Análisi Térmico De Pe

Thermal Analysis & Rheology

Thermal Analysis Application Brief
Number TA-123

Determination of Polymer Crystallinity by DSC*
Summary
Perhaps no fundamental property affects the physicalproperties of a polymer in so general a way as the degree of crystallinity. Differential scanning calorimetry (DSC) provides a rapid method for determining polymer crystallinity based on the heat requiredto melt the polymer. were evaluated both "as received" and after being subjected to a "thermal treatment" designed to impart equivalent thermal history to all three samples. This thermal treatmentconsisted of heating at 10oC/minute to 180oC, followed by controlled cooling at 5oC/minute to ambient.

Results
Figure 1 shows the melting endotherm for one of the polyethylene samples during theinitial "as received" heating. DSC Standard Data Analysis software was used to calculate the % crystallinity based on 290 J/g for a 100% crystalline material (16). The results for the three samplesstudied are summarized below.
Sample 1 2 3 Melt Onset Melt Peak Enthalpy Temperature(oC) Temperature(oC) (J/g) Crystallinity(%) 121.9 121.3 122.3 132.9 132.6 131.6 195.9 194.5 180.1 67.6 67.1 62.1Introduction
An understanding of the degree of crystallinity for a polymer is important since crystallinity affects physical properties such as storage modulus, permeability, density, and melting point.While most of these manifestations of crystallinity can be measured, a direct measure of degree of crystallinity provides a fundamental property from which these other physical properties can bepredicted. Differential scanning calorimetry (DSC) is a technique which measures heat flow into or out of a material as a function of time or temperature. Polymer crystallinity can be determined with DSC byquantifying the heat associated with melting (fusion) of the polymer. This heat is reported as % crystallinity by ratioing against the heat of fusion for a 100% crystalline sample of the same...