ASTM D4273 Determination of Primary Hydroxyl Content of Polyether Polyols

Scope:

ASTM D4273 delivers information about the relative reactivities of polyols. It also provides a good balance between hydrophobicity and reactivity. Sometimes, poor reactivity ethylene oxide is added to the tail of the polyether polyols.

Procedure:

For ASTM D4273, a solution of the polyol sample in deuterated acetone having tetramethyl silane (TMS) as an internal standard is prepared. Then transfer a suitable amount of the sample solution to an NMR tube. The NMR tube is then placed in a spinner and the optimized field-homogeneity is acquired from the NMR data. Apply a spectral weighting function (apodization) to the Free Induction Decay and Fourier Transform (FID). Internal TMS reference is set to around 0 ppm. The primary hydroxyl peaks usually resonate between 61.0 and 62.5 ppm, while the secondary hydroxyl peaks generally resonate between 65.5 and 67.5 ppm.

Specimen size:

The suggested broadening line value is 1 per acquisition time.

Data:

The following equation is used in ASTM D4273 to calculate the primary hydroxyl content of polyether polyols

Primary hydroxyl, % 5 = A* 100/A+B

A= primary hydroxyl peak

B= secondary hydroxyl peak

Conclusion:

ASTM D4273 delivers information about the relative reactivities of polyols.