Recorded March 15th, 2012
Presented by RTP Company
Can thermoplastic compounds be used in applications that experience wear at demanding temperature, speed, and loading conditions?
Sam Pederson, product development engineer for wear resistant products at custom compounder RTP Company, will go beyond the basics of wear and friction and focus on materials that are engineered to push the limits to which thermoplastic compounds can be used in “Ultra” wear resistant applications. RTP Company’s webinar will examine test results of wear resistant properties for high temperature thermoplastic compounds, such as PEEK, PPS, and PPA, against Rulon®, Torlon®, and Vespel® at ‘ultra wear’ conditions of elevated temperature and higher PV loadings than these plastics have been typically been tested at. (Related Webinar: Wear Resistant Compounds )
Questions and Answers
Q: When planning the tests, did RTP consider (and why didn’t they) choose equivalent resins from other providers (PEEK / PPS / PPA) instead of choosing non-melt-processable materials and materials requiring post-cure for comparison?
A: We wanted to see how traditional thermoplastic materials would compare to materials that are considered excellent, high performance materials; materials that are used where thermoplastics would not normally be considered. The main goal was to show that comparable performance results are achievable. To compare RTP compounds based on PEEK, PPS, and PPA with other supplier compounds would mainly be formulation dependent. Comparing similar formulations from various suppliers would generally prove similar results.
Q: How do the wear resistant (ultra) materials perform for coefficient of friction? They do not always appear to be the same (since low friction does not mean it is wear resistant).
A: This is true in that low friction doesn’t always mean low wear. Overall, dynamic coefficient of friction (COF) values for these materials maintained good ranges, until the samples were about to fail and then they would have a temperature and/or friction runaway (meaning the values will rise rapidly and cause part failure). Please feel free to contact Tom Schell at tschell@rtpcompany.com to examine specific test results.
Q: Are these materials available for testing or fabrication of test parts?
A: Yes, the RTP Compounds listed in this webinar are available for sampling. Please contact us at 800-433-4787 to speak with your local sales engineer to discuss pricing, sampling, and general assistance.
Q: Is there a relationship between fiber orientation and wear resistance in melt processable compounds?
A: Generally not really. A few things about fibers can influence the wear resistance. If the part design (geometry, wall thickness, gate location, etc…) causes a concentrated amount of fibers or increased amount of fibers with the ends pointed towards the wear surface, wear rate can increase.
Q: Do you intend to expand your project to include comparison of UV/Chemical resistance?
A: UV and chemical resistance is mainly dictated by the base resin of the compound. Please see our website for more information or contact us directly.
Q: How would you test a product for a slurry application?
A: With this test you can submerse the wear system in a slurry solution to try to replicate the application. However, we would try to send the test to a lab that has a setup to keep the slurry circulating.
Q: Are there any example applications that you can share where these RTP materials have replaced other materials that you have tested?
A: There are a few bushing and bearing applications were one of our PEEK products has replaced thermosetting materials. This type of application exhibits very high loads, but low speeds and is a good fit for the 10/10/10 type product described in the webinar.
Q: In your testing did you characterize wear particles and investigated wear pattern via SEM or other methods?
A: No, the tests presented in this webinar we have not used SEM or similar analysis methods. However, we have used resources like SEM imaging for various research projects while working with customers.
Q: The RTP products are melt processable and no curing needed. Could you give an example, how could we apply your compound as a coating for our wire products?
A: One example is if a profile extrusion process is being used then we can formulate our compounds to have low melt flow, which is more ideal.
Q: Is the test machine is developed by you or externally?
A: We have 6 ASTM D3702 wear testing machines at our headquarters in Winona, MN. These are machines that we purchased to ensure they conform to the standard.
Q: You are offering the additives mixed with compound, or additives separately to add into customer’s compounds?
A: Majority of our products are compounds, thermoplastics with the additives and ready to process. Additionally, we offer masterbatch products that contain a concentrated amount of additives that can be dry blended with resins “at the press”. These can be wear additives, stabilizers, VLF, and especially color.
Q: Is the specimen for wearing test is limited to disc-like shape as I am afraid this standard wearing test is not a good mimic of our application, our product is wire/ wire ropes?
A: No, there are a few other geometry configurations that can be used. All of our test results use the disc unless specified. We can certainly work with you to find a test that would best represent your application.
Q: Is the ASTMD test always carried out dry?
A: We test in dry conditions since this highlights the advantage of internally lubricated thermoplastics. External lubricants can attract dust and foreign objects that can increase the wear rate of a material. However, we perform some tests in the presence of lubricants or submersed in water.
Q: Do you intend to test any of the injection moldable grades of the VESPEL polymers?
A: Initial material selection was based off of some of the most common high performance materials. At this time we have not considered it, but we are continually growing our data and can consider this type of material for the future.
Q: Do you have data on class VI materials for medical devices with any of these compounds
A: The compounds used would not have USP Class VI ingredients. High temperature and performance resins and wear additives limit the selection of USP Class VI ingredients.
Q: Need alts to both Vespels 21 and 211
A: Please contact Tom Schell at tschell@rtpcompany.com to discuss in detail…Thanks
Q: Can you help with extrusion grades
A: Yes, as we formulate our compounds we can use resins that have a low melt flow that would be more ideal for a profile extrusion process.
Q: What kind and amount of noise or acoustic emissions were noticed during testing of these materials?
A: It all depends on the material tested and also at the condition, but some of the glass filled products can produce a very loud squeaking or chirping sound. Finding the right combination of wear and friction reducing additives with softer fibers like carbon or aramid fibers can help reduce or eliminate this.
Q: Does long fiber carbon additives produce less abrasion on the steel plate than short fiber carbon?
A: We have not tested long carbon fiber products to much extent at this time.
Q: Can a similar test be performed for friction performance
A: The machines we use to test for wear also provide a dynamic coefficient of friction values. Also, we have a ASTM D1894 apparatus that can obtain static and dynamic COF values.
Q: The concept of PV implies that P and V are interchangeable. e.g. 50 psi x 100 fpm = 100 psi x 50 fpm. Was this premise verified?
A: This is a great question that we go into more depth in our general wear resistance webinar. Basically, having the same PV values does not mean the wear resistance will be the same at the different speeds/loads. Some additives, like silicone, will work really well if there is a low load/high speed condition, but if you take the same PV and flip it to a high load, low speed it will not work as well. This is why we test the ultra materials at 10,000, 25,000 and 50,000 PV at two different speeds to expand our data to capture a better picture of the material performance.
Q: What material family would be good for gasoline/diesel/ethanol (fuels)
A: EtherKetones such as PEEK, PEK, or PEKK have excellent chemical resistance against hydrocarbons. PPA also has good chemical resistance and is also a high temperature resin. To find out more check out our chemical resistance data.
Q: Have you ever considered testing phenolics such as Vyncolite
A: Initial material selection was based off of some of the most common high performance materials. At this time we have not considered it, but we are continually growing our data and can consider this type of material for the future.
Q: Are these high PV tests all done for 100 hours?
A: Answered through email
Q: Do you have any materials available with infused lubrication for cam/follower applications?
A: To pick the best compound for an application we like to look at as many factors and variables as possible that may influence the performance of a material. We would be glad to help you select the best compound for your application and provide assistance with wear resistance, structural properties, and even assist with mold design with our CAE experts. So depending on your conditions we can have a solution in PP to PEEK.
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