Workshop (STFI): Understanding the surface properties of fibres and their use in composites by iGC

Thank you to you to Service Measurement System for the possibility to join the workshop as a co organization. First of all, I want to give you a short presentation about the institute and of the Department for Lightweight Engineering and Surface Functionalization. Yeah. Our name is really long. It's Saxony Textile Research Institute, shorten stfi. We are located. We are located in Saxony, in Chemnitz especially. It's between Leipzig and Dresden, in the eastern part of Germany and the former European capital of culture. In 2025, I hope you all will visit Chemnitz. It will be, George. Really great. So what we are. We are an innovation partner and service provider for our customers. We collaborate with a lot of association institutes, small and medium sized and also big companies. We try to support them in their research activities. Yeah, and that's our field where we are working quite nice, near to the industry. Some data about the institute. We was founded in 1992 as a consolidation of two institutes of the GDR per year. We are working on about 100 or 120 national research projects. That's our main task. We are also involved in European projects. Yeah. And at the moment we are more than 153 employees. We're nearly 160. That's quite a lot. And we do tests and certification for companies worldwide. Yeah. What are our main field? Research and development. As I told you, we also do testing and certification for textile structures. Perhaps, you know, Ecotex, everybody wearing it. It's about some to detect materials and your clothing and so on. We also do testing for personal protection clothing and so on. We have our own training projects. And one big part is also the transfer of the results to the partners to get as much of effort from. From the results we generated in the research projects. Yeah, we nearly completely cover the whole textile chain. We start with fiber. We are not a fiber manufacturer. We have a lot of cooperation with fiber production industries. We can go to the yarn. We have our own spinning field. Then we go to the surface. We have weaving and knitting technologies in house. We have possibilities to functionalize the surface. That's what my colleague later will talk on. And we go to the semi finished product or the textile product in the application. And that's where we try to support the industry or the companies which we are working with. So our main competence fields are the center of lightweight construction. That's where I'm working. One main field is the carbon fiber recycling. We are working with pyrolysic or solvolithic fibers which are gained from the earlier product. We can manufacture them by non woven technologies to a new semi finished products. Another competence center is the center for non woven technologies. We can work with fibers from the fiber to the non woven. We can do extra extrusion non wovens. And one big part there is the textile recycling. Especially at the moment, the recycling of smart materials or smart textiles. What is getting much bigger now. Yeah, these non wovens, the extrusion on woven for example, are made for masks. At the moment we have a quite big plant to produce masks and or materials for masks. And that's at the moment one big topic, you know. And the other innovation center is for technical textiles. There are the technologies for weaving and knitting and also for reinforced structure, also geotextiles and so on. Smart textiles and also the department for functionalization and chemical analysis. So shot some information about the center of lightweight engineering. What we do, we do it since 2006, the recycling of carbon fibers back to composite materials. We have a non woven production line from Auteva and Nomaco in our house. We can work on a width of 1 meter. We can produce non wovens based on synthetic glass or natural fibers, depend on what the customer need. We can do blends with thermoplastic materials or other materials that's also possible. And for these non woven materials we have two technologies in house. The Airlay and the Cardig system where we can influence the fiber orientation with both technologies in some way. Yeah, that's it. We can also go to the sliver and yarn. That's a project I think two or three years ago, which gained also or wins innovation prize. It's some kind of secondary roving material which can be used in the textile chain. So we do the recycling to non wovens. And I told we go back to composite. If we do mixtures with thermoplastic fibers and carbon fibers or glass fibers and so on, on everything is possible. We have different kind of press technologies in our house. We have discontinuous compression systems like downstroke or different downstroke presses. We can do injection methods like RGM and vacuum infusion. But we also have since three years a continuous compression molding system where we can produce they called organo sheets on a continuous way. Yeah. And we do the testing of the materials. Classic composite testing like tensile test and bending test, interlaminar shear strength. But we also investigate or do the testing for the fibers or the roving materials according to fineness and tenacity and also the roughness of the fibers. Yeah, one result of a project what I show often Is what's the possessibility of the non woven materials we gained from the recycling materials or the recycling cabo fibers. We do these sheets repress them to laminate. And at the moment we are a bit above glass fabrics. And we want to increase at these levels of the properties much more to fill the gap between. Between endless glass and endless carbon fibers. Yeah. And now it's part for. Or it's time for. Mr. Siegel, I think you have to unmute your.

Okay, now it's working. So I was not able to switch me on. So the administrator has done this. Thank you very much. So my name is Frank Siegel. So I am the head of the department of functionalization and chemical analytics today more in the part of functionalization surface functionalization. And so Christopher, please make the next slide. So what we do, we are living in houses. No, it's fun. Just kidding. So normally we are working in a span of different typical questions and research and everything is. Let's say it's getting to get getting together. So of course we have a lot of material issues and also approaches and methods how to manufacture it. And that's why we have here the alignment there to work together with material and methods. And of course we have always in behind the.

Yeah.

The reason of ecology and environmental protection. If we do surface functionalization and of course we have the part of textile chemical analysis. And in the best case, if everything works well together, we have at the end a product, a running process and of course innovation. Okay, next slide. Classic textile finishing processes we have here in the. In our institute just to have a short overview. Of course it's.

