A repetitive process in which plastic is melted and injected into a mould cavity where the article is cooled down. After cooling, the mould opens and the article is ejected. ). The melt is prepared in a screw setup similar to an extruder; the screw acts in melting and homogenising the polymer while slowly retracted to build up the melt reservoir necessary for the injection step. Then, the screw is used as a plunger in a forward movement to inject the melt through the runner , a manifold in case of a multiple mould and the gate into the mould. In the injection moulding process, filling of the mould and solidification takes place partially at the ssame time, resulting in a very complex morphology in case of semicrystalline polymers.
Impact Strength characterizes material behaviour under high speed loading. Pendulum and falling weight type testers are applied here. Specimen can be either plaques, notched or unnotched bars or parts of finished products. There are several impact methods like Charpy impact test, instrumented puncture test and tensile impact test. Generally impact test shows the energy which is needed to break or puncture specimen under specified conditions. In some tests it is possible to accurately record force - deformation transient curves and calculate specific parameters describing material behaviour under impact loading.