Near‐Infrared Spectroscopy of Polymers and Rubbers

Abstract

AbstractMolecular spectroscopy as provided using the near‐infrared (NIR) measurement technique is valuable for polymer identification, characterization, and quantitation. NIR spectroscopy can be completed for in situ process applications where no sample preparation is required, and where rugged optical systems are a necessity. The NIR region is a complimentary band of the electromagnetic spectrum to the mid‐infrared (MIR) region (4000–500 cm−1), encompassing 13 333–4000 cm−1or 750–2500 nm (nanometers, 10−9 m).NIR and infrared (IR) spectroscopy are routinely used to qualify monomers prior to polymerization reactions. NIR is used to measure the kinetics of polymer onset and can be used to detect end‐point completion and initiator compound levels in polymerization reactions. NIR spectroscopy can also be used to sort polymers and to control the quality of incoming raw monomers and finished polymeric materials. Molecular spectroscopy using the NIR and IR measurement techniques is often used for competitive analysis and to determine thermal or photoinduced oxidation or degradation reactions in polymers. This article delineates the background, theory, band assignments, and applications of NIR spectroscopy for the measurement of polymers and rubbers.