Yeah.

We have mechanical thermal processes there we have thermal processes. And in our case why it's interesting here to speak about the characterization of surfaces, the chemical and physical processes. That means we do impregnations, we do spraying, we do coating, printing and laminating to functionalize textile surfaces. Next slide. Just to give you a short hint what we do with different novel methods of manufacturing. So in this case we are speaking about digital coating methods on textile. That means inkjet printing, Wolfrat printing, also spray on demand or 3D printing methods we apply and of course we are also looking for different curing methods. Not only temperature curing, also UV curing is interesting for us. And we also use different laser technologies to pre treat and also to cut textiles. Next slide. Also a big topic is for us the material characterization. That means we need or we have the need to characterize inks, fluids, pastes and of course surfaces of textiles. That's why we have the ability to do rheological measurements to see the flow behavior of pastes or fluids. We are able to measure the dynamic surface tension with a bubble pressure tensiometer. And we also have the ability to do contact angle measurements onto the textiles. Another thing is to have a look more onto the printing part of the digital printing part. We are able to do dropped characterization with inkjet printhead and a system for jet expert to characterize the droplets by size, volume, velocity, angle and so on. Okay, next. That's it. Everything is there. So that's why it's interesting for us to have a look onto other technologies to characterize surfaces. That's my point.

Yeah. Short 10 minutes. That's the range we were given.

Brilliant. Thank you. Thank you, Christopher. And thank you, Frank.

Yeah, thank you very much.

Yeah, thank you to you both. And of course any of our attendees who would like to find out more about STFI or who would like to kind of place a query with them and hear more from them, you can go to www.stfi.de or you can email them at stfi.de. so please do do that. Now moving on to our workshop presentation for the day and as discussed previously, this the title of today's workshop is Understanding the Surface Properties of Fibers and Their Use in Composites by Inverse Gas Chromatography. Our speaker for today who will be presenting on Today's topic is Dr. Sabiha Ahmed of Surface Measurement Systems. She is our application scientist for DVS and our IDC SCA instrument. Sabiha has a Master's Degree in Pharmaceutical Chemistry at the Queen Mary University of London and a PhD in chemical engineering at the Imperial College London. After gaining her PhD, she started working for Surface Measurement Systems as an application scientist on both our sorption systems and on our DVS and ITC instruments. So I will now pass over to Subia and I would like to remind everyone that we will be stopping to take questions at the end of each application discussion. So please do submit your questions as they come up throughout the presentation. Thank you.

