Unsaturated Polyester Resin Hydroxyl Number Determination as per DIN EN ISO 2554

The hydroxyl number denotes the quantity of potassium hydroxide (in milligrams) needed in order to neutralize acetic acid required for acetylation of 1 gram of an unsaturated polyester resin (UPR) with free hydroxyl groups. This application note describes the determination of hydroxyl number using DIN EN ISO 2554 compliant automated potentiometric titration method utilizing KOH in methanol as titrant.

Sample

Unsaturated polyester resin (UPR)

Sample Preparation

Sample preparation is not required.

Analysis

Blank

The blank is determined the same way as the sample, just without UPR.

Sample

Approximately 5.6 grams of UPR is weighed and placed in the sample beaker. 10 mL of acetylating solution is added to the sample using an automated program. The mixture is allowed to react for 45 minutes in a water bath with 50 °C ± 1 °C temperature.

10 mL of pyridine/water and 2 mL of deionized water are then added using an automated program. 20 mL solvent mixture is added just prior to the titration. Titration is then carried out using KOH with a 0.5 mol/L concentration and continued until after the equivalence point is reached.

Configuration

. .
907 Titrando 2.907.0010
800 Dosino, 5x 2.800.0010
814 USB Sample Processor (2T/0P) 2.814.0130
Dosing unit 50 mL, 2x (solvent mixture, titrant) 6.3032.250
Dosing unit 10 mL, 2x (acetylating solution, pyridine/water mixture) 6.3032.210
Dosing unit 2 mL, (deionized water) 6.3032.120
741 Magnetic stirrer, 2x 2.741.0010
843 Pump station (peristaltic) 2.843.0150
Sample rack, PP, 22 x 120 mL 6.2041.470
Titration head, 3x NS 14 6.1458.040
Sample beaker, PP, 22 x 120 mL 6.1459.300
Titration head with DIS-Cover 6.9914.158
DIS-Cover lids for 120 mL PP beakers 6.9914.164
Solvotrode easyClean, c(TEABr) = 0.4 mol/L in ethylene glycol 6.0229.020
Tiamo™ 2.5 6.6056.252

Solutions

. .
Titrant c(KOH) = 0.5 mol/L in methanol, if possible this solution should be bought from a supplier.
Acetylating solution w(Toluene-4-sulfonic acid) = 1.14% in ethyl acetate and acetic acid, Φ (ethyl acetate) = 90.2% (v/v)
Solvent mixture 1-Butanol / Toluene, Φ (1-Butanol) = 66.6% (v/v)
Pyridine/water mixture Pyridine / Water, Φ (pyridine) = 60.0% (v/v)

Parameters

. .
Mode DET U
Start volume 5 mL
Signal drift 50 mV/min
Stirrer speed 8
Max. waiting time 26 seconds
Meas. point density 4
Min. increment 10 µL
Max. increment Off
EP criterion 5
EP recognition Greatest, evaluation with window
Lower limit mL 2
Upper limit mL 50
Stop volume 50 mL
Volume after EP 2 mL

Results

. .
Hydroxyl number / (n = 5) s(rel)
42.60 mg KOH / g 0.5%

Remarks

The hydroxyl number is finally calculated by taking into account the total acid number (TAN), determined separately by DIN EN ISO 2114.

This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.

For more information on this source, please visit Metrohm AG.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Metrohm AG. (2019, April 02). Unsaturated Polyester Resin Hydroxyl Number Determination as per DIN EN ISO 2554. AZoM. Retrieved on June 19, 2019 from https://www.azom.com/article.aspx?ArticleID=15568.

  • MLA

    Metrohm AG. "Unsaturated Polyester Resin Hydroxyl Number Determination as per DIN EN ISO 2554". AZoM. 19 June 2019. <https://www.azom.com/article.aspx?ArticleID=15568>.

  • Chicago

    Metrohm AG. "Unsaturated Polyester Resin Hydroxyl Number Determination as per DIN EN ISO 2554". AZoM. https://www.azom.com/article.aspx?ArticleID=15568. (accessed June 19, 2019).

  • Harvard

    Metrohm AG. 2019. Unsaturated Polyester Resin Hydroxyl Number Determination as per DIN EN ISO 2554. AZoM, viewed 19 June 2019, https://www.azom.com/article.aspx?ArticleID=15568.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit