N-Ethyl-2-Pyrrolidone (NEP) CAS 2687-91-4

Introduction to NEP

N-Ethyl-2-Pyrrolidone is a dipolar aprotic solvent combining a cyclic lactam structure with an ethyl alkyl group. The structure balances polar and lipophilic character, enabling it to dissolve a wide range of organic compounds, polymers and solid active ingredients. It appears as a colorless to pale yellow liquid at room temperature, miscible with water and most common organic solvents.

The compound exhibits good thermal stability at elevated temperatures, and is not classified as a Substance of Very High Concern under REACH. It is highly hygroscopic; excess moisture triggers ring-opening hydrolysis at high temperatures, forming basic amine byproducts that disrupt acid-sensitive formulations.

NEP Chemical & Physical Properties

Applications of NEP

Agrochemical formulations: Serves as a carrier solvent for emulsifiable concentrates and suspension concentrates. It dissolves solid active ingredients such as pyrethroids, maintaining low-temperature stability and preventing crystallization during cold storage.

Photoresist stripping: Used in semiconductor manufacturing to swell and remove crosslinked photoresist polymers from silicon wafers. It breaks adhesive bonds between resist layers and substrate surfaces under moderate temperature conditions.

Polyimide processing: Dissolves dianhydride and diamine monomers for polyamic acid preparation. It supports controlled viscosity for film casting and coating processes in electronic and advanced material applications.

Industrial process solvent: Functions as a specialty solvent for specialty chemical reactions, polymer processing and surface cleaning operations, with low evaporative loss due to its low vapor pressure.

Storage & Safety Precautions for NEP

• Store in sealed HDPE or stainless steel drums below 35 °C. Blanket bulk tanks with dry nitrogen to prevent moisture ingress. Excess water causes ring-opening hydrolysis, pH drift and formulation incompatibility.
• Wear splash goggles, nitrile gloves and protective aprons during bulk transfer. The material causes serious eye irritation. Contain spills with absorbent material and flush with water.
• Heat IBC containers to 30 °C with band heaters before winter transfer. Low temperatures increase viscosity significantly, which can cause pump cavitation during dispensing.

NEP FAQ

Q: How do you test water content in N-Ethyl-2-Pyrrolidone (NEP)?

A: Tested via Karl Fischer titration per ASTM E203. Strict moisture control below 0.10% prevents hydrolysis and amine formation.

Q: Does NEP require MEHQ stabilizers for bulk storage?

A: No. It has no double bonds so polymerization cannot occur. Dry nitrogen blanketing is sufficient for stabilization.

Q: Why does pH rise in aged NEP drums?

A: Moisture ingress triggers ring-opening hydrolysis, forming basic amines. Nitrogen blanketing controls moisture and prevents pH drift.

Q: What happens to NEP in cold winter conditions?

A: Viscosity increases sharply at low temperatures, causing pump cavitation. Pre-warm containers to 30 °C before transfer.