Welcome to Formulating Functional Films and Coatings III
19th August 2020 - Online
Morning Session
Afternoon Session


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

Presentation - pdf

M. G. Unthanka,*C. Cameronb, A. Wrightb,  A. Alamc, M. R. Probertd
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


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.


Professor Joe Keddie - Adding functionality to coatings with non-growing metabolically-active bacteria

Presentation - pdf
Yuxiu Chena, Simone Kringsb, Joshua R. Boothc, Stefan A. F. Bonc, Suzanne Hingley-Wilsonb and Joseph L. Keddiea
aDepartment of Physics, University of Surrey, Guildford, UK
bDepartment of Microbial Sciences, University of Surrey, Guildford, UK
cDepartment of Chemistry, University of Warwick, Coventry, UK

The commonly-used biomimetic strategy attempts to mimic Nature when designing the structure and properties of materials. In the design of coatings with targeting wetting properties, surface textures take inspiration from the lotus leaf or the rose petal. One could also imagine adding functionality – such as responsiveness to the environment, the remediation of pollutants, catalysis of chemical reactions, or even the creation of useful by-products – by copying Nature. As an alternative to this strategy, we envisage directly using Nature (in the form of viable cells) to add these types of functionality to coatings. Specifically, we have successfully made a biocoating, which confines non-growing, metabolically-active bacteria within a synthetic colloidal polymer (i.e. latex) film. A biocoating needs to have a high permeability to allow a high rate of mass transfer for rehydration and the transport of both nutrients and metabolic products. It therefore requires an interconnected porous structure. In this talk, I will describe how we exploited rigid tubular nanoclays (halloysite) and non-toxic latex particles (with a relatively high glass transition temperature) as the colloidal “building blocks” to tailor the porosity inside biocoatings containing Escherichia coli bacteria as a model organism. Electron microscope images revealed inefficient packing of the rigid nanotubes and proved the existence of nanovoids along the halloysite/polymer interfaces. Single-cell observations using confocal laser scanning microscopy provided evidence for metabolic activity of the E. coli within the biocoatings through the expression of yellow fluorescent protein. Whereas there was no measurable permeability in a coating made from only latex particles, the permeability coefficient of the composite biocoatings increased with increasing halloysite content up to a value of 1x10-4 m h-1. The effects of this increase in permeability on the cell viability was demonstrated through a specially-developed resazurin reduction assay. Bacteria encapsulated in halloysite composite biocoatings had statistically significant higher metabolic activities in comparison to bacteria encapsulated in a non-optimized coating made from latex particles alone. Enhancing bacterial viability in biocoatings has enormous potential in applications including waste-water treatment and the production of biomass and biofuel gases


From  Justin Perry: How long does E. coli live for within these halloyside films?
Answer: Well, there have been other people that have made biocoatings with a variety of bacteria, and if you keep them rehydrated they can survive for weeks, we checked the viability essentially after a couple of days, in future work we definitely want to check but in this experiment we just looked at a few days.

From  Wai Lee : The work on graphene is really interesting. Will the size of graphene affect the packing of the film and thus the optical properties? Also, will the way to prepare the film affect too for example,  layer-by layer rather than mixing?
Answer: you don’t want big sheets, the graphene sheets we used were about 350 nm which is a bit larger than the size of the polymer colloids. I do think we nanotubes would be the same. Big sheets can disrupt the packing and we didn’t want that. In that work, the sample preparation is essential. You have to keep high order, we didn’t do layer by layer so it is hard to comment on that. But this is kind of simpler, a one step process. It is interesting that the crystals form from the top down, so we are not doing a sedimentation, just as it dries forms skin layer at the top.

From  Bob Luigjes : If I understood correctly, the film formation was done at temperatures slightly above latex Tg. Have you looked at the influence of adding coalescing agents on the bacteria?
Answer: I guess I would be a little nervous about adding coalescing agents because it could harm the bacteria. I guess it would be interesting ones that they could use as food, but the short answer is that we haven’t looked at that and just played with the temperature.

From  Craig Allan : Thanks for your talk, have you looked at other bacteria?
Answer: We have just started to use cyanobacteria, which will undergo photsynthesis. We are also looking at bacteria found in soils.

From  Jordan Petkov : More of a comment than question, but osmotic pressure measurements would have given water permeability and not that of the fluorescent molecule, i.e. you might have had the right permeability at lower level of halloyside.
Answer: Thanks. Yes, we are measuring the permeability of the fluorescein (and not water). I'll look into osmotic pressure measurements. That's a good idea.

From  Peter Collins : Have you looked at other minerals with different morphologies?
Answer: So far, we've only tried halloysite. But disk-like particles would probably similarly introduce porosity.

From  Bob Luigjes : If coalescing agents are not an option, did you look at / are you planning to look at latex particles with low Tg, to from films at ambient temperature?
Answer: There is some older work on biocoatings that have film-formed at room temperature. The key problem is that coalescence is quite good, which means that the cooatings are not permeable to water. "Soft" particles will continue to deform and coalesce slowly over time. By using a high-Tg polymer, we retained porosity at ROOM temperature over time.


