1. Consider a case in which you have a material that support a certain stress at 75°C and you have several candidate polymers for which you need to determine the Tg using DSC or DMA(both of these are in your lab). Which technique would you select? Please provide a basis for your selection in terms of how the type of information it provides (based on how it works) and how/why it would be best suited for this application.
Differential Scanning Calorimetry or DSC is a traditionally common method used to estimate Transition temperature (Tg) for a wide range of polymeric materials such as thermoplastics and thermosetting polymers.
The physical transition of the material such as phase change is the basic principle for this technique. A reference sample is taken and a measured amount of heat is provided to it. Then the heat provided to the material whose Tg is to be estimated is provided. The difference in the amount of heat for both the material and sample is calculated as a function of the temperature. It is not suited for materials that have a wide range of Tg.
Dynamic Mechanical Analysis or DMA is a technique which is the most sensitive method used to estimate Tg of a material. The oscillatory strain is applied to a material and its response is measured as it varies with temperature or frequency or on both. For polymers, their elastic and viscous components can be separately measured by this method.
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