**1. Issues related to the use of polymeric materials in tribological applications**

Plastics and materials based on plastic have become an acceptable replacement of metallic materials and, as a consequence, they have to face the challenge of having also a good tribological behavior, implying a set of characteristics favorable to a reliable functioning of the application.

Issues that an engineers (both designers and users) have to pay attention when using polymeric materials in tribological applications include dimensional stability. These materials have higher thermal expansion coefficients, shorter durability, sensitivity and particular behavior to high and low temperatures. As they are

characterized by lower hardness, they are not prone to be introduced in rolling contacts, will few exceptions (here including car tires and gears), most applications being for sliding motion (belt, sliding bearing, seals, brakes etc.).

the component durability (life time). The design should be done so that the working conditions will vary in narrow ranges (temperatures, load, velocity, material com-

The majority of tribological applications with polymeric materials are involving couples with one element made of metallic materials, the other being polymeric. Sometimes, the polymeric material is moving against a body made of the same

**Figure 2** summarizes the main aspects of tribological performance when using

**2. Polymers, and materials with polymers for tribological applications**

**Table 1** presents the polymers used in tribological applications, several features

PTFE Low friction, but high wear rate. Used both neat, as matrix and as solid lubricant. More

powder as copper. High working temperature [9, 10] PA Moderate friction coefficient, low wear rate, but too sensitive to water and humidity.

PEEK Polyetheretherketone, semicrystalline High working temperature and very good

UHMWPE Very good wear resistance, especially against abrasion, even in water. Moderate friction coefficient. Modest working temperature.

PU Good wear resistance in rolling contacts. Relatively high friction coefficient in sliding. PI High performance polymer with very good behavior in high contact pressure. Higher

PBT A reliable behavior in sliding contact, lower wear as PA, but more restrictive condition in molding. Usually with a solid lubricant or reinforcement [15, 16]

PEI Amorphous thermal stability, very good mechanical and physical properties, easy

PPS Semicrystalline, polyphenylenesulphide, water lubrication high glass transition and

PPP Polyparaphenylene, semicrystalline, very high mechanical stability at room

coefficient, with controlled wear evolution in time)

PBI Polybenzimidazole semicrystalline, high heat resistance and mechanical property

Working temperature quite low [11]. POM Similar performance as PA. Good durability in rolling contacts.

polyimides, blended with PEEK [13]

temperature, poor wear resistance [12]

retention, even under high temperatures [12]

neat polymer [12–14]

friction coefficient.

*Tribological characteristics of thermoplastic polymers [5–8, 20].*

PES Amorphous [17]

Epoxy and phenolic polymers

**Table 1.**

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recently, added in polymers, resulting polymer blends; in composite as solid lubricant or matrix in composite with reinforcements as glass fibers, carbon fibers, metallic

chemical resistance. Accept higher contact pressure but high friction coefficient as

processability, applicability and possibility of recycling and repair, thermosetting

high melting temperature and high mechanical strength, high COF on steel in dry regime (0.4...0.5), PPS + SWCNT (0.5 wt.%) + WS2 (1.5 wt.%) [18, 19]

Used especially as binder agents in composites, they induce high friction, but constant. Their brittleness induces wear by micro-detaching harder particles (as a dust) that could damage the smooth functioning of the tribosystem. The composites with these resins usually are designed for frictional applications (high and constant friction

position and morphology) [8].

polymer-based materials.

and usual components made of them.

**Polymer Tribological characteristics**

materials, an example being gear transmissions.

*Tribological Behavior of Polymers and Polymer Composites*

*DOI: http://dx.doi.org/10.5772/intechopen.94264*

The advantages of using polymeric materials (polymers, blends and composites) [1–5] include self-lubricity, lower density as compared to metallic materials, resistance to tribocorrosion [6] or general oxidation, non-toxic nature and potential processing to final shape, usually, by injection molding. But their favorable properties come in a package with disadvantages. One is that a slight change in working conditions (load, velocity, temperature etc.) could substantially modify tribological characteristics [7], especially wear rate and low friction is not related to low wear rate. Also, negative temperatures have different influences on polymeric materials (some become brittle, some resist without problems and some are conditioned by the working conditions and environment).

**Figure 1** presents materials based on polymers and elastomers that could be used in tribological applications.

When using polymeric materials, the designer should pay attention how the component will obey design requirements, if it has dimensional stability, mechanical characteristics with reliable values, if issues related to aging are acceptable for

#### **Figure 1.**

*Materials based on polymers and elastomers, involved in tribological applications [1–5].*

#### **Figure 2.**

*A chart of significant aspects related to tribological performance implying polymeric materials.*

*Tribological Behavior of Polymers and Polymer Composites DOI: http://dx.doi.org/10.5772/intechopen.94264*

characterized by lower hardness, they are not prone to be introduced in rolling contacts, will few exceptions (here including car tires and gears), most applications

The advantages of using polymeric materials (polymers, blends and composites) [1–5] include self-lubricity, lower density as compared to metallic materials, resistance to tribocorrosion [6] or general oxidation, non-toxic nature and potential processing to final shape, usually, by injection molding. But their favorable properties come in a package with disadvantages. One is that a slight change in working conditions (load, velocity, temperature etc.) could substantially modify tribological characteristics [7], especially wear rate and low friction is not related to low wear rate. Also, negative temperatures have different influences on polymeric materials (some become brittle, some resist without problems and some are conditioned by

**Figure 1** presents materials based on polymers and elastomers that could be used

When using polymeric materials, the designer should pay attention how the component will obey design requirements, if it has dimensional stability, mechanical characteristics with reliable values, if issues related to aging are acceptable for

*Materials based on polymers and elastomers, involved in tribological applications [1–5].*

*A chart of significant aspects related to tribological performance implying polymeric materials.*

being for sliding motion (belt, sliding bearing, seals, brakes etc.).

*Tribology in Materials and Manufacturing - Wear, Friction and Lubrication*

the working conditions and environment).

in tribological applications.

**Figure 1.**

**Figure 2.**

**66**

the component durability (life time). The design should be done so that the working conditions will vary in narrow ranges (temperatures, load, velocity, material composition and morphology) [8].

The majority of tribological applications with polymeric materials are involving couples with one element made of metallic materials, the other being polymeric. Sometimes, the polymeric material is moving against a body made of the same materials, an example being gear transmissions.

**Figure 2** summarizes the main aspects of tribological performance when using polymer-based materials.
