In injection molding it is important to take into account the specific properties of the polymer used in the manufacture of this product. The fact is that from its features depends type of items to be installed on equipment. It is particularly important in injection molding to choose the correct design of the screw – a device, which melts the polymer. In addition, the auger includes a piece lodged heated substance in the form below. Molding plastics uses various substances, which differ from each other viscosity, melting temperature and other characteristics. In order to facilitate the selection of the desired screw design, as well as other pieces of equipment, all polymers divided into three groups.
The first group includes those substances which are in injection molding smoothly change their physical state. In addition, they maintain viscosity over a wide temperature range, as well as demonstrate good performance of thermal stability. The latter means that the polymer used in injection molding, can long remain in the molten state without losing their basic properties. This includes such substances, such as polystyrene, polyethylene, polycarbonate and others. In general, casting plastics in their application does not require the creation of special conditions, it is easily and inexpensively. The second group of materials used in molding plastic, characterized in that the transition to a plastic condition is restored.
Because of this it is necessary to apply a special design screw, where the loading zone will be long, and the zone of mastication on the contrary, short-lived. This need to avoid getting unmelted pieces of matter in injection molding. Finally, the third group of polymers is characterized by low thermal stability. This means that in injection molding with the use of such substances should be as small as possible subject them to shear and bulk, as well as to comply with precise temperature control. You can use the special channels through which coolant is supplied or heated liquid. The first requires that, when molding plastics happened decomposition of thermally unstable polymers. The second – to keep them in a molten state.