Abrasion-resistant plastics with a low coefficient of friction are highly sought after materials for use in a wide variety of industrial applications. Plastic components that require contact with mating surfaces must offer outstanding resistance to wear, along with displaying long life and high performance under constant friction. Plastics that are abrasion resistant are designed to retain their appearance, and also reduce costs associated with maintenance, wear and tear, and the subsequent system downtime that would follow.

NFJ Product Page

What Is Friction?

Wear and friction are two properties that interact with solid surfaces that, over time, result in the deforming of a component and the loss of material. Wear of any material is the measurement of loss that occurs under-recorded loads, speeds, temperatures, and surface roughness.

Abrasion is a type of wear that causes the material to deteriorate by means of friction when they rub or slide against each other. Friction is a measure of the resistance to motion and loss of energy when two surfaces interact. The coefficient of friction is a term that measures the ratio of the force of friction when two surfaces interact with a numerical value. The range of coefficients of friction is near zero to greater than one, with the higher number having the greater force of friction, e.g., rubber on pavement.

The wear resistance of plastic material used for industrial components must be able to perform, but also endure, in real-world applications under the most abrasive conditions. PEEK, UHMW, Acetal, and pDCPD are all good examples of &#;hard wearing,&#; abrasion resistant plastics with low-friction that can be used in applications that require high performance and superior mechanical properties.

Best Abrasion-Resistant Plastics

PEEK

PEEK is a thermoplastic known for its naturally low-friction material, and well-rounded abrasive and fatigue wear resistance. Its impressive durability and performance in punishing environments make it a choice material for components across a wide variety of industries. It is useful at temperatures up to nearly 500 degrees Fahrenheit and self-extinguishes in heat and fire, making it highly recommended for use in electrical components with high continuous service temperatures, e.g. in aerospace. When reinforced with PTFE graphite and carbon, it is one of the strongest polymers available at room temperature. Unfilled grades are highly resistant in chemically aggressive environments. Because of its biocompatibility, high strength and modulus that approximates the human bone, PEEK has been used in such procedures as spinal implants and skull reconstruction. It is also a favorite choice for chemical processing and oil and gas companies.

pDCPD

Polydicyclopentadiene, or simply pDCPD, is a liquid plastic raw material with excellent abrasion resistance and low-friction. This thermoset resin has elasticity and is lightweight, but is also extremely impact and corrosion resistant. Its exceptional mechanical properties such as high temperature and corrosion resistance make it ideal for manufacturing of large specialty-shaped parts. Its excellent surface quality is abrasion resistant, reduces friction, and increases its paintability and glue adhesion. As a material, its features offer unlimited freedom of design for finished products. pDCPD is widely used in commercial and industrial applications around the world, such as for body panels for cars, trucks, buses and all types of parts of off-highway equipment and machinery.

UHMW

Ultra High Molecular Weight Polyethylene is another thermoplastic that exhibits a very low coefficient of friction, along with 10 times the resistance to abrasion than carbon steel. It is also self-lubricating with extremely low moisture absorption, and it has the highest impact strength of any thermoplastic polymer presently on the market. UHMW is a cost-effective and versatile plastic known for its durability and machinability. UHMW is ideal for applications where the coefficients of friction are high, such as in wear strips, belt scrapers, guides, and rollers. It can also be machined for small bearings, large sprockets, and liner systems. Its exceptionally low coefficient of friction and inherent self-lubricating properties result in a smooth, noiseless operation that outperforms many metals.

Acetal

Acetal boasts low-friction and high abrasion resistance and offers strength and excellent performance whenever wear applications are needed. High tensile strength, fatigue endurance, and creep resistance make it ideal for high-performance parts. It has excellent dimensional stability and is highly resistant to solvents and chemicals. Because of its good electrical properties and long-term stability, acetal is used in electrical applications. Its low-friction and moisture absorption give molded acetal parts high perform reliably in humid environments.

Custom Formulated Thermosetting Resins

Unlike many plastics manufacturing companies, Osborne Industries has the capability to custom formulate its resin systems for high abrasion resistance. These polyester resins, typically reinforced with fiberglass, offer excellent abrasion resistant and low friction properties for extreme applications. Resistant to deformation at high temperatures and brittleness in extreme cold, Osborne&#;s polyester resins are a great solution for plastic components in outdoor environments or &#;under-the-hood&#; applications.

Friction of Materials

Introduction

The friction of materials is an important property to be studied to understand its role in any mechanical applications. The tribological properties of any material are determined by its frictional behaviour, this behaviour will determine the life of the materials. Every material has its own behaviour for friction, and it depends on the material properties which need to be understood in order to study its frictional behaviour. This article discusses the frictional properties of metals, ceramics, polymers and solid-lubricated contacts.

Fig-1 materials that defy friction on the atomic scale [1]

Friction of metals

The friction on metals mainly depends on the surface cleanliness, when the metallic surface is clean then it exhibits high adhesion leading to high friction and wear. The metallic bonds are formed at the interfaces of the two materials in contact leading to the transfer of one metal layer over the other causing the wear debris. The formation of any contamination or any oxide layers can reduce the friction loss at the surface of the metals. There are also various other factors affecting the friction on the metals such as the operating conditions which include the applied loads, temperature, sliding velocity, pressure, gaseous environment, humidity etc [2].

