M e h m e t K a n ı k

http://bg.bilkent.edu.tr

P r e s e n t a ti o n S e r i e sClubournalJ

Thermal Conductivity in Polymers

Bulk Polymer

Known as thermal insulaters.

Individual Chainof Poly Ethylene (PE)

Extremely high thermal conductivity. In practical application individual chain form offiber or films.

In this study :

Ultra drawn PE nanofibers.

Lenght : Tens of milimeters ???? Diameter : 50 – 500 nm

Thermal Conductivity:

Applications

Methods

Composite :

+ =

Similarly alingment of the polymer chains can increase the thermal conductivity.

Methods

0.8 wt% ultra-high molecular weight PE Powder

140 C N2 Environment

Gel PE at 120 C

90 C Heating (Dry)

Diameters rangingfrom 50 to 500 nm

Measuremet is doneat the most necked Region along 300 um long fiber.

Methods

Measurement

High Vacum 50 uTorr

Conductive silver epoxy. Motorized Stage

Measurement

First Step : Calibration

Thermal conductance of the cantilever is 1000 times largerthan the fibre.

Nanofiber heat absorbance is0,1 %

Varying absorbed power on the end of the cantilever.

Second Step: Calibration

Laser power held constant. Andthermocoupol temperaturevaryed

Initial bending of cantilever is fixed.

Change in temperature bends the cantilever.

+ =

Results

is the highest thermal conductivityThat achieved.

It is ;

higher than micrometer size fibers.

300 times higher than bulk PE .

higher than half of pure metals including:patinum, iron and nickel.

Reasons

1 ) Small crystalline structures are broken and during streching they transformed in lamels.

2 ) Folded chains become unfolded.

3 ) Defects and impurities moved out to the surface or disappeared.

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