So in today's presentation I'm going to give an overview of the inverse Gas chromatography surface Energy analyzer. So I'm going to go through what the system looks like and what it does and then I'll be going through some case studies, hopefully relating to a few materials that you have. I'm going to go through variety of different materials that we've used the IGC SCA for. And like John mentioned, after each application I will stop and hopefully if you have any questions, please do ask. So inverse gas chromatography was first developed in the 1950s. It used gas vapor probes as molecules to understand a material. In 2009, a surface measurement system developed an IGCSEA. This is a surface energy analyzer. So this was specifically designed to determine surface energy heterogeneity. And also because of this interlated properties, we can also understand things like absorption, isotherms, heat absorption, and so on. So compared to the typical analytical gas chromatography, you usually have a mixture of gas molecules injected into a known column. And upon the separation and interaction between the column material and the gas molecules, what you would have is a separation of these probes. And as a result, each probe will elute out and you'll obtain a different retention time. However, in our case, in inverse gas chromatography, we're actually packing the column with the sample of interest. That's your sample material. And then we will inject a few known probes. We typically will inject a few alkanes and a few non polar probes and a few polar probes as well. And upon the interaction between your sample and these probe molecules, we would then obtain different peaks based on different retention times. We can go ahead and analyze these peaks. This is what the typical IGC SCA system looks like. It has two drawers on either side and a door in the middle. And each drawer opens up to accommodate six reservoirs. This is where your solvent material will go. You have six on either side. Typically, like I mentioned, for some polyprobes and some non polyprobes, the carrier gas in the system is either helium or nitrogen. And when you open the door in the middle, you will see places to put your column. So here we have two column positions, so 1 and 2. And this is surrounded by a column oven. And the column oven can go from 20 degrees to 150 degrees. We're also able to understand the effect of humidity on your samples. So in this case we have a background humidity controller. If this was the case that you wanted to understand this parameter, then we would change one of our solvents in the drawers to water. We use an fid, which is a flame ionization detector, and this accurately measures the concentration of organic material. We also have at the panel at the front, a few safety features. So the FID needs hydrogen to ignite the fid. So we have safety features for that. And we also have an organic vapor leak detector too. And here at the bottom, we've got a few examples of materials that we can analyze using the igcse, we have carbon fibre, cotton, hair granules, powders and medical implants. And effectively, if we can fit them into a column, we can happily run them in our system. So this is what a typical igcsea column looks like. It's relatively straightforward to pack compared to the standard GC column. We have cyanized glass tubes and what you would firstly do is insert some cylinized glass wall. You would then funnel in your material of interest and then close off with some more silanized glass. This just ensures that no material is going into the system during the experiment. We also have a nice YouTube clip to kind of show how simple and straightforward itchy pack column. So our columns come in different sizes. So we have 2 millimeter, 3 millimeter, 4 millimeter and 10 millimeter. Our 2 millimeter column is used for very fine particles. Slightly bigger powders, we would use 3 millimeter columns. And the 4 millimeter columns is typically used for fibrous materials. The 10 millimeter column you would use for materials that you are quite larger materials, let's say a tablet or a block of wood that you wouldn't wish to break up, we can place it into a 10 millimetre column. And if you were to go for this, then we would just need to accommodate for a slightly larger column oven. Alternatively, if you have some material, some quite viscous material, what we can then go ahead and do is prepare into the column in a different way. So for more kind of liquid materials, what you would first do is put some cylinized beads. So you would take your sample outside of the column and you will coat your sample with the silanese glass beads. Then you would place into your column. So just ensuring that all the beads are kind of evenly distributed with your sample material and again plugging in with some sidonised glassware at the bottom and at the top, just to ensure that none of the material would go into the system. And in this case, because of the liquid nature of the sample, is best to run experiments at room temperature just to ensure that there's no leakage of the column. So typically for an IGCsent, the first thing you would do is pack the column of the sample of interest. We would then go to the IGCSE system and choose some probe molecules. So we choose a few non polar solvents and this will give rise to the dispersive interactions and also some polar solvents, and this will give rise to the specific interactions. And using the software, we would then choose how to inject these probe molecules. So we can inject them in very small concentrations, infinite dilution or larger concentrations, then start the experiment. And depending on the interaction between the probe molecule and your sample, we would obtain different retention times. We can analyze these retention times and understand the physical chemical properties. So there's a variety of different probes we can use in the igcse. So here is a few standards that come with the system. So we can see a variety of both polar probes and non polar probes. But if you did want to add your own solvent in there, something that you would particularly want to do the interaction of, then it's pretty straightforward to calibrate onto the system. You would need a few essential properties known for the probe molecule, and you can then calibrate onto the system. So the system comes with two different softwares. You have a control software which is directly linked to the IGCSEA system. And this is where you would do your method development and start your experiments. We also have an advanced, sorry, an analysis software. And this is where after the experiment is finished, you would then analyze the raw data and then you can understand the different properties of your sample. And we can analyze based on these properties here. So to analyze the data is relatively quite straightforward. You would first have a panel here which is basically telling you the solvents that you've injected and the concentrations that you've injected it at. We also do some methane injections prior to and at the end of each experiment to calculate dead volume. So in relation to this, you will obtain a peak based on different retention times based on the different probe molecules. And simply what you would do is select the beginning and the end of the peak and click calculate. And what this does is it automatically calculates these parameters here. You can also export some raw data. So if you wish to kind of go back and do some calculations yourself, that's also possible as well. IDCSCA has excellent reliability and reproducibility of our experiments. This is just showing a quick example here of paracetamol. And we have done a bet experiment in this case, and we've done 10 consecutive runs and we calculated mean value. And as you can see, we have excellent reproducibility and reliability of the results. We also have excellent reproducibility in terms of instrument to instrument. So if you're using two different instruments with the same sample, we have excellent reproducibility between those two systems. Also from experiment to experiment and column to column. So if you wish to pack completely two same sample, two different columns, we also have excellent reproducibility in that aspect too. So there's a few benefits of using the igcsea. First is the two column position. And this can offer two