Description of Equipment
• The Differential Scanning Calorimeter can scan through
arrange of temperatures while heating and cooling and it determines a phase
transition, i.e. melting, crystallization, or glass transition, by measuring
the amount of heat needed to reach a set temperature.
• The machine is calibrated with a set of pure metals (zinc, indium, and
tin) that have a known heat capacity, Cp and melting point, Tm.
• The reference material is placed or located at the rear of the sample
compartment while the sample is placed in front.
• There is a heat source at the bottom of the DSC sample chamber that
supplies heat to both the sample and reference pans and a thermocouple that
records the temperature
• Cooling nitrogen is supplied at the top through the cooling jacket by
the refrigerator on the floor next to the machine and nitrogen gas is purged
throughout the system to maintain an inert environment.
• The equipment has three insulating lids and the first one should be
placed on carefully to avoid knocking off the sample in the chamber
Sample Preparation
• First turn on the refrigeration unit next to the DSC
• Lay down some aluminum foil to work on
• Get the sample press from the work shelf above the countertop and clean
a spatula and a pair of tweezers with some solvent
• Obtain the standard pan and lid from the drawer and be careful not to
knock them over with the tweezers. The pan has higher walls than the lids.
• The pans and lids should be kept away from all contamination and this
could have adverse effects on results. Note that oil from fingers can affect
your results.
• Weigh a filter paper and tare the balance
• Weigh the pan and lid, and remember to weigh by difference to maintain
accuracy
• Remove pan and lid from balance and carefully place the sample on the
pan
• You should have approximately 8-12mg of sample in the pan; DO NOT have
an excess amount as this can spill over and greatly contaminate the entire DSC
apparatus. A spill will require a new calibration (that can only be done by
an authorized personnel, i.e Lola)
• Place the lid face up on the pan and squash slightly.
• Carefully put the pan and lid in the sample press and pull down the
handle.
• Weigh the crimped sample to check that the weight is constant and no
sample has been lost
• Clean the working area
Operation of the DSC
• Remove
all three lids and gently place the sample in the center of the empty sample
stage (the one in front)
• Put the lids back on
• Set the N2 flow rate to 50 cm3/min and check the nitrogen flow rate
to the chamber is at 80 and that to the chiller is at maximum
• Enter all the necessary information into the computer and define your
procedure.
• Make sure to change the operator name to yours and do not forget to
save your data
• Click apply and hit the green play button
Cleaning the DSC (should be done at least every 6 months)
Please follow the procedure outlined below in the event of a polymer spill or
for regular maintenance:
• Turn off the cooler if it is on
• Remove all three lids and place in the reference pan in the case
• Carefully unscrew the arm and place on the holder next to the wall.
NEVER move the arm while it is frozen as it is made from ceramic and becomes
extremely brittle at low temperatures.
• Remove the orange rubber insulation
• Go to the mode menu and uncheck “RCS attached”
• The appropriate heating procedure is: ramp up at 20oC/min to 600oC
• After the run is completed, brush the surface with the fiber glass brush
• Reassemble the arm perform necessary calibrations
Calibrating the DSC
Baseline Test
• Change the mode from standard to calibration
• Input baseline as the sample name and set the sample size to 0.0mg
• Save in a new folder under the calibration folder
• Change the test mode from custom to baseline
• In the procedure, choose a range from -50oC to 400oC at a heating rate
of 10oC/min (this is the limit of the cooling arm)
• Change the pan type to none and take out the reference pan
• The heat capacity should be approximately constant and zero
Indium Test
First is the cell calibration:
• Change the sample name to indium and set the weight at 8.1mg
• Save in the appropriate data file and change the test mode to cell constant
• Skip the procedure tab and change the pan type to aluminum
• Make sure that there are no calibration files loaded while you are in
the calibration mode
• Place the empty reference cell and indium cell in the DSC and start
the experiment
Next is the indium temperature test:
• Change the test type to temperature test and file name following previous
protocol
Tin Test
• Run tin on the temperature mode test
• Change sample name and size (11.7mg)
Zinc Test
• Run zinc on temperature test; however this test goes above 400oC so
follow procedure above for removing the cooling arm disengaging the RCS attached
(refrigeration control system) in the mode dialog box
When you are finished with either the cleaning the calibration, run the PEO
homopolymer sample and be sure that you get the expected plot.
Please see Lola if you have any questions or if you encounter any trouble with
the DSC