1、Designation: D 4676 94 (Reapproved 2006)Standard Classification forRubber Compounding MaterialsAntidegradants1This standard is issued under the fixed designation D 4676; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. 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 antidegradants used in rubberand where appropriate defines their important chemical andphys
3、ical characteristics for use in rubber.1.2 The general term “antidegradant” describes materialsused in rubber to protect against the effects of oxygen andozone. Materials that fall in this general category include bothantioxidants and antiozonants.1.3 This standard does not purport to address all of
4、 thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1218 Test Method for R
5、efractive Index and RefractiveDispersion of Hydrocarbon LiquidsD 1519 Test Methods for Rubber ChemicalsDetermination of Melting RangeD 1747 Test Method for Refractive Index of Viscous Mate-rialsD 2702 Practice for Rubber ChemicalsDetermination ofInfrared Absorption CharacteristicsD 3461 Test Method
6、for Softening Point of Asphalt andPitch (Mettler Cup-and-Ball Method)D 4571 Test Methods for Rubber CompoundingMaterialsDetermination of Volatile MaterialD 4574 Test Methods for Rubber CompoundingMaterialsDetermination of Ash ContentD 4937 Test Method for p-Phenylenediamine Anti-degradants Purity by
7、 Gas ChromatographyD 5376 Test Method for Rubber Compounding MaterialsDetermination of the Basic Nitrogen Content in RubberAntioxidant: Polymerized TMQE28 Test Methods for Softening Point of Resins Derivedfrom Naval Stores by Ring-and-Ball Apparatus3. Significance and Use3.1 There are many different
8、 antidegradants available foruse in the rubber industry.3.2 This classification of the various materials covers theirchemical structure along with a brief reference to their overalluse and their properties.4. Basis of Classification4.1 Rubber antidegradants included in this classificationdocument ar
9、e divided into the six classes shown below. Theclassification in general is based on the chemical structurecategorization but in most cases it also classifies the materialsaccording to their potential rubber applications.4.2 Class 1, p-Phenylenediamines (PPDs)This group ofadditives represents the pr
10、imary materials used in tires andother mechanical goods to impart ozone protection. Theseadditives are also used as antioxidants and antiflex agents in anumber of applications but are considered to be stronglystaining and thus limited to black rubber applications. They canalso be used as raw polymer
11、 stabilizers.4.2.1 Although all PPDs have similar performance charac-teristics, the different types are frequently preferred for certainend use conditions; for example, selection is based on the typeand degree of flexing to be experienced by the rubber article.4.3 Class 2, Trimethyl-dihydroquinoline
12、s (TMQs)Thesematerials are primarily used to protect rubber articles fromdegradation by atmospheric oxygen at higher temperatures.They are moderately staining.4.3.1 Although all TMQs have similar performance charac-teristics, different types are frequently preferred to accommo-date processing or end
13、 use needs.4.4 Class 3, PhenolicsPhenolic antidegradants represent agroup of “nonstaining” and “nondiscoloring” additives usedprimarily in light colored mechanical goods and tires. They canalso be employed as raw polymer stabilizers. The term “non-discoloring” is used somewhat loosely, as products y
14、ielding1This classification 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 Oct. 1, 2006. Published November 2006. Originallyapproved in 1987. Last previous edition approv
15、ed in 2001 as D 4676 94 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International,
16、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.slight discoloration are included in this classification. This isdone to distinguish them from the strongly staining anddiscoloring amine type antidegradants (for example, PPDs).4.4.1 The different types of phenolic
17、 antidegradant affordvarying degrees of protection against oxidation, heat aging,rubber “poisons,” and crazing. In general they are weakerantioxidants than the staining amines types.4.5 Class 4, Alkylated Diphenylamines (DPAs)This classof additives is generally considered representative of substi-tu
