ASTM D7050 - 04(2019)

    Standard Practice for Rubber from Natural Sources—Sampling and Sorting Bales Based on Predicted Processing Properties

    Active Standard ASTM D7050 | Developed by Subcommittee: D11.22

    Book of Standards Volume: 09.01


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    Significance and Use

    3.1 In accordance with Specification D2227, shipments of TSR10 and TSR20 must meet a minimum initial Wallace plasticity (Po) of 30 to be accepted. However, even with this minimum restriction, the uncured viscoelastic or “processability” properties are allowed to vary greatly. This variation in properties can significantly affect the quality and efficiency of a factory operation.

    3.2 Bales of TSR10 or TSR20 which are lower in their uncured elastic quality (“soft” rubber) in some cases may impart better processing properties to tire innerliners, cushion gums, and sidewalls. “Soft” bales sometimes impart better building tack, better mold flow, and lower extrusion die swell with better dimensional stability. Also, these “soft” rubber bales may dissolve faster in solvents for adhesion dipping.

    3.3 Bales of TSR10 or TSR20 that are higher in their uncured elastic quality (“hard” rubber) in some cases generate greater 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 segregating TSR10 or TSR20 shipments into “soft” and “hard” categories can improve the efficiency and quality of a factory operation.

    1. Scope

    1.1 This practice covers the sorting of natural rubber bales of TSR10 or TSR20 in the factory according to their predicted processing performance based on differences in viscoelastic properties.

    1.2 This practice determines which bales should be used in factory compounds which benefit from using “soft” natural rubber versus which work better with “hard” natural rubber.

    1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.


    2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D1485 Practice for Rubber from Natural SourcesSampling and Sample Preparation

    D2227 Specification for Natural Rubber (NR) Technical Grades

    D3194 Test Method for Rubber From Natural SourcesPlasticity Retention Index (PRI)

    D6204 Test Method for RubberMeasurement of Unvulcanized Rheological Properties Using Rotorless Shear Rheometers


    ICS Code

    ICS Number Code 83.060 (Rubber)

    UNSPSC Code

    UNSPSC Code 13101500(Natural rubber)


    Referencing This Standard
    Link Here
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    DOI: 10.1520/D7050-04R19

    Citation Format

    ASTM D7050-04(2019), Standard Practice for Rubber from Natural Sources—Sampling and Sorting Bales Based on Predicted Processing Properties, ASTM International, West Conshohocken, PA, 2019, www.astm.org

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