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Abrasion Resistance in Epoxy

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    Abrasion Resistance in Epoxy

    I started a new test last night to determine if I can add some extra abrasion resistance to the outside of a hull. Most of the rivers I paddle are shallow and sandy or shallow and rocky, and it's tough to bear the scratches from every single trip in my boats. Running aground is guaranteed several times every trip. I already use s-glass on the outer layer of my hulls but it still shows scratches in the epoxy even if it doesn't cut into the glass. On the boat I'm building now I laminated several strands of polyester rope onto the hull to act as rub strips, but I want something that can take abuse and not effect the hydrodynamics. So, I just received three jars of powder to mix into the epoxy fill coats to hopefully improve the abrasion resistance. The compounds I have are aluminum oxide and silicon carbide. These are sold as abrasive grit typically used for sandblasting. I have the aluminum oxide in 600 and 1200 grit and the silicon carbide in 1200 grit. They have the texture of talc powder. Both of the materials are extremely hard. 9-9.5 on the mohs scale. For reference diamond is 10. Last night I mixed epoxy and mixed differing amounts of each powder in to get a feel for the consistency. I mixed 5, 10, and 20% powder to epoxy by volume. I actually did it by weight, but the volumetric amount makes much rounder numbers. After mixing and observing viscosity I poured the epoxy concoctions into Petri plates, so I will have pucks to do scratch tests on. Observations so far, the epoxy is definitely thickened by adding the powder, but not like adding cabosil. I think I will use system three clear coat if I actually put this on a canoe, so the thickening will be negated by the already low viscosity epoxy. Even with standard epoxy at 20% powder the mix is still nicely flowable, but certainly not like straight epoxy. I thought the aluminum oxide would be the one I would actually use on a boat because it is white. It is actually more dense than the silicon carbide but not as hard. When it's mixed in the epoxy becomes a light grey. It is still a pleasing color but not the pure white I was hoping for. The silicon carbide I got is light green, most offerings are black. When mixed in the epoxy it becomes a pale olive drab which actually looks much better than I expected. Once the pucks are all set up I'll go about scratching them with various implements; screw drivers, rocks, sand, etc, so we'll see if it's actually worth adding. After my base scratch tests I'll actually lay up some fiberglass tape and use the abrasive powders in the fill coat. I think I'll have to put on a final fill coat of straight epoxy, because once this stuff hardens it should be nearly impossible to sand, the material is harder than sandpaper. Without the final coat of straight epoxy I'm afraid I'd never be able to fair the boat. I'll report back after my scratch tests on the pucks and when I do the same to the glass laminates. This will all be an ecomic balancing act since the powders are denser than epoxy and add extra weight to the layup. I have to find the balance between abrasion resistance and weight. It might turn out that an extra layer of s-glass works out better.
    Last edited by Muskrat; 04-24-2015, 10:18 PM. Reason: Edit to add better photos

    #2
    Muskrat,
    I live and breathe in the field of tribology...(miti.cc)
    We are the recognized world leader in our technology.
    Countless dollars have produced studies that delve into the fundamentals of friction, wear and lubrication. Through the years, I have read most of these studies.
    If all you are looking for is abrasion resistance, there is still no better material than Dynel fiber.
    No, you won't like the look, and it will soak up resin like an old sweatshirt.
    If you can find a way to include some Dynel into your layups that doesn't irritate you too much, you will have superior abrasion resistance.

    See stripperguy's photos

    Comment


      #3
      Stripprguy,

      Sure dynel will add better abrasion resistance, but I don't really want to put on an extra 5.5 oz layer of fabric and all the resin that entails. Having said that I'll order some and add it to my testing. I know nothing comes for free. Adding the powders to the fill coats adds a weight penalty I'm more comfortable with, with no real extra work.

      I'm a scientist too, I don't want to portray this as some wonder powder that is bomb proof. I will weigh the results of the test and make an objective decision that best suits my criteria for weight added and abrasive resistance. If that rules out the abrasive powders I won't use them.

      You don't happen to have a sclerometer in that lab of yours? I was planning on dragging weighted test blocks of coated glass laminated to 2x4s across a river rock bed in my back yard.

      While we're at it, do you have any opinion of dynel vs xynole?

      Comment


        #4
        Muskrat. What about graphite powder in epoxy, seems like many people swear by it as great for durability.

        Comment


          #5
          Sclerometer?? No, we would perform standard Taber tests for the type of wear we're discussing. I've seen comparisons of Dynel, xynole, vectra and nylon layups, specifically for use in boat building. I've never personally used xynole. IIRC, Dynel was tops in abrasion resistance, followed by nylon or vectra, with xynole a close third.
          I know well the down sides of using Dynel...I never looked to see if the same material was available in anything other than the 5.5 oz sponge.

          If you're creating a new epoxy/powder matrix, did you also include some tungsten carbide powder?

          I like wysedav's suggestion of graphite mixed in, or maybe some tungsten disulfide. The TiO2(less $$ and lower density than tungsten carbide) can release particles as the epoxy is abraded and created some third body lubrication for you, not much, but maybe enough to reduce those scratches. Any of these schemes will be compromised by the steady wash from the environment. So, the powder lubricated hull would work better in dry conditions, like dragging over the desert sands...
          See stripperguy's photos

          Comment


            #6
            Great experiment Muskrat !
            Looking forward to your results !

            Years ago I started using Graphite powder mixed with epoxy, at the time, I was using System Three's products, Clear Coat.

            The mix ratio I used was by volume, 3 parts mixed epoxy, to 1 part powdered graphite.

