Double screw extruderWhen processing materials, screws are used inside the cylinder to complete conveying, mixing, and pumping. The modularity of the cylinder facilitates segmented transportation of individual units along its length. The material barrel adopts electronic heating and liquid cooling methods, and serves as an independent temperature control zone. The segmented components are combined on a high torque shaft to optimize the screw configuration according to process requirements. The typical length to diameter ratio (L/D) that can be used for reactive extrusion and/or multi-stage solvent removal ranges from 32 to 48:1, with a maximum of 60 L/D (or longer). Electric energy is converted into mechanical energy through a transmission system (motor gearbox), and then the material is sheared by a rotating screw.
The modular cylinder and segmented screw have controllable wiping and pumping characteristics, allowing people to adjust the geometric configuration of the screw and barrel to match the requirements of the process task. Solid transportation and plasticization usually occur in this preparation process. Mixing, downstream feeding, liquid injection, and ventilation are commonly used, and their principles are determined by the process. The structural configuration range of screws includes both shear sensitive and shear passive types.
Screw extruderIt is a type of equipment for material shortage and replenishment; The feeding rate is determined by the measuring equipment. It can be a solid feeder or a liquid feeder. The independence of screw output speed enables optimization of mixing efficiency by adjusting the shear strength of the twin-screw extruder. In addition, due to the control of pressure gradient in the extruder and the fact that some parts of the process are zero, the material can be introduced into the downstream section of the barrel. This is beneficial, for example, in high loading starch blends, all feeds cannot be in just one place, or in the case of the same feed temperature and/or shear sensitive additives (such as natural fibers), if processed over the entire length range of the barrel, they will decrease.
Double screw extruderFirstly, twin-screw extruders have the same extruder principle as single screw extruders: solid conveying, melting, pressurization, and pumping mixed stripping and devolatilization, but it is not simply the case. The research on twin-screw extrusion theory started late, and coupled with its diverse types, complex screw geometries, and intricate extrusion processes, it has brought many difficulties to the study of twin-screw extruders.
Overall, the research on twin-screw extrusion theory is still in its initial stage, which is known as' more skill than science '. The study of its extrusion process can be roughly divided into three stages:
1. The changes in the physical state of polymers during the extrusion process, the conveying principle, the truth and laws of solid melt conveying and exhaust, and the establishment of mathematical and physical models to guide the design of twin-screw extruders and the optimization of extrusion processes.
2. To understand the true changes in the physical state of two or more polymers and materials during extrusion, the process of mixing morphology, structural changes, and the relationship between the final mixture and performance.
3. As a twin-screw extruder, a model is established to guide the reaction process, speed, performance, screw configuration, and operating conditions during extrusion reaction molding.