Moulds are used to shape polyurethane products.
Polyurethane is flexible foam that is used for insulating purposes. It is versatile in nature and it exists in many forms with varying levels of hardness. It is classified as the hardest rubber available. Its production process involves the blowing of chloroform gas through urethane gas so as to produce the foam. Before being processed, it must be dried properly since poor drying results in loss of its properties.
Polyurethane Extrusion Method
In this method, the polyurethane film is extruded using two methods; blown extrusion and cast extrusion. Blown extrusion method involves melting the plastic material and then forcing the material through a hollow tube. The hollow tube is then placed in a cooled metal mold in order for the cooling process to take place. Air is then blown which inflates the molten material into the desired shape. After cooling , the mold is opened and the part is removed.
Cast Extrusion
In the cast extrusion method, the material is heated up to melting point. The molten material is then cooled in a drum before the winding can take place. The molten material is then forced through a flat slot die where it forms a thin film of polyurethane. The thin film materials are then passed through a set of chill rolls where it is cooled.
Injection Moulding
During this process, the molten polyurethane material is first injected into a core pin where it is supposed to take the shape of the core. The spinning of the core pin then follows so as to blow the molding station for both the inflation and the cooling processes to take place. The injection molding process is divided into three parts; the injection, blowing and ejection of the mold.
Core Rod Method
The material is first melted and then fed into a manifold. It is then forced out through nozzles into an already preheated and preformed mold. The preformed mold forms the external shape of the polyurethane while a core rod within forms the internal shape. The preformed mold is then opened while the core rod is rotated. The core rod is then opened to allow the compressed air to inflate the molten material into the desired shape of the article. The cooling process then follows after which the blow mold opens up and the core rod rotated up to the ejection position. The finished article is then removed from the core rod.
Tags: molten material, material then, preformed mold, take place, cast extrusion
