Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry
The benefit of knowing a material's Melting Temperature Tm needs little explanation: If the
temperature of a solid polymer or plastic reaches the material's Tm, the material will begin to melt.
Additionally, a polymer material having a melting temperature also means the material has at least some crystallinity to it and scientists
have the ability to determine the amount of crystallinty in a polymer material using DSC Analysis.
What is Glass Transition Temperature Tg? -- Simply put, when a polymer material reaches its
glass transition temperature, it's molecular structure becomes wobbly during transition from liquid to solid state.
Why Does Glass Transition Temperature Matter? -- A material will reach its Tg before
it reaches its Tm. At temperatures between Tg and Tm the polymer has the
ability to shift and/or deform, thus affecting the material's structural properties. Example: Silicone typically has
a Tg lower than room temperature and therefore has a fair amount of pliability at room temperature.
One can also use Tm & Tg to confirm the identification of a polymer material made by FT-IR Analysis.
Possible reasons why a company might request differential scanning calorimetry include:
- Checking for Uncured Polymer Material
- Determination of Melting Temperature (Tm)
- Determination of Glass Transition Temperature (Tg)
- Verifying Results of FT-IR Analysis
- Determination of Percent Crystallinity
Below you will find a brief description of the ASTM Test Method related to the topics covered above:
Significance and Use
Thermal analysis provides a rapid method for measuring transitions due to morphological or chemical changes, in a polymer as it is heated/cooled through a specified temperature range. Change in specific heat capacity, heat flow and temperature values are determined for these transitions. Differential scanning calorimetry is used to assist in identifying specific polymers, polymer alloys, and certain polymer additives, which exhibit thermal transitions. Chemical reactions that cause or affect certain transitions have been measured with the aid of this technique; such reactions include oxidation, curing of thermosetting resins, and thermal decomposition.
This test method is useful for specification acceptance, process control, and research.
1.1 This test method covers determination of transition temperatures and enthalpies of fusion and crystallization of polymers by differential scanning calorimetry.
Note 1—True heats of fusion are to be determined in conjunction with structure investigation, and frequently, specialized crystallization techniques are needed.
1.2 This test method is applicable to polymers in granular form or to any fabricated shape from which it is possible to cut appropriate specimens.
1.3 The normal operating temperature range is from the cryogenic region to 600°C. Certain equipment allows the temperature range to be extended.
1.4 The values stated in SI units are the standard.
Note 2—This test method does not apply to all types of polymers as written (see 6.8).
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 3—This standard is similar but not equivalent to ISO 11357-1, -2, -3. The ISO procedures provide additional information not supplied by this test method.
2. Referenced Documents
- E1142 Terminology Relating to Thermophysical Properties
- E1953 Practice for Description of Thermal Analysis and Rheology Apparatus
- E473 Terminology Relating to Thermal Analysis and Rheology
- E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
- E967 Test Method for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers
- E968 Practice for Heat Flow Calibration of Differential Scanning Calorimeters
- ISO11357-3 Plastics--Differential Scanning Calorimetry (DSC)--Part 3: Determination of Temperature and Enthalpy of Melting and Crystallization
crystallization; crystallization temperature; differential scanning calorimetry (DSC); enthalpy; first-order transition; glass transition; heat of crystallization; heat of fusion; heat of transition; melting; melting temperature; polymer; transition temperature; Differential scanning calorimetry (DSC); Polymers; Temperature tests--plastics; Thermal analysis (TA)--plastics; Transition temperatures; ICS Number Code 83.080.01 (Plastics in general)
( Download ASTM D3418 From www.ASTM.org )