Determination of Plastic Properties

Testing with a Gieseler plastometer (ASTM D-2639) gives a semiquantitative measurement of the plastic property, or apparent melting of coal when heated under prescribed conditions in the absence of air. The chemical nature of the constituents that account for a coal s plastic properties is not known. The material thought to be responsible for the plastic properties of coal has been removed from coal successfully by solvent extraction, leaving a nonplastic residue. Such residue has been rendered plastic by returning to it the extracts obtained by the solvent extraction. No definite relationship has been established between the amount of extract and the plastic properties of the coal. 

FIGURE 7.4 Plasticity curve for coal. (Adapted from Berkowitz, 1979.) 

The values normally determined with the Gieseler plastometer are  

Initial softening temperature temperature at which the dial movement reaches 1.0 dial division per minute (100 dial divisions = one complete revolution of the stirrer) may be characterized by other rates, but if so, the rate must be reported. 

Maximum fluid temperature temperature at which the dial pointer movement (stirrer revolutions) reaches the maximum rate. 

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Several examples were presented in Section 7.4 on the use of substrate curvature method for the determination of plastic properties of thin films. 

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