different samples to be measured sequentially. So one after another there's no need for any outgassing facilities. So in the case where you have it's necessary to do some column conditioning, we can actually offer a column conditioning prior to any experiments in the system. We have a relatively quite straightforward packing procedure. And also because we are injecting in the vapour phase and not the liquid phase, we are able to accurately and precisely measure the exact concentrations of what's being injected. Our injections are all automatic and like I showed you that we have excellent reproducibility throughout our experiments. So there's a few different properties that can be measured by igcsea. The most common is the surface energy. Because we are also introducing polio probes, we can also understand the acid base interactions. We can also calculate the BT specific surface area of your material. We can also understand properties such as sorption, isotherms, permeability, diffusion, work of adhesion, cohesion. And because we are able to inject different concentrations of our vapour phase probe, we can obtain a heterogeneity map across the surface of our samples. We also have an additional feature, and this is called a film cell. And for the film cell it analyzes more planar materials. In this example we've got a sheet of paper here. In this case we don't necessarily want to strip up the sample and place it into the column, so, so we want to put it into a film cell. This film cell has a panel here where you place your sample. And these lines here are directly linked to the IGCSEA system. And this film cell sits beside the IGC sca. And in this case you will have a full background humidity control, but not necessarily the temperature control because it's not surrounded by and oven. So what is surface energy? So surface energy is one of the most commonly measured properties of igcsea. It's analogous to the surface tension of liquid. And you want to understand the ability of the surface to react compared to the bulk. And in this case, to measure surface energy we need two different components dispersive component, and this is the form of non polar probes. And this is to understand the long range physical interactions. We also need a Lewis acid base component. In this case, we want to understand the short range chemical interactions. So prior to doing surface energy experiments, there's a few things we need to know. First. First is the BT surface area of the sample. So in this case the IDC SCA is able to actually calculate and determine the specific BT surface area. However, if you do know the BT surface area and you've used it, calculated it using alternative techniques, then we can use that as well. We also need to know the molecular size of the probes. So in the case of the igcse we have a library of different probe molecules and what we have is their physical properties as well. So this is all stored on the database. So once we know these, these two here, what the IHC SCA does, it calculates the amount of material you need to obtain a certain coverage across the surface of your sample. This is how we carry out our experiments. Once we do this, we start the experiment and based on the interaction between the probe molecule and your material, we'll obtain different retention times and volumes which we can then go ahead and analyze. Surface energy is an interesting property because it can be related to other different types of properties. With increasing surface energy, we can also get an increase of wettability. We also get an increase of worker cohesion. This is how likely your sample material is to interact with itself. And this can lead to things like aggregation and different flow properties. Because we can inject at multiple concentrations, we can actually analyze the surface heterogeneity or homogeneity on the surface. And we can also calculate the work of adhesion. This is between two unlike materials. So if we have sample A and sample B, we could actually calculate the work of adhesion between these two samples. So like I mentioned, we can do a vet determination using our system. So with typical nitrogen absorption technique, we can calculate and determine the BT's surface area from about 1 meter squared per gram to 1400 meters squared per gram. The at Surface Measurement Systems we have two sorption instruments. One is the DVS and one is IGC. The DVS can also cover a similar range, but going just lower than 1 meter squared per gram and as high as 1,400 meters squared per gram. The IGC SCA can actually focus on a lower range, so from 0.1 meters squared per gram to 100 meters squared. And this entails materials such as drugs, excipients, minerals and fibres. The benefits of using both the IGC and the DBS system compared to the nitrogen is firstly the temperature. So with nitrogensorption technique you need a very low temperature to analyze the material. And in this case we may actually be causing some defects in our material, which is maybe given an overestimation of VT as surface area however, in our systems we can carry out these experiments room temperature or even higher temperatures, depending on how you're actually using your sample. With the nitrogen absorption technique, you're only limited to using nitrogen or even krypton. However, in the DVS and IGC we can use a range of organic vapours. The nitrogen absorption technique you need to carry out the experiment under vacuum. With the DVS and IGC we can carry out ambient pressures. In the case of the dbs, we also have a DBS vacuum which can also accommodate carrying out the experiments under vacuum as well. So before I go on to some case studies, I just wanted to ask if anyone had any questions just regarding to operation of the system. So feel free to type in your questions using the chat box, but I will be stopping here and there. So please do write your questions in the chat. Or alternatively I will be taking questions at the end as well. So just moving on. This example is looking at how we calculate the BET specific surface area. In this case we have a standard reference material, CRM170. This is an aluminium material. And in this case we have our sample of 500 milligrams. We have our temperature of experimental temperature of 30 degrees and we've preconditioned 100 degrees for six hours. In this example we use octane as our probe molecule and we've obtained the resulting isotherm here. So what we do is apply the BET equation. And when you apply the BET equation, you come up with a BET plot. So in this case what we really wanted to do is actually compare the volumetric technique compared to our chromatographic technique and see how the results vary. And in this case what we can understand is compared to the nitrogen absorption technique, which actually have very similar values. So they're very comparable with each other. Also, just another example here with CRM171. And again, we actually wanted to see how comparable it is to the volumetric technique. So like I mentioned, we can also apply relative humidity on the surface of the material. So in this case we're calculating the BET of the material and increasing relative humidity. So we start off with 0% RH and giving about 2.95 meters squared per gram. As we increase relative humidity, what we can actually see is a trend of a decrease of BT specific surface area. So what this is telling us is that as what this is telling us is that when we introduce humidity, we're actually introducing water molecules onto our surface. So when we inject our probe molecules, in this case octane, octane is actually competing for these sites. In this case, we have a limited kind of surface area of the material for octane. So as a result we have very less a lower B2 surface area as we increase relative humidity. We also have some papers comparing the volumetric technique to our chromatographic technique. And in the case of spray dried material, we've actually, they actually kind of compared the two techniques and found that because of the harsh conditions of using the volumetric technique and in this case using kryptonite, you're actually causing more damage to the material at these conditions. And when we calculate the BT surface area, we're not really getting a more representative value of how we're actually using our material. So is there any questions on calculating bet?

