Surface-tolerant epoxy

High-build, surface-tolerant epoxy 80 125-200 2.5 h 6 h For maintenance where blast cleaning is not possible... 

Bar-Rust [Devoe Coatings] Surface-tolerant epoxy. 

Other new technology developments in this market segment include surface-tolerant epoxy coatings for aged or marginally-prepared surfaces, interval-firee... 

A good practice would be to apply a general use epoxy primer 3-5 mils dry film thickness (dft) (75-125 pm). If the surface cannot be abrasive blasted, a surface tolerant epoxy mastic may be used. 

Epoxy Surface tolerant epoxy (STE) Hand/power 1 1.3 12 8 5 5... 

Epoxy Surface tolerant epoxy/STE Hand/power 2 2.5 17 12 9 9... 

Epoxy Surface tolerant epoxy/polyurethane Hand/power 2 1.8 17 11 6 6... 

Epoxy Surface tolerant epoxy/STE/polyurethane Hand/power 3 3.0 23 17 12 12... 

Mastics are high-solids, high-build epoxy coatings designed for situations in which surface preparation is less than ideal. They are sometimes referred to as surface tolerant because they do not require the substrate to be cleaned by abrasive blasting to Sa2 1/2. Mastics can tolerate a lack of surface profile (for anchoring) and a certain amount of contamination (e.g., by oil) that would cause other types of paints to quickly fail. 

The characteristics of the three most common thermoset resin systems used in pultrusion are compiled in Table 11.2 [3]. It is noteworthy that unreinforced polyesters and vinylesters shrink 7-9% upon crosslinking, whereas epoxies shrink much less and tend to adhere to the die. These epoxy characteristics translate into processing difficulties, reduced processing speed, and inferior component surface finish. It is normal practice to use resin additives to improve processability, mechanical properties, electrical properties, shrinkage, environmental resistance, temperature tolerance, fire tolerance, color, cost, and volatile evaporation. It is normally the resin, or rather its reactivity, that determines the pulling speed. Typical pulling speeds for polyesters tend to be on the order of 10-20 mm/s, whereas speeds may exceed lOOmm/s under certain circumstances. Apart from the resins characterized in Table 11.2, several other thermosets, such as phenolics, acrylics, and polyurethanes, have been tried, as have several thermoplastics (as will be discussed in Sec. 11.2.6). 

Coating formulations and properties have been detailed in technical bulletins (31). The epoxy-polyamide system is popular because it provides an unusual degree of inherent corrosion resistance. This will be discussed in detail later. The system is unusually tolerant as compared to related systems, such as amine cured, since the ratio of components is not particularly critical. Tolerance is also demonstrated because it may be applied to wet surfaces and to surfaces with tightly bound rust. Indeed, formulations are available that may be applied under water to structures such as submarines and off-shore oil well riggings. Both the corrosion resistance and the tolerance relative to application on poorly prepared wet surfaces are believed to be functions of the surface activity of the polyamide resin. Related also to the surface activity are the unusually strong adhesive properties that the system demonstrates with a broad range of substrates. 

The ideal die attach material has a short cure time at a relatively low-cure temperature, exhibits low moisture absorption, provides good adhesion to multiple surfaces, contributes low stress to the die and can be processed within a very tight tolerance. Many epoxies are now available meet some of these demands to a high degree, yet each material has limitations. 

The use of epoxy adhesives as thread-locking adhesives is somewhat limited by poor adhesive tolerance of oily surfaces. The use of a variety of... 

Organic (epoxy) zinc-rich primers are used in place or to repair imperfections of the inorganic zinc-rich primer. Their advantages over inorganic zincs include improved adhesion to the epoxy primer coating and better tolerance to poor surface cleaning. 

For the most part, oil-based coatings (alkyds, epoxy esters, and modifications thereof) have a greater tolerance for poor surface preparation and an ability to wet, penetrate, and adhere to poorly prepared surfaces or old coatings. Consequently, these coatings are often specified for these purposes, even though they do not provide as long a term of corrosion protection. 

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