ISO/TR 20436:2017
(Main)Buildings and civil engineering works — Sealants — Paintability and paint compatibility of sealants
Buildings and civil engineering works — Sealants — Paintability and paint compatibility of sealants
ISO/TR 20436:2017 reviews and evaluates the methodology that can be employed to assess the paintability of or paint compatibility with sealants used in building and construction. The term "paintability" is used throughout this document and is a generic term to refer to the application of paint or a coating to a sealant.
Bâtiments et ouvrages de génie civil — Mastics — Peignabilité et compatibilité des mastics avec les peintures
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Standards Content (Sample)
TECHNICAL ISO/TR
REPORT 20436
First edition
2017-07
Buildings and civil engineering
works — Sealants — Paintability and
paint compatibility of sealants
Bâtiments et ouvrages de génie civil — Mastics — Peignabilité et
compatibilité des mastics avec les peintures
Reference number
ISO/TR 20436:2017(E)
©
ISO 2017
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ISO/TR 20436:2017(E)
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ISO/TR 20436:2017(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Evaluation of paintability of a sealant . 1
5 Methods for assessment of initial coating application . 3
5.1 General . 3
5.2 Reticulation/fish eyes . 3
5.2.1 Principle . 3
5.2.2 Evaluation . 3
5.2.3 Reporting . 3
5.3 Flow of paint/wet surface finish. 3
5.3.1 Principle . 3
5.3.2 Evaluation . 3
5.3.3 Reporting . 4
5.4 Effect of sealant on curing/drying time of paint/coating . 4
5.4.1 Principle . 4
5.4.2 Evaluation . 4
5.4.3 Reporting . 4
6 Test methods for assessment relating to cure effects . 4
6.1 Principle . 4
6.2 Evaluation . 4
6.3 Reporting . 5
7 Test methods to assess surface appearance of dried coating . 5
7.1 General . 5
7.2 Colour difference between painted sealant and painted substrate . 5
7.2.1 Overview . 5
7.2.2 Principle . 5
7.2.3 Evaluation . 5
7.2.4 Reporting . 5
7.3 Surface wrinkling . 6
7.3.1 Overview . 6
7.3.2 Principle . 6
7.3.3 Evaluation . 6
7.3.4 Reporting . 6
7.4 Surface sheen or bloom . 6
7.4.1 Overview . 6
7.4.2 Principle . 6
7.4.3 Evaluation . 6
7.4.4 Reporting . 7
7.5 Surface tack . 7
7.5.1 Overview . 7
7.5.2 Principle . 7
7.5.3 Evaluation . 7
7.5.4 Reporting . 8
7.6 Staining . 8
7.6.1 Overview . 8
7.6.2 Principle . 8
7.6.3 Evaluation . 8
7.6.4 Reporting . 9
7.7 Surface cracking of paint only . 9
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ISO/TR 20436:2017(E)
7.7.1 Overview . 9
7.7.2 Principle . 9
7.7.3 Evaluation . 9
7.7.4 Reporting .10
7.8 Adhesion of coating to sealant .10
7.8.1 Principle .10
7.8.2 Evaluation .10
7.8.3 Reporting .11
8 Test methods to assess effects of overcoating on sealant performance .11
8.1 General .11
8.2 Surface microcracking resulting in crack initiation in the sealant .14
8.2.1 Overview .14
8.2.2 Evaluation .14
8.2.3 Reporting .14
8.3 Effect of coating the sealant on final mechanical and adhesion characteristics.14
8.3.1 Overview .14
8.3.2 Principle .14
8.3.3 Evaluation .14
8.3.4 Reporting .15
8.4 Elasticity .15
8.4.1 Overview .15
8.4.2 Principle .15
8.4.3 Evaluation .15
8.4.4 Reporting .15
9 Durability assessment .15
10 Methodology to reduce test pieces .16
11 Overall assessment of compatibility of the coating with sealant .16
Annex A (informative) Suitable test pieces for measurement of paintability and paint
compatibility of sealants .17
Bibliography .20
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ISO/TR 20436:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 59, Buildings and civil engineering works,
Subcommittee SC 8, Sealants.
