1、Designation: D4528 88 (Reapproved 2017)Standard Classification forRubber Compounding MaterialsSulfur1This standard is issued under the fixed designation D4528; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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 for s
3、ulfur are shown. Sulfur is principally used inunsaturated rubbers as a vulcanizing agent.2. Referenced Documents2.1 ASTM Standards:2D4569 Test Method for Rubber Compounding MaterialsDetermination of Acidity in SulfurD4571 Test Methods for Rubber Compounding MaterialsDetermination of Volatile Materia
4、lD4572 Test Method for Rubber ChemicalsWet SieveAnalysis of SulfurD4573 Test Method for Rubber ChemicalsDeterminationof Oil Content in Oil-Treated SulfurD4574 Test Methods for Rubber Compounding MaterialsDetermination of Ash ContentD4578 Test Methods for Rubber ChemicalsDeterminationof Percent Sulfu
5、r by Extraction3. 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 so
6、ft 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
7、sulfur 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 seco
8、nd 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 rubbe
10、r. 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. A
11、t 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 generaltype
14、s 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
15、polymeric sulfur.This level of insoluble sulfur is often insufficient to prevent1This classification is under the jurisdiction of ASTM Committee D11 onRubber and Rubber-like Materials and is the direct responsibility of SubcommitteeD11.20 on Compounding Materials and Procedures.Current edition appro
16、ved Feb. 1, 2017. Published February 2017. Originallyapproved in 1988. Last previous edition approved in 2012 as D4528 88 (2012).DOI: 10.1520/D4528-88R17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMS
17、tandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized princi
18、ples on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1bloom, and its use is restricted to rubber compounds containinghigh levels o
19、f fillers or rubber compounds using modestamounts of sulfur. Historically, this was the first commercialinsoluble sulfur available.4.2.2 High Insoluble Content SulfurIn this type of in-soluble sulfur, the major constituent is polymeric sulfur. Thepolymeric sulfur level ranges from 60 to over 95 %. T
20、heproduct 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 particular insoluble sulfur specification.
21、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 may range as high as 35 % of the tot
22、almaterial. 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 insoluble sulfur; rhombic sulfur; sulfurAST
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28、ties 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, % D4573 . . 0.5to2 0to2.0Additive, % D4574 . . . up to 2.5Acidity, % as H2SO4D4569 0.01 0.01 0.01 0.01depends onAsh
29、, % D4574 0.02 0.02 0.02 additiveHeat loss,% D4571 0.04 0.04 0.10 0.10Fineness, D4572Residue 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 be added to any grind without changing the sieve residues. Refer
30、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 99.8 99.8 78.8Insoluble sulfur, % D4578 34.0 63.0 93.0 74.5Rubber process oil,% D4573 . . . 19.0 to 21.0Acidity, % as H2SO4D4569 0.1 0.01 0.01 0.01Ash,% D4574 0.01 0.01 0.01 0.01Heat loss, % D4571 0.10 0.20 0.20 0.30Fineness, D4572Residue on standard sieve180 m, % 0.2 0.2 0.2 0.2150 m,% 1.0 1.0 1.0 1.0D4528 88 (2017)2
