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Experimental Measurement of Glass Transition Nandula Wanasekara EMAC 403

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Experimental Measurement of Glass Transition Nandula Wanasekara EMAC 403

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    1. Experimental Measurement of Glass Transition Nandula Wanasekara EMAC 403 1

    2. Outline Glass Transition and Associated Properties Determination of Glass Transition Temperature Dilatometric Method Thermomechanical Method Calorimetric Method Dynamic Mechanical Method Conclusions

    3. Glass Transition And Associated Properties Tg is the transition from glassy state to rubbery or viscoelastic state. Rubbery state does not necessarily mean the polymers is flowing. So flow temprature is defined for the transition from rubbery state to visco-fluid state. Tg is the transition from glassy state to rubbery or viscoelastic state. Rubbery state does not necessarily mean the polymers is flowing. So flow temprature is defined for the transition from rubbery state to visco-fluid state.

    4. Determination Of Glass Transition Temperature Dilatometry (DIL): volume Differential scanning calorimeter (DSC): heat difference Thermomechanical analysis(TMA): dimension Dynamic mechanical analysis(DMA) : mechanical stiffness & damping

    5. Dilatometric Method

    6. Dilatometry Graph The curves shown here are for amorphous and highly crystalline polymers.The curves shown here are for amorphous and highly crystalline polymers.

    7. Determination Of Glass Transition Temperature Dilatometer(DIL): volume Thermomechanical analysis(TMA): dimension Differential scanning calorimeter (DSC): heat difference Dynamic mechanical analysis(DMA) : mechanical stiffness & damping

    8. Thermo-mechanical Analysis The sample is placed in a temperature controlled environment with a thermocouple or other temperature sensing device, such as a platinum resistance thermometer, placed in close proximity. The atmosphere around the sample is usually controlled by purging the oven with air or nitrogen from a cylinder. Because of the much larger thermal mass of the sample and oven compared to a differential scanning calorimeter or a thermobalance, the heating and cooling rates employed are usually much slower for TMA. The sample is placed in a temperature controlled environment with a thermocouple or other temperature sensing device, such as a platinum resistance thermometer, placed in close proximity. The atmosphere around the sample is usually controlled by purging the oven with air or nitrogen from a cylinder. Because of the much larger thermal mass of the sample and oven compared to a differential scanning calorimeter or a thermobalance, the heating and cooling rates employed are usually much slower for TMA.

    9. Thermodynamic Graph

    10. Determination Of Glass Transition Temperature Dilatometer(DIL): volume Thermomechanical analysis(TMA): dimension Differential scanning calorimeter (DSC): heat difference Dynamic mechanical analysis(DMA) : mechanical stiffness & damping

    11. Calorimetric Method

    12. Calorimetric Graph

    13. Determination Of Glass Transition Temperature Dilatometer(DIL): volume Thermomechanical analysis(TMA): dimension Differential scanning calorimeter (DSC): heat difference Dynamic mechanical analysis(DMA) : mechanical stiffness & damping

    14. Dynamic Mechanical Analysis Force (stress) is applied to the sample through a motor. The stress is transmitted through the drive shaft onto the sample which is mounted in a clamping mechanism. As the sample deforms, the amount of displacement is measured by a sensor. The strain can be calculated from the displacement. During the measurement the temperature of the sample is defined and can be changed.

    15. DMA Graph

    16. Conclusions Tg is determined by measuring properties change near the glass transition region. Coefficient of expansion and heat capacity are widely used two important properties. By measuring one of these properties as a function of temperature, Tg can be determined. DSC is the classic and "official" way to determine Tg even though in some cases there are polymeric materials that do not exhibit a sharp Tg by DSC.

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