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ISO/TR 20436:2017(E)
Introduction
There are current International Standards to classify sealants for façade, glazing and pedestrian
walkways. These International Standards refer to a number of established test methods relating to
the performance of the sealants, but until now, no methodology has been developed to evaluate claims
regarding paintability and paint compatibility of sealants.
This is a complex subject and generally, although the expert opinion is that ideally it is not recommended
that sealants are overpainted, it is recognized internationally that manufacturers are marketing
sealants that are actively promoted as being “paintable” in marketing and sales literature and that for
many refurbishment projects, sealants will be overpainted or overcoated rather than be removed and
fresh sealant reapplied. It is therefore important to review the current state-of-the-art methods and
characteristics relating to overpainting sealants, ultimately to at least standardize the test methods
used when manufacturers make claims relating to this characteristic in future. This document can
then be used in the development of future international standards relating to paintability of sealants, if
required.
This document considers ways of defining sealant and coating performance and aesthetics in order to
be able to suggest the aspects that are relevant when referring to a sealant as “overpaintable”. There is
also guidance over the form that reporting of the results should take.
The intention is that, if required, this document can be followed with the publication of a set of standard
test methods leading to the possible drafting of a technical specification if necessary.
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TECHNICAL REPORT ISO/TR 20436:2017(E)
Buildings and civil engineering works — Sealants —
Paintability and paint compatibility of sealants
1 Scope
This document reviews and evaluates the methodology that can be employed to assess the paintability
of or paint compatibility with sealants used in building and construction. The term “paintability” is
used throughout this document and is a generic term to refer to the application of paint or a coating to
a sealant.
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 6927, Buildings and civil engineering works — Sealants — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6927 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Evaluation of paintability of a sealant
A number of characteristics can be part of an evaluation to determine the overall compatibility of any
sealant with a specified paint or coating applied to the sealant.
Any claims of paintability will only relate to a combination of a specific paint and a specific sealant when
tested together, as the coatings themselves may be subject to frequent changes in formulation. Also,
the sealants may be subject to reformulation, thus necessitating regular rechecks regarding continued
paintability performance. Generic claims regarding paintability are unlikely to be substantiated unless
it can be guaranteed that no formulation changes have occurred since the initial evaluation.
The performance is usually evaluated as a broad assessment of overpaintability, focusing on certain
aspects; see Figure 1.
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ISO/TR 20436:2017(E)
Figure 1 — Characteristics of overpaintability
These characteristics are evaluated and the overall results are used to make an assessment of
paintability. Not all characteristics are used by all sealant manufacturers, but to standardize any claims,
it would be important to establish a suitable overall assessment schedule that could be used if sealants
carry claims that they can be overpainted/coated. It is unlikely that this will be a blanket claim for all
paints, and would need to be specific to a paint or coating and sealant combination, so it is important to
consider this aspect when deciding the test protocol to avoid excessive testing.
It would be desirable to combine the characteristics so that they can be evaluated on a reduced number
of test pieces if possible.
There are no comprehensive specifications available that define paintability of sealants; however,
there are a variety of standards available internationally that cover various aspects of paintability and
compatibility.
There are also manufacturers’ test methods that have been developed to allow them to substantiate
their own claims and to verify any recommendations they make to their customers.
In terms of reporting results, the following should be included in any test report in addition to any
specific requirements listed in each individual test:
a) specific sealant details including manufacturer, type of product, product name, batch number or
date of manufacturing;
b) specific coating or paint: manufacturer, type of product, colour of product system/specification of
product, name of product, batch number or date of manufacturing;
c) barrier primer (if applied): manufacturer, type of product, system/specification of product, name
of product, batch number or date of manufacturing;
d) length of time between application of wet/uncured sealant and any paint or coating;
e) details of substrate that sealant is applied onto including specific details of the test pieces used;
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ISO/TR 20436:2017(E)
f) information regarding how paint or coating was applied including coat weight or thickness applied;
g) time after coating before test evaluation is carried out.
