Shrinkage (material science)
In the case of materials , especially plastics and metals , shrinkage means the movement of oriented macromolecules into an energetically more favorable state with a constant volume . Dimensions and shape can change.
Examples
The molecules have been pre-tensioned in a deep-drawn yoghurt pot . The deep drawing gave them an orientation .
If this plastic cup is now heated (in the case of polystyrene to 120 ° C ), it will shrink (approximately) back into the shape it had as a semi-finished product . The volume of the plastic remains the same, shape and dimensions change.
The phenomenon is used in practice with shrink tubing .