1. Scope

1.1 This specification covers dry-powder resins of polytetrafluoroethylene (PTFE) that have been prepared from dispersions of PTFE by manufacturing techniques that involve controlled coagulation of the dispersion. These resins are generally known as 'fine-powder' resins or 'coagulated-dispersion powder' resins. The conversion of these resins to finished products normally involves a process called 'paste extrusion,' and sometimes involves formative processes such as calendering. A volatile liquid is present as a processing aid during these formative stages of conversion, and is subsequently removed during the finishing stages of conversion. These PTFE resins are homopolymers of tetrafluoroethylene, or, in some cases, modified homopolymers containing not more than 1% by weight of other fluoromonomers. The usual methods of processing thermoplastics generally are not applicable to these materials because of their viscoelastic properties. The materials covered herein do not include mixtures of PTFE with additives such as colors, fillers, or plasticizers; nor do they include reprocessed or reground resin or any fabricated articles because the properties of such materials have been irreversibly changed when they were fibrillated or sintered. The methods and properties included are those required to identify the various resins. An additional procedure is provided in the appendix for further characterization of the resins.

1.2 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.

1.3 The following safety hazards 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 Note 3 for a specific hazards statement.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D618 Practice for Conditioning Plastics for Testing

D638 Test Method for Tensile Properties of Plastics

D792 Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

D883 Terminology Relating to Plastics

D1895 Test Methods for Apparent Density, Bulk Factor, and Pourability of Plastic Materials

D3892 Practice for Packaging/Packing of Plastics

D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter

D4441 Specification for Aqueous Dispersions of Polytetrafluoroethylene

D4591 Test Method for Determining Temperatures and Heats of Transitions of Fluoropolymers by Differential Scanning Calorimetry

D4894 Specification for Polytetrafluoroethylene (PTFE) Granular Molding and Ram Extrusion Materials

E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves

E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications

E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods

Keywords

coagulated dispersion polytetrafluoroethylene; fluoropolymers; polytetrafluoroethylene; PTFE; Paste extruded PTFE; Plastics--specifications; Pressure testing--plastics; Specimen preparation (for testing)--plastics; Stretching void index (SVI); PTFE (polytetrafluoroethylene)--specifications; Resins--specifications; Thermal stability--plastics; Water analysis--plastics processing; Density--plastics; Dispersion; Karl Fischer reagent method--plastics; Particle analysis--plastics;

ICS Code

ICS Number Code 83.080.10 (Thermosetting materials)

DOI: 10.1520/D4895-98

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