ISO 21037:2026

International
Standard
ISO 21037
First edition
Adhesives — Guideline for
2026-03
separating adhesively bonded joints
enabling repair and improving
recycling
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Procedure . 1
4.1 Systematics .1
4.2 Mechanical methods for separating adhesively bonded joints .2
4.2.1 Cutting .2
4.2.2 Peeling .2
4.2.3 Stretching of the adhesive carrier .3
4.2.4 Elongation of the adherends .3
4.3 Physical methods for separating adhesively bonded joints .3
4.3.1 Temperature effects .3
4.3.2 Electricity .3
4.3.3 Solvents . .4
4.4 Chemical methods for separating adhesively bonded joints .4
4.4.1 Expanding and blowing agents .4
4.4.2 Decomposition of the adhesive .4
4.4.3 Decomposition of the adherent .4
Annex A (informative) Debonding — Established examples . 5
Bibliography . 9

iii
Foreword
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iv
Introduction
Given the background of a growing world population, increasing demand for goods, a continuing rise in
waste production and environmental pollution and, last but not least, the expected effects of climate change,
the transition from a linear economy to a circular economy is becoming increasingly important.
The aim of the circular economy concept is to establish closed material cycles through circular strategies
and thereby to build a regenerative system in which value creation, prosperity and security of supply are
achieved within planetary boundaries. In addition to a reduction in the use of resources, the preservation
of the value of raw materials, materials and products are at the forefront of the strategies compiled in the
framework of 9 R-strategies.
The contents of the 9 hierarchically structured R-strategies can be described by the following keywords:
— Refuse;
— Rethink;
— Reduce;
— Reuse;
— Repair;
— Refurbish;
— Remanufacture;
— Repurpose;
— Recycle.
When considering the various R-strategies in the design of products, conflicting goals between the different
R-strategies are certainly conceivable. For example, the weight of a product (e.g. rail vehicle) can be
significantly reduced by using different materials that are joined together in an adhesive bonding process,
thus reducing the energy requirement during the utilization phase. It is also conceivable that the service
life of a product (e.g. electronic components) can be extended by adhesive bonding. On the other hand, the
disadvantage is that bonded joints may make it more difficult to repair or recycle the materials at the end of
the product's life cycle.
In order to identify the most favourable solution from the point of view of resource consumption in the
event of conflicting objectives, a holistic assessment of the resource requirements is required, starting with
the manufacture of the product, through the entire product life to the end of life with the recycling of the
materials and consideration of the type and quantity of residual waste to be removed from the cycle that
cannot be recycled.
With this document, procedures are provided and further explained in Annex A by practical examples
with which the apparent contradiction between adhesive bonding and reparability and recyclability of the
product can be avoided.
v
International Standard ISO 21037:2026(en)
Adhesives — Guideline for separating adhesively bonded
joints enabling repair and improving recycling
1 Scope
This document specifies the methods commonly available for separating adhesively bonded joints enabling
repair and improving recycling.
This document applies to adherends made of metallic and non-metallic inorganic material, plastics including
both filler-containing and fibre-reinforced types, wood and wood-based materials, coated materials,
adherends of natural and polymeric fibres as well as paper and cardboard.
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 472, Plastics — Vocabulary
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 terminology 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
separating
process for disassembling structures or components by disengaging cohesion or adhesion
3.2
recycling
processing of waste materials for the original purpose or for other purposes, excluding energy recovery
[SOURCE: ISO 472:2013, 2.1706]
3.3
debonding
separating an adhesively bonded joint for the purpose of repairing the bonded component, for reuse or
recycling of the adherends
4 Procedure
4.1 Systematics
The available processes for separating adhesively bonded joints can be divided into mechanical, physical and
[1][2][3][4]
chemical process groups according to their mechanisms of action. Figure 1 provides an overview
of the main groups and subgroups according to this systematics. For a further explanation of the various

