1、Designation: D 7050 04Standard Practice forRubber from Natural SourcesSampling and Sorting BalesBased on Predicted Processing Properties1This standard is issued under the fixed designation D 7050; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of revision, the year of last 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 practice covers the sorting of natural rubber balesof TSR10 or TSR20 in the factory ac
3、cording to their predictedprocessing performance based on differences in viscoelasticproperties.1.2 This practice determines which bales should be used infactory compounds which benefit from using “soft” naturalrubber versus which work better with “hard” natural rubber.2. Referenced Documents2.1 AST
4、M Standards:2D 1485 Test Methods for Rubber from Natural SourcesSampling and Sample PreparationD 2227 Specification for Natural Rubber (NR) TechnicalGradesD 3194 Test Method for Rubber From Natural SourcesPlasticity Retention Index (PRI)D 6204 Test Method for RubberMeasurement of Unvul-canized Rheol
5、ogical Properties Using Rotorless ShearRheometers3. Significance and Use3.1 In accordance with Specification D 2227, shipments ofTSR10 and TSR20 must meet a minimum initial Wallaceplasticity (Po) of 30 to be accepted. However, even with thisminimum restriction, the uncured viscoelastic or “processab
6、il-ity” properties are allowed to vary greatly. This variation inproperties can significantly affect the quality and efficiency ofa factory operation.3.2 Bales of TSR10 or TSR20 which are lower in theiruncured elastic quality (“soft” rubber) in some cases mayimpart better processing properties to ti
7、re innerliners, cushiongums, and sidewalls. “Soft” bales sometimes impart betterbuilding tack, better mold flow, and lower extrusion die swellwith better dimensional stability. Also, these “soft” rubberbales may dissolve faster in solvents for adhesion dipping.3.3 Bales of TSR10 or TSR20 that are hi
8、gher in theiruncured elastic quality (“hard” rubber) in some cases generategreater shearing during the initial stages of a factory mix,which result in a faster breakdown and a shorter mix cycle.3.4 Therefore, in a factory operation, sometimes segregatingTSR10 or TSR20 shipments into “soft” and “hard
9、 categoriescan improve the efficiency and quality of a factory operation.4. Sampling4.1 Sample SizeThe number of samples to be selected torepresent the lot may be determined by the size of the lot asindicated in Test Methods D 1485, Table 1.4.2 Alternatively, five bales from a 36-bale pallet may be
10、sampled.4.3 Samples from these bales should be taken from withinthe bale, not from the edges, because bale surface exposure tothe air will cause surface samples to not be representative ofthe rubber inside the bale.5. Lot Sorting5.1 The criteria for sorting should be based on a repeatablemeasure of
11、uncured elasticity of the raw natural rubber.5.2 Measuring uncured elastic modulus G8 at 1 Hz, 100 %strain, 100C in accordance with Test Method D 6204, Part B,has been found to be an effective method for segregating “soft”natural rubber from “hard” natural rubber used in production.See also Test Met
12、hod D 3194.5.3 The segregating elastic modulus value G8SEGis estab-lished as the criteria for separating “soft” natural rubber from“hard” natural rubber as shown in Fig. 1.5.4 The value assigned to G8SEGwill depend on the factorysetting. It will be dependent on the type of different compoundsbeing m
13、ixed. A value must be assigned that will provide thebest balance for quality and cost effectiveness for each pro-duction plant site.6. Keywords6.1 hard rubber; natural rubber; processability; processingproperties; sampling; soft rubber; sorting bales1This practice is under the jurisdiction of ASTM C
14、ommittee D11 on Rubber andis the direct responsibility of Subcommittee D11.22 on Natural Rubber.Current edition approved June 1, 2004. Published July 2004.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM
15、Standards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.ASTM International takes no position respecting the validity of any patent rights asserted
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18、reful 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 views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Internatio
19、nal, 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).FIG. 1 Segregating Raw Natural Rubber Shipments of TSR10 or TSR20 for Factory ProductionD7050042
