Lab Set 2 - THERMAL TRANSITION BEHAVIOR Thermal Transition...

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THERMAL TRANSITION BEHAVIOR Thermal Transition – A change that takes place in a material when heated or cooled, such as melting, crystallization, or glass transition. Glass Transition Temperature – The temperature at which a solid-state polymer shows a decrease in heat capacity and the polymer becomes softer. Melting Temperature – The temperature at which molecules become fluid like and lose three- dimensional order. Melting is a first order thermodynamic property and is an endothermic process (requires heat). The observed melting temperature is the temperature at which the thermal input is sufficient to overcome secondary bonding in the crystalline regions of the polymer. Crystallization Temperature – The temperature at which the heat capacity of the polymer shows an increase. Molecules within the polymer become mobile and pack together tightly. Crystallization occurs beyond the glass transition stage and is an exothermic process (the polymer gives out heat during crystallization). Heat Capacity (C p ) – The amount of heat energy required to increase the temperature of 1 gram of material by one degree at a constant pressure. Specific Heat – Heat capacity divided by molecular weight (J/kg-K) Latent Heat – Heat absorbed or given out without causing an increase in temperature. The heat given off or absorbed when a material melts, freezes, boils or condenses is latent heat. For example, when ice is heated, once the temperature reaches 0 0 C, it's temperature won't increase until all the ice is melted. The ice has to absorb heat in order to melt. But even though it's absorbing heat, its temperature stays the same until all the ice has melted. The heat required to melt the ice is called the latent heat. The water will give off the same amount of latent heat when
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This note was uploaded on 09/12/2011 for the course PTFE 2200 taught by Professor Kumar during the Spring '10 term at Georgia Institute of Technology.

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Lab Set 2 - THERMAL TRANSITION BEHAVIOR Thermal Transition...

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