ASTM D4894-98a

1.1 This specification covers granular resins of polytetrafluoroethylene (PTFE) that have never been preformed or molded and are normally processed by methods similar to those used in powder metallurgy or ceramics, or by special extrusion processes. These PTFE resins are homopolymers of tetrafluoroethylene, or, in some cases, modified homopolymers containing not more than one percent by weight of other fluoromonomers. The usual methods of processing thermoplastics generally are not applicable to these materials because of their viscoelastic properties at processing temperatures. The materials included herein do not include mixtures of PTFE resin with additives such as colorants, fillers or plasticizers; nor do they include reprocessed or reground resin or any fabricated articles. The methods and properties included are those required to identify the various types of resins. Additional procedures are provided in the Appendix for further characterization of the resins.

1.2 The materials covered by this specification formerly were covered in Specification D1457 as Types I, IV, V, VI, VII and VIII.

1.3 The values stated in SI units as detailed in Practice E380 are to be regarded as the standard, and the practices of E380 are incorporated herein.

1.4 The following precautionary caveat pertains only to the Specimen Preparation section, Section 9, and the Test Methods section, Section 10, of this specification: 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. See Notes 1, 3 and 9 for specific cautionary statements.

Note 1-Most of the technical content of this standard is included as part of ISO 12086-1 and ISO 12086-2 Part 2. These standards have been approved for publication and are in the final editing process.