Plasticity Retention Index (PRI) Explained: ISO 2930 and the Rapid Plastimeter



In the fast-paced rubber industry, maintaining top-notch standards is a must. ISO 2930:2018 is a key player in ensuring the quality and performance of raw natural rubber. This article breaks down the essentials of ISO 2930, the lab equipment you need, its critical applications, and why it matters.

What is ISO 2930?

ISO 2930:2018 lays out a precise method for determining the Plasticity Retention Index (PRI) of raw natural rubber. PRI is a crucial indicator of how well rubber withstands heat and oxygen, maintaining its plasticity over time.

ISO 2930:2018 is performed on a Rapid Plastimeter. These instruments are typically found in laboratories for major consumers of natural rubber (NR), including tire manufacturers, and NR plantations found in central Africa, Thailand, Malaysia, Indonesia, and others. PRI testing, utilizing the Rapid Plastimeter, is the most common test performed.

Plasticity Retention Index (PRI)

PRI is a measure of the resistance of raw natural rubber to oxidation. The oxidation effect is assessed by measuring the plasticity before aging (P0) and after aging for 30 minutes in an aging oven for plasticity testing at 140°C (P30)


Other common tests typically performed in high-end NR laboratories:

  • Mooney Viscosity ML1+4
  • ASTM D 6204
  • ASTM D 7057
  • Rapid Plasticity
  • Ash Content (from smoking)
  • Foreign Matter (dirt / contamination)

Performing other tests outside of the PRI may give indications into the rubber’s oxidation and impacts from travel.

Key Laboratory Equipment for ISO 2930

To meet ISO 2930 standards, you'll need specific, high-precision lab equipment:

  1. Rapid Plastimeter: The cornerstone for PRI measurement, this instrument applies a controlled force to rubber samples, measuring their deformation over time to determine initial plasticity. For proper data comparison and calibration of the device, separating paper must be used.
  2. Aging Oven: Aging ovens expose rubber samples to controlled heat, oxygen, airflow, thermal stability and aging time.
  3. Specimen Preparation Tools: This includes a volumetric sample cutter and rubber slicer. Proper sample preparation is crucial for consistency. Tools for cutting and shaping samples ensure uniformity, which is critical for reliable test results.

The Importance of ISO 2930 in Application

Applying ISO 2930 is crucial for several reasons:

  1. Quality Assurance: Accurate PRI measurements ensure rubber products perform reliably under thermal and oxidative stress, which is critical for tire manufacturers, NR plantations, universities, contract laboratories and other possible consumers of NR.
  2. Global Compliance and Standards: Adhering to ISO 2930 ensures rubber products meet stringent international standards, facilitating global trade and building customer trust.

The Significance of ISO 2930 in the Rubber Industry

ISO 2930 is more than a standard; it's a benchmark for excellence:

  1. Standardization: Ensures consistency and reliability across labs and manufacturers, setting a universal quality benchmark.
  2. Benchmarking Excellence: PRI is one of the definitive metrics for comparing NR grades and ensuring consistency over time.
  3. Regulatory Compliance: Many industries have regulatory requirements tied to PRI values. ISO 2930 helps manufacturers meet these mandates, avoiding legal and financial risks.
  4. Market Competitiveness: Products meeting ISO 2930 standards are seen as high-quality and reliable, enhancing market reputation and competitive edge.


ISO 2930:2018 is a pivotal standard in the rubber industry, offering a robust framework for measuring the Plasticity Retention Index of raw natural rubber. With precise lab equipment like the rapid plastimeter and aging oven, manufacturers can ensure their products meet the highest standards of quality and durability. The application and significance of ISO 2930 highlight its critical role in advancing industry standards and fostering global competitiveness.


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