What is skydrol?

 

Skydrol is a brand name of fire-resistant hydraulic fluid used in aviation and aerospace applications. It is a phosphate ester-based fluid that is known for its excellent fire resistance and ability to withstand extreme temperature and pressure conditions. It is manufactured by Solutia (now part of Eastman Chemical Company), and formerly manufactured by Monsanto. There are various lines of Skydrol including

1.     Skydrol 500B-4

2.     Skydrol LD-4

3.     Skydrol 5

Skydrol, a type of hydraulic fluid used in aviation, is corrosive to concrete floors primarily due to its chemical composition. Skydrol contains phosphate esters, which can react with the calcium compounds in concrete.

Why it causes damages the concrete floor?

1.  Chemical Decomposition: Skydrol contains phosphate ester-based fluids, which hydrolyze over time, especially in the presence of moisture, forming phosphoric acid. This acid attacks the calcium silicate hydrate (C-S-H) gel in concrete, leading to its decomposition.

2.     Alkali-Silica Reaction (ASR): The acidic byproducts from Skydrol can accelerate the alkali-silica reaction in concrete. This reaction causes the formation of an expansive gel, which can lead to cracking and spalling of the concrete surface.

3.     pH Reduction: The acids formed from Skydrol hydrolysis reduce the pH of the concrete surface. Concrete typically has a high pH due to the presence of calcium hydroxide. Lowering the pH weakens the concrete and can cause dissolution of the cement paste, leading to surface damage and loss of material.

4.     Efflorescence: The reaction between Skydrol and concrete can lead to the formation of soluble salts. When these salts migrate to the surface, they can create a white, powdery deposit known as efflorescence. This not only affects the appearance but can also indicate deeper chemical damage within the concrete.

5.     Surface Softening: The plasticizing effect of Skydrol makes the concrete surface softer and more susceptible to mechanical wear and abrasion. This can lead to faster deterioration under traffic and mechanical loads.

6.     Permeability Increase: Chemical reactions and physical changes induced by Skydrol can increase the permeability of concrete, allowing more aggressive chemicals and water to penetrate deeper into the structure, exacerbating the damage. 

Why it causes damages the normal epoxy and PU floorings/coatings?

Normal epoxy and polyurethane (PU) floorings are not suitable for areas exposed to Skydrol due to the following reasons:

1. Chemical Resistance:
• Epoxy: While epoxy coatings are generally resistant to many chemicals, they do not have sufficient resistance to the aggressive chemical nature of Skydrol. Skydrol can cause the epoxy to soften, swell, or even blister, leading to rapid degradation of the coating.
• PU: Polyurethane coatings also lack adequate resistance to Skydrol. The phosphate ester components in Skydrol can penetrate and chemically attack the PU material, leading to loss of adhesion, discoloration, and surface breakdown.
2. Hydrolytic Stability:
• Epoxy: Epoxy resins can be prone to hydrolysis in the presence of moisture and certain chemicals. Skydrol's hygroscopic nature can exacerbate this, causing the epoxy to break down more quickly.
• PU: Polyurethane coatings can also suffer from hydrolysis, particularly when exposed to the acidic byproducts formed by Skydrol. This results in the loss of structural integrity and protective properties of the PU coating.
3. Thermal Stability:
• Epoxy: Epoxy coatings can become brittle over time, especially when exposed to thermal cycling. Skydrol can exacerbate this brittleness, leading to cracking and flaking of the epoxy layer.
• PU: Polyurethane coatings can also degrade under thermal stress, particularly when exposed to the temperature fluctuations common in industrial environments. Skydrol can accelerate this degradation process.
4. Mechanical Resistance:
• Epoxy: The mechanical properties of epoxy can be compromised by Skydrol exposure, making it less resistant to impact, abrasion, and wear.
• PU: While PU has good flexibility and mechanical properties, exposure to Skydrol can lead to loss of elasticity and mechanical strength, making the flooring less durable under mechanical loads.
5. Adhesion Loss:
• Epoxy: Skydrol can penetrate through micro-cracks and defects in the epoxy coating, leading to undercutting and loss of adhesion to the concrete substrate.
• PU: Similar to epoxy, polyurethane coatings can lose adhesion due to Skydrol penetration, resulting in peeling and delamination.

