ASTM D6437 Alkalinity in Low-Alkalinity Polyols (Determination of CPR Values of Polyols)

Scope:

The ASTM D6437 test method is important in determining the alkaline number of Polyols with the help of titration. This test method is important to get accurate readings at different sample concentrations. It defines a standard to control the quality and measure uniformity of these Polyols. It characterizes the Polyols found in polyurethane products and is applicable for research purposes. It determines the hydroxyl number with the help of correction factors. It provides information about the performance of Polyols in polyurethane systems which helps specify their reliability and the extent of their reaction with isocyanates to form polyurethane polymers.

Procedure:

The apparatus consisting of a potentiometric automatic titrator, buret, pH glass electrode, and an analytical balance is set up. The sample is taken in large quantities and titrated with a dilute acid solution.  The auto-titrator is set up, and the sample is poured in a 50mL flask filled with the methanol solvent and indicator solution. The sample is titrated by adding aqueous hydrochloric acid, which helps determine the alkalinity number. The endpoints of the potentiometric titration are noted, and the alkalinity is determined. 

Specimen Size:

30 ± 1.00 grams of sample are taken in a titration cup.

Data:

The CPR as meq/30 kg of the polyol is calculated as follows:
CPR = (Vsam – Vblk) ·N·30 000/W
The alkalinity number, in micrograms of KOH/gram of sample, is calculated as follows:
Alkalinity number ꞊ [(Vsam– Vblk) .N.56.1/W