Polyurethanes (PU) are synthetic polymers used to create a wide range of products, from flexible or rigid foam structures to safety features in cars. The physical properties for PU products can vary widely. PU is formed by reacting liquid di/polyisocyanates and polyols with a catalyst and additives. Therefore, determining the free isocyanate content (%NCO) in the manufacturing process is a critical parameter to optimize production. Generally, spot samples are taken and analyzed in a laboratory by titration methods which are slow and generate waste. Inline monitoring of %NCO in real-time is a safer and more efficient way to monitor and improve PU production and reduce waste.

This Process Application Note presents a method to accurately monitor the percentage of NCO in the PU manufacturing process in «real-time» using near-infrared (NIR) spectroscopy. This can be done safely, reliably, and optimally with a 2060 The NIR-Ex Analyzer from Metrohm Process Analytics.