ISO 7681:2024 PDF

Overview

ISO 7681:2024 specifies a laboratory method for determining the dry rubber content (DRC) of natural rubber field latex from Hevea brasiliensis. The standard defines the principle, apparatus, reagents, two sheeting methods (hand and mechanical), calculation and reporting requirements. It is not applicable to latices from other natural sources, compounded or vulcanized latex, or artificial rubber dispersions.

Key topics and technical requirements

• Scope and limitation: Applies only to field latex (raw latex with or without preservative) from Hevea brasiliensis.
• Principle: Coagulate a weighed portion of latex, remove non‑rubber components, dry the coagulum and express DRC as a percentage by mass:
  • DRC (%) = (mass of dry rubber / mass of latex test portion) × 100
• Apparatus: ordinary lab equipment plus dish (glass/porcelain/aluminium), oven (70 °C ± 5 °C), desiccator, steam/water bath, analytical balance (1 mg readability), roller or laboratory mill, thickness gauge.
• Reagents: 2.0% acetic acid (for coagulation) and 95% ethanol (to clear serum when required); use analytical grade reagents and distilled water.
• Procedure options:
  • Method A (hand sheeting): press coagulum into ~2 mm sheet, wash thoroughly, drain, oven‑dry to translucence, cool and weigh; repeat drying until mass loss