Foreword

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This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes, Subcommittee SC 14, Protective paint systems for steel structures.

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Introduction

In ISO 12944-5:2019, 6.2.5, fluoroethylene vinyl ether (FEVE) fluoropolymer topcoats are characterized as a specialized type of polyurethane based on fluoropolymers. This document describes the characteristics of the fluoropolymer topcoats with the intention of helping users understand both their advantages and limitations. Joint research on enhancing the weatherability and durability for a variety of coatings was launched in 1983 managed by the Public Works Research Institute of the Ministry of Construction in Japan and was continued until the publication of this document. The fluoropolymer topcoat systems were included in the joint research and results were obtained on the durability and weatherability over 30 years. These fluoropolymer topcoats systems were reported at several international conferences.^[1^]-[9^] This document incorporates valuable findings from the joint research on weathering tests conducted over the past 30 years, which are beneficial for users. Moreover, users are encouraged to contribute their own results to enhance the comprehensiveness of this document. FEVE type waterborne fluoropolymer topcoats and their coating systems have been developed and used in the market since around 2015, but long-term outdoor weathering data as has been obtained for the solvent borne type have not been achieved at present.

This document contains weathering performance data such as the rate of gloss retention and chalking resulting in film thickness loss of the topcoat system, along with chemical analysis data focusing on the coating film deterioration of fluoropolymer topcoat. All data has been obtained from the outdoor exposure testing. The chemical analysis relating to coating film deterioration was conducted using FTIR spectroscopy, covering analysis of both the surface and the cross-section (depth direction from the surface).

Users of this document can use the results of the long-term outdoor exposure test to predict the durability of the coating system.

Finally, this document points to the technological development of coating materials with state-of-the-art weathering performance in future, such as extremely slow chalking deterioration. This coating can be the standard reference for observing and evaluating short-, medium- and long- term weatherable coatings using the outdoor exposure data of these topcoats.

By using the data in this document, the real time durability of the coating film can be efficiently estimated using a short-term exposure test or an accelerated weathering test, or both.

1 Scope

This document describes the basic characteristics of fluoroethylene vinyl ether copolymer (FEVE) type fluoropolymer topcoats and their coating systems. Information on the weathering performance of the fluoropolymer topcoats and associated coating systems for over 30 years is also provided.^[1^],[4^]-[12^]

This document covers:

weathering data of FT (FEVE fluoropolymer topcoat);
chemical analysis of outdoor exposed coated panels focusing on the paint surface and their cross-sections.

This document does not include FEVE type waterborne fluoropolymer topcoats and their coating systems.

2 Normative references

3 Terms and definitions

4 General introduction of FEVE type fluoropolymer

4.1 Chemical structure of FEVE type fluoropolymer

4.2 Chemical curing system

5 Weatherability of fluoropolymer topcoats

5.1 Weatherability by fluorescent UV condensation cycle testing

5.2 Fifteen years weatherability test of FEVE type fluoropolymer topcoats

5.3 Actual bridges situation

6 Durability of fluoropolymer topcoat system

6.1 Results of collaboration study

6.2 Evaluation of the durability

6.3 Summary

7 Health and safety

Bibliography