Coefficient of Friction - Vistamaxx Performance Polymer Against Glass and Stainless Steel

Transcription

1 Coefficient of Friction - Vistamaxx Performance Polymer Against Glass and Stainless Steel Technical Literature - TL34 Introduction Vistamaxx performance polymer is a unique semi-crystalline copolymer of propylene and ethylene that possesses a unique compatibility with polypropylene (PP). This document presents results for the coefficient of friction (COF) against glass and stainless steel surfaces for two Vistamaxx polymer grades and blends with polypropylene homopolymer (ExxonMobil PP534E resin) and a polypropylene random copolymer (ExxonMobil PP974MED resin) at different percentages. Five grades of Vistamaxx polymer (3, 32, 398, 62 and 622) were tested. The trends of the 3 and 6 series were similar, and only one grade from each group is reported. The test results for the unreported grades are available upon request. Overview of Grades used in this Evaluation Grade Nominal Density MFR 2 Ethylene, wt% 3 Vistamaxx Vistamaxx ExxonMobil PP534E resin ExxonMobil PP974MED resin ASTM D55, g/cm 3 2 ExxonMobil Method, g/ min (23 C/2.6 kg) 3 ExxonMobil Method Description and Test Method COF is a test frequently used to determine the relative ease with which one material slides along another. Its principle and basic test method are: Friction is typically characterized by a COF (µ) that is the ratio of the frictional resistance force (F) to the normal force (N) that presses the surfaces together (see Figure ). Load N Sliding Body Friction Force F µ = F / N Body 2 Figure : COF test description Page of 6

2 There are two forms of friction, kinetic and static. When trying to slide two objects past each other, a small amount of force will result in no motion. The force of friction is greater than the applied force. This is static friction. If more force is applied, the object "breaks free" and slides, although force still needs to be applied to keep the object sliding. This is kinetic friction. The force applied to keep the object sliding is not as much as that needed to initially break free of the static friction. Static frictional forces will increase to prevent any relative motion until a certain limit where motion occurs. It is that threshold of motion that is characterized by the coefficient of static friction. The coefficient of static friction is typically larger than the coefficient of kinetic friction. Static friction resistance will match the applied force up until the threshold of motion is reached. Once the threshold of motion is attained and the object is forced into motion, the kinetic force required to maintain constant motion remains relatively constant (see Figure 2). When two surfaces are moving with respect to one another, the frictional resistance is almost constant over a wide range of low speeds. Test Method Figure 2: Graphic description of static vs. kinetic A Thwing-Albert Model 225- Friction/Peel Tester was used to do the testing. During the test, the load cell travels from left to right pulling a COF test sled. Test data is collected, processed and displayed for both static and kinetic coefficients. Procedure. A flat stainless steel or glass support is placed on apparatus. 2. Samples cut from the center of a molded ISO plaque are placed on the flat support. 3. A 2 gram sled is placed on sample. 4. The sled that is attached to a load cell is pulled 6 inches at a speed of 6 inches per minute. 5. Readings from the load cell are recorded. 6. Five (5) samples are tested. Page 2 of 6

3 Figure 3: Schematic of test fixture Results Graphs and 2 show the test results and their values plotted. The first and last bars in each graph show the neat polypropylene and Vistamaxx polymer material. The bars between are the results of blends at the percentages noted. Summary The higher the ethylene content in the Vistamaxx performance polymer grade, the higher the COF. The COF of the neat PP is lower than the Vistamaxx polymer. When blended, Vistamaxx polymer will increase the COF of the neat PP. The lower the ethylene content in the Vistamaxx polymer, the less it affects COF when blended. Adding Vistamaxx polymer to PP increases COF. Page 3 of 6

4 Graph Vistamaxx Performance Polymer against Stainless Steel Vistamaxx 3 Against Stainless Steel Vistamaxx 3 Against Stainless Steel Neat and Blended with hpp (PP534E) Neat and Blended with RCP (PP974MED) % 534 3% 3, 7% 534 5% 3, 5% 534 7% 3, 3% 534 9% 3, % 534 % 3 % 974 3% 3, 7% 974 5% 3, 5% 974 7% 3, 3% 974 9% 3, % 974 % 3 Static Kinetic Static Kinetic Vistamaxx 622 Against Stainless Steel Neat and Blended with hpp (PP534E).6 Vistamaxx 622 Against Stainless Steel Neat and Blended with RCP (PP974MED) % 534 3% 622, 7% 534 5% 622, 5% 534 7% 622, 3% 534 9% 622, % 534 % 622 % 974 3% 622, 7% 974 5% 622, 5% 974 7% 622, 3% 974 9% 622, % 974 % 622 Static Kinetic Static Kinetic Page 4 of 6

5 Graph 2 Vistamaxx Performance Polymer against Glass.3 Vistamaxx 3 Against Glass Neat and Blended with hpp (PP534E).3 Vistamaxx 3 Against Glass Neat and Blended with RCP (PP974MED) % 534 3% 3, 7% 534 5% 3, 5% 534 7% 3, 3% 534 9% 3, % 534 % 3 % 974 3% 3, 7% 974 5% 3, 5% 974 7% 3, 3% 974 9% 3, % 974 % 3 Static Kinetic Static Kinetic Vistmaxx 622 Against Glass Vistamaxx 622 Against Glass Neat and Blended with hpp (PP534E) Neat and Blended with RCP (PP974MED) % 534 3% 622, 7% 534 5% 622, 5% 534 7% 622, 3% 534 9% 622, % 534 % 622 % 974 3% 622, 7% 974 5% 622, 5% 974 7% 622, 3% 974 9% 622, % 974 % 622 Static Kinetic Static Kinetic Page 5 of 6

6 Contact your ExxonMobil Chemical representative for more information. vistamaxxelastomers.com 24 ExxonMobil. ExxonMobil, the ExxonMobil logo, the interlocking X device and other product or service names used herein are trademarks of ExxonMobil, unless indicated otherwise. This document may not be distributed, displayed, copied or altered without ExxonMobil's prior written authorization. To the extent ExxonMobil authorizes distributing, displaying and/or copying of this document, the user may do so only if the document is unaltered and complete, including all of its headers, footers, disclaimers and other information. You may not copy this document to or reproduce it in whole or in part on a website. ExxonMobil does not guarantee the typical (or other) values. Any data included herein is based upon analysis of representative samples and not the actual product shipped. The information in this document relates only to the named product or materials when not in combination with any other product or materials. We based the information on data believed to be reliable on the date compiled, but we do not represent, warrant, or otherwise guarantee, expressly or impliedly, the merchantability, fitness for a particular purpose, freedom from patent infringement, suitability, accuracy, reliability, or completeness of this information or the products, materials or processes described. The user is solely responsible for all determinations regarding any use of material or product and any process in its territories of interest. We expressly disclaim liability for any loss, damage or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information in this document. This document is not an endorsement of any non-exxonmobil product or process, and we expressly disclaim any contrary implication. The terms we, our, "ExxonMobil Chemical" and "ExxonMobil" are each used for convenience, and may include any one or more of ExxonMobil Chemical Company, Exxon Mobil Corporation, or any affiliate either directly or indirectly stewarded. S29-557E98 Page 6 of 6