scholarly journals A New Extensional Mixing Element for Improved Dispersive Mixing in Twin-Screw Extrusion, Part 1: Design and Computational Validation

2015 ◽  
Vol 36 (4) ◽  
pp. 455-465 ◽  
Author(s):  
Sidney O. Carson ◽  
José A. Covas ◽  
João M. Maia
Keyword(s):  
Twin Screw Extrusion ◽  
Screw Extrusion ◽  
Twin Screw ◽  
Dispersive Mixing ◽  
Computational Validation

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.

Definition of a JA-2 Equivalent Propellant to be Produced by Continuous Solventless Extrusion

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
Thelma G. Manning ◽  
Joseph Leone ◽  
Martijn Zebregs ◽  
Dinesh R. Ramlal ◽  
Chris A. van Driel
Keyword(s):  
Extrusion Process ◽  
Continuous Manufacturing ◽  
Twin Screw Extrusion ◽  
Extrusion Processing ◽  
Roll Mill ◽  
Screw Extrusion ◽  
Twin Screw ◽  
Ballistic Properties ◽  
Definition Of ◽  
Double Base

In order to eliminate residual solvents in ammunition and to reduce the emissions of volatile organic compounds to the atmosphere, the U.S. Army ARDEC has teamed with TNO in developing a new process for the production of solventless propellant for tank ammunition. To reduce the costs of solventless propellants production, shear roll mill and continuous extrusion processing was investigated. As described in this paper JA-2 a double base propellant cannot be processed without solvent by the extrusion process. An alternative JA-2 equivalent propellant was defined. The aim of this work is to demonstrate the manufacturing of this propellant by solventless continuous twin screw extrusion processing while maintaining gun performance characteristics of conventional JA-2 propellant. This is elucidated by explicitly researching the relationship between interior ballistic properties of the gun propellant and utilizing a continuous manufacturing process. Processing conditions were established, and the propellant was manufactured accordingly. The extruded propellant has the desired properties, which resulted in a comparable gun performance as the conventional JA-2 propellant.

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