Plastic molding allows us to produce various products inexpensive and quick way. The essence of the plastic molding is that the polymer from which the product must first be melted, then pour in specially prepared form. Once it hardens, the form is removed from the finished product. All know that the products of this type can be made from different materials: polyethylene, polypropylene, polystyrene and many others. Each of them has special characteristics that must be considered when casting plastics. Parameters such as temperature range of the host in a plastic condition, thermal stability, sensitivity to shear stresses, as well as a number of other indicators, define the conditions which must create the device used in molding plastics. Moreover, for different substances should be used certain types of parts, or molding plastic is not able to provide good quality products. When designing equipment for molding plastics, as a rule, adhered to the classification of substances according to their physical properties.
For each of the classes developed special items, the most suited to their characteristics. The first class of the most easy to use. This polystyrene, polyethylene and other widely used polymers. In injection molding is most important that they have the ability to move seamlessly in a plastic condition and keep it in a large temperature range. This avoids in injection molding thin hardware configuration, summing up the extra thermoregulatory systems and use of special construction details. The principle on which distinguish the materials related to the second class – this is especially the transition to a liquid (A plastic) state. In injection molding is very important to keep all the proportions of equipment, the length of canals and other indicators that will provide a complete meltdown of polymers before getting into shape. Substances such as polypropylene or polyamide change their state abruptly, and this should be reflected in the equipment used in molding plastics. The third class is probably the most difficult to process. Plastic molding should be conducted at carefully drawn conditions, as the substance of this group termonestabilny and can change their properties even at small temperature difference. As an example, polyvinyl chloride and polyformaldehyde.