ISO 247-1:2018

Overview

ISO 247-1:2018 - Rubber - Determination of ash - Part 1: Combustion method describes standardized laboratory procedures to determine the ash content of raw rubbers, compounded rubbers and vulcanizates. It specifies three combustion-based methods (A, B and C), the required apparatus and reagents, procedural controls (heating profiles, crucible handling, weighing), and reporting requirements. The standard is intended for M, N, O, R and U family rubbers as defined in ISO 1629, with specific limitations for halogen-containing materials and recommendations for fluorine- or lithium-containing rubbers.

Key topics and technical requirements

• Three methods defined
  • Method A: Direct heating - gentle gas‑burner decomposition followed by muffle furnace ashing (typically 550 °C ±25 °C; 950 °C ±25 °C may be used for compounds/vulcanizates).
  • Method B: Sulfuric acid-assisted ashing - for compounded or vulcanized rubbers containing chlorine, bromine or iodine (never for uncompounded rubbers); final ashing at 950 °C ±25 °C.
  • Method C: Filter‑paper wrap - test portion wrapped in ashless filter paper, pre‑ignited (300 °C ±25 °C for 1 h) then incinerated at ~550 °C ±25 °C.
• Apparatus & materials
  • Crucibles of porcelain, silica or platinum (platinum mandatory for fluorine-containing and lithium‑polymerized rubbers to avoid volatile losses).
  • Muffle furnace with controlled temperature and air flow; Bunsen burner; ashless filter paper; analytical balance (0.1 mg resolution).
• Procedural controls
  • Test portion preparation (homogenization, comminution) per ISO 1795/ISO 248-1 references.
  • Repeated heating and weighing until constant mass (specified acceptance tolerances: absolute or relative limits are provided).
• Reporting & interpretation
  • Test report must state sample identification, method used (A/B/C), furnace temperature (and reason if 950 °C used), ash percentage, and test date.
  • The standard explicitly does not cover chemical interpretation of ash composition - analysts must account for additive behavior at elevated temperatures.

Applications and users

ISO 247-1:2018 is used by:

• Quality control and materials testing laboratories in the rubber industry
• Rubber compounders and manufacturers verifying inorganic filler/load levels
• R&D and materials scientists assessing formulation effects or contamination
• Independent testing bodies and regulatory labs requiring reproducible ash-content data

Practical uses include routine QC of raw and processed rubber, verification of filler loading, and comparative testing between formulations or production batches.

Related standards

• ISO 1629 - Rubber and rubber products: designation of rubber types
• ISO 248-1 - Determination of volatile‑matter content (raw synthetic rubbers)
• ISO 1795 - Sampling and preparative procedures

Keywords: ISO 247-1:2018, ash determination, rubber testing, combustion method, muffle furnace, crucible, compounded rubbers, vulcanizates.