Potentiometric Determination of the Epoxy Number

Potentiometric Determination of the Epoxy Number


Equipment
Potentiometer = 751 GPD Titrino / Titroprocessor
Electrodes = 6.0430.100 Ag Titrode; input 1

Reagents
c(HClO4) = 0.1 mol/L; D0

Sample
app. 0.2 g UHU resin
25 mL c(TBA) = 0.2 mol/L in acetic acid
TBA = Tetrabutyl ammonium bromide

Remarks
Determination reaction:
O OH
R-CH-CH-R’ + H+ → [R-CH-CH-R’]+
OH OH
[R-CH-CH-R’]+ + Br - → R-CH-CH-R’
Br
Calculations:

Epoxy.No=EP1*C01*C02*C03/C00;3;

Epoxy.No = epoxy number, number of epoxide groups per 100 g of sample
C01 = factor for conversion mL L (0.001)
C02 = concentration of titrating agent (0.1 mol/L)
C03 = factor for 100 g of sample (1000)
Stir sample in solvent during 3 minutes before titration


Answer

Epoxy.No = 8.828 x 0.001 x 0.1 x 1000 / 0.2261 = 0.390

EP1 = 8.828 mL
C00 = 0.2261 g

Literature
I. Gyenes, “Titrationen in nichtwässrigen Medien“
Ferdinand Enke Verlag, Stuttgart (1970), p. 598

Method documentation
'pa
751 GPD Titrino 15215 751.0010
DET U Epoxy.No
parameters
>titration parameters
meas.pt.density… 4
min.incr. …10.0 ml
dos.rate max…. ml/min
signal drift …OFF mV/min
equilibr.time …20 s
start V: …OFF
pause …0 s
dos.element:… internal D0
meas.input: …1
temperature …25.0 °C
>stop conditions
stop V: …abs.
stop V …12 ml
stop U …OFF mV
stop EP ….9
filling rate max…. ml/min
>statistics
status: ….OFF
>evaluation
EPC ….5
EP recognition:… all
fix EP1 at U ….OFF mV
pK/HNP: …OFF
>preselections
req.ident: ….OFF
req.smpl size:… value
activate pulse: …OFF
------------
'fm
751 GPD Titrino 15215 751.0010
DET U Epoxy.No
>calculations
Epoxy.No=EP1*C01*C02*C03/C00;3;
C00= 0.2261
C01= 0.001
C02= 0.1
C03= 100
------------
'fr
751 GPD Titrino 15215 751.0010
U(init) 646 mV DET U Epoxy.No
smpl size… 0.2261 g id#1 UHU
id#2 plus
EP1 …8.828 ml…. 795 mV
Epoxy.No ….0.390
stop V reached
============
'cu
751 GPD Titrino 15215 751.0010
start V 7.000 ml DET U Epoxy.No