Dr Matt Unthank, Northumbria University, Newcastle - Controlling transport phenomena of molecules into coatings

Presentation - pdf

M. G. Unthank^a,*C. Cameron^b, A. Wright^b,  A. Alam^c, M. R. Probert^d
a Department of Applied Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK.
^b AkzoNobel, Stoneygate Lane, Felling, Gateshead, NE10 0JY.
^c HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL
^d School of Natural and Environmental Sciences, Bedson Building, Newcastle University, Kings Road, NE1 7RU

The development of new high performance materials, coatings, composites and adhesives relies on insight into the origin of performance on a molecular level.  Particularly for applications which include aerospace and automotive composites, as well as coatings for the global transport and storage of solvents and chemicals across the chemical, oil and gas industries can benefit from this insight.

This research explores a new type of epoxy-amine-borate (EAB) hybrid material for control of penetrant solvent molecules into cross-linked thermoset polymer networks.  The new epoxy-amine-borate (EAB) hybrid material is prepared through the network forming reaction of trialkylborate esters, an amine curing agent and a Novolac epoxy resin.

The properties of these materials are explored through material and mechanical testing and model studies are used to probe the mode-of-action through which EAB materials deliver their improved performance properties.  It is proposed that the removal of both H-bond donor (i.e. OH groups) and Lewis basic functionality (i.e. NH2 groups) from the polymeric matrix network reduce the affinity of polar solvent molecules with the EAB hybrid material result in an overall reduction in solvent uptake behaviour

Q&A

From  Philip Gill: Matt -  Have you investigated the different reactivity of TEB in your system at different temperatures?
Answer: Well, I suppose the complexation of the TEB with the model ligand so when we made the amino alcohol and beta-amino diol model ligand, we studied those across a range of different temperatures, particularly with the one that we couldn’t get to react, so that has definitely been done, and as I said, even at high temperature we couldn’t get the triethylboril to react with the secondary amino alcohol. In terms of looking at it in the coating, I think probably we only looked looked at ambient curing and postcuring we also studied TEB without the post curing and it was also effective in that situation but not as effective, so I don’t think we have done a comprehensive study in the coatings at different temperatures, probably just at room temperature and an elevated 80C.

From  Maria Pin: Thank you for the presentation, Matt. In the absorption-desorption tests, do you mimic the cleaning of the tanks (if they are actually cleaned)?
Answer: Yes, in the simple study we just take out the slides and let it desorb for 28 days and then measure weight loss over that time, but obviously a tank will not be left over 28 days, it would be more like 5-7 days, depending on which cargo it has been carrying, the cargo comes with the cleaning protocol depending on t the coating it has as well. We also looked at cleaning protocols immersing in hot water, etc, do all sort of studies and you can mimic those in the lab as well.

From  Steve Edmondson: Do you think this post-cure complex formation could be a more general effect, or specific to boron? e.g. could it work with well-chosen metal atoms?
Answer: Yes, that is interesting, we looked at that as well. I kind of cut a good of a year or two of work in the front end of the presentation where we ended up studying the borate system in detail but we also looked at tetra-alkyl titanium and tetra alkyl aluminimum species and I agree in principle that it should work, but we couldn’t get the aluminium and titanium systems to work but that is not to say that somebody else could, because on paper you should be able to complex those, the nucleophilic amine and alcoxy hydroxy species with metal atoms as well. The challenge I suppose is how you get the key most selectivity,  so how you make it that your metals don’t complex with your amine nucleophile or complex the secondary amines once they started to react. I think the reason why this system works well is because the inherent latent reactivity of the boron system. I think there is definitely more work you can do in trying to manipulate these functional groups in expoyamine coatings to try to study new effects with metal atoms or other organic or inorganic atoms.

From  Stuart Lyon: So is the modified structure less polar and is this the reason for reduced absorption of polar solvents? How does free volume play a role?
Answer: That is exactly what it is. We complex the very polar amino diol functional group within the polymer network with the borate complex reducing the polarity of the organic network and reducing the affinity of polar molecules to absorb in the polymer and that goes hand in hand with the free volume.