Search results for " Extrusion"

Analysis of Joint Quality along Welding Plane

2009

Porthole die extrusion is an always more important process for industrial applications. It is, however, characterized by a considerable complexity; in fact, different parameters have to be carefully set for improving the final part. A critical zone that strongly influences the goodness of the extruded component is the so called “welding plane”. It is the junction area where material flows converge inside the welding chamber. The variables that have to be controlled for improving the material characteristics in this zone are the effective stress, the pressure and the time that the material takes to cross the welding chamber. Moreover, material temperature is another fundamental issue that in…

Chemical Modification of Nitrile to Oxazoline Functionality on a Styrene-Acrylonitrile Copolymer in the Melt

1998

Oxazoline is a very interesting functionality for reactive extrusion and other applications. In this paper, we report the possibility of chemically transforming nitrile group attached to a copolymer of styrene and acrylonitrile (SAN) to oxazoline group using 2-amino-ethanol (AE). The chemical modification of SAN with AE was done in the molten state. Among various catalysts tested, zinc acetate turned out to be the most efficient. The effects of the catalyst concentration, temperature and mixing on the overall kinetics were studied. The formation of the expected oxazoline functionality was confirmed by infrared spectroscopy and by reacting with 1-naphthylacetic acid. The reaction between the…

Mechanical and barrier properties of extruded film made from sodium and calcium caseinates

2014

Abstract Over the past few years, much interest has been placed into the investigation of increased barrier and mechanical properties of protein films via a multitude of approaches. Generally, these techniques involve modifications of interactions among protein molecules, such as ionic crosslinking using divalent ions. To evaluate the crosslinking effect of Ca 2+ cations, films were made from calcium caseinate (CaCAS) and/or sodium caseinate (NaCAS). The production of caseinate thin films was carried out in two steps: first thermoplastic pellets were made using a co-rotating twin-screw extruder, then they were transformed into thin films (60 μm) using a classical film blowing machine. Tensi…

Morphology and mechanical properties of extruded ribbons of LDPE/PA6 blends compatibilized with an ethylene-acrylic acid copolymer

2003

Two grades of low density polyethylene (LDPE) were blended with polyamide-6 (PA) in the 75/25 and 25/75 wt/wt ratios and shaped into ribbons with a Brabender single screw extruder. An ethylene-acrylic acid copolymer (EAA) was used in the 2 phr concentration as a compatibilizer precursor (CP). The morphology of the ribbons and its evolution during high temperature annealing were investigated by scanning electron microscopy (SEM). The results confirmed that EAA does actually behave as a reactive compatibilizer for the LDPE/PA blends. In fact, in the presence of EAA, the interfacial adhesion is improved, the dispersion of the minor phase particles is enhanced and their tendency toward fibrilla…

EVA-montmorillonite nanocomposites: effect of processing condition

2004

The aim of this study is to examine the effect of the compounding apparatus and of processing conditions on the properties of an organoclay-poly[ethylene-co-(vinyl acetate)] (EVA) nanocomposite. The filled materials were prepared using either a discontinuous batch mixer, a single screw extruder, a counter rotating intermeshing twin-screw compounder or a corotating intermeshing twin-screw extruder. The characterization of the obtained nanocomposites was performed by XRD, thermogravimetry, mechanical and rheological measurements. The study has shown the possibility of producing nanocomposites based on EVA and a commercial organoclay (Cloisite 15A) by several mixing equipments. In fact all the…

Does muscular activity related to vertical facial divergence influence the time needed for orthodontic extrusion of palatally impacted maxillary cani…

2018

Background The aim of the present study was to evaluate if the different muscular activity correlated to different degrees of facial divergence has an effect on the time needed to extrude a palatally impacted maxillary canine. Material and methods Twenty-six patients were retrospectively selected, all treated with a specific cantilever appliance that allows extrusion of the impacted canine applying a physiologic amount of force below 0.6 N in a predictable way. For all the patients, pre-treatment cephalometric tracings were used to evaluate facial divergence through the FMA angle, the angle between the maxillary and mandibular plane, and the angles between the occlusal plane and either the …

Management of a crown-root fracture : a novel technique with interdisciplinary approach

2018

Anterior teeth with subgingival fractures require a complex treatment plan that addresses biologic, functional and aesthetic factors. This case report describes the management of a crown-root fractured maxillary left central incisor. An interdisciplinary approach was used to restore the tooth due to the complex nature of the treatment. Orthodontic extrusion was performed to move the fracture line above the alveolar bone and periodontal surgery to recontour the altered gingival margin. Finally, the incisor was restored performing a root canal retreatment with a fiber post and a full ceramic crown. The treatment resulted in secured periodontal health and good aesthetics. Key words:Crown-root …

Design and development of a new machine tool for continuous friction stir extrusion

2023

In the present paper the Continuous Friction Stir Extrusion process (CFSE), derived from the already known Friction Stir Extrusion (FSE), is proposed for effective solid-state recycling of metal scraps. A new dedicated machine tool was designed and developed. A Lagrangian implicit thermomechanical numerical model was set up and used to determine the proper ranges of the most relevant process parameters. An effective case study is proposed, involving the actual extrusion of a recycled wire in a continuous way. Metallurgical observations and mechanical characterization tests were carried out on the obtained specimen showing the potential of the process and its industrial feasibility.(c) 2023 …

Meshless Simulation of Friction Stir Welding

2007

This paper encompasses our first efforts towards the numerical simulation of friction stir welding by employing a Lagrangian approach. To this end, we have employed a meshless method, namely the Natural Element Method (NEM). Friction Stir welding is a welding process where the union between the work pieces is achieved through the extremely high deformation imposed by a rotating pin, which moves between the two pieces. This extremely high strain is the main responsible of the difficulties associated with the numerical simulation of this forming process. Eulerian and Arbitrary Lagrangian-Eulerian (ALE) frameworks encounter difficulties in some aspects of the simulation. For instance, these ap…

Lightweight Alloys Recycling and Processing through Innovative Friction Based Direct Technologies

In the last decades, the use of lightweight alloys has been spreading in almost any industrial field thanks to the relevant weight reduction allowed by the use of such materials. On the other hand, aluminium alloys are characterized by high-energy demands primary production cycles that are responsible for a relevant share of the global CO2 emissions. In order to limit and reverse such phenomenon, putting in place strategies to keep the material in the circle over multiple life cycles is mandatory and the concepts of circular economy, closed loop society and industrial symbiosis are progressively gathering more and more pace. Nevertheless, metal scraps are often mainly composed of chips resu…