1、Designation: D 4528 88 (Reapproved 2002)Standard Classification forRubber Compounding MaterialsSulfur1This standard is issued under the fixed designation D 4528; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This classification covers the variety of sulfur gradesused in the rubber industry. Typical chemical and physicalproperties fo
3、r sulfur are shown. Sulfur is principally used inunsaturated rubbers as a vulcanizing agent.2. Referenced Documents2.1 ASTM Standards:D 4569 Test Method for Rubber ChemicalsDetermination of Acidity in Sulfur2D 4571 Test Methods for Rubber ChemicalsDetermination of Volatile Material2D 4572 Test Metho
4、ds for Rubber ChemicalsWet SieveAnalysis of Sulfur2D 4573 Test Method for Rubber ChemicalsDetermination of Oil Content in Oil-Treated Sulfur2D 4574 Test Methods for Rubber ChemicalsDetermination of Ash Content2D 4578 Test Methods for Rubber ChemicalsDetermination of Percent Insoluable Sulfur by Solv
5、entExtraction23. Significance and Use3.1 Sulfur is one of the principal rubber vulcanizing agents.It is a critical additive. When chemically combined withrubber, sulfur develops basic performance properties in thevulcanized compound such as: tensile strength, elongation,modulus, and hardness. In sof
6、t or elastic rubber compounds,sulfur is an essential but minor additive. In semi-hard rubberand ebonite, sulfur becomes a major compounding materialwhile retaining its role as a vulcanizing agent.3.2 The most stable molecular form of sulfur at ambientconditions is a ring structure containing eight s
7、ulfur atoms.Depending on conditions these molecules orient into one oftwo crystalline structures. At room temperature the crystals arerhombic and above 95C they rearrange to monoclinic. Lessthan 1.5 % of either crystalline structure of sulfur is soluble inany rubber at room temperature.3.3 The secon
8、d common molecular form of sulfur is poly-meric sulfur, made up of unbranched chains of sulfur atoms. Itis commonly referred to in the rubber industry as insolublesulfur. When this material is created by rapid heating to above160C and quenching to room temperature, the sulfur isamorphous. If formed
9、under other conditions, the polymerchains may develop regions of pseudo crystallinity.3.4 Insoluble sulfur is an important form of sulfur used onlyin the rubber industry. It is not soluble in any type of rubberhydrocarbon. When it is mixed in rubber, it disperses butremains undissolved in the rubber
10、 The use of insoluble sulfurprevents the development of a supersaturated solution of sulfurin rubber that occurs when rhombic sulfur is used. No sulfurbloom will develop on the surface of uncured rubber pieceswhen the rubber cools after mixing or processing; therefore,building tack is preserved. At
11、 curing temperatures, insolublesulfur rapidly transforms to a soluble species, dissolves in therubber, and enters into the vulcanization process.4. Basis of Classification of Sulfurs4.1 Rhombic Sulfur (ordinary ground sulfur)Rhombicsulfur, which is the ordinary form of sulfur under normalconditions,
12、 is ground and classified to meet specific particlesize requirements. The various grades of this type of sulfurcontain less than 1 % polymeric sulfur. The ground types ofsulfur may also contain additives to enhance performance. Oilis added to sulfur to help control sulfur dust and improvedispersion
13、in rubber. Finely ground solid minerals are alsoadded to improve dispersion in rubber. Ordinarily the totaladditive level is 5 % or less of the sulfur formulation. Many ofthese types of sulfur may be added to rubber compounds as100 % sulfur.4.2 Insoluble Sulfur (polymeric)There are two generaltypes
14、of insoluble sulfur and the general description of each isdetailed as follows:4.2.1 Low Insoluble Content Sulfur or Flowers of SulfurThis product is made by vaporizing pure sulfur and quenchingthe vapors in an inert gaseous atmosphere. A select grade ofthis product contains between 30 and 40 % of po
15、lymeric sulfur.This level of insoluble sulfur is often insufficient to preventbloom, and its use is restricted to rubber compounds containinghigh levels of fillers or rubber compounds using modestamounts of sulfur. Historically, this was the first commercialinsoluble sulfur available.1This classific
16、ation is under the jurisdiction of ASTM Committee D11 onRubber and is the direct responsibility of Subcommittee D11.20 on CompoundingMaterials and Procedures.Current edition approved Dec. 10, 2002. Published February 2003. Originallyapproved in 1988. Last previous edition approved in 1998 as D 4528
17、 88 (1998).2Annual Book of ASTM Standards, Vol 09.011Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2.2 High Insoluble Content SulfurIn this type of in-soluble sulfur, the major constituent is polymeric sulfur. Thepolymeric sulfur
18、 level ranges from 60 to over 95 %. Theproduct is made by heating sulfur to temperatures greater than160C with subsequent rapid quenching. The polymeric sulfurcontent is increased by extracting rhombic sulfur from the solidwith an appropriate solvent. The amount extracted is deter-mined by the parti
19、cular insoluble sulfur specification.4.2.3 Insoluble sulfur also contains added oil and occasion-ally finely ground minerals. These are added to aid dispersionin rubber and to limit sulfur dusting. However, the additivelevels are usually much higher than those used with rhombicsulfur. Oil treatments
20、 may range as high as 35 % of the totalmaterial. Mineral additives may amount to as much as 25 % ofthe final sulfur formulation. The treatment levels are alwayssignificant enough to require adjustment in the formulation toprovide the necessary sulfur for complete vulcanization .5. Keywords5.1 insolu
21、ble sulfur; rhombic sulfur; sulfurTABLE 1 Typical Properties of Rhombic (Ordinary Ground) SulfurTypical Properties ASTM Test MethodSulfur GradeGeneralPurposeFine Oiled ConditionedSulfur,% . 99.8 99.8 98 to 99.5 95.5 to 99Rubber process oil, % D 4573 . . 0.5 to 2 0 to 2.0Additive, % D 4574 . . . up t
22、o 2.5Acidity, % as H2SO4D 4569 0.01 0.01 0.01 0.01depends onAsh, % D 4574 0.02 0.02 0.02 additiveHeat loss,% D 4571 0.04 0.04 0.10 0.10Fineness, D 4572Residue on standard sieve180 m,% 0.3 0.2 0.3 0.375 m, % 515 0.5 to 1 variableAvariableA45 m,% NAB2 variable variableAOils and conditioning agents may
23、 be added to any grind without changing the sieve residues. Refer to the values given for the untreated ground sulfur.BNAnot available.TABLE 2 Typical Properties of Insoluble (Polymeric) SulfursTypical Properties ASTM Test MethodFlowers ofSulfur60 %Insoluble90 % InsolubleRegular OiledSulfur,% . 99.8
24、 99.8 99.8 78.8Insoluble sulfur, % D 4578 34.0 63.0 93.0 74.5Rubber process oil,% D 4573 . . . 19.0 to 21.0Acidity, % as H2SO4D 4569 0.1 0.01 0.01 0.01Ash,% D 4574 0.01 0.01 0.01 0.01Heat loss, % D 4571 0.10 0.20 0.20 0.30Fineness, D 4572Residue on standard sieve180 m, % 0.2 0.2 0.2 0.2150 m,% 1.0 1
25、0 1.0 1.0D 4528 88 (2002)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infri
26、ngement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standar
27、d or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your view
28、s known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D 4528 88 (2002)3
