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Differential Scanning Calorimetry (DSC) Of Powder Coating Materials

Introduction This manual provides instructions to prepare samples for and subsequently perform a DSC (differential scanning calorimetry) test on thermoset powder coating materials. The DSC machine used in this instruction manual is the Perkin Elmer DSC-6. DSC tests are used to determine a number of temperature related physical properties of materials, such as Tg (glass transition temperature), degree of cure, and reaction onset temperature. Methods for the analysis of DSC results are beyond the scope of this set of instructions, and will be covered in a separate document. In order to perform the described task, minimal laboratory experience is necessary. The time to complete one full measurement cycle is approximately one half hour. Sections

• Sample Preparation. • Loading the DSC. • Sample DSC Run. • Sample DSC Run Completion

Equipment List

1. Perkin Elmer Sample pans and lids 2. Perkin Elmer Pan Press 3. Tweezers 4. Perkin Elmer DSC 6 Differential Scanning Calorimeter 5. Razor Blades 6. Copy paper (Not shown)

DSC Created By: Mike Shirey & Steve Howard

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Step 1 – Sample Preparation

Caution: Razor blades are dangerous. Take care to ensure you do not cut yourself during their use.

Note: Do not touch the collected samples, sample pans or lids with your fingers. The DSC test is sensitive to contamination from skin oils and this could affect the accuracy of your results.

A. Scrape or cut shavings of the cured powder coating material onto a piece of clean paper, using a razor blade. Collect enough sample material to fill a sample pan.

B. Transfer the sample material onto a 3”x2” piece of paper with a fold lengthwise down the center as shown.

Step 2 – Sample Preparation

Note: Use tweezers to handle sample pans and lids to prevent contamination from hand oils or foreign materials.

Note: It is normal for small amounts of the sample to spill as it is transferred into aluminum sample pan.

A. Add sample material to the sample pan until it is level with the top edge of the pan.

B. Place a pan lid over the sample material in the pan. The lids are non-directional so it does not matter which side is up.

C. Press the lid into pan using tweezers.

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Step 3 – Sample Preparation

Note: Use tweezers to handle prepared samples.

A. Using tweezers, place the prepared sample pan on the cylinder body at the base of the pan press.

B. Pull the cylinder body downward to expose the center anvil. The cylinder body is spring loaded in the up (closed) position.

C. Slide the sample to a centered position over the anvil.

D. Gently allow the cylinder body to rise back up into the closed position.

E. The sample should now be positioned on top of the anvil, at the bottom of the anvil-cylinder assembly.

Step 4 – Sample Preparation

Note: Use tweezers to handle prepared samples.

A. Push down on the hand pad at the top of the press; this drives a crimping piston into the anvil chamber and seals the pan. Press the pad downward until you hear a soft click, indicating the pan edge has been crimped over the lid. B. Remove the sealed pan from the press by pulling the cylinder body downward to expose the sealed sample pan. Remove with tweezers. C. Place the sealed sample pan on a hard surface, like the press base, and poke a small hole in the top of the pan lid using the tip of the tweezers. The hole allows gasses to escape during the DSC process.

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Step 5 – Loading the DSC.

Note: Do not remove the sample pan from the cavity on the left hand side of the furnace; this is a calibration standard and must be in place for the test to run correctly.

A. Pick up and remove the outer furnace access door, using your tweezers, and set it aside.

B. Remove the inner furnace access door with your tweezers and set it aside.

C. Remove sample from previous DSC run from the cavity on the right hand side of the inner furnace.

D. Place the sample you just prepared into the cavity on the right hand side of the inner furnace. The pan will center itself on the raised button in the center of the cavity.

E. Replace inner furnace access doors. F. Replace outer furnace access door.

Step 6 – Sample DSC Run

A. Turn on the computer and the DSC machine. The on-off switch for the DSC machine is at the back of the instrument.

B. Wait for the computer to finish its start routine. After startup, the screen will have a number of icons displayed on the left hand side. Double click the “Pyris Manager” icon.

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Step 7 – Sample DSC Run

Note: When the software is opened, a menu tool bar will appear at the top of the desktop.

A. Open the instrument viewer screen by double clicking on the “DSC 6” button located on the menu tool bar at the top of the desktop.

Step 8 – Sample DSC Run

Note: The Instrument Viewer screen is a real time graphical display of the instrument. The graph shows endothermic heat flow vs elapsed time.

A. Open the Method Editor screen by single clicking on the page icon as shown; this allows you to input the run parameters.

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Step 9 – Sample DSC Run

Note: The Method Editor Window will open. This window contains three tab selectable pages for user to interface with. These windows are used to program the test parameters.

Note: Hitting the “enter/return” key on your computer keyboard enters any value or text you have typed, as does the “Tab” key and “clicking” on a different text block.

A. Click on the sample tab to ensure that it is selected and active.

B. Click in the white text block area labeled “Sample ID:” and type in the sample information: Part#, lot# sample#. Click in the “Operator ID:” text area and type in your initials.

Step 10 – Sample DSC Run

A. Click on the “Initial State” tab to activate this

interface window. B. Ensure that the “Temperature” value is set to

“40.00°C” and that the “Y Initial” value is set to “20.00mW”. These are preset default values but they can be adjusted if necessary by using the arrow buttons next to each entry area, or by clicking in the text block and typing in a value.

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Step 11 – Sample DSC Run

A. Click on the “Program” tab to activate this interface window.

B. Ensure that the “Initial Temp” value is set to “30.00°C”. The value you set in the initial temp text block will be displayed as the first step, highlighted in blue, in the program display area below the initial temp value.

Step 12 – Sample DSC Run

A. Click on the “Add a step” button located just

the right of the program display area. This will button opens a pop-up window named “Method Step Options”.

B. Click on “Temperature Scan” from the list. C. Click on the “OK” button at bottom of pop-up

screen to return to program screen.

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Step 13 – Sample DSC Run

Note: The Temperature Scan Window will open. This window allows you to set the conditions for the second step of the program, a scan, in which the temperature will be increased to the set point at the rate you have set.

A. Ensure that the “To” temperature option is set to

“250.00°C.” B. Ensure that the “Rate” option is set to

“20.00°C/min.” Step 14 – Sample DSC Run

A. Click on the “End Condition” button to open the

“End Condition” interface window. B. Set the “Go To:” temperature to “40.00°C”. The

end condition value sets the temperature of the furnace at the completion of the program cycle.

C. Click on the “Done” button.

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Step 15 – Sample DSC Run

A. Press the DSC start/stop run button to begin the program.

Sample DSC Run Completion The DSC run will be complete after the equipment reaches the end condition set in Step 14. As stated in the introduction, analysis of the resulting data is beyond the scope of this set of instructions and will be addressed in a separate document. Concluding remark on DSC testing Differential Scanning Calorimeters work by comparing the ability of two separate samples, placed on two separate heating elements, to take on energy in the form of heat. The DSC measures and graphs the difference in energy needed to maintain both samples at the same temperature. The graph is then evaluated for inflection points, peaks and peak areas, to determine results.