Properties of Starve-Fed Extrusion on a Material Containing a VHMWPE Fraction

A review paper is presented on optimization and scale-up for polymer extrusion, both single screw and twin screw extrusion. Optimization consists in obtaining a multidimensional space of process output variables (response surface) on the basis of an appropriate set of input data and searching for extreme values in this space. Scaling consists in changing the scale of the process according to specific criteria, that is, changing the process while maintaining the scaling parameters at a level that is as close to the reference process parameters as possible. It consists in minimizing the differences between the parameters characterizing the reference process and the resulting process. This may be obtained by using optimization techniques leading to the minimization of discrepancies between the parameters of scaled processes. In the paper, it was stated that optimization and scale-up based on process simulation are more effective than those based on experimentation which is time consuming and expensive. The state-of-the-art on extrusion process modeling which is the basis of optimization and scale-up has been presented. Various optimization techniques have been discussed, and the Genetic Algorithms have been identified as powerful and very efficient. Optimization and scale-up based on the process simulation using Genetic Algorithms have been broadly reviewed and discussed. It was concluded that, up to date, there is a lack of optimization studies on the counter-rotating twin screw extrusion, although the global models of this process are known. There is also a lack of process simulation-based scaling-up studies, both on the counter-rotating twin screw extrusion and on the starve fed single screw extrusion. Finally, development perspectives in this field have been discussed.

Section: Modeling Of Extrusionmentioning

confidence: 99%

Section: Modeling Of Extrusionmentioning

confidence: 99%

Optimization and Scale-Up for Polymer Extrusion

Nastaj

Wilczyński

2021

“…Extrusion with metered feeding, also called extrusion with starving, has some advantages over extrusion with flood feeding [30,[60][61][62][63][64][65]. Mixing action is improved, melting is faster, and process control is better.…”

Section: Extrusion With Flood Feeding and Metered Feedingmentioning

confidence: 99%

Computational Scale-Up for Flood Fed/Starve Fed Single Screw Extrusion of Polymers

Nastaj

Wilczyński

2022

A novel scaling-up computer system for single screw extrusion of polymers has been developed. This system makes it possible to scale-up extrusion process with both starve feeding and flood feeding. Each of the scale-up criteria can be an objective function to be minimized, represented by single values or functional dependencies over the screw length. The basis of scaling-up is process simulation made with the use of the GSEM program (Global Screw Extrusion Model). Scaling-up is performed using the GASES program (Genetic Algorithms Screw Extrusion Scaling) based on Genetic Algorithms. Scaling-up the extrusion process has been performed to increase extrusion output according to the scaling-up criteria defined by the single parameters of unit energy consumption, polymer plasticating rate and polymer temperature, as well as by the process parameters profiles of the temperature and plasticating. The global objective function reached the lowest value for the selected process parameters, and extrusion throughput was significantly increased.

“…The starve fed extrusion has several advantages over the flood fed extrusion, as discussed in the literature, e.g., [2][3][4][5][6][7], and very recently in [8]. The pressure development in the extruder is lower, the polymer does not agglomerate, and mixing is substantially better.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of metered feeding, the rotational speed of the screw can be changed at the constant extruder throughput, and the extruder throughput can be changed at the constant rotational speed of the screw, which enables for better process control. In general, the extruders with metered feeding may be applied to perform the more advanced processing tasks, e.g., [8], although this way of feeding also has some drawbacks. The extrusion throughput is lower, and the process is more complicated since an additional device is used to deliver the polymer to the extruder.…”

Section: Introductionmentioning

confidence: 99%

A Computer Model of Starve Fed Single Screw Extrusion of Wood Plastic Composites

Wilczyński¹,

Buziak

2021

In this study, we present a computer model of starve fed single screw extrusion of wood plastic composites (WPC). Experimental studies have been performed on the extrusion of the polypropylene (PP) based composites with various wood fiber contents (WF). The melting mechanisms of the composites in the extruder have been observed, and melting models have been proposed for partially and fully filled sections of the screw. It was observed that in the partially filled section the material is melted by conduction, as in the case of extrusion of neat polymers. On the other hand, in the fully filled section, the Tadmor melting mechanism appears, which is different compared to the melting mechanism of neat polymers at starve fed extrusion, where dispersed melting is observed. Using the melting models, the global computer model of the process has been developed which makes it possible to predict the process flow, i.e., the polymer melt temperature and pressure, the polymer melting rate, and the degree of screw filling. To build the model, the specific forward/backward procedure was developed, which consists in determining “forward” the melting profile, and “backward” the pressure and screw filling profile. The temperature profile in the melting section is computed “forward”, while “backward” in the metering section. This procedure makes it possible to solve the crucial problem of modeling of the starve fed extrusion process, which is to find the location of the point where the screw is fully filled, and the pressure is developed. The model has been tested by pressure measurements in the extruder.