            It works great, and I still have canoes with it on. The only real drawback is the color !
            A good friend, left a canoe coated with this mix of graphite and epoxy, upside down in the Sun one Summer. It bubbled big time !
            When I applied the graphite mix. I wet out the cloth with Clear coat, and used the graphite mix as a fill coat. It adhered good, because the texture of the cloth was still there to give it something to cling to.

            It will wear in time, but a lot better than just epoxy and varnish .

            Jim
            Keep your paddle wet, and your seat dry !

            Comment


              #7
              How about PTFE (teflon) powder? We put it in the paint on the aircraft I work on in areas that are designed to rub on each other. Not actually sure if it would help in this case but just thought I'd put it out there.
              My Youtube Channel

              Comment


                #8
                You know, there is a flouropolymer coating you could use, Emralon 333, from Acheson Colloids.
                It's has a polyimide amide binder and a cure schedule that could work for a canoe by using some heat lamps.
                The adhesion is great and coefficient of friction approaches that of Teflon.
                See stripperguy's photos

                Comment


                  #9
                  Wow. That's a lot of new options to test. So far I haven't been thinking much on the additives that increase lubrication. I'm a little skeptical of those claims, but who am I to say otherwise since I haven't actually tested it. I was only thinking of increasing the abrasion resistance. I also don't like the graphite for the reasons Jim mentioned pertaining to the heat absorption. If I can avoid dark colors I will. That's the reason I didn't order any tungston carbide. I'm hoping the aluminum oxide works well because I will still be able to add pigment without much trouble.

                  That emralon flouropolymer looks promising. Could it be used to fill the weave? I'll have to look into it more.

                  Stripperguy, can you direct me to the ASTM method you use for taber tests. I'd like to look over it and try to replicate it as much as possible in my home tests. My planned methods leave a lot to be desired when it comes to repeatability and quantitative measurements. Depending on the costs I might even send samples out to a lab after I gather some basic data and narrow down my treatments.

                  Comment


                    #10
                    ASTM D4060 would be the standard you would want for your situation...

                    We have an entirely different set of parameters in our work. Our testing involves measuring the static and dynamics coefficients of friction of our proprietary(and much sought) solid lubricant coatings applied to a representative compliant surface as the compliant element develops hydrodynamic film with increasing journal(or disk) velocity. Our bearings, much the same as an airfoil, develop film and achieve lift off with adequate surface velocity. This lift off speed, and ultimately, the load capacity is dependent upon load, lube coating, counter surface material and surface finish, compliant element config, fluid viscosity and density.
                    For most of our customers, the bearing life is the main hurdle to accepting foil bearing technology. Bearing life is closely linked to start/stop performance as the bearing (or more accurately, shaft) lifts off and touches down. Hence the need for specialized tribometers to evaluate bearing performance and life. We recently completed 300,000 start/stops on a few different bearing(thrust, in this case) designs. These specialized tribometers must be capable, in some cases, of repeatable and reliable accelerations to 500,000 rpm, of course while measuring friction force and power loss. As a point of reference, there is no practical limit to the speeds attainable on foil bearings, other than turbine aero performance and shaft material properties.

                    Sorry to go so far in, but I am pretty wrapped up in the realm, having spent the last 30 years advancing the technology to the point where it may finally be universally accepted. It's a tough nut to crack, something I call "industrial inertia". I do truly believe that once foil bearings are accepted by high speed machine designers everywhere, foil bearing technology will force a whole new wave of material development, much the same as turbine engine advancements forced the development of superalloys like Rene 41, Inco 718 and X750.

                    But all of this has nothing to do with making your boat less abrasion prone...or does it?
                    See stripperguy's photos

                    Comment


                      #11
                      No worries about the long description. I've already looked up foil bearings when you posted about it on another thread possibly another forum long ago. Thanks for the ASTM reference. I looked into those taber machines already. We'll see how close I can replicate my test without the fancy spinning dual bench grinder contraption.

                      Edit and side note: I posted my revised solo guideboat design over at boatdesign.net in the Designing a Fast Rowboat thread for anyone that is interested. Its a 127 page long thread. You cant miss it.
                      Last edited by Muskrat; 04-27-2015, 11:01 PM.

                      Comment


                        #12
                        Muskrat,

                        I'll take a look...as I've mentioned before, I'm really intrigued with the idea of a SOF guideboat.
                        Good luck with your abrasion tests.
                        See stripperguy's photos

                        Comment


                          #13
                          You guys are like the mad scientists of boat building. I love it.
                          I love the fact that there are people like yourselves that will test and try new materials to help all of us out.
                          I am no scientist but certainly like to learn about ways to protect my newly crafted canoe. Afterall, I am the one who will use and maintain it year after year for my kids and theirs too.
                          Thanks guys

                          Comment


                            #14
                            I finally got to piddle with my epoxy pucks today. I just scratched at them with rocks and knives and a piece of scrap steel. So far it doesn't look too promising. They all seem to scratch as easily as the pure epoxy puck. Also, the abrasive additives seem to offer slightly more resistance to the objects I'm dragging across them. One interesting thing I noticed which gives me some promise for further testing, I was scratching with a cheap knife, cutting in fairly deeply, and the scratches were black instead of white. I threw the puck under my microscope and sure enough there were metal shavings. The epoxy compound was abrading the steel. Instead of lightly scratching I'm going to start cutting in as hard as I can to look for differences.

                            Comment


                              #15
                              Any new revelations ?

                              If I was planning on dragging my canoes down the cement road, I'd definitely go back to graphite.

                              That would be a good real world test ! If you could get a donor canoe to drag ?

                              Jim
                              Last edited by Jim Dodd; 07-11-2015, 08:33 AM.
                              Keep your paddle wet, and your seat dry !

                              Comment

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