Standard Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential Scanning Calorimetry
Possible reasons why a company might request differential scanning calorimetry of fluoropolymers include:
- Checking the Sintering of a Fluoropolymer Material
- Comparing the Crystallinity of Fluoropolymer Materials
Below you will find a brief description of the ASTM Test Method related to the topics covered above:
Significance and Use
DSC analysis may be used with fluoropolymers to achieve at least four different objectives as follows:
4.1.1 To measure transition temperatures to aid in the identification of the various fluoropolymers, individually or in mixtures;
4.1.2 To compare the relative levels of crystalline content of two or more specimens of a sample of a fluoropolymer relative to another sample by measuring the heat of fusion;
Note 2—Absolute values of crystalline content cannot be determined until values for heats of fusion of the completely crystalline polymers are available.
4.1.3 To characterize PTFE (DSC thermal curves determined on powders or products of PTFE that have never been melted convey appreciable information about details of morphology and molecular structure);4
4.1.4 To supplement the test for standard specific gravity (SSG) described in Specifications D 4894 and D 4895 by using the heat of crystallization of pure PTFE homopolymer, depending on the relative molecular weight of the specimen. The scopes of these specifications, however, include PTFE resins modified with small amounts of comonomers, and many commercial PTFE resins are modified in this manner. These modifications can have profound effects on crystallization behavior. Published relationships4 between heat of crystallization and molecular weight refer to pure PTFE homopolymers and, therefore, cannot be applied to the modified resins.
1.1 This test method defines conditions for the use of differential scanning calorimetry (DSC) with fluoropolymers. It covers the use of DSC analyses with the fluoropolymers, PTFE, PVDF, PCTFE, and PVF and their copolymers PFA, MFA, FEP, ECTFE, EFEP, VDF/HFP, VDF/TFE/HFP, VDF/CTFE. The test method is applicable to the analysis of powders as well as samples taken from semi-finished or finished products. The nature of fluoropolymers is such that special procedures are needed for running DSC analysis and interpreting the results.
1.2 The values stated in SI units as detailed in IEEE/ASTM SI-10 are to be regarded as the standard.
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.
There is currently no ISO standard that duplicates this test method. ISO 12086-1 and ISO 12086-2 cover similar testing and reference this test method for testing conditions.
2. Referenced Documents
- D1600 Terminology for Abbreviated Terms Relating to Plastics
- D3418 Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry
- D4894 Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials
- D4895 Specification for Polytetrafluoroethylene (PTFE) Resin Produced From Dispersion
- E473 Terminology Relating to Thermal Analysis and Rheology
- E793 Test Method for Enthalpies of Fusion and Crystallization by Differential Scanning Calorimetry
differential scanning calorimetry; DSC; fluoropolymer(s); heats of fusion; melting point; thermal analysis; ICS Number Code 83.080.20 (Thermoplastic materials)
( Download ASTM D4591 From www.ASTM.org )