18、ted amine antioxidants and they are used as raw polymerstabilizers and in vulcanizate applications. They are moder-ately discoloring and staining.4.6 Class 5, Aromatic PhosphitesThese are phosphorouscontaining fully nonstaining-nondiscoloring additives used asstabilizers for synthetic elastomers in
19、“white rubber” applica-tions. They also have application as peroxide decomposers andradical traps in many polymer systems.4.7 Class 6, Diphenylamine-Ketone CondensatesThisgroup of additives is used primarily in carbon black loadedcompounds to protect against both oxygen and heat deteriora-tion.5. Ba
20、sic Description of Antidegradants5.1 p-PhenylenediaminesThe individual materials in theclass of compounds designated as p-phenylenediamines vary inchemical structure and in performance characteristics depend-ing on the substitution on the nitrogen atoms in the parentcompound, p-phenylenediamine. The
21、 three general types ofPPDs used in rubber are defined below:5.1.1 PPD Type I: N,N8-dialkyl-p-phenylenediamines (seeFig. 1)R and R1are secondary alkyl groups, usually C6orlarger. These additives are generally liquids at ambient condi-tions and represent single chemical components (90 %).5.1.2 PPD Ty
22、pe II: N-alkyl-N8-aryl-p-phenylenediamines(see Fig. 2)R is a secondary alkyl group and R1is hydrogenor a primary alkyl substituent (usually methyl). These productsgenerally consist of a single component or purposeful mixtureof two or more major components. They can be either liquidsor solids.5.1.3 P
23、PD Type III: N,N8-diaryl-p-phenylenediamines (seeFig. 3)R and R1can be the same or different groupsconsisting of hydrogen or alkyl groups (usually methyl).Therefore, this type can be individual components or mixturesof three or more isomers. This type of PPD is generally solidat ambient conditions.5
24、.2 Trimethyl-dihydroquinolinesCompounds designatedas TMQs represent a group of antidegradants based on poly-merized aniline-acetone condensation products. The individualproducts differ by the degree of polymerization as well as theratio of aniline to acetone in the monomer preparation.5.2.1 Since th
25、ese products are complex mixtures they arebest described with chemical reactions (see Fig. 4).5.2.2 The generally accepted chemical structure for TMQoligomers (polymers) is given in Fig. 5.5.2.3 Alternate structures may also be present containinganiline end groups or acetone bridges, or both, as sho
26、wn in Fig.6.5.2.4 Other complex structures are also present in all TMQproducts. The precise nature of the oligomeric mixture is afunction of the monomer preparation conditions, monomerpurification, and polymerization conditions.5.3 PhenolicsPhenolic antioxidants are classified chemi-cally according
27、to the number of phenolic groups in themolecule. In general the more sterically hindered phenolicantioxidants are less discoloring but have lower antioxidantactivity in rubber applications.5.3.1 Monofunctional phenols (Type I) are frequently re-ferred to as hindered phenols. They develop little disc
28、olorationhowever they show the weakest antioxidant activity and arerelatively volatile due to the low molecular mass. Theirprimary use is as polymer stabilizers. In the general structure(see Fig. 7), R1, R2, and R3can be hydrogen, alkyl, aryl,aralkyl, or thioalkyl groups, or a combination thereof. T
29、hesegroups may also contain carboxylic acid esters, thioesters, ortriazine functions.5.3.2 Bifunctional phenols (Type II) are also referred to ashindered bisphenols. They represent the most important classof phenolic antioxidants used in rubber applications. In generalFIG. 1 Type IN-N*-dialkyl-p-phe
30、nylenediaminesFIG. 2 Type IINalkylN*arylpphenylenediaminesFIG. 3 Type IIIN,N*diarylpphenylenediaminesFIG. 4 TMQ ChemistryFIG. 5 TMQ Oligomeric StructureFIG. 6 TMQ Oligomers with Aniline End Groups and an AcetoneBridgeD 4676 94 (2006)2they have good antioxidant activity with minimal discolora-tion. I
31、n the general structure (see Fig. 8 and Fig. 9), the Rgroups are normally located in the “ortho” or “para” position inrelation to the phenol function. R is generally alkylidene(methylene) or thio. R1, R2, R3, and R4can be hydrogen, alkyl,aryl, aralkyl, or thioalkyl groups, or a combination thereof.