Hi Sabia, we haven't seen any come in yet, but just to remind the audience, you can submit these questions either through the chat window or through the questions panel on your right. So please do submit any questions you have as we go along in the presentation.

Thanks, John. Okay, so in this case I'm going to move on to different case study. So in this case we're looking at D Mannitol and we want to use IGCSEA to understand the heterogeneity of two samples. So we have the D Mannitol and we have a silanized D Mantol. So when we carry out the experiments using the igcsea, this is one of the results that we have. So this is looking at the dispersive surface energy, so focusing on our non polar probe molecules. And on the x axis we have surface coverage. So this is the injections that we've, the concentrations that we've injected our probe molecules at. So we see two different profiles here. For our cyanide zomanitol we see quite a linear profile and our untreated Imanitol we see a more curved profile. So first of all what we can see is that our standard D Manitol has a lower dispersive surface energy than our untreated Humanitol. And the curved nature, and the linear nature is actually suggesting how homogeneous or heterogeneous our surface of the material is. So what it's telling us is the more linear the profile, the more homogeneous and the more curved a profile, the more heterogeneous. And the difference is particularly in the infinite dilution region here. So injecting small concentrations. So what we're actually doing at these small concentrations, specifically in the untreated D Mannitol, you're actually accessing higher surface energy sites. So These red molecules can interact with these sites and as a result give a higher disperse of surface energy. As you increase the concentration, you actually get gradually getting a plateau out of a more stable surface energy. What we can also do is plot this in a different way. So we can take a point by point integration of the data points here and plot to obtain the the dispersive surface energy distribution. What it's telling you is the broadness and the narrower narrowness of each peak. So the more broad the peak, the more heterogeneous the surface of the sample and the more narrower the peak, the more homogeneous the material of the sample. So that was just like a brief kind of example of how to analyze what we would actually obtain from the igcsea. So we're going to go into a different case study now. So this is the surface energy heterogeneity of carbon fibers. So in this case we have carbon fibers from Hexcel. We are treating, have a few surface treatments. We have sized and unsized. And because IGC offers column conditioning, we've actually pre treated the column and the sample, one at 30 degrees and one at 120 degrees. So we wanted to use IGCSE to measure the differences in the size and unsize as well as the pre treatment conditions. So this is the results here. So we have dispersive surface energy on the Y axis and the X axis. We have surface coverage. So what we can understand here, if we see both our sized material at the bottom, we can understand that this has a lower surface energy compared to our unsized material. And what can also see that this is much more linear. This is suggesting a more homogeneous surface compared to our unsized material which is showing a more heterogeneous surface. And again, if we look at infinite dilution region, we are seeing that the unsized material has high surface energy sites which can be accessed by using a small concentration of our probe molecule. So again, taking a point by point integration, we can obtain a dispersive surface energy distribution. So again, the more wider the peak, the more heterogeneous surface sample and the more narrow a peak, the more homogeneous surface of the sample. In this case, if we have a look at the temperature differences, we can see that at 120 degrees when the sample is conditioned, that we're actually accessing actually more heterogeneous surface. What it's telling us is that at 120 degrees we're actually removing, maybe removing or making more higher surface energy sites more accessible. And at 30 degrees you don't have enough energy input into the system to actually release any of these contaminants that may kind of occlude high surface energy, high energy sites. So in this case, increasing the temperature to 120 actually will give rise to more higher energy size and which can be reflected by the IGC results here. So using these materials, we also have an oxidized material. We've also treated it oxidized with epoxy agents and we have an unoxidised and unsized material. So in this experiment we've oxidized some materials and kept a few as they are, and we want to understand.

The.

Acid base properties of this material. So because we are injecting acidic invasive components during the experiment, what we can understand is the Ka and KB of our material. And compared to the, with regards to our oxidized species, these of course have a higher KA value, which you can see here compared to our untreated material. So it gives us a good indication of whether this oxidization surface treatment has occurred and to what extent. So again, any questions at all regarding the case study so far? So I'm going to.

Oh, sorry, Savia. We have a question here from a Ramese. They ask how long does it take to run a typical experiment to get a heterogeneity plot, for example, in the case of carbon fiber study that you presented.

Okay, sure. So experimental time depends on a few things. Firstly on how many probe molecules you're using. So in this case, typically we would try to use around three or four non polar molecules. So we're looking at maybe from hexane all the way to undocane. And from this selection we can choose three molecules. And once you've chosen these molecules, we then can have the option of what concentrations we wish to inject at. So that's, typically we would want to at least reach about 20% of the surface of the material because as you can see, we do get a plateau eventually. So increasing the concentrations will only give you so much information. So in this case we can typically have probably about 10 injections for each of our polar probes, sorry, each of our non polar probes. So yeah, so we would have it depend, depends on what kind of probe molecules you choose and the amount of injections that you want. And again, it also depends on the retention time of your molecule. So typically lower alkanes will elute out quite quickly and higher alkenes will loot out a lot later. So if you're, let's say you've Injected hexane and it elutes out within six minutes. You would typically just have about six or seven minutes for your run time for each injection. So it does depend on a few different variables, all depending on what kind of probe molecules you use, the concentrations you wish to inject and the interaction between the molecule and your material. So I hope that answers your question.

I think it does. Thank you, Sevilla. That's all the questions we have for the last section. Oh wait, actually no one has just come in. Fantastic. Sorry, I just missed that. Frank Siegel asks at the plot points, only the dispersive surface energy is shown. I guess for the polar part the experiment should be done again with another process gas. Is it possible to do it directly afterwards? And what is the process?

