Hydroxyl value titration is a chemical analysis method that calculates the molecular weight by quantifying the terminal hydroxyl value in the diol based on the chemical nature of the hydroxyl groups. Polyurethanes are usually obtained from polyols and polyisocyanates through a polyaddition reaction between hydroxyl groups (—OH)and isocyanate groups (—NCO)

and the ratio between them is particularly important in the process of producing polyurethanes. Therefore

it is necessary to accurately calculate the hydroxyl value of used polyols. Due to the high viscosity and poor water solubility of polycarbonate diol (PCDL) synthesized from epoxides and CO

2

directly

we used an improved hydroxyl value titration strategy (acetic anhydride-methylimidazole-dimethylformamide method) to measure the hydroxyl value of commmercial and synthesized PCDL. The effects of various factors in the process of titration on hydroxyl value were discussed in detail. Compared with the industrial standard method

this optimized method can reduce the amount of samples and chemical reagents

moreover

the acylation reaction can be completed in a 45 ℃ water bath for only 20 min

which saved the test time and thus improved the efficiency.