Product

Technically Specified Rubber (TSR), also commonly referred to as block rubber, is the most widely traded commercial form of natural rubber, representing the dominant portion of global natural rubber supply. Unlike older grading systems that relied on visual inspection, TSR is classified and traded based on precise, laboratory-measured technical parameters, making it the preferred choice for large-scale industrial procurement.

Definition & Production

TSR is produced by processing natural rubber latex, field coagulum (rubber that has naturally coagulated in collection cups), or a blend of both, into uniform compressed blocks — typically 33.3 kg — wrapped in polyethylene film. The production process involves coagulation, milling, granulation, drying in hot-air tunnel ovens, and final compression into blocks before quality testing and dispatch.

Technical Grading Parameters

What distinguishes TSR from all other natural rubber grades is its reliance on measured, objective specifications rather than appearance. Each grade is classified against the following parameters:

• Dirt content — maximum allowable insoluble particulate matter (% by weight)
• Ash content — residue remaining after combustion
• Nitrogen content — related to protein levels
• Volatile matter — moisture and other evaporable compounds (typically ≤0.8%)
• Wallace Plasticity (P₀) — measure of initial hardness/processability
• Plasticity Retention Index (PRI) — resistance to oxidative degradation during processing

Grade Classification

TSR grades are designated by numbers that directly correspond to maximum allowable dirt content:

TSR-Specific Technical Parameters

These are the quality-control parameters measured per ISO 2000 for TSR grading:

Physical Properties

Mechanical Properties (Vulcanized NR Compound)

Key Applications

TSR's standardized, consistent quality makes it indispensable across several industrial sectors:

• Tire manufacturing — the single largest consumer, covering passenger car, truck, and aircraft tires
• Industrial belts and hoses — conveyor belts, hydraulic hoses, and pneumatic systems
• Seals, gaskets, and O-rings — automotive and mechanical precision parts
• Footwear — shoe soles and other flexible components
• Pharmaceutical and food-grade applications — high-grade TSR 5 used where purity is critical

Advantages Over Traditional Grades

TSR offers several practical advantages over RSS and crepe grades:​

• Easier material selection and quality assurance through objective specifications
• Consistent batch-to-batch uniformity, critical for automated manufacturing
• Better protection against degradation during storage and transport
• Cost-effectiveness due to bulk standardized processing
• Globally interchangeable — a manufacturer can source TSR 20 from Thailand, Malaysia, or Indonesia with identical guaranteed specifications

References

1. Agriculture Institute (Dec 25, 2023). Processing and Grading of Technically Specified Rubber (TSR)
2. Madapally Trading. Technically Specified Rubber (Accessed Mar 4, 2026)
3. Akrochem. natural rubber — technically specified & specialty grades (Document version: Jun 3, 2022)
4. Malani Y., L.D. College of Engineering. Rubber Technology (Accessed Mar 4, 2026)
5. DataUncover Solutions Insights (Oct 11, 2025). Technically Specified Rubber in the Real World: 5 Uses You'll Actually See (2025). Linkedin post
6. RubbLatex (Sep 22, 2024). Technically Specified Rubber (TSR) Supplier UK & Worldwide
7. ChemScr. Natural Rubber (Accessed Mar 4, 2026)
8. ECHEMI. Natural Rubber (Accessed Mar 4, 2026)
9. Piotrowski R., Power Rubber (Jan 16, 2026). Rubber Density
10. Oriental Rubber. TSR 20 Technically Specified Rubber (Accessed Mar 4, 2026)