Standard Classification for
Rubber Compounding Materials—Vulcanization
This standard is issued under the fixed designation D 4818; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of the last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1.1 This classification describes vulcanization accelerators
and defines their important chemical and physical characteristics. The properties outlined herein are useful for quality
control; they can frequently be directly or indirectly related to
the performance characteristics of rubber compounds.
1.2 Test Methods D 1519, D 4571, D 4572, and D 4574, for
measurement of these properties, are not yet adapted for the
vulcanization accelerators. Draft methods are being developed
and will be submitted through Subcommittee D11.11 for
processing and approval. A discussion of the reasons for
determining these properties is contained in Section 6.
2. Referenced Documents
2.1 ASTM Standards:
D 1519 Test Method for Rubber Chemicals—Melting
D 4571 Test Methods for Rubber Chemicals—
Determination of Volatile Material2
D 4572 Test Method for Rubber Chemicals—Wet Sieve
Analysis of Sulfur2
D 4574 Test Methods for Rubber Chemicals—
Determination of Ash Content2
3. Significance and Use
3.1 Class 1, Sulfenamides:
3.1.1 As a group, the 2-benzothiazole sulfenamides are the
principal sulfur vulcanization accelerators used in the rubber
industry today. The role of these materials in vulcanization is
dual. They provide scorch time (delay period) in the crosslinking or vulcanization operation at processing temperatures. The
delay avoids premature crosslinking during the processing, for
example, mixing, extrusion, etc. Once the mixed rubber is at
the curing temperature, these materials promote a rapid rate of
curing (crosslinking, vulcanization).
3.1.2 The presence of certain impurities in this class of
materials can affect their performance characteristics.
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