NMP turns red
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NMP, whose scientific name is N-methylpyrrolidone, has shown yellowing or orange discoloration after recent repackaging； All materials were stored in a sealed condition, and no increase in moisture was detected after analysis. After thorough research, it was found that NMP undergoes a decomposition reaction at temperatures above 45°C: NMP → NXOY + CO + CO2 ； After multiple observations, it was found that the color of the NMP mixture becomes darker and redder! I’m not sure if any of the seniors have had a similar experience; I’d like to ask for advice. Thank you!
I looked up information online: a colorless and transparent oily liquid with a slight amine odor. It is miscible with water, alcohols, ethers, esters, ketones, halogenated hydrocarbons, aromatic hydrocarbons, and castor oil. It has low volatility, excellent thermal and chemical stability, and can volatilize along with water vapor. It is hygroscopic. Sensitive to light. LD50 (rats, oral) 3.8 mg/kg. Density: 1.028 Melting point: -24 °C Boiling point: 203°C, 81–82 °C/10 mmHg Flash point: 91 °C Refractive index n20/D: 1.47 ------------------------------------------------------------------------------------------ Good thermal stability! Could there be other reasons for the discoloration?
Due to its structural characteristics, NMP is primarily used as a high-boiling solvent; it is generally colorless. A red color may indicate the presence of impurities or the dissolution of certain substances. Its chemical properties are relatively stable, so reactions with other compounds that could cause color changes are not a concern. NMP has a high water absorption capacity; even a slight increase in air humidity can lead to an increase in the water content after analysis.
During use, color changes are rarely observed; could it be that some impurities are present?
Thank you all for your concern. What I’m doing is switching from large packages to smaller ones; I use a PP diaphragm pump to draw out the material, with the small packages being PE drums. There are no impurities present during this process. I wondered about the dissolving and corrosive effects of NMP on PP, but I couldn’t find any useful information on that!
This post was last edited by gyvine on 2023-6-28 09:09. I wonder if the original poster has resolved the issue; I often encounter situations where NMP turns red or green, and it becomes colorless and transparent as soon as it is exposed to air...
The specific reason for the color change is unknown; it seems to be related to the pH value
From experience, it’s a temperature issue, because I’ve analyzed the moisture level here and there’s almost no change!
Is the decomposition product after peroxidation N-methylsuccinimide?
It might be due to the presence of trivalent iron ions. I manufacture NMP, and over time storage can affect its pH value. The sample hasn’t changed color after 3 years, which suggests it may have been purified from recycled material.
Hello, can we have a conversation? I also produce NMP. QQ3056772295