ISO 248-2:2019

Overview - ISO 248-2:2019 (Rubber, raw - Thermogravimetric methods)

ISO 248-2:2019 specifies two thermogravimetric procedures using an automatic analyser with an infrared drying unit to determine moisture and other volatile‑matter content in raw rubbers. The standard is intended for routine determinations (e.g., quality control) of synthetic rubbers listed in ISO 1629 and covers multiple sample forms (bale, block, chip, pellet, crumb, powder, sheet). Results depend on fixed analyser conditions for a given rubber type or grade.

Key topics and technical requirements

• Scope and applicability
  • Applies to many synthetic rubbers (SBR, NBR, BR, IR, CR, IIR, halogenated IIR, EPDM).
  • Not applicable to raw rubbers that require homogenizing as per ISO 1795.
  • Applicable only when mass loss is due to original volatile matter, not rubber degradation.
• Two thermogravimetric methods
  • Method A - pre-defined drying time: set a drying temperature (preferably 100–120 °C) and a drying time determined for each rubber grade; analyser stops when that time elapses.
  • Method B - end point by mass‑loss rate: drying stops when the mass-loss rate falls to a pre-defined value determined for the grade.
• Apparatus and measurement
  • Automatic analyser with an infrared (near/far IR acceptable) drying unit, balance accurate to 1 mg, and microprocessor for control and calculation.
  • Typical test portion mass: 2 g to 15 g; bale samples should be cut to small pieces quickly to avoid volatile loss.
• Calibration and system accuracy
  • Performance check with sodium l‑tartrate dihydrate (reference volatile-matter ~15.66 ± 0.5 %); relative standard deviation must be < 1.0 % over 10 determinations.
• Calculation and reporting
  • Volatile-matter content computed as percent mass loss: (mA − mB) / mA × 100.
  • Test report must reference ISO 248-2:2019, sample ID, method (A or B), apparatus and conditions, related ISO 248‑1 procedure used to set endpoints, result and date.

Practical applications and users

• Quality control and incoming raw‑material inspection in rubber manufacturing.
• Independent testing laboratories validating moisture/volatile content in synthetic rubbers and different sample forms.
• R&D and process monitoring where fast, repeatable volatile-matter determinations are needed.
• Useful for routine screening when analyser conditions are fixed per rubber grade.

Related standards

• ISO 248-1 (Hot‑mill and oven methods) - note: oven method, procedure A in ISO 248‑1:2011 is the referee method if discrepancies arise.
• ISO 1795 (Sampling and preparative procedures) - for sampling and homogenizing requirements.

Keywords: ISO 248-2:2019, volatile-matter content, raw rubber, thermogravimetric methods, automatic analyser, infrared drying unit, moisture determination, quality control.