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    Plasticity Retention Index — Its Measurement and Significance for Natural Rubber

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    Plasticity Retention Index (PRI) of raw natural rubber is expressed as a percentage ratio of aged plasticity over unaged plasticity of raw natural rubber, the plasticities being measured on standard samples before and after the samples have been subjected to standard conditions (140°C, 30 min) of oven aging. A parallel-plate plastimeter is used in the measurement of plasticities.

    This paper describes the measurement of PRI and discusses the various experimental conditions which are important to the accuracy and reproducibility of testing.

    The various factors which are known to have an adverse effect on PRI are surveyed as this property of raw natural rubber is somewhat subject to change with time.

    A brief outline is then given on the technological importance of PRI of raw natural rubber to the consumer.


    elastomers, viscosity, viscoelasticity, test equipment, dynamic properties

    Author Information:

    Loke, KM
    Standards officer, The Rubber Institute of Malaya, Kuala Lumpur,

    Committee/Subcommittee: D11.22

    DOI: 10.1520/STP38950S