Methyl Ethyl Ketone (MEK) CAS 78-93-3

Introduction to Methyl Ethyl Ketone (MEK)

Methyl Ethyl Ketone (MEK) is a colorless, low-boiling aliphatic ketone solvent with a polar carbonyl group. That carbonyl dissolves polyurethane, nitrocellulose, vinyl copolymers and many adhesive resins, so MEK is used in fast-dry coatings, gravure inks, PU adhesives and industrial cleaners.

The practical value is fast film formation: MEK boils at 79.6 °C (175.3 °F) and evaporates quickly, helping reduce tack time and residual solvent in dried films. The main handling risks are flammability and static: flash point is about -9 °C (15.8 °F), vapors are heavier than air and can travel to ignition sources. Keep drums sealed, grounded and below 30 °C (86 °F), away from oxidizers; for moisture-sensitive polyurethane systems, check water content before use and record batch COA results.

Key Features of Methyl Ethyl Ketone (MEK)

• Polar carbonyl solvency. The ketone group swells and dissolves PU, nitrocellulose and vinyl copolymers, supporting smooth resin flow in coatings and inks.
• Fast drying profile. A boiling point of 79.6 °C (175.3 °F) helps films reach low tack quickly, which suits high-speed gravure and printing ink lines.
• Partial water solubility. MEK dissolves oils and resins while water solubility is about 275 g/L (2.30 lb/gal) at 20 °C (68 °F), useful in controlled cleaning blends.
• Low-viscosity dosing. About 0.43 mPa·s at 20 °C (68 °F) makes transfer, metering and solvent blending stable in automated systems.
• Flammability control. Flash point -9 °C (15.8 °F) requires grounding, bonding and sealed transfer to prevent static ignition in plant use.

Methyl Ethyl Ketone (MEK) Chemical & Physical Properties

Applications of Methyl Ethyl Ketone (MEK)

Polyurethane coatings: MEK solvates PU chains through dipole interaction, lowering spray viscosity and supporting resin leveling. Typical formulation usage is 5–30% by weight of coating, adjusted to solids content and target application viscosity.

Nitrocellulose inks: The ketone carbonyl dissolves nitrocellulose and modified resins, while fast evaporation reduces tailing and blocking on high-speed printing lines. Common ink solvent loading is 10–40%, depending on drying speed and resin system.

PU adhesives: MEK dissolves PU elastomers to a coatable viscosity and helps control open time. Typical solvent proportion is 20–50% of total adhesive weight, depending on solids level and coating method.

Industrial cleaning and degreasing: MEK dissolves uncured adhesive, oil films and some coating residues. It can be used neat or blended at 5–50% in cleaning formulations, with ventilation used to remove residual vapor after wiping or dipping.

Storage & Safety Precautions for Methyl Ethyl Ketone (MEK)

Storage: Store below 30 °C (86 °F) in a cool, sealed drum away from ignition sources, strong oxidizers and strong bases. MEK has a low flash point and vapors are heavier than air, so bond and ground drums, pumps and receiving vessels before opening bungs. For frequent opening or long storage, nitrogen padding reduces vapor loss and static risk; QC can verify water by Karl Fischer per ASTM E203 because water above 0.10% may trouble isocyanate systems.

Safety: Treat as highly flammable liquid, eye irritant and drowsiness hazard (typical GHS: H225, H319, H336). Use antistatic clothing, chemical goggles, solvent-resistant gloves and organic-vapor respiratory protection. For spills, eliminate ignition sources, ventilate at floor level, collect with explosion-proof pumps or non-sparking tools into a closed drum, and do not discharge to drains.

Transport: Dangerous goods: UN 1193, Class 3, Packing Group II. During loading keep drums upright and check bungs and bonding continuity; a leaking drum in a closed container can create an ignitable vapor mixture.

Methyl Ethyl Ketone (MEK) FAQ

Q: Why does Methyl Ethyl Ketone (MEK) CAS 78-93-3 require grounding during transfer?

A: MEK has a -9 °C flash point and heavy vapors that travel along the floor to ignition sources. Static from pouring or pumping easily ignites the vapor cloud. Bond and ground all drums, pumps and receiving vessels. Use closed transfer and run floor-level ventilation before opening bungs.

Q: How much water in MEK is acceptable for polyurethane coating systems?

A: Target below 0.10% water by Karl Fischer test. Excess moisture reacts with isocyanate prepolymers, releasing CO2 that causes bubbles, blushing and pinholes in the film. Reseal drums immediately after use. Never charge damp MEK into moisture-sensitive PU batches without retesting.