Shrinkage means shrinking the volume of polymers during the cooling phase of the polymer forming process. This shrinkage is partially  related to the difference in density of polymers in solid and molten state

In the production processes of polymer products, shrinkage occurs mostly in injection molding. When the molded product is cooling, it may show some shrinkage until it reaches temperature and humidity stabilization conditions. In materials such as nylons and steel, this shrinkage is more

If shrinkage in polymer parts is uneven, it creates stresses that may cause cracks later in the use of the part

The importance of shrinkage

The amount of shrinkage should be accurately predicted and taken into consideration when designing plastic parts. Shrinkage is more 

critical in some applications, for example in parts that may have electrical boards, shrinkage can lead to damage to the boards

: Shrinkage shrinkage of polymer materials