Friction

Friction, a fundamental concept in physics and materials engineering, describes the resistance force that opposes movement between macromolecules in plastics or at the surfaces of components. This interaction between molecules or surfaces converts kinetic energy into heat, which has a wide range of effects in various applications.

1. Internal friction: This aspect of friction concerns the sliding of macromolecules within a plastic material. During the process of plasticisation, for example, in which plastic is melted and shaped, mechanical energy is generated by friction between the molecules. This energy is then converted into thermal energy, which causes the plastic to be melted homogeneously from the inside out. This homogenisation is crucial for the quality of the end product.
2. External friction: This refers to the resistance to surfaces sliding against one another. This resistance is determined by the coefficient of sliding friction, which is a dimensionless quantity. This external friction is of great importance in many technical applications, as it influences, for example, the efficiency of machines or determines the behaviour of vehicles on the road.