I'm working on a project and I need to increase the surface energy of polypropylene. I want you to tell me a way in order to increase surface energy of polypropylene?
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$\begingroup$ Would Chemistry be a better home for this question? $\endgroup$– Qmechanic ♦Commented Aug 24, 2019 at 8:07
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1 Answer
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The surface of polypropylene has a low energy because it's most C-H bonds. These have no significant dipole moment and none of the atoms at the surface have lone pairs available to interact with external dipoles.
The usual way to increase the surface energy is to oxidise it to produce polar C-O-H groups. This is hard to do chemically because the surface is so inert, so it's usually done by plasma etching the surface with an oxygen plasma. This sounds complicated but the equipment to do it is surprisingly simple and widely available.
I used to plasma etch silica surfaces for similar reasons, but I have never worked on polypropylene so I can't advise you on the details e.g. pressures, etch times, etc. However a Google will find you hundreds of papers on the subject.
answered Aug 4, 2019 at 7:29
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$\begingroup$ actually I do it with Spark .now i want to reduce the surface energy of polypropylene.can you help me? $\endgroup$ Commented Aug 4, 2019 at 8:00
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$\begingroup$ @zahraasgary do you mean reduce the surface energy of untreated polypropylene, or do you mean first increase the energy, e.g. using a plasma, then decrease it again? If the latter then I would try annealing in a vacuum at the glass transition temperature of polypropylene. $\endgroup$ Commented Aug 4, 2019 at 8:33
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$\begingroup$ we have pp cups that printed by UV inks.in this process,first we increase the surface energy of polypropylene like that method you said.now we think by decreasing of the surface energy ,can remove inks from cups.what do you think about this? $\endgroup$ Commented Aug 4, 2019 at 8:42
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$\begingroup$ @zahraasgary I doubt it would work though I guess it's worth trying. The only way I can think of to reduce the surface energy is to anneal the polypropylene, but I doubt that will break the bonds holding the ink to the surface. It's more likely to allow the ink to diffuse into the bulk. $\endgroup$ Commented Aug 4, 2019 at 8:45
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$\begingroup$ agree with @JohnRennie, I used to do this with various plastic films to get proper adhesion with UV curable inks. $\endgroup$ Commented Aug 4, 2019 at 17:49