technologies, Annex A describes various processes that have already demonstrated their effectiveness in
practice.
Figure 1 — Systematics of the main and subgroups for separating adhesively bonded joints
4.2 Mechanical methods for separating adhesively bonded joints
4.2.1 Cutting
If the strength of the adhesive is sufficiently low, bonded joints can be mechanically separated using cutting
tools such as knives, wires or ropes.
Proven application examples can be found in the replacement of windshields in vehicle repair. The use of
auxiliary equipment can reduce the amount of force required and reduce the risk of accidents from handling
sharp-edged tools.
4.2.2 Peeling
When designing adhesively bonded joints, one tries to avoid peeling stresses under service conditions.
Peeling stress is characterized by the fact that the applied load is concentrated linearly, and adhesive
debonding or cohesive separation produces a crack that is driven forward by the applied load. This principle
can be used to separate bonded joints when the tensile strength of the parts being joined is greater than
the peel resistance of the bond. Examples of applications can be found in self-adhesive resealable packaging
closures, hygiene products and removable labels. In combination with the physical processes of subgroups
2.1.1 (heating) or 2.1.2 (cooling) (see Figure 1), the level of peel resistance can be influenced. Examples of
applications for such process combinations can be found in the repair of displays of mobile devices (so-called
smartphones and tablets). Heating with hot air or a heating panel can reduce the peeling resistance of the
edge bonding to such an extent that separating by peeling becomes possible with the use of auxiliary tools.

4.2.3 Stretching of the adhesive carrier
The adhesion of pressure-sensitive adhesives can be reduced by strongly stretching a carrier material
plastically. This principle can be used both for residue-free removable adhesive films and for residue-free
removable double-sided adhesive tapes.
4.2.4 Elongation of the adherends
Similar to that described under 4.2.3, bonded joints can be released by plastic stretching of the adherends.
The working principle is based on the effect that the local fracture strain of the adhesive in the contact
zone to the adherent is lower than the maximum elongation of the adherent. This principle has already been
successfully applied in the design of releasable adhesive brackets in dental technology.
4.3 Physical methods for separating adhesively bonded joints
4.3.1 Temperature effects
4.3.1.1 Heating
The mechanical properties of polymeric adhesives are highly dependent on temperature. Depending on the
type of adhesive used, heating leads to different changes in properties.
— With thermoplastic adhesives, strength decreases with increasing temperatures until flow occurs as the
melting temperature is approached. Bonded joints can be released in this state, preferably under peeling
stress, by cohesive separation of the adhesive joint. So-called “thermoplastic joining interface materials”
applied to the surface of at least one adherend prior bonding using a conventional adhesive allow to
tailor the temperatures required for separation of adhesively bonded joints.
— In the case of low-modulus partially crosslinked adhesives (e.g. crosslinked pressure-sensitive adhesives),
heating also leads to a reduction in peel resistance. However, melting does not occur and such bonded
joints can be separated at elevated temperatures without visible residues.
— In the case of duromeric load-bearing structural adhesives, heating to the vicinity of or above the glass
transition temperature leads to a reduction in strength and peel resistance due to the activation of
relaxation mechanisms. In joints bonded in this manner, the bonded parts and adhesives can be separated
and recovered in this temperature range by peeling or cleavage stress.
Hot air blowers, electric heating wires, infrared radiators, inductors and microwaves have proven to be
suitable heating methods for separating adhesively bonded joints in a wide variety of applications.
4.3.1.2 Cooling
In the case of adhesives being used above their glass transition temperature under the intended service
conditions, cooling to lower temperatures can provoke embrittlement. In the embrittled state, such bonded
joints can be separated with little force by peeling or impact stress due to their low critical crack propagation
energy in the glassy state.
Cooling can be achieved, for example, by liquid refrigerants, expansion of carbon dioxide or by dry ice.
4.3.2 Electricity
By applying a DC voltage in the range of 10 V to 50 V, debonding of joints formed by adhesives specially
formulated to react to electrical stress can be facilitated. The process takes advantage of the low ionic
conductivity of the adhesives to achieve an electrically stimulated weakening of the adhesive zone. The
adherends shall be electrically conductive and electrically insulated from one another to use this principle.

4.3.3 Solvents
In this case, dissolving substances in solvents is the physical principle of action. According to this method,
thermoplastic or water soluble adhesives can be completely dissolved or their cohesive strength is reduced
by swelling to such an extent that easy separation by applying peel or cleavage stress is possible. To some
extent, this can also be achieved by suitable solvents swelling elastomeric polymers. The suitability of the
solvent depends on the composition of the adhesive. Suitable solvents include water and organic solvents
with different polarities.
4.4 Chemical methods for separating adhesively bonded joints
4.4.1 Expanding and blowing agents
Adhesive bonds can be weakened if chemical blowing or foaming agents have been added to the adhesives or
to a functional coating pre-applied to at least one of the adherends. The working principle is similar to that
of so-called baking soda. Above a threshold temperature, which is determined by the agent used, a chemical
reaction leads to the formation
...