Total acid number (TAN) describes the quantity of potassium hydroxide needed for neutralizing free acids, free anhydride groups, and all carboxyl-terminated groups of an unsaturated polyester resin (UPR).
This Application Note explains the determination of TAN with an automated potentiometric titration in accordance with DIN EN ISO 2114. The technique employs KOH in ethanol as the titrant.
Sample
Unsaturated polyester resin (UPR)
Sample Preparation
Sample preparation is not required.
Analysis
Blank
A blank is determined without UPR, using the same methodology as the sample.
Sample
Approximately 5 grams sample of UPR is weighed and kept on the rack. 60 mL of solvent mixture is added to the sample by automated program. The mixture is allowed to react for 20 minutes, after which 15 mL of acetone is added using automation. The titration is then carried out using KOH with 1.0 mol/L concentration. The process is continued until after the equivalence point is reached.
Configuration
| . |
. |
| 907 Titrando |
2.907.0010 |
| 800 Dosino, 3x |
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 20 mL, (acetone) |
6.3032.220 |
| 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, LiCl sat. in EtOH |
6.0229.020 |
| tiamo™ 2.5 |
6.6056.252 |
Solutions
| . |
. |
| Titrant |
c(KOH) = 0.1 mol/L in ethanol, if possible this solution should be bought from a supplier. |
| Solvent mixture |
MEK / Pyridine / Water, v/v/v(7.5 / 4.0 / 0.5) |
Parameters
| . |
. |
| Mode |
DET U |
| Pause |
30 seconds |
| Signal drift |
20 mV/min |
| Stirrer speed |
8 |
| Max. waiting time |
38 seconds |
| Meas. point density |
4 |
| Min. increment |
50 µL |
| Max. increment |
Off |
| EP criterion |
5 |
| EP recognition |
all |
Results
| . |
. |
| Total acid number / (n = 5) |
s(rel) |
| 23.79 mg KOH / g |
0.9% |
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This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.
For more information on this source, please visit Metrohm AG.