Overview
ISO 25179:2018 specifies a laboratory test method for determining the solubility of water‑soluble or alkali‑soluble pressure‑sensitive adhesives (PSAs). The method quantifies adhesive solubility by measuring the loss in mass of an adhesive‑coated test specimen after controlled immersion and agitation in water or an aqueous alkali solution. Solubility data from ISO 25179 are used to assess the recyclability of products with PSA‑fixed labels and to compare dissolution behavior across adhesive formulations.
Key topics and technical requirements
- Scope and principle: Measures adhesive mass loss from PSA coated on repulpable kraft paper by shaking sealed bottles in a temperature‑controlled orbital shaker and sampling over time.
- Apparatus: orbital shaker with heated chamber (40–80 °C range, ±2 °C), 500 ml glass bottles with prepared caps, stainless steel specimen holder (AISI 316), forced‑air drying oven (50–120 °C), and precision balance (0.0001 g).
- Solutions: distilled or deionized water for water‑soluble adhesives; aqueous NaOH solution (1 part NaOH : 99 parts water by mass) for alkali‑soluble adhesives.
- Specimen preparation: coat repulpable kraft paper (80–100 g/m²) to a wet film ~40 µm, dry at 80 °C for 30 min, cut specimens (110 × 20 mm) and condition per ISO 291.
- Test procedure: bottles preheated (typical test temperature 50 °C ±2 °C) and shaken at a typical speed of 50 r/min (other speeds/temperatures allowed by agreement). Remove specimens at predetermined intervals (5–20 min categories for fast/medium/slow dissolving adhesives), dry to constant mass and calculate adhesive loss.
- Results expression: adhesive loss reported as mass percent using the formula in Clause 9; plot percentage lost vs time and report times to 25 %, 50 % (t50) and 75 % loss, plus dissolution pattern and gradient to 50 %.
- Reporting: test report must include reference to ISO 25179, adhesive identification and coat weight (g/m²), kraft paper details, conditioning, solvent used, test temperature and shaker speed, dissolution plot, key times (25/50/75 %), number of specimens, dates and responsible personnel.
Applications and users
- Applications: evaluating recyclability of label‑applied packaging, screening PSA formulations for water or alkali removability, quality control and R&D for repulpable products, and regulatory or customer compliance testing where adhesive solubility affects recycling.
- Typical users: adhesive manufacturers, packaging converters, label producers, recycling facilities, independent testing laboratories, and product development teams focused on sustainable packaging.
Related standards
- ISO 291 - Plastics: standard atmospheres for conditioning and testing (referenced for specimen conditioning).
- ISO 472 - Plastics: vocabulary (terminology support).
Keywords: ISO 25179, pressure‑sensitive adhesive, adhesive solubility test, water‑soluble adhesive, alkali‑soluble adhesive, recycling, repulpable kraft paper, adhesive mass loss, t50.