- Friction and Wear of Polymer Materials

Polymers are materials comprised of unit chemical groups, or mers, which repeat to build up extended molecules. Depending on the conditions under which the polymerization reaction is conducted, the resulting molecules may either be linear chains or also have branches oµ the main chains. Furthermore, the collection of molecules comprising the polymer may either be amorphous, or semicrystalline with domains in which collections of neighboring molecular segments are able to adopt a densely packed arrangement, depending on the structure of the mer repeating unit and branching of the chain molecules, as well as conditions such as cooling rate and pressure of any prior thermal processing. In addition, the polymer may either be a thermoplastic where above a melt temperature the crystalline domains dissociate and individual molecules are free to move relative to one another, thus enabling melt processing, or a thermoset where chemical bonds are introduced between neighboring chains cross-linking them into a network which may no longer melt.