ASTM D4274 Determination of Hydroxyl Numbers of Polyols
ASTM D4274 test method determines the primary and secondary hydroxyl groups present in polyester and polyether polyols. This test method defines different reagents for determining the hydroxyl groups of different polyols such as polymer polyols, polyether polyols, polyester polyols, and amine-started polyols. The final results are expressed in SI Units.
The ASTM D4274 test method is vital for the determination of hydroxyl groups of Polyols. This method is valid for a wide range of hydroxyl-containing substances. It determines the reliability and quality of different Polyols along with their specifications. This helps in quality control and research, which is essential for the formation of polyurethane systems. The hydroxyl content of Polyols is determined, and its applications are specified along with the purification of the reagents.
For ASTM D4274, the sample is prepared by mixing a solution of acetic anhydride in pyridine at 98°C. The sample is transported to the pressure bottle and weighed. For tests B and C, the esterification of hydroxyl solution with phthalic anhydride in pyridine is done at different temperatures. For tests D and E, the esterification of hydroxyl solution is done with the solution of imidazole and pyromellitic dianhydride. The hydrolysis and titration with automatic titrators are done using a standard sodium hydroxide solution. The differences in titration volumes hint at the hydroxyl content. The purification of reagents and water is done.
In ASTM D4274, the specimen size is taken as per the requirements. In this case, 127 mL of acetic anhydride is mixed with 1000 mL of pyridine to prepare an acetylation reagent.
The hydroxyl number, mg KOH/g, of the sample is calculated for ASTM D4274 as follows:
Hydroxyl number ꞊ [(B – A) N × 56.1]/W Where: A = NaOH required for titration of the sample, mL. B = NaOH required for titration of the blank, mL. N = normality of the NaOH and W = sample used, g.
The ASTM D4274 test method is vital for the determination of hydroxyl groups of polyols.
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