Optimization Of Modulated DSC Analysis For Rubber Compounds

Differential Scanning Calorimetry (DSC) is commonly used to characterize the thermal properties of materials such as rubbers and plastics. The typical conventional DSC analysis is done using a constant heating rate under controlled purge flow and pressure.  In some elastomeric materials several thermal events may occur simultaneously or in close proximity and it is not always possible to decouple such responses using conventional DSC methods.  This paper examines situations in which Modulated DSC would provide more benefit and applied statistical design of experiments (DOE) to establish the optimal test parameters for the production environment. These tests utilized a single frequency sinusoidal heating. The DOE’s considered a range of heating rates, temperature amplitudes and heat modulation periods for various elastomeric materials. The list of material types studied includes the polyacrylate, ethylene acrylate, fluoroelastomer, nitrile and polyisoprene.

The response plots showed that the main factor effects and variable interactions may be different for the different materials. It is therefore necessary to investigate test conditions for the various types of materials. The reversible heat flow and heat capacity signals allowed reliable calculation of glass transition temperature, however, the definition of the glass transition declined for amplitudes close to 10°C and for modulation periods close to 100 seconds. The time dependent, non-reversible signals were more sensitive to parameter changes.