Ander Cervellera Dominguez - The effect of particles size distribution and cross-linking agent on the leaching behaviour of anti-corrosion species for long-term active corrosion protection on AA2024-T3 alloy

Presentation - pdf
A. Cervellera-Dominguezb, X. Zhoua, Peter Visserb, S.R. Gibbonc
Corrosion and Protection Centre, School of Materials, University of Manchester, Oxford Road, Manchester, M13 9PL, UK. This email address is being protected from spambots. You need JavaScript enabled to view it.
AkzoNobel, Specialty Coatings, 2171 AJ Sassenheim, The Netherlands
AkzoNobel, Supply Chain, Research & Development, Stoneygate Lane, Felling, Gateshead, Tyne and Wear, NE10 0JY, UK

Leaching of corrosion inhibitors from organic coatings, and fast effective and irreversible corrosion inhibition are key properties for active protective coatings to provide optimal long-term corrosion protection. Previous studies suggest that leaching of the active species occurs via interconnected pathways in the coating and showed that the leaching behaviour is strongly influenced by the pigment volume concentration in coatings. However, the influence of parameters such as cross-linking agent and particles size distribution on the leach-rate is not fully understood yet.

The thorough understanding of the effect of the cross-linking agent and the particles size distribution will provide essential knowledge for the development of coatings with long-term corrosion protection. The work presented aims to correlate the release rate of active inhibitor from coatings matrix with the particles size distribution, cross-linking agent properties, moisture ingress, coating morphology, and corrosion protection.

For this purpose, model epoxy-based primers have been formulated with lithium carbonate as leachable corrosion inhibitor. Moisture ingress and corrosion properties were measured by electrochemical impedance spectroscopy (EIS). The release of lithium carbonate was monitored by ICP.


From  Jordan Petkov : Have you replenished your solution upon taking 2 ml aliquots in the Lithium leaching experiment?
Answer: Yes, basically what I was doing was that I was removing 2 ml aliquots and putting 2 ml more. I actually did the calculation as I was using 250 ml beakers, adding 2 ml or removing it doesn’t change significantly the total concentration.

From  Emma Michailidou : If I understood correctly you investigate lithium salts within a primer. Have you looked into possible diffusion of lithium salts towards a topcoat and how would that affect the corrosion performance of the overall coating?
Answer: So I didn’t look at systems with topcoat. There is some literature in it and what is observed and what I would expect is that adding a topcoat will create a barrier between the primer and the environment and that could lead to blistering because of the difference in concentration and that would decrease the corrosion protection because we would not allow the lithium ions diffuse into the defect.

From  Simon Gibbon : Interesting decrease in leaching with particle size with Li makes sense if connectivity has changed.  How do you measure particle size of multiple different particles in coating?
From  Reza Emad : Thank you very much for nice presentation. How did you reduce the particle size distribution? What was the range? Do you know the hydrated size of Li, Ba and Mg?
Answer: I don’t know the hydrated sizes. I know that lithium has two hydration layers, so the size can be quite large. I just control the PSD by grinding times. The size is up to 10 microns. See slide 11 to see the information. That is the total particles, not just the lithium, because we grind the base paint. Now we are looking into grinding them individually. If you decrease the connectivity you have less leaching. All the particles seem to be decreasing the size based on the images (slide 12)

From  Bob Luigjes : Concerning the cross-linking agent – did you also look at the performance with the variation in cross-linker in resin systems only (without Lithium inhibitor) and the effect on the barrier properties?
Answer: No, I always looked at inhibitor because I was looking at the leaching.

From  A Legrix : Have you tried other minerals (eg platey) that may improve corrosion resistance, eg. wollastonite or talc?
Answer: No, the project focused on understanding leaching and not the corrosion protection, I tried lithium carbonate, but also lithium phosphate and lithium oxalate to see how the solubility affects the leaching.

From  Jordan Petkov : Do you go above the glass transition temperature of PVC? during grinding.
Answer: the system does get hotter during grinding. The more we grind the lower the PVC of the coating. Larger particles induces defects like cracks and pits, and changes the properties of the system.

From  Peter Collins : How did the different anions you tried effect the solubility and hence corrosion protection?
Answer: for lithium we see that lithium phosphate has a very low solubility and leaches too slowly to provide corrosion, lithium oxalate leaches too fast, so it produces blistering and depletion. So what we have is a sweet spot in the middle that may not be lithium carbonate, between the solubility and corrosion protection properties that we need to find.

From  Dr Tolutope Siyanbola : Adhesion is an important coating property, did you use any other polyol system aside from bisphenol A.
Answer: I looked at different bisphenol A and Bisphenol F based systems, and saw that adhesion was very similar. However, leaching of Li increased with the functionality of the binder system.


