Microcellular Co-Extrusion Process and Selected Properties of Thin-Walled Products

Abstract

The microcellular extrusion process takes place with the use of conventional technological line for extruding shapes and coatings under the changed processing conditions, such as temperature for particular zones of the plasticizing system and extruder head zones. The process differs from the conventional method with regard to the method of shaping the extruder product. In the conventional extrusion process, the plastic has a homogenous structure across the whole section, whereas during microcellular extrusion process the plastic, containing the input plastic and a special blowing agent, obtains a two-phase structure changing its structure into microcellular. One phase is solid and the other is microcellular. Microcellular phase is obtained by inserting the blowing agent into the input plastic during its manufacture. It takes place in the penultimate zone of the plasticizing system of the extruder under suitable process conditions which enable expansion of the blowing agent. Currently applied blowing agents have the form of gases and liquids (then they are inserted into the plasticizing system of the extruder by means of a special installation) but also powders and granulates inserted into the plasticizing system of the extruder together with the input plastic after previously mixing thereof. The article presents characteristics of the microcellular extrusion process and it describes selected research results of the process and microcellular extruder product properties.