeter" proposed by ASTM D09.21.04.

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References

Kessel, S.L. , J.G. Bennett, Jr. and C.E. Rogers. 1991. "Corrosivity Test Methods for Polymeric Materials," 40th International Wire & Cable Symposium Proceedings, November, p. 348.

Rogers, C.E. , S.L. Kessel and J.G. Bennett, Jr. 1992. "Corrosivity Test Methods for Polymeric Materials, Part 2-CNET Test Method," 17th International Conference on Fire Safety, January, p. 392.

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Keogh, M.J. , C.E. Rogers and G.A. Schmidt. 1991. "Polyolefin Resin Blends and Additive Technology: Advanced Non-Halogen Flame Retardant Compounds," Flame Retardant Chemicals Association Meeting, March.