Quantitative determination of isocyanate group content in polyurethane prepolymer by ATR-FTIR
Attenuated total reflection Fourier transform infrared(ATR-FTIR)tests were performed on a se-ries of polyurethane prepolymer samples prepared from polymeric methylene diisocyanate(pMDI)and polyether polyol.The absorbance A of the infrared characteristic peak(～2 245 cm-1)and the corrected peak area S of isocyanate group(—NCO)were used to linearly fit with the content of—NCO obtained by potentiometric titration,respectively.The results showed that the linear relationship of the latter was better than the former,the correlation coefficients R2 were 0.996 7 and 0.985 6,respectively.According to the working curve between the corrected peak area S and the content of—NCO,the content of—NCO of newly prepared prepolymers were determined.Compared with the potentiometric titration method,the rela-tive error of new working curve was<0.2%,and the relative standard deviation was<0.5%,indicating that the test accuracy is good enough and the method is reliable.As ATR-FTIR is used to determine the—NCO content of polyurethane prepolymer,the sample does not need any pretreatment and volume of samples are tiny.In this way,it does not produce waste liquid and is environmentally friendly.The test re-sults are reliable,and it is convenient for operation and application in industrial production site.
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