Yes, exactly. So this, you would use it in the same experiments. If I just scroll all the way to the beginning. So here for each method you've actually shown an injection of a non polar probe at a specific concentration. So you would typically have, you would just carry on injecting your probe molecules. So after you've chosen your dispersive components and your alkanes, you would then go ahead in the same method introduce your polar components in the exact same way, so you wouldn't have to. So it's just all one experiment, you wouldn't have two separate experiments, you would just have them all in one experiment.

Okay, great, thank you. That's the last question for that previous section, so I think we can move on.

Thank you. Okay, so this example we're looking at the BET surface area of fibers. So the slide that I'm going to show, we do have a paper discussing in more detail the experimental procedures and also the results. So in this case we're looking at comparing a few different fibres. So we have cellulose fibres, biomed fiber, and this is processed by dry jet wet spinning process. We also have natural fibres. So these are two blast fibers, this is a knife fiber, a flax fiber. And here at the bottom are the SEM images for each of the fibers. So as you can see already just looking at the SEM images, we can see that our processed fibres are much more thinner, much more uniform compared to our natural fibres, which of course will have some variation and as a result a few bit of heterogeneity on the surface of the samples. So what we've done is calculated the BET specific surface area because we were interested in understanding the surface, how the beta surface area, how the heterogeneity of the fibers is affected by PET surface area. So we've carried out three runs and calculated a mean value for each of them and we have a very good standard deviation. So what we can actually understand from this is that if we look at the standard deviation of the VT of our material, we can see that our biomid and our kino fibres have similar surface areas and the flax fibers have a more higher surface area. We can also see how standard deviation varies. So we can see that for our process five, we have very small standard deviation and we have a relatively high standard deviation for our KNAP and our flux fibres. And this really correlates to the variation of our natural fibers because of course they're not processed and therefore will have some variation on the surface of the samples. And this is directly related to the surface roughness of the fibres. We've also carried out a batch to batch variability of our material. So we've actually done column two column experiments and calculated the BT specific surface areas. What we can see is that our biomid processed fibres have very small standard deviations and our natural fibres have larger deviation. And this again relates to sampling of the natural fibres and the surface heterogeneity and the roughness of the material. And this is due to the irregularities on the surface of the material. We've also carried out some surface energy experiments and what we want to understand, have a look at is the surface heterogeneity. So this is showing you the dispersive and the specific interactions of the material and showing you the distributions. So the two natural fibres, if we have a look at the specific surface energy, our two natural fibers have a very narrow peak width compared to our. Sorry, our natural fibres have a wider heat width than our processed fibres. So this is showing you that there is more right variation of heterogeneity across these fibres. Again similarly with the dispersive component as well. So the next case study is looking at the influence of leaching and in this example we're looking at hair samples. So we've got some hair samples which were treated differently. So one is the untreated hair sample, one is using bleach for 60 minutes, one having a UV treated sample for 74 hours and pre treatment was made for 5 hours. So we've carried out the experiments at 0% RH and 303 Kelvin. So the experiments that we carried out, the alkanes we used were from tridocane to heptodecane. What we could understand is firstly, by looking at the dispersive surface energy, we can see that our untreated has a lower dispersive surface energy compared to our treated samples. This is already suggesting some differences in heterogeneity on the surface of our samples. And our untreated sample is more homogeneous. What we've also done is injected a few specific probe molecules. So we've injected hexanol and butyl acetate. So we choose these components based on their interactions between the hair samples. So we've injected them and seen how they interact with the hair samples and as a result we've got the surf synergies here, sorry, the free energy here. So what we can see that first of all, with regards to the butyl acetate, all three of our samples interacted most strongly with butyl acetate compared to our hexenol. This is suggesting to us that there are some functional groups on the surface of these materials that you have a higher affinity for butyl acetate compared with hexanol. So the surface treatment has actually caused some functional groups to be exposed and therefore can interact with butyl acetate. So the next case study we're looking at is the evaluation of protein hydration. So in this case we have some materials, polypropylene, and we've treated the polypropylene with a protein called zine protein, which has a high hydrophobic content of amino acids. This is a relative humidity study. We preconditioned for two hours at 30 degrees and carried out the experiment at 0, 40, 50, 60, 70 and 80% relative humidity. We want to understand the effect of humidity on the differences of these two samples. So in this, these results here, we're looking at the dispersive surface energy profiles and these are the surface coverages we've obtained. So firstly, we can see that our polypropylene treated with our zine protein actually has a lower dispersive surface energy compared to our polypropylene on its own. What we can also see that at higher surface coverages, these actually become quite similar. The differences are mainly in the infinite dilution region. So what is telling us is that at this region here, when we inject at very small concentrations, we are actually accessing higher energy sites, therefore giving such a distinct curvature of the profile in regards to just polypropylene on its own. And at lower coverages, the protein incorporated on the surface of the sample actually result into a more homogeneous sample. So looking at the distribution, we can have a look at the peak width. So the peak width of our polypropylene is significantly quite wide compared to the polypropylene with the zine treated material. And this again is suggesting that the wider the peak, the more heterogeneous the surface of the sample. So in this example, this result, we're looking at the specific surface energy. So in this case, we've used our chloromethane and ethyl acetate as probe molecules and we can see that the polypropylene sample has a relatively higher specific surface energy compared to the zine protein. And again, we have the same trend where incorporating the zine protein, we're actually causing the surface to be much more homogeneous and therefore we see a narrower peak width compared to polypropylene on its own. We've also calculated the Ka and KB of the material and what we can see is that the protein incorporation doesn't significantly cause a change in the surface acidity, but it does reduce the basic properties. This is looking at the electron donating functional groups of the surface. So we then carried out the experiments using different relative humidities and calculated the polarity of the material. So if we just look at the polypropylene with zine protein incorporated, what we can see is when we increase relative humidity, actually increasing polarity up until about 70% RH, where we actually falls off when we go up to 80% RH. And this can be correlated to maybe the functional groups on the surface of the sample. And looking at just the polypropylene on its own, we have an increase polarity up until about 50% RH, where this then drops off and then we have a bit of variation when we increase humidity. Further, we've also calculated the surface energy of the material. So we have specific dispersive and total surface energy for polypropylene and the polypropylene zine sample. So what we can see is looking at 0% RH, we can see they look quite similar. We can see that the polypropylene sample doesn't really show much of a change with regards to the specific surface energy upon the increase of relative humidity. What we can also see is that the dispersive surface energy increases gradually with increasing relative RH. If we look at the PPZ, we have more of a variation. So compared to 0% RH and we increase relative humidity, we're actually seeing a drop in dispersive surface energy. So this is interesting. Just to compare the different surface engines in relation to relative humidity.

