Overview
ISO 14309:2019 specifies a laboratory method for determining the volume resistivity and/or surface resistivity of vulcanized or thermoplastic rubbers. The procedure covers a very wide resistivity range (approximately 10 to 10^17 Ω·m) and uses a guarded‑electrode arrangement to minimise stray currents and contact errors. The standard defines required apparatus, test piece preparation and conditioning, test conditions, measurement procedure and calculation of resistivity values.
Key topics and technical requirements
- Measurand and range: Volume and surface resistivity for rubbers with resistivity from about 10 to 10^17 Ω·m.
- Measurement principle: Apply a DC voltage (1–1 000 V) and measure current; calculate resistivity using the standard’s formulae (volume and surface resistivity formulas and corrections for effective electrode area).
- Guarded‑electrode system: Three‑electrode arrangement (main/guard/opposed) to shunt stray currents and reduce measurement error. The standard explains electrode geometry, guarding practice and circuit configurations for both volume and surface tests.
- Apparatus specs:
- Stabilized DC supply: 1–1 000 V.
- Voltmeter accuracy: ±2 %.
- Ammeter/current meter range suitable for 0.01 pA to 100 mA with better than 5 % accuracy (depending on sample resistivity).
- Electrodes and dimensions:
- Main (circular) electrode diameter must be at least 10× the sample thickness.
- Typical example dimensions given (e.g. main electrode D1 ≈ 50 mm, ring D3 ≈ 80 mm, gap g ≈ 5 mm) and recommended gap ranges (1–15 mm depending on resistivity).
- For surface resistivity, gap must be at least twice the sample thickness to minimize volume effects.
- Test pieces and conditioning:
- Flat sheets, nominal thickness 0.5–5 mm (recommended 1 or 2 mm).
- Thickness measured to 0.01 mm; variation ≤10 %.
- Use three test pieces; condition per ISO 23529 (minimum 16 h at standard laboratory temperature/humidity).
- Test procedure:
- Discharge sample, apply voltage, measure current 1 minute after application.
- Limit power dissipation in sample to ≤0.1 W to avoid self‑heating.
- Ancillary requirements: Calibration guidance (Annex C), electrode materials (Annex A) and effective area correction (Annex D).
Practical applications - who uses ISO 14309:2019
- Rubber compounders and manufacturers for quality control of conductive, dissipative or insulating rubbers.
- Test and calibration laboratories performing electrical property verification.
- Product engineers in electronics, automotive, aerospace, medical devices and flooring where ESD control, shielding, leakage or insulation properties matter.
- Procurement and compliance teams specifying material electrical performance.
Related standards
Keywords: ISO 14309:2019, rubber resistivity test, volume resistivity, surface resistivity, guarded electrode, electrode dimensions, test conditioning, DC voltage, ESD control.