Design of an Innovative Three-Dimensional Print Head Based on Twin-Screw Extrusion

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Joaquim M. Justino Netto ◽  
Zilda de C. Silveira
Keyword(s):  
Mechanical Design ◽  
Three Dimensional ◽  
Polymer Processing ◽  
Twin Screw Extrusion ◽  
Print Head ◽  
Embodiment Design ◽  
Screw Extrusion ◽  
Twin Screw ◽  
Alternative Material ◽  
3D Printers

This paper presents the embodiment design of an interchangeable print head based on twin-screw extrusion, specially developed to allow in-process multimaterial mixing and direct deposition of the product to structure three-dimensional (3D) parts. The print head focus on research applications with middle-end 3D printers. Commercial extrusion-based 3D printers have limited applicability due to the scarce variety of plastic filaments available. In that context, one important trend for the advance of additive manufacturing (AM) is the design of systems capable of using alternative material types in different states. The systematic process is presented as a case study and brings together concepts from mechanical design and polymer processing. The main contribution of this paper is to provide general guidelines to be used on similar projects, in view of the crescent demand for more adequate and flexible additive processes.

scholarly journals Computer modeling for polymer processing co-rotating twin screw extrusion – nonconventional screw configurations

Mechanik ◽  
2017 ◽  
Vol 90 (4) ◽  
pp. 282-287
Author(s):  
Adrian Lewandowski ◽  
Krzysztof Wilczyński
Keyword(s):  
Computer Modeling ◽  
Three Dimensional ◽  
Polymer Processing ◽  
Twin Screw Extruder ◽  
Twin Screw Extrusion ◽  
Screw Extruder ◽  
Polymer Flow ◽  
Screw Extrusion ◽  
Twin Screw

Computer modeling of co-rotating twin screw extrusion with the use of nonconventional screw configurations has been presented. The polymer flow in the co-rotating twin screw extruder has been described. Some examples of three-dimensional, non-Newtonian modeling are shown. CFD generally oriented software ANSYS Polyflow has been used for modeling.

scholarly journals Properties of Mosquito Repellent-Plasticized Poly(lactic acid) Strands

Molecules ◽  
2021 ◽  
Vol 26 (19) ◽  
pp. 5890
Author(s):  
António B. Mapossa ◽  
Jorge López-Beceiro ◽  
Ana María Díaz-Díaz ◽  
Ramón Artiaga ◽  
Dennis S. Moyo ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Poly Lactic Acid ◽  
Mosquito Repellent ◽  
Twin Screw Extrusion ◽  
Desorption Process ◽  
Dsc Studies ◽  
Screw Extrusion ◽  
Twin Screw ◽  
Alternative Material ◽  
Release Data

Poly(lactic acid) (PLA) is an attractive candidate for replacing petrochemical polymers because it is fully biodegradable. This study investigated the potential of PLA as a sustainable and environmentally friendly alternative material that can be developed into commercially viable wearable mosquito repellent devices with desirable characteristics. PLA strands containing DEET and IR3535 were prepared by twin screw extrusion compounding and simultaneously functioned as plasticizers for the polymer. The plasticizing effect was investigated by thermal and rheological studies. DSC studies showed that the addition of DEET and IR3535 into PLA strands reduced the glass transition temperature consistent with predictions of the Fox equation, thus proving their efficiency as plasticizers. The rheology of molten samples of neat PLA and PLA/repellents blends, evaluated at 200 °C, was consistent with shear-thinning pseudoplastic behaviour. Raman studies revealed a nonlinear concentration gradient for DEET in the PLA strand, indicating non-Fickian Type II transport controlling the desorption process. Release data obtained at 50 °C showed initial rapid release followed by a slower, near constant rate at longer times. The release rate data were fitted to a novel modification of the Peppas-Sahlin desorption model.

scholarly journals In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2128
Author(s):  
Paulo F. Teixeira ◽  
José A. Covas ◽  
Loïc Hilliou
Keyword(s):  
Local Heating ◽  
Polymer Nanocomposite ◽  
Structural Rearrangement ◽  
Particle Dispersion ◽  
Optical Investigation ◽  
Twin Screw Extrusion ◽  
Clay Particles ◽  
Clay Dispersion ◽  
Screw Extrusion ◽  
Twin Screw

The dispersion mechanisms in a clay-based polymer nanocomposite (CPNC) during twin-screw extrusion are studied by in-situ rheo-optical techniques, which relate the CPNC morphology with its viscosity. This methodology avoids the problems associated with post extrusion structural rearrangement. The polydimethylsiloxane (PDMS) matrix, which can be processed at ambient and low temperatures, is used to bypass any issues associated with thermal degradation. Local heating in the first part of the extruder allows testing of the usefulness of low matrix viscosity to enhance polymer intercalation before applying larger stresses for clay dispersion. The comparison of clay particle sizes measured in line with models for the kinetics of particle dispersion indicates that larger screw speeds promote the break-up of clay particles, whereas smaller screw speeds favor the erosion of the clay tactoids. Thus, different levels of clay dispersion are generated, which do not simply relate to a progressively better PDMS intercalation and higher clay exfoliation as screw speed is increased. Reducing the PDMS viscosity in the first mixing zone of the screw facilitates dispersion at lower screw speeds, but a complex interplay between stresses and residence times at larger screw speeds is observed. More importantly, the results underline that the use of larger stresses is inefficient per se in dispersing clay if sufficient time is not given for PDMS to intercalate the clay galleries and thus facilitate tactoid disruption or erosion.

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