Overview - ISO 24376:2022 and low protein natural rubber (LPNR)
ISO 24376:2022 defines guidelines and requirements for technically specified low-protein natural rubber (LPNR) produced from Hevea brasiliensis latex. The standard establishes a grading system that distinguishes LPNR by the source material and by the protein-removal process - enzymatic (E) or non‑enzymatic (NE) - and by whether viscosity is controlled (constant viscosity, CV). It covers material composition, grade structure, specification limits, sampling and packaging for deproteinised natural rubber (DPNR/LPNR).
Key topics and technical requirements
- Grade structure: Grades combine raw material and process labels (examples: E-WFS, E‑CV55, E‑CV65, NE‑WFS, NE‑CV55, NE‑CV65). CV indicates viscosity-stabilized rubber.
- Chemical and physical limits (typical values specified):
- Dirt retained on sieve: max 0.03%
- Ash: max 0.25%
- Nitrogen content: max 0.15%
- Volatile matter: max 0.5%
- Plasticity retention index (PRI): min 40
- Mooney viscosity (ML(1+4) at 100 °C) for CV grades: 55 ± 5 or 65 ± 5
- Extractable protein: max 100 µg/g (ASTM D5712)
- Antigenic protein (for food/medical-suitable grades): max 10 µg/g (ASTM D6499)
- Sampling and testing: Sampling per ISO 1795; normative test methods referenced include ISO 1656 (nitrogen), ISO 247-1 (ash), ISO 249 (dirt), ISO 289-1 (Mooney viscosity), ISO 248-1 (volatile matter), ISO 2930 (PRI).
- Production processes: Describes enzymatic proteolysis and non‑enzymatic extraction methods (e.g., fumed silica, urea, aluminium hydroxide, surfactants) and their impacts on protein removal.
- Packaging: Typical bale mass (33.30 kg ± 0.17 kg), crate packing (1.2 t), bale dimensions and recommended polyethylene wrapping characteristics.
Practical applications
- Medical and food-contact rubber where low antigenic protein is critical.
- Seals, joint rings, hydro-mounts and anti‑vibration mountings benefiting from lower creep, reduced stress relaxation and better dynamic properties.
- Undersea and humidity-sensitive applications where low water absorption and consistent modulus are required.
- Compounding and formulation where controlled viscosity (CV grades) aids processing and product consistency.
Who should use ISO 24376:2022
- Natural rubber producers and processors implementing deproteinisation (DPNR/LPNR)
- Rubber compounders and product manufacturers (automotive, medical, food-contact)
- Quality, procurement, and regulatory teams specifying raw rubber grades
- Test laboratories and standards bodies referencing consistent test methods
Related standards
Keywords: ISO 24376:2022, low protein natural rubber, LPNR, deproteinised natural rubber, DPNR, Hevea brasiliensis, enzymatic protein removal, Mooney viscosity, extractable protein.