ASTM E793 Standard Test Method for Enthalpies of Fusion and Crystallization by DSC

Get Certified ASTM E793 Testing for Reliable Thermal Transition Performance 

Certification confirms that a material’s enthalpy of fusion and crystallization meets ASTM E793 requirements, including uniform transition behavior between production batches. Manufacturers use ASTM E793-certified testing to determine a material’s thermal transition properties before accepting it for quality control or specification acceptance. Testing and certification ensure that the product meets the requirements of ASTM E793 and minimize the possibility of variable thermal performance in downstream applications. 

The main objective of ASTM E793 is to determine the enthalpy of fusion and crystallization of thermally stable materials that exhibit well-defined transition behavior. This test is employed for quality control, specification acceptance, and in materials research in industry. 

• Material type: Solid samples in granular form, or in any fabricated shape, and liquid samples that crystallize within the operating range of the instrument. 
• Purpose: To determine the enthalpy of fusion and crystallization. 
• Properties evaluated: Enthalpy (heat) of fusion and enthalpy of crystallization.
• Testing Method: Heating or cooling of a specimen in a DSC instrument until it reaches the transition temperature to measure heat flow and to calculate the enthalpy value from the area of the transition peak. 
• Result: The units of measurement for enthalpy are J/g. 
• Test Limitations: In general, the test standard applies to thermally stable materials with well-defined endothermic or exothermic characteristics; results may vary with specimen shape and size.  
• Use conditions: Enthalpy values measured are influenced by specimen mass, specimen shape, and heating or cooling rate. 
• Applications: Polymer and material quality control, specification acceptance testing, thermal transition research, accredited materials testing. 

What are the Uses of ASTM E793 Testing?

ASTM E793 testing helps laboratories to establish the enthalpic variations associated with a material’s melting or crystallization transition. Engineers use these results to ensure quality control and to understand the fit of a material’s transition behavior to a set specification. This standard-

• Compares the enthalpy of fusion of solid and liquid substances.
• Manually alters the heating and cooling rates of a DSC instrument.
• Calculates the value of the enthalpy of crystallization as a material cools through its transition point.
• Helps ensure quality control throughout production runs.
• Facilitates specification acceptance testing of thermally stable materials.
• Helps with materials research and characterization of thermal behavior.
• Supports selection of consistent, predictable transition behavior in materials 

What Materials Can Be Tested Under ASTM E793? 

ASTM E793 is applicable to solid samples in granular form or to any fabricated shape from which a suitable specimen can be cut by the technician. It also applies to liquid samples that crystallize within the instrument’s operating range. This test method is suitable for most thermally stable materials that have clearly defined endothermic or exothermic transitions; technicians select a specimen form and mass appropriate to the instrument and the transition under evaluation.

Why is ASTM E793 Important? 

ASTM E793 is significant as it is a quick and standardized method for measuring enthalpic variations associated with a material’s first-order thermal transitions. Manufacturers and researchers use these measured enthalpy values for quality control, specification acceptance, and materials research. 

ASTM E793 Testing Process and Data Collection

Testing begins when the technician cuts and weighs the sample and places it in the DSC sample pan along with a reference pan. The technician then programs the heating or cooling rate and the temperature range for the melting or crystallization transition of the specimen. The instrument continuously measures heat flow as the specimen passes through its transition temperature. The software then calculates the area under the resulting transition peak. Lastly, the analyst uses this peak area to determine the enthalpy of fusion or crystallization, and reports the result in units of joules/gram. 

Common Challenges and Troubleshooting

The results vary depending on specimen form and mass as stated by the standard, and inconsistent mass or form of the specimens often gives variable enthalpy readings. Poor thermal contact between the specimen and the sample pan also alters the heat flow measurement. Baseline drift during a long heating or cooling program complicates accurate peak integration. Laboratories solve these problems by using a weighing balance with a high degree of precision, good thermal contact of the specimen in the sample pan, and by checking baseline stability prior to each test. 

• The laboratory records enthalpy of fusion and crystallization in joules per gram, calculated from the transition peak area.
• The technicians determine the form and mass of the specimen tested, along with whether it is solid granular, fabricated shape, or liquid form.
• The analyst makes note of the enthalpy measured at the given heating or cooling rate, correlated with the tested material and its transition behaviour under the mentioned heating/cooling rate. 
• The engineer understands how to apply the results of the enthalpy measurement, taking into account the specimen mass, specimen shape, and heating or cooling rate.
• Engineers use the measured enthalpy values to support quality control, specification acceptance, and materials research decisions. 

Link to ASTM E793