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Thursday, September 30, 2010

One Coats and Binders - A Selection Guide

One Coats & Binders - A Selection Guide

We commonly receive inquires to determine the best one coat system for a given application.  Here is some information that my be helpful in understanding the various products.

 In general, knowledge of a coating chemistry and how that chemistry will standup in a given environment is a big help in selecting the correct coating or coating system.  We asked a DuPont Chemist to help us understand the primary strengths and weaknesses for some of the organic resins used in one coats and primers to aid us in selecting the best system for a given application.

There are several common organic resins used in the one coat products:

PAI = Polyamide - Imide resin.  These resins have relatively high temperature resistance, excellent adhesion to most metals and are fairly easy to put in water systems.  However, basic chemical resistance is not as good as some other choices.

Epoxy = Epoxy carriers of various types.  Characterized as having excellent adhesion and easy to work with, the relatively low use temperature (300 to 400 F) limits use of these resins.

PES = Polyethersulfone.  Excellent toughness, good chemical resistance makes these resins an excellent choice except in harsh solvent environments.  These resins are difficult to put in water systems therefore coatings are usually solvent based.  Coatings made with PES tend to soften above 400 F.

PPS = Polyphenylene Sulfide.  Excellent toughness and chemical resistance.  These resins are excellent choices for water systems at lower temperature uses but tend to soften at temperatures above 400 F.

The most common DuPont one coat systems are shown below listed by major resin type used in the system.

Product Line Resin
420-10x PES
954-10x Epoxy
958-303 PAI
958-406 PAI
958-414 PAI
959-20x PAI

For chemical environments, understanding how the resin interacts with the chemicals will help you to choose the right one coat for an application.

Resin Type Solvents Strong Solvents* Bases Strong Bases Acids Strong Acids
PAI OK Poor Poor Poor Fair Poor
Epoxy OK Poor OK Fair OK OK

* Examples of strong solvents are NMP, THF, DMF and Methylene Chloride.


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