1. Effect of load: The formation of the metallic oxide layer on the surface of the material reduces friction. During the operation, if the applied load is high there is the formation of wear debris at the interface which forms the transfer layer. This transfer layer helps in reducing the friction at the surface whereas the low causes elastic deformation breaking the oxide layers and leading to high friction.
2. Effect of sliding velocity/ contact pressure: The increase in sliding velocity or contact pressure causes the surface frictional heating leading to a drop of COF as a function of sliding velocity.
3. Effect of temperature: The increase in temperature causes the phase transformation from the solid state which degrades the mechanical proper of the materials. Further, the melting point and the strength of materials drop causing increased adhesion on the surface and resulting in high friction. In some cases, the increased temperature also causes a reduction in friction by increasing the rate of oxidation at the interface.

For more friction resistant materialsinformation, please contact us. We will provide professional answers.

Fig-2 Friction in metallic applications [3]

Friction of ceramics

The friction in ceramics is quite different in comparison to metals because of their bonding nature with respect to their inter-atomic forces with covalent and ionic bonding. They show very limited plastic flow at room temperature and less ductility in comparison to metals. However, they have good mechanical strength, oxidation at elevated temperatures and resistant properties towards corrosive environments. There are properties such as fracture toughness, sliding speed, applied load and temperature which affects the frictional properties of the ceramics [2].

1. Effect of fracture toughness: fracture toughness is one of the important properties which affects the friction of ceramics. The increase in fracture toughness reduces the friction of the ceramics. At the full contacts, a fracture occurs that dissipates the energy at the contact interface contributing to the friction.
2. Effect of normal load: The increase in normal load causes an increase in friction at the ceramic surface. The increased loads lead to the formation of cracks which in turn causes the increase in friction and wear at the surface.
3. Effect of temperature and velocity: The effects of temperature and velocity on the ceramics can be understood in the formation of tribochemical films and the extent of fracture at the surface. The friction coefficients increase with the increase in temperature, this is due to the high interface temperature which leads to the material softening which results in a lower contact area and high friction.

Fig-3 Schematic representation of ceramic bearings [4]

Friction of polymers

The frictional behaviour of the polymers is quite different in comparison to the metals and ceramics. They exhibit very low friction coefficients due to their low elastic modulus and lower strength. They lack rigidity and strength, and they flow at modest pressure and temperatures. Hence the polymer composites are used to improve their frictional properties thereby applying in various applications. The basic forces are responsible to vary the frictional properties of the polymers are adhesion, deformation, and elastic hysteresis. As per the adhesion analysis, it is found that the surface roughness and the normal load affect the friction coefficients in the polymers. There are also factors such as asperity deformation, sliding velocity, and temperature that affect the frictional properties of the polymers.

1. Effect of normal load on asperity deformation: The increase in the normal load causes the large asperity deformation which results in a decrease in friction coefficient.
2. Effect of sliding velocity and temperature: In polymers, there are various materials that react differently with the sliding velocity and temperatures. In Viscoelastic materials, the increase in temperature causes deformation which is equivalent to a decrease in sliding velocities that affects the frictional behaviours.

Fig-4 Image of polymer gears experiencing friction [5]

Friction in solid lubricated contacts

The most used solid lubricants are graphite and molybdenum disulphide which exhibit lower frictional behaviour the lubrication. The reasons mainly include

1. Graphite: In the case of graphite, it has a layer-lattice crystal structure which has the ability to form a strong chemical bonding with gases such as water vapours. This adsorption of the molecules on the surface results in lower friction coefficients. The graphite structure has lamellae that slide parallel to the plane which is low energy surface and causes little adhesion.
2. Molybdenum disulphide: In molybdenum disulphide, they have a hexagonal lamellar crystal structure same as the graphite. These layers in the crystal structure are tightly packed and are covalently bonded between the atoms which are very strong. These layers are separated by a large distance which is supported by weak van der Waals forces. Thus the materials are strongly anisotropic with very mechanical and physical properties thus they act as self-lubricants and exhibit better frictional properties.

Fig-5 Structure of graphite [6]

Reference

[1] https://www.sciencenews.org/article/scientists-seek-materials-defy-friction-atomic-level

[2] Bhushan, B., . Introduction to tribology. John Wiley & Sons.

[3] https://metalpowdergroup.com/powders-for-friction-applications/

[4]http://www.sinomanitride.com/Product/Ceramic-Bearings/Full-Ceramic-Bearings/82/Full-Ceramic-Bearings/

[5]https://www.hardiepolymers.com/knowledge/what-determines-friction-between-thermoplastic-components/

[6] https://www.substech.com/dokuwiki/doku.php?id=graphite_as_solid_lubricant

If you want to learn more, please visit our website China Iron-carbon microelectrolysis for hazardous waste.