ISO 7972:2023

Adhesives - Absorption of water into an adhesive layer using an open-faced specimen and determination of shear strength by secondary bonding

This document specifies a method for the rapid permeation of water to an adhesive layer using a specimen with one side open, the secondary bonding of the specimens with the adhesive layer that is still moistened, and a shear strength test of the secondary bonded specimen, for the selection of water-resistant adhesives and the determination of suitable surface treatments. It does not assess the water resistance of the actual joint itself, as the distribution of water in the adhesive layer is different. This test procedure does not provide design information.

Adhésifs — Absorption d'eau dans une couche adhésive au moyen d'un échantillon ouvert et détermination de la résistance au cisaillement par collage secondaire

General Information

• Status: Published
• Publication Date: 03-May-2023
• ICS: 83.180 - Adhesives
• Technical Committee: ISO/TC 61/SC 11 - Products
• Drafting Committee: ISO/TC 61/SC 11 - Products
• Current Stage: 6060 - International Standard published
• Start Date: 04-May-2023
• Due Date: 30-Jul-2024
• Completion Date: 04-May-2023

Overview

ISO 7972:2023 specifies a laboratory method to evaluate how water is absorbed into an adhesive layer and how that moisture affects shear strength. The standard uses an open-faced specimen (one side of the adhesive layer exposed to water) to accelerate permeation, then performs secondary bonding of two wet specimens and a single-lap shear test while the adhesive layer is still moist. ISO 7972 is intended for selecting water‑resistant adhesives and assessing surface treatments - it does not evaluate the water resistance of a real joint nor provide design information.

Key topics and technical requirements

• Test principle: Rapid water permeation through the open face, secondary bonding of wet specimens, and tensile shear testing while wet.
• Specimen preparation:
  • Open-faced adherends made from rigid metals or hard plastics.
  • Typical primary adhesive layer thickness ~0.15 mm (unless specified otherwise); thickness control methods (e.g., glass spheres) are described.
  • Cleaning and surface treatment per manufacturer instructions or ISO 4588 (metals) / ISO 13895 (plastics).
• Immersion and conditioning:
  • Immersion procedures follow ISO 175 (liquid chemical immersion) with water temperature controlled to ±2 °C.
  • Conditioning and testing atmospheres conform to ISO 291.
• Secondary bonding:
  • Use a secondary adhesive that cures at ambient temperature and hardens within 24 hours (examples: cyanoacrylates).
  • Bonding and cure should be completed so the tensile shear test is performed within one day after immersion.
• Testing and measurement:
  • Single-lap overlap length: 12.5 mm ± 0.25 mm.
  • Dimensional accuracy: measure to ±0.01 mm.
  • Tensile shear testing per ISO 4587.
  • Minimum recommended number of specimens: not fewer than five.
• Results and reporting:
  • Report arithmetic mean of maximum force or shear stress (MPa).
  • Test report must reference ISO 7972:2023 and include adhesive IDs, adherend details, immersion conditions, average adhesive thickness, bonding process, and more.
• Limitations: Does not reflect water distribution in an actual bonded joint; precision data were not available at publication.

Applications and who uses this standard

ISO 7972 is useful for:

• Adhesive manufacturers and R&D teams screening water‑resistant adhesives.
• Materials and surface‑treatment engineers evaluating surface preparation impact on wet strength.
• Quality control laboratories performing comparative studies and batch evaluation.
• Industries where moisture exposure is critical (automotive, aerospace, electronics, marine, and consumer products) for material selection and comparative testing - not for joint design validation.

Related standards

• ISO 175 - immersion effects for plastics
• ISO 291 - conditioning atmospheres
• ISO 4587 - tensile lap‑shear testing
• ISO 472 - plastics vocabulary
• ISO 10365 - failure pattern designation
• ISO 4588 / ISO 13895 - surface treatment guidance

Keywords: ISO 7972, adhesive testing, water absorption, open-faced specimen, secondary bonding, lap-shear test, shear strength, water-resistant adhesives, surface treatment.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7972
First edition
2023-05
Adhesives — Absorption of water into
an adhesive layer using an open-faced
specimen and determination of shear
strength by secondary bonding
Adhésifs — Absorption d'eau dans une couche adhésive au moyen
d'un échantillon ouvert et détermination de la résistance au
cisaillement par collage secondaire
Reference number
© ISO 2023
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test specimens . 2
6.1 Open-faced specimen . 2
6.1.1 Cleaning . 2
6.1.2 Surface treatment . 2
6.1.3 Deposition and control of the adhesive thickness . 2
6.1.4 Immersion in water. 3
6.2 Specimen for single lap shear test . 3
6.2.1 Dimensions and alignment . 3
6.2.2 Number of specimens . 3
6.3 Accuracy . 3
7 Conditioning of test . 4
8 Procedure .4
8.1 Immersion in water . 4
8.2 Secondary bonding . 4
8.3 Tensile shear test . 4
9 Precision data .4
10 Calculation and expression of results . 5
11 Test report . 5
Annex A (informative) Example of preparation of open-faced specimen .6
Annex B (informative) Example of secondary bonding . 8
Bibliography .10
iii
Foreword
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iv
Introduction
Adhesives absorb moisture from the environment over a long period of time. The absorbed water often
decreases the strength of the adhesive. Therefore, it is important to evaluate the effect of absorbed
water properly to ensure the durability of adhesive bonding joints. Such an evaluation is generally time-
consuming because the penetration of water into the adhesive layer is a slow process. Additionally, the
moisture in the adhesive layer can alter the chemical and physical properties of the adhesive layer and
interface over time.
v
INTERNATIONAL STANDARD ISO 7972:2023(E)
Adhesives — Absorption of water into an adhesive layer
using an open-faced specimen and determination of shear
strength by secondary bonding
1 Scope
This document specifies a method for the rapid permeation of water to an adhesive layer using a
specimen with one side open, the secondary bonding of the specimens with the adhesive layer that is
still moistened, and a shear strength test of the secondary bonded specimen, for the selection of water-
resistant adhesives and the determination of suitable surface treatments. It does not assess the water
resistance of the actual joint itself, as the distribution of water in the adhesive layer is different. This
test procedure does not provide design information.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 175, Plastics — Methods of test for the determination of the effects of immersion in liquid chemicals
ISO 291, Plastics — Standard atmospheres for conditioning and testing
ISO 472, Plastics — Vocabulary
ISO 4587, Adhesives — Determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies
ISO 10365, Adhesives — Designation of main failure patterns
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
open-faced specimen
specimen with an adhesive layer on an adherend, such that one side of the adhesive layer is not in
contact with the adherend and is open
3.2
primary adhesive
adhesive used to prepare an open-faced specimen
3.3
secondary adhesive
adhesive for adhering open-faced specimens together
4 Principle
The adhesive layers of the open-faced specimens
...