ASTM D 6338 : 1998

1.1 This classification system covers highly crosslinked themoplastic vulcanizates (HCTPVs) for extrusion, molding and other fabrication methods. HCTPVs are thermoplastic elastomers (TPEs) consisting of two or more polymer systems at least one of which is rubbery and highly (ᢗ %) crosslinked and at least one of which is thermoplastic, with each system having its own phase. The thermoplastic phase will tend to be continuous and the rubbery phase discontinuous. The high level of crosslinking and ultrafine particle size (ca 1 µm diameter) of the rubbery phase give rise to properties more closely approaching those of conventional thermoset rubber, when compared to the same thermoplastic/rubbery polymer compostion with a lower level (< or = 95%) of crosslinking. the HCTPV polymer compostions may contain fillers, reinforcing agents, plasticizers, resins, antidegradants, colorants and other beneficial constituents. Recycled HCTPVs are not covered in this classification system.

1.2 Included in this classification system are the properties necessary to identify the respective compositions. For specialized applications, other requirements may be needed to identify specific characteristics.

1.3 As given in Practice E380, values in SI units are to be regarded as standard.

Note 1-There is no equivalent ISO standard.

1.4 The following safety hazards caveat pertains only to the test methods portion, Section 12, of this classification system. 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.