Thermal Properties DSC Differential Scanning Calorimetry

The range of physical and chemical changes that occur on heating polymers can be monitored using DSC and thermogravimetry (TGA). These thermal techniques are commonly used in plastics industry to characterize plastics. 

FIGURE 3.11 L Basic features of a DSC instrument. Right A generalized DSC tracing. 

The DSC curve shows the crystallization exotherm (B) and a melting endotherm (C) followed by an exothermic decomposition of the plastic (E) at higher temperatures (Bruns and Ezekoye, 2014). At a lower temperature, a first-order step change in the curve (A) is apparent and signifies the Tg of the material (Feng et al., 2013), and in some instances, a transition that signifies cross-linking (D) is also observed. 

The first term on the right-hand side is the change in and the second is the temperature-dependent kinetic response of the plastic. It is the second term that yields peaks (positive or negative) on the baseline of the specific heat versus T tracing in 

FIGURE 3.12 DSC tracings of two blends of atactic and isotactic PP showing the area under the melting curve. The designations indicate the weight fraction of isotactic and atactic PP in the blend. Source Reprinted with permission from D AnieUo et al. (2000). 

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