5 Methods for assessment of initial coating application
5.1 General
Assessment of the actual application of the paint/coating to the sealant is unlikely to be made
when the sealant will be fully dry or cured and therefore the application time before overcoating is
recommended and will be specified by the manufacturer. Typical claims are “overpaintable 1 h after
sealant application” and so the first aspect that needs to be specified in any testing is how long after
sealant application the coating is applied.
On application of the coating, initially, an assessment of the visual appearance of the freshly applied
coating is made in terms of the quality of the applied coating and the appearance of the sealant surface
relative to the surrounding substrate.
5.2 Reticulation/fish eyes
5.2.1 Principle
“Fish eyes” are round spots, resembling fish eyes, in a newly applied coating that appear to be pulling
away from the sealant surface. Reticulation is a similar effect and is a surface defect that creates a net-
like appearance in the coating surface.
5.2.2 Evaluation
This is assessed via a visual inspection after the paint is applied to the sealant at the time claimed by
the sealant manufacturer that his sealant will be overpaintable. It might involve brush application of
the paint/coating to the sealant at a specified time point after sealant application or it might be a more
controlled application method. It is possible that the sealant could be applied to a flat substrate and
then after a specified time, the paint/coating is applied over this, overlapping at the sides so that the
coating is only applied to the substrate in some areas. An assessment of the appearance of the coated
and uncoated sealant areas is then made subjectively, perhaps with photographic record being taken.
5.2.3 Reporting
This is normally in the form of a comment and will either be that faults are observed (reticulation or
pin holes or other incomplete coating surfaces observed) or that an even coating with no defects is
observed.
5.3 Flow of paint/wet surface finish
5.3.1 Principle
There may be a difference in the coating of the sealant and surrounding substrate. It is possible to carry
out a determination of recoatability at the time point claimed by the sealant manufacturer that the
sealant is overpaintable.
5.3.2 Evaluation
This involves the application of the coating, by brush, to the newly through-dried film or bead of sealant.
The evaluation would involve applying either a defined layer of sealant or a bead of sealant onto a
substrate allowing the sealant to dry or cure for the time recommended by the sealant manufacturer
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ISO/TR 20436:2017(E)
regarding overpaintability and then applying the paint or coating under evaluation using a paint brush
or roller.
5.3.3 Reporting
Any drag on the brush experienced while applying the coating is noted.
5.4 Effect of sealant on curing/drying time of paint/coating
5.4.1 Principle
Once an even coating is applied, the next stage is to examine the effect that the sealant may have on the
drying/curing of the coating due to any chemical incompatibility or migration of substances that might
interfere with the drying, film formation or curing of the coating. The coating itself may also retard any
drying or curing of the sealant for the same reasons.
5.4.2 Evaluation
The evaluation would involve applying either a defined layer of sealant or a bead of sealant onto a
substrate allowing the sealant to dry or cure for the time recommended by the sealant manufacturer
regarding overpaintability and then applying the paint or coating under evaluation using a paint brush
or roller. The paint would be applied so that it overlapped the sealant, thus allowing both the coated
substrate and coated sealant to be assessed at the same time.
Assessment of the overpainted sealant is made and compared with the painted substrate for properties
like tack/drying time/cure time. There are defined methods for measuring surface tack; however, a
subjective assessment is sufficient for evaluation purposes.
5.4.3 Reporting
Any differences between the coating applied to the sealant and the coating applied only to the substrate
are noted. The drying time of the coated neutral substrate and the coated sealant should be mentioned
in the test report.
6 Test methods for assessment relating to cure effects
6.1 Principle
Once an even coating is applied, the next stage is to examine t
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