Determination of NCO content of the urethane prepolymers by 19F NMR spectroscopy

Quantitative NMR Studies of Multiple Compound Mixtures

“…Quantitative 1D 19 F NMR is widely applied in pharmaceutical, polymer, and organic industries [51][52][53]. Fluorine ( 19 F) nucleus is similar to hydrogen ( 1 H) with nuclear spin I ¼ 1/2, a large gyromagnetic ratio of 40.05 MHz/T, and natural abundance of 100% [54], which opens a way to selective, sensitive, and quantitative detection of fluorinated compounds in complex matrices.…”

Synthesis and research of epoxy resin toughening agent

“…Bromocresol green was used as indicator during the titration process, while the color of bromocresol changes from green to yellow, which can record the volume of hydrochloric acid consumption. Then the −NCO content (Moghimi et al 2014 ) was calculated according to the following formula, in which V 0 and V 1 mean the volume of hydrochloric acid consumption of the blank sample and the testing sample, c means concentration of hydrochloric acid standard solution, m means the quality of the sample. The residual isocyanate group ratio is 2.185 %, which comes from the experimental measured after polymerization.…”

A novel treatment and derivatization for quantification of residual aromatic diisocyanates in polyamide resins

“…Numerous methods were published that detail isocyanates analysis in polymer matrices by using fast infrared spectroscopic techniques, such as MIR and NIR 21 , but these methodologies are widely used to monitor high concentration of diisocyanates, so they are not suitable for PAs due to the low concentration of residuals. Another interesting analytical technique is the nuclear magnetic resonance spectroscopy of fluorine-19 ( 19 F-NMR) 22 , usable modifying the isocyanate derivative with 1,1,1,3,3,3-hexafluoro isopropyl alcohol (HFIP). Unfortunately, also in this case, quantitative magnetic resonance technique (qNMR) proves to be inaccurate due to the matrix complexity.…”