Eugenio Bonetti - A Cellular Automata model for the release of corrosion inhibitors from primer coatings

Presentation - pdf

Eugenio Bonetti a, Flor R. Siperstein a, Peter Visser d, Simon Gibbon c
Department of Chemical Engineering and Analytical Science, The University of Manchester, Manchester, UK

b AkzoNobel, Sassenheim, The Netherlands
c AkzoNobel, Felling, UK

Primer coatings are commonly employed to provide active corrosion protection through the release of corrosion inhibitors upon exposure to moisture. Experimental studies have highlighted the key role of the microstructure of the coatings in the process of leaching, as the pigment particles form a network of clusters that provides the pathway for the transport and release of the active species. However, a clear relationship between the characteristics of the microstructure and the observed leaching behaviour has not been established. Understanding and controlling this relationship will lead to the possibility to design better coatings with improved protection performance.

For this purpose, the aim of this work is the development of a model to investigate the relationship between microstructure of coatings and release of corrosion inhibitors. The modelling approach consists of an algorithm to generate virtual coatings with specific formulation parameters and a method based on a Cellular Automata model to simulate the dissolution and transport of inhibitors. The results of simulations show the changes in the release of inhibitors which result from changes in the microstructure of the coating. This proves that modelling and simulation techniques can be valid tools to assist the research and help improving the understanding of the effect of the formulation on the protection properties of organic coatings.


From  Simon Gibbon : Could you speculate on what is missing in the model?
From  Philip Gill : What do you think is the main understanding missing from them model?
Answer: I think as I said, the characterisation of the microstructure is quite important. This work is based on the reconstruction of a pixel generation of the material. It is not based on tomographic data of a coating to be used directly as input of the simulation. One thing that is missing is the validation of the microstructure. It is necessary to be sure that the virtually generated microstructure reproduces the main features of the real microstructure. Also regarding the process of release it is important to better understand the parameters of the real process. For example, it is considered that the fillers are inert and do not play any role in the leaching and corrosion protection, but recent work has shown that fillers actually dissolve and leach out of the coating which means that they are not as inert as they thought to be. It is important to better identify the processes that occur during the leaching.

 From  Stefan Bon : How does the geometry (aspect ratio e.g.)of the particles influence the percolation threshold?
Answer: the particle shape is another parameter that affects the structure and the arrangement. I noticed that in this work I used a random shape particles that is the shape of the pigments in the coatings formulation we considered. For example, strontium chromate has more elongated shape, like needle and this result in decrease in the percolation threshold, and the formation of a large cluster forms at low PVC than in the formulations we considered.

From  Beatriz Rocha De Moraes : What type of pigment did you study? can they affect in the analyzes performed?
Answer: I based the work on lithium carbonate, magnesium oxide, barium sulphate, and titanium dioxide, it is mainly the same formulation that Ander presented.

From  Koray Yıldırım :  I have a question regarding the simulation principle, is the only leaching interface where the electrolye is in touch with the inhibitor salts? was the transport through polymeric media considered in this model?
Answer: No, I didn’t considered the transport in the polymer phase. The presence of the ions was not detected in the polymer during experiments. Possible some degree of transport happens, but the transport through the polymer is negligible for the overall release. The mechanism that provides the most release is through the cavity. It is possible that some transport occurs through the polymer but it is not the main mechanism.

From  Simon Gibbon : WRT Eugenio/Ander computationally you know PSD / shape / etc., experimentally very difficult to measure - this limits our abilities to predict / control properties - how do we move this forward?  Is the issue of particle characterisation similar in other formulated products?
Answer: Quantitative data for validation is not available, but you need something from the real system to show that the model does represent the real coating. The model does not have interaction between particles, it can be included but the complexity of the model will increase, but then the requirement of parameters as input may increase, as you would need to quantify these interactions.

From  Anabelle Legrix : Many thanks Eugenio, very interesting modelling work with great insight into the leaching mechanism and the effect of particle size/packing etc. Modelling of packing depending on size and shape is indeed difficult with broad psd and various shapes.

From Simon: Does anybody knows from other formulations have similar challenges where knowing what happens of particles in liquids allow you to model what happens in the formulation? It seems that particle dispersion and what happens in the fluid stage is important, where characterisation is a limitation. It seems that we can model more than what we can characterise.
Answer: we can introduce into the model a lot more complexity.
From  Philip Gill : Simon - Yes for novel mixing methods (solids in polymers/liquids) such as resonant acoustic mixing, we are really limited on what we can measure.  So modelling of particle distribution/mixing is key for the future.


Dr Stephen Edmondson - The Henry Royce Institute Sustainability Hub and Coatings
Department of Materials, The University of Manchester, Manchester, UK

Presentation - pdf

The Henry Royce Institute for advanced materials research and innovation has been awarded £5M from the European Regional Development Fund to launch a £10M Sustainable Materials Innovation Hub (SMIH) for Greater Manchester.  Plastic waste is forecast to reach 40 billion tons per year globally and is increasingly associated with major world cities. Urgent action is needed to find sustainable solutions to making, using and disposing of plastics.

The SMIH will bring together material science expertise and business intelligence to offer a defined workflow of ‘Advice’, ‘Assess’ and ‘Innovate’, the SMIH will help businesses to understand where they can make efficiencies, realise opportunities and avoid unintended consequences in their plastics management.

This talk will specifically describe who SMIH will impact on the development of new coating materials.

Website: https://www.royce.ac.uk/smi-hub/
Latest Royce promotional video: https://www.youtube.com/watch?v=q_agKY6JJYg