32、The“ortho” bridged structures (Fig. 8) are commonly used inrubber.5.3.3 Multifunctional phenols (Type III) are similar to thebifunctional phenols in activity and discoloration but are morepersistent in the end use product due to higher molecular massand lower volatility. In the generalized structure
33、 (see Fig. 10and Fig. 11), the R groups are defined in 5.3.2. The substitutionis also normally in the “ortho” and “para” positions relative tothe phenol group.5.4 Alkylated DiphenylaminesThese antioxidants arecomplex reaction products of diphenylamine and variousalkylating agents. The substituents a
34、re selected to achieve adesired balance of cost and performance characteristics. In thegeneral structure (see Fig. 12) R can be hydrogen, alkyl, oraralkyl groups. There can be multiple substituents on either orboth rings. Alternate structures also have substituents on thenitrogen atom.5.5 Aromatic P
35、hosphitesAromatic phosphites are phos-phorous esters of aromatic phenols. In the general structure(see Fig. 13) the R groups can be hydrogen, alkyl, aryl, oraralkyl.5.6 Diphenylamine-Ketone CondensatesThese antioxi-dants are complex reaction products of diphenylamine andalkyl ketones, primarily acet
36、one (see Fig. 14), some of whichare further condensed with formaldehyde producing productsof high molecular weight. They are low melting resins orliquids, essentially non-volatile and readily dispersable inrubber.6. Composition and Properties6.1 The important properties and characteristics of anti-d
37、egradants vary with antidegradant class and intended appli-cation. Those composition and property characteristics listedbelow are judged to be more significant for one or more of theclasses or individual types of antidegradants being considered.6.2 Purity of AssayEven though performance is not di-re
38、ctly related to chemical purity a measurement of purity isgenerally specified for those antidegradants used in highperformance applications. This parameter is particularly appli-cable to those antidegradants that represent individual (or adefined number) of specific chemical entities; that is, PPDs
39、andmost phenolics.6.2.1 PPD purity should be determined according to a gaschromatographic method defined in Test Method D 4937.6.2.2 The purity of phenolic antioxidants can be determinedby various chromatographic techniques including gas chroma-tography (GC) and high pressure liquid chromatography(H
40、PLC). ASTM methods specific to these materials have notyet been developed. The melting point of solids (Test MethodsD 1519) and the refractive index of liquids (Test MethodsD 1218 and D 1747) are often used as an indicator of purity.6.2.3 Since TMQs, alkylated diphenylamines, and phosphiteantidegrad
41、ants generally represent reaction mixtures ratherthan individual chemical entities, their quality is usuallyestablished by indirect methods. HPLC or GC techniques, orboth, are being utilized to analyze these materials but ASTMprocedures have not been developed.6.2.3.1 This is accomplished for TMQs b
42、y measuring theamount of basic nitrogen by a perchloric acid titration (TestMethod D 5376). This indirectly defines the relative proportionof reactants in the mixed product.FIG. 7 Type I Phenolic AntioxidantsFIG. 8 “Ortho” Bridged Type II Phenolic AntioxidantsFIG. 9 “Para” Bridged Type II Phenolic A
43、ntioxidantsFIG. 10 “Ortho” Bridged Type III Phenolic AntioxidantsFIG. 11 “Para” Bridged Type III Phenolic AntioxidantsFIG. 12 Alkylated Diphenylamine General StructureFIG. 13 Aromatic Phosphites General StructureFIG. 14 DiphenylamineKetone Condensate General StructureD 4676 94 (2006)36.2.3.2 The rel
44、ative purity of the complex alkylated diphe-nylamines can be assessed by comparison of the ultravioletspectrum with that of standard or reference materials.6.2.3.3 The relative purity of mixed aromatic phosphites canbest be established from the infrared (IR) spectrum obtainedaccording to Practice D
45、2702. Comparison of the spectra withstandard or reference materials is required to obtain a qualityparameter.6.2.3.4 Melting range gives an indication of thediphenylamine-ketone condensate type and relative molecularweight within types. The infrared spectrum also is an indicatorof antidegradant type
46、.6.3 Volatile Materials (including moisture) in anti-degradants can be important in some end use applications. Amethod for this determination in PPDs is given in Test MethodsD 4571.6.4 Ash ContentThe presence of ash or noncombustiblesin antidegradants is important for applications where inorganicres
47、idues in the rubber compound would present an end useproblem (undissolved or undispersed inorganics in rubberformulations could initiate flaws). Ash measurement on PPDsis described in Test Methods D 4574. This methodology couldbe adapted to the other antidegradant classes.6.5 Softening PointThis par
48、ameter has typically beenused to characterize TMQ antidegradants since these materialsare generally not crystalline solids. The softening point isindicative of the degree of TMQ oligomerization. The deter-mination can be done according to Test Method D 3461 or withTest Methods E28.6.6 Hydrolysis Sta
49、bilityOne particularly important char-acteristic of aromatic phosphite antioxidants is their relativeresistance to hydrolysis, since these materials are typicallyadded as aqueous emulsions. The hydrolysis is acid catalyzed;thus a neutral pH of the aqueous emulsion is required for goodstability. The relative rate of phosphite hydrolysis can also bedirectly monitored by using an appropriate analytical tool todetermine acidic hydrolysis products or free alkylated phenols.7. Keywords7.1 alkylated diphenylamines; antidegradants; antioxidants;antiozon
