Temperature Measurement in PU Samples during the Chemical Reaction - 20120 pages

Temperature Measurement in PU Samples during the Chemical Reaction

TC holder
Box Foam Container
BFC 200

TC

Standard laboratory methods for measuring the temperature profile of
polyurethane samples during the chemical reaction are mainly based on
thermocouples (TC) or PT sensors which are positioned manually inside
the test samples. In polyurethane foam samples the highest temperatures
are normally reached in the lower third part of the sample. Non foaming
polyurethane samples of Coatings, Adhesives, Sealants and Elastomers
(C.A.S.E.) have their hot spot in the center of the reaction volume. Strong
temperature gradients are typical inside of the samples. The exact
positioning of the temperature probe is therefore critical in order to achieve
reproducible and reliable temperature data. Based on this, Format
Messtechnik GmbH has introduced three new test containers for measuring
the reaction parameters of PU samples including improved temperature
profiles.
The Box Foam Container BFC 200 (fig. 1) is a new test container
especially designed for low density foam formulations. The BFC 200 is
made of SRBP boards forming a cube with an edge length of 200mm. For
easy access to the finished foam sample two of the boards are hinged and
can be flapped aside. Temperature is measured by a metal sheathed
thermocouple rod. Precise positioning of the thermocouple is enabled by a
specially designed holder mounted at the edge of the BFC 200. It has a
boring at an angle of app. 30 degrees and a stopper for positioning the
thermocouple right into the hot spot of the sample. For easy removal after
the test a release agent is recommended.
The Advanced Test Container ATC (fig. 4) is a heated conically shaped
container for testing PIR and PU foam formulations under elevated

temperature conditions. The core temperature is measured by a glass fibre
insulated thermocouple. There are three fixed thermocouple ports available
in the Al body of the ATC. The flexible thermocouple is inserted from the
side into the lower third part of the foam sample. In case of the
thermocouple being stuck in the cured foam, it can be cut and then a new
tip can be prepared. The BFC 200 and the ATC are part of the Foam
Qualification System FOAMAT®. A measurement result of a rigid foam
formulation, measured with the ATC can be seen in fig. 2. The red curve
shows the temperature profile.
SubCASE® is a test device for monitoring the pot life and the curing
reaction of non-foaming PU formulations. The basic principle is measuring
the dielectric polarization and the temperature during the polymerization
reaction. A PT temperature probe is integrated into the bottom surface of
the test container. This is used for a closed loop temperature control of the
polarization sensor. A new cover plate featuring a bushing has been
introduced for precise and repeatable core temperature measurement. A
thin metal sheathed thermocouple is inserted into a glass tube, the tip of
which is pre-positioned into the center of the sample going to be tested (fig.
5). There is no direct contact between the thermocouple and the reactive
mixture. The thermocouple can be easily removed from the glass tube after
the test. No cleaning is needed and it can be reused for the next test. A
measurement result of a PU composite formulation is shown in fig. 3. The
green curve is the core temperature. The red curve shows the contact
temperature at the bottom of the sample.
patents 10200806053.4 and 102004001725

www.format-messtechnik.com

core temperature

4000 1600

3000 1200

80 80

2000 800

diel. polarization

rise pressure

GEL TIME

1000 400

CURING
0 0
0

0 0
100

200

300

400

500

time [s]

Fig. 1: The Box Foam Container BFC 200 is placed onto the
base plate of the extended mechanical set. The metal
sheathed thermocouple is inserted into the lower third part of
the foam sample through a holder mounted at the upper edge
of the BFC 200.

Fig. 2: Core temperature T of a rigid PU foam formulation,
measured in the Advanced Test Container ATC. Additional
parameters such as rise height H, rise pressure P and the
dielectric polarization D are acquired simultaneously by the
Foam Qualification System FOAMAT®.

800

160 160

POT LIFE

dielectric polarization
120 120

600

core temperature
80 80

400

bottom temperature
40 40

200
CURING

glass tube
TC
temp. sensor
cardboard cylinder

CMD-sensor

SubCASE HT

Fig. 5: The test device SubCASE® HT measures the
temperature and the dielectric polarization of C.A.S.E.
samples. The thermocouple (TC) is inserted into a disposable
glass tube; the tip of which is centered in the probe.

temperature controlled
Advanced Test Container ATC

TC ports
TC

0 0

0
0

D. JEFFREY GROSS
Eurotech Distributors, Inc.
Northfield, Ohio 44067
USA

cover plate

T1[°C] T2[°C]
200 200

bottom temperature / core temperature

MAX. TEMPERATURE

40 40

PU Composite Temperature in SubCASE®

rise height

160 160

120 120

D
1000

dielectric polarization

RISE TIME

rise height / core temperature

P[Pa] D
5000 2000

Foam Temperature in ATC

rise pressure / dielectric polarization

H[mm] T[°C]
200 200

ERLAND E. HOFMANN
Format Messtechnik GmbH
D-76187 Karlsruhe
Germany

400

800

1200

1600

2000

time [s]

Fig. 3: The bottom temperature T1, and the core temperature
T2 of a PU composite is measured by the Temperature and
Curing Monitor SubCASE®. The dielectric polarization D
reveals the pot life and the curing of the test sample.

Fig. 4: The core temperature of a reactive foam sample is
measured with a thermocouple, inserted through fixed ports in
the mantle of the temperature controlled Advanced Test
Container (ATC). ATC is part of the Foam Qualification System
FOAMAT®.