Modeling of Twin Screw Extrusion of Polymeric Materials

An issue of modeling of twin-screw extrusion of polymeric materials is reviewed. The paper is written in honor of Prof. James L. White who was a pioneer in studying this issue. A global approach to process modeling is presented which includes solid polymer transport, polymer plasticating, and the flow of molten polymer. The methodology of CFD modeling of twin-screw extrusion is presented as well as the examples of this modeling which show the details of the process. Optimization and scaling of twin-screw extrusion are also covered. And finally, the future prospects of developments and research of twin screw extrusion is discussed.

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

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.

Improving the Oxygen Barrier of Polyamide Food Packaging by Using Nanoclay

The effect of nanoclay additive on polyamide film oxygen permeability is investigated from the perspective of possible use as a laminate component for low-cost food packaging material. Montmorillonite nanoclay was melt-mixed in an industrial grade polyamide by twin-screw extrusion and the mixture was hot-pressed to a ~50 µm thick film. The film with 10 wt.% of nanoclay loading showed a 17 % decrease in the oxygen transmission rate (OTR), as compared to the pristine polyamide film (72 and 87 cm3/m2∙24 h, respectively). Despite the relatively high loading of the filler the obtained OTR exceeds that of the food packaging preferred upper limit of 10 cm3/m2∙24 h. XRD measurements confirmed the near-complete exfoliation of the nanoclay platelets. The platelets were found to be at an average angle of 9.5 degrees relative to the film’s surface plane. To comply with the requirements for food packaging, this angle needs to be decreased down to 0.4 degrees. To achieve this, different film-making methods enabling better control over the filler particles’ orientation need to be explored. Nanoclay addition increased the films’ yield strength (23 % for 10 wt.% film) and stiffness, while not affecting the films’ optical appearance.

Influence of Twin-Screw Extrusion on The Dispersion of Nanoclay in Vinylester Composites

This paper reports the dispersion of nanoclay in vinylester using co-rotating twin screw extrusion and ultrasonication for preparing nanoclay/vinylester gel coat. Two sets MMT/vinylester specimens, namely Type 1 and Type 2 were prepared for comparative studies. While Type 1 specimens were prepared using ultrasonication only, Type 2 specimens were prepared using both ultrasonication and twin-screw extrusion. Type 2 specimens showed lower levels of nanoclay intercalation and higher levels of exfoliation. By using the MMT/vinylester gel coat so prepared by the two different routes, MMT/vinylester/glass specimens were fabricated and tested for mechanical properties. Type 2 based nanocomposite specimens showed greater values of ultimate tensile strength, flexural strength, interlaminar shear strength and impact strength. Scanning Electron Micrographs (SEM) of tensile fractured Type 2 based specimens showed less agglomeration of nanoclay than that of Type 1 based specimens.

Wire arc additive manufacturing of AA5183 with TiC nanoparticles

Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse microstructure with a columnar morphology. A powerful measure to refine the microstructure and to enhance mechanical properties is to promote grain refinement during solidification. Addition of ceramic nanoparticles has shown great potential as grain refiner and strengthening phase in aluminium alloys. Thus, an Al-Mg alloy mixed with TiC nanoparticles was manufactured by the novel metal screw extrusion method to a wire and subsequently deposited by WAAM. Measures to restrict oxidation of magnesium during metal screw extrusion were examined. Purging of CO2 gas into the extrusion chamber resulted in a remarkable reduction in formation of MgO and Mg(OH)2. TiC decomposed to Al3Ti during WAAM deposition, leading to a significant grain refinement of 93% compared to a commercial benchmark. The presence of remaining TiC nanoparticles accounted for an increased hardness of the WAAM material through thermal expansion mismatch strengthening and Orowan strengthening. Exposure of TiC to moisture in air during metal screw extrusion increased the internal hydrogen content significantly, and a highly porous structure was seen after WAAM deposition.

Influence of the parameters of the extrusion process on the properties of PLA composites with the addition of graphite

The main purpose of the work is to determine the influence of the screw diameter on the parameters of the single screw extrusion process, such as power consumption, torque, throughput, the actual temperature of the melt on the extruder die, as well as phase s with the use of a laboratory single-screw extruder.. The research was carried out with the use of various plasticizing systems. Two types of graphite: pre-expanded and normal grade with different grain sizes were used in the research. Flammability tests of the obtained composites were carried out using cone calorimeter.