The three basic functional screw element types are classified as forwarding, mixing and zoning. Forwarding elements are usually flighted. They convey material away from the feed opening towards the die. Mixing elements can be dispersive or distributive.
Based on design and function of the screws an extruder is typically divided into three sections along its length. In the feeding section the material will be transferred from the hopper to the barrel. Once the material enters the compression section it will begin to soften or melt. The temperature of this section is normally set at 30–60°C above the glass transition temperature (Tg) of amorphous polymers or the melting point of a semi‐crystalline polymer.
Especially in co‐extrusion it is important to make sure that the design of the screws is ensuring a stable throughput. Sometimes a melt pump is used to reduce the pressure and throughput instability.
Apart from this technological solution, melt pulsation can also be prevented by constructional screw and barrel adaptations such as changing the length, diameter and pitch of the screws.
The benefits of Co-extrusion Profiles by twin-extruder processing
Highly skilled engineering on Co-extrusion dies design. It will benefit the construction of the co-extrusion profiles and enable the molten plastic to evenly flows from a cylindrical profile to the profile shape of the product required. By combining several materials together, we can deliver one unique product with new and exciting characteristics, it can maximum save your cost and multi-function features.