We'Ve received one here. Sabiha, it asks, all these different parameters that you showed are calculated by Your software or does the, or does the user just get the data of the initial peak?

So yes, so they are all calculated using the software, if I can. So if we go back to this slide, once you've actually calculated your data and analyzed all your peaks, you actually have a few tabs here that you can go ahead and select. And so using just the same experiment you've done, just injecting polar and non polar probes, you can actually calculate the KAKB isotherms, bt specific surface areas, work of adhesion and cohesion and surface energy. So with just this experiment, we can easily just calculate all these parameters for other properties such as heat absorption, glass transition temperature and solubility and so on. They require a different method setup. So with the ones I've shown you in my case studies, these are as a result of just one experiment, injecting a mixture of both polar probes and non polar probes at different concentrations. So the next example we're looking at is looking at a polymer matrix. So in this case we have a few different materials. We have carbon nanotubes, so we have as received carbon nanotubes and carbon nanotubes functionalized with carboxylic acids. We also have nanoclays and we have as received manatees and functionalized anaclase with isocyanate. We also have a polyurethane matrix. So we want to this is a work of adhesion studies. So to understand the dispersion and work of adhesion of materials in the polyurethane matrix. So this is a result of the total surface energy of the materials. And what we can see is different surface energies of all our materials that I've mentioned. And with higher surface energy we would have a greater work of cohesion. So what we can see is our und received nanoclay and our carbon nanotubes of carboxylic acid. Functional groups have relatively higher total surface energies. And what this is telling us is that it will have a greater work effect, cohesion and greater particle particle interactions. And this can actually result in a poor dispersion and a deeply slow transfer in our polyurethane matrix. We've also calculated the work of adhesion and cohesion for each of our materials. We've also calculated the work of adhesion and cohesion ratio. So if it's too strong or too weak, the particles we have particle particle interactions which are too strong or too weak, it can either lead to kind of segregation inside the matrix or lead to poor dispersion inside the matrix. So it's A good idea to optimize the work of adhesion and cohesion ratio to actually develop different formulations and give an idea of what is best to actually have a better dispersion in your polymer matrix. What we also see is that the work of adhesion cohesion ratio is highest for the as received carbon nanotubes and our functionalized nanoclave. So we've also actually correlated these results to some mechanical performance techniques. So looking at tensile strength, and what we can understand is that the two components with the highest work of adhesion to cohesion ratio actually have a higher tensile strength. So we've correlated the work of adhesion and cohesion with a separate technique to calculate tensile strength. And this is the results here. So it's a good way of kind of using it as a formulation technique as well to understand the material and obtain better properties of the material. So this next example we're looking at polyolefins, and these are different materials and they have low surface energies. We're looking at a few six different thermoplastic polyolefins, so TPOs with different degrees of elastomer loadings. So we've got 12% and 25%. And these are the samples here. So we've carried out our experiment at 30 degrees, 0% relative humidity and pre treatment for 30 degrees for about two hours. So we wanted to understand the material adhesion. We're looking at an adhesion study and want to understand the adhesion of our paints as a top coat on the material. So what we can see here is the dispersive surface energy of all of our samples. What we can understand by looking at this is that each of our samples, when we increase to about 25% each of our samples, we actually have a greater dispersive surface energy. And especially in the case of our 4049 sample, where increasing the last much 25% has a significant increase in dispersive surface energy. And this could as a result correlate to the higher, better work of adhesion between two materials. So in this case we've actually correlated the dispersive surface energy and to measure the work, the traction force and the measure of adhesion. So as the dispersive surface energy increases also so does the practical work of adhesion. And this can be used as a predictive tool to understand what kind of paints in this case could easily be coated on the surface of the sample. So, any questions on those two case studies?

