... and why ink is the first indicator

When components in a vehicle are to be joined with adhesive tape, a single physical value determines whether the result is a success or a failure:
surface energy.
It describes how "open" a surface is to the adhesive – in other words, whether the adhesive can make contact with the entire surface.
Put simply, surface energy is crucial when it comes to how well a surface can be bonded.

But did you know what ink has to do with it? – Something very important! It can help to determine the surface energy of a substrate.??????? This, in turn, determines how well or whether adhesive tape sticks to the material.

ink test

The principle is astonishingly simple, but extremely meaningful. With the so-called ink test, it is possible to assess in seconds whether a substrate is suitable for bonding.

If the ink runs, the surface energy is high. It is sufficiently moistened and therefore easy to stick. If droplets form instead, the surface energy is low and adhesion is correspondingly more complex.

This is precisely why the ink test is a standard step in the automotive industry when introducing new materials – before adhesive formulations or process parameters are discussed.

Overview

Low- and high-energy surfaces

Here you can see an overview of the most common materials and their surface tensions.

Aluminium and iron are high-energy surfaces with 840 and 2030 mN/m respectively and offer the adhesive good adhesion.

Low-energy surfaces, on the other hand, include PP (polypropylene) and PE (polyethylene). They have a surface tension of 29 and 31 mN/m, respectively. However, even these substrates can be bonded without any problems with the help of appropriate pre-treatment.

High- vs. low-energy surfaces

related to the automotive industry

Metals such as aluminium or galvanised steel are among the high-energy substrates, with values ranging from ~840 to >2000 mN/m.
Result: An excellent basis for adhesive tape applications — e.g. for mountings, shielding, sensors or structural components.

Low-energy plastics such as the following are significantly more demanding:

Substrate	PP / TPO	PE
Typical areas of application (vehicle)	Bumpers, exterior trim, mounting clips	Cable protection, covers, fastening clips
surface energy	~29–31 mN/m	~31 mN/m
pre-treatment	difficult without	usually required

low energy
Material	abbreviation	mN/m
polytetrafluoroethylene	PTFE	18
silicone	SI	24
polyvinyl fluoride	PVF	25
natural rubber	NR	25
butyl rubber	BR	27
polypropylen	PP	29
polyethylene	PE	31
polybutylene terephthalate	PBT	32
acrylonitrile butadiene styrene	ABS	35
polyamide	PA	<36
polymethyl methacrylate	PMMA	<36
Epoxy	EP	<36
Polyacetat	POM	<36
polyvinyl alcohol	PVA	37

HIGH ENERGY
Material	abbreviation	mN/m
polystyrene	PS	38
ps-phemoloxid	PSPO	38
polychloroprene	CR	38
polyvinyl chloride	PVC	39
cellulose acetate	CA	39
polyester	PET	41
polyimide	PI	41
phenolic resin	PF	42
polyurethane	PUR	43
polyethylene terephthalate	PETP	43
polyamide 6.6	PA	43
unbleached polyester	UP	43
polycarbonate	PC	46
polyphenylene oxide	PPO	47
styrene butadiene rubber	SBR	48
polyethersulphone	PES	50
lead	PB	450
aluminium	AL	840
copper	CU	1100
iron	Fe	2030

Do you have any questions?

If you have any questions about bonding specific materials, please do not hesitate to contact us. We will be happy to help you.

info@innotape.de
+49 5181 80687 0

Back to overview

Name	alto. Cookie
Provider	Provider
Purpose	Saves the visitor's settings
Identifier	alto-cookie
Validity	1 year

Accept
Name	Google Analytics
Provider	Google LLC
Purpose	Google cookie for website analyses. Creates statistical data on website usage.
Privacy	https://policies.google.com/privacy
Identifier	_ga,_gat,_gid,_ga_DW4LLZSHQV,_gcl_au
Validity	2 years

Accept
Name	LinkedIn
Provider	LinkedIn Ireland Unlimited Company
Purpose	LinkedIn Insight tag cookie used for website analytics, ad targeting and ad measurement.
Privacy	https://de.linkedin.com/legal/privacy-policy
Identifier	bcookie,li_gc,lidc
Validity	1 Year

Accept
Name	YouTube
Provider	YouTube, LLC
Purpose	Used to unlock Youtube contents.
Privacy	https://policies.google.com/privacy
Identifier	yt-remote-fast-check-period, yt-remote-session-app, yt-remote-session-name
Validity	Session

Accept
Name	Vimeo
Provider	Vimeo, LLC
Purpose	Used to unlock Vimeo contents.
Privacy	https://vimeo.com/privacy
Identifier	vuid
Validity	2 Years

surface energy in the automotive industry

... and why ink is the first indicator

ink test

Do you have any questions?

surface energy
in the automotive industry