ISO 48-5:2018

Overview

ISO 48-5:2018 specifies a portable method for measuring the indentation hardness of vulcanized or thermoplastic rubber using an IRHD pocket meter (a handheld durometer calibrated in IRHD). The method is intended primarily for production control and quality checks rather than formal specification testing (see ISO 48-2 for specification methods). The standard defines apparatus, sample preparation, measurement procedure, calibration and reporting requirements to ensure repeatable rubber hardness readings.

Key topics and technical requirements

• Apparatus: IRHD pocket hardness meter with a pressure foot (square 20 mm ±2.5 mm or circular Ø22.5 mm ±2.5 mm), central hole Ø2.5 mm ±0.5 mm, hemispherical indentor (Ø1.575 mm ±0.025 mm), indicating device calibrated in IRHD and a calibrated spring applying ~2.65 N ±0.15 N.
• Test pieces: Minimum single-layer thickness of 6 mm. For thinner sheets, up to three layers may be laminated provided none is thinner than 2 mm; surface must be flat and measurements taken ≥12 mm from edges.
• Conditioning: Condition test pieces for at least 1 hour at a standard laboratory temperature per ISO 23529; maintain consistent temperature during comparisons.
• Procedure: Place specimen on a hard flat surface (e.g., glass), apply the pocket meter without shock, keep indentor normal to surface. Standard test time: 3 s for vulcanized rubber, 15 s for thermoplastic rubber. Take five readings at positions ≥6 mm apart and report the median.
• Calibration & checking: Calibrate per ISO 48-9. Check against standard rubber blocks (≈30–90 IRHD) and adjust the instrument to read 100 IRHD on a hard surface. Frequent checks (weekly for regular use) are recommended.
• Reporting: Include sample description, test method reference (ISO 48-5:2018), temperature/humidity, instrument type, test time, any deviations and full measurement data.

Applications and users

• Quality control and in-process monitoring in rubber manufacturing (tires, seals, gaskets, hoses)
• Incoming inspection of rubber compounds and thermoplastic elastomers
• R&D and formulation development where quick, portable hardness checks are needed
• Field testing or on-site troubleshooting where bench durometers are impractical

Primary users: QC laboratories, production engineers, materials scientists, and third‑party testing services requiring portable IRHD hardness checks.

Related standards

• ISO 48-2 - Hardness by dead-load (specification method)
• ISO 48-9 - Calibration and verification of hardness testers
• ISO 23529 - Preparation and conditioning of test pieces
• ISO 868 - Hardness testing for plastics (reference for thermoplastic test time)

Keywords: ISO 48-5, IRHD pocket meter, rubber hardness, indentation hardness, pocket durometer, vulcanized rubber, thermoplastic rubber, hardness testing, IRHD calibration.