Thank you. Thank you. Sabir. Yes, we have a few questions coming in our first asks, which probe analyte was used to determine the properties of the nanomaterials?

Okay, so the probe molecules in this case, again with the dispersive surface energy, we are looking at a series of N alkanes and this can be from around hexane to up until lidocaine, so about C6 to about C12. And typically you'd use three or four non polar probes, the exact probes. We have a case study and application note for this particular example which we can send you. And they'll have the exact probe molecules that we've used for this experiment.

Great, thank you. And another question we have here. Let me just get up so I can see they ask. You showed there is a range of surface energy values that we can acquire calculating the work of adhesion, cohesion, which value did you use?

So, work of adhesion, cohesion, we're looking at the dispersive surface energies. So in this case, again I can show you the case study for this as well. But typically you could use an average of all the injections, or alternatively you can use the highest, so the highest coverage for about 20%. And this is where the dispersive or specific surface energy plateaus out. And this is where you could use this value as well. So you can use an average of all data points or you could just stick to one. Again, could you have a case study on this as well?

Thank you, Sabia. That's all the questions we have for that last section, so I think we can continue.

Thank you. So in this example we're looking at the effect of the cleaning process on surface energy heterogeneity. So in this case we're actually using our film cell, which I showed you previously, and we're inserting our sample material in the planes of the film cell here. So the materials we're looking at are aluminium and Teflon. So we need a sample area of about, about, I think about 22 inches by 8 inches. And we want to understand the cleaning procedures and the effect of surface energy using the material. So in this case study we are looking at aluminium, bleached aluminium and aluminium treated with nitric acid. So in this case what we can see is that the aluminium treated with nitric acid has a higher dispersive surface energy compared to the aluminium. And our bleached material, which you can see are relatively quite similar to each other, which is quite interesting. Looking at the heterogeneity profiles, if we look at the peak width, we can also see that the nitric acid actually has a greater peak width compared to the other two materials. This is again suggesting a more heterogeneous surface and a more active surface. So in this case, the nitric acid actually has treated the sample in a way where it's actually exposing or causing more defects on the material and as a resulting in a more heterogeneous sample. And we can also conclude that the nitric acid is much more harsher compared to our bleached treatment. So we've also carried out the same experiments for Teflon. And what we can see here is that for our Teflon, our untreated Teflon, she has higher dispersive surface energy. And secondly, our Teflon treated with bleach has the next highest dispersive surface energy and treated nitric acid has the lowest dispersive surface energy. Looking at the dispersive surface energy distribution, what we can see is that our Teflon actually has a much more homogeneous surface correlation to a more linear line here. And our nitric acid, even though it has a lower dispersive surface energy, actually has much more defects on the surface of the sample, suggesting that it's much more rough than the amber bleached Teflon. So that was one of the last case studies I had to show you. And just to kind of summarize that the SCA is a versatile technique. It is sensitive to gas phase vapor, so vapor molecules. We can understand a range of different properties such as Bt, specific surface area, surface heterogeneity, and we can also carry out these experiments on a range and variety of different samples, from powders to fibres and to films. So I hope this has given you an insight of what the system can do. And here's just a small acknowledgement of the different organizations that we have been involved in in terms of research using the IGCSEA and who have used our systems for their research and scientific endeavors. So thank you for listening. If you have any other questions, I'm happy to answer them.

Thank you very much. Sabiha. Yes, we'll just give the audience a few few minutes to submit any questions they have in the questions panel or panel. So please, anyone who has any questions for Sabir on any part of her presentation, please submit them now. Hi Sabir, we have one question here from Ramees. Again they ask for the surface energy contact angle method also used. Can you please comment on what are the benefits of using IGC and if the results are comparable?

So using a contact angle to understand surface energy, there's a few differences. One of course, is the liquid nature of the probe molecule. So in this case, we have. Using vapor probes is much more accurate way of calculating the concentration of how much probe molecule you've used. And for calculations. And also the liquid probe molecule you actually have can cause a type of wetting on the surface of the sample, which can also affect the results. Another thing, when using contact angle, we're actually just focusing on a localised area of the surface of the material and not really getting a more representative value of surface energy. However, when you're looking at the igcsea, we're actually able to inject at different concentrations across the surface of the sample, so we'll have a much more representative value for surface energy.

Great, thank you. Frank Siegel asks for the film cell. Is it possible to apply textures too, because of possible leakages at the sides?

So with regards to the film cell, if you have a textile material that, let's say it's one side is coated with a particular modification and one side is not, we're actually focusing on this panel here. So where these lines go in, this is where your probe molecules will be injected. You want to put the surface of interest on this panel here. Closing the film cell, you do have to ensure there are O rings on either side. They have to ensure a very tight and firm closure of the film cell just to ensure no leakage. But if it is a porous material where the molecules can actually absorb through the front and the back of the material, you will only be limited to kind of you. You won't be able to have the kind of differentiation between both sides of the surface. But yes, you have to ensure that it's closed very well and that you can use leak detectors to kind of ensure before your experiment that there is no leaks during the experiment as well.