Due to these reasons, specialized coatings with enhanced chemical resistance, such as those specifically formulated for aviation hydraulic fluids, are necessary to ensure long-term performance and durability in areas where Skydrol is used.

What kind of epoxy or PU floorings are suitable for Skydrol?

For areas exposed to Skydrol, it is essential to use specially formulated epoxy and polyurethane (PU) floorings that offer enhanced chemical resistance. Here are the types of epoxy and PU floorings suitable for Skydrol exposure:

Epoxy Floorings:

1. Novolac Epoxy:
• Chemical Resistance: Novolac epoxies are highly resistant to a wide range of chemicals, including aggressive solvents and acids. This makes them particularly suitable for environments exposed to Skydrol.
• Thermal Stability: They offer better thermal stability compared to standard epoxies, which helps in maintaining their integrity under varying temperatures.
• Durability: Novolac epoxy coatings provide excellent mechanical properties, including abrasion and impact resistance.
2. High-Build Epoxy Systems:
• Thickness: High-build epoxy systems can provide a thicker protective layer, offering better resistance to chemical penetration and mechanical wear.
• Performance: These systems often incorporate additional chemical-resistant additives to enhance their performance in harsh environments.

Polyurethane Floorings:

1. Aliphatic Polyurethane:
• UV Resistance: Aliphatic polyurethanes offer excellent resistance to UV degradation, making them suitable for both indoor and outdoor applications.
• Chemical Resistance: They provide good resistance to Skydrol and other aggressive chemicals, maintaining their mechanical properties and appearance over time.
• Durability: These coatings are highly durable, with excellent abrasion and impact resistance.
2. Polyaspartic Polyurethane:
• Fast Curing: Polyaspartic polyurethanes cure quickly, reducing downtime during application.
• Chemical Resistance: They offer superior resistance to a wide range of chemicals, including Skydrol, and are less prone to yellowing or discoloration.
• Mechanical Properties: These coatings provide excellent flexibility, toughness, and abrasion resistance.

 Key Features to Look for in Suitable Epoxy and PU Floorings:

1. Enhanced Chemical Resistance: The flooring must be specifically formulated to resist phosphate esters and other aggressive chemicals.
2. High Build Thickness: A thicker application can provide better protection against chemical penetration.
3. Thermal and Mechanical Stability: The flooring should maintain its integrity under thermal cycling and mechanical stress.
4. Adhesion Promoters: Formulations that include adhesion promoters ensure better bonding to the concrete substrate, preventing delamination.
5. Seamless Application: A seamless, monolithic application minimizes joints and cracks where Skydrol can penetrate and cause damage.

 Suitable Products available in the market:

1. Laticrete Spartacote Guard - Superior resistance to punishing industrial traffic, Skydrol and other harsh chemicals. Popular where cleanliness is a must. A logical choice for demanding environments such as aviation hangers, manufacturing and shop floors.
2. Sherwin-Williams ArmorSeal® 1000 HS: A high-solids, novolac epoxy that provides excellent chemical resistance and durability.
3. SikaFloor®-390: A chemical-resistant epoxy coating designed for areas exposed to aggressive chemicals.
4. Mapei Mapefloor™ I 300 SL: A self-leveling, solvent-free epoxy that offers high chemical resistance.
5. BASF MasterTop® 1230: A polyurethane-based flooring system that provides robust chemical resistance and mechanical durability.
6. PPC PUMABOARD: A polyaspartic polyurethane coating with fast curing times and superior chemical resistance.

When selecting a flooring system for areas exposed to Skydrol, it is crucial to consult with manufacturers or suppliers to ensure the chosen product meets the specific requirements of the environment and expected chemical exposure.

This data is taken from the website and the google.

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