Extrusion Experiments Research Articles

High pressure water intrusion investigation of pure silica 1D channel AFI, MTW and TON-type zeolites

Experimental water intrusion–extrusion isotherms were performed at room temperature on various 1D channel pure silica AFI, MTW and TON-type zeolites. The water intrusion is obtained by applying a high hydraulic pressure corresponding to the intrusion step. Whatever, the zeosil, when the pressure is released, the water extrusion occurs at a similar pressure to that of the intrusion one. These “zeosil–water” systems behave like a spring and the phenomenon is reproducible over several cycles. Several characterizations have been realized before and after water intrusion–extrusion experiments in order to reveal the presence or the absence of defects after such experiments. For all samples, no structural modifications at the long range order are observed by XRD analysis. However for the MTW-type zeosil, solid state NMR spectroscopy get evidence of the presence of Q 2 and Q 3 groups revealing the breaking of some siloxane bridges. Nevertheless, the amount of defects is very low (<2%) and seems not to have an influence on the intrusion–extrusion data for numerous cycles. The stored energy is relatively important and close to 5.8, 15 and 14 J/g for AFI, MTW and TON-type zeosils, respectively.

Influence of the die configuration on the gross melt fracture of linear polyethylene

AbstractIn this study, capillary extrusion experiments and rupture visualization experiments were carried out with a combined die configuration where two different dies were attached in a capillary rheometer. We observed that the gross melt fracture (GMF) and rupture of the melt occurred simultaneously when the diameter of the die located at the upstream position was larger than that of the die located downstream. However, when the location of the dies were interchanged, that is, the diameter of the upstream die was smaller than that of the downstream die, the upstream rupture did not accompany GMF up to a certain extent of shear rate. From these observations, we present a new theory on the origin of GMF. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Modification of the Mechanical Anisotropy in Extruded AZ31 Sheets

Due to its low density and good mechanical properties Magnesium holds a high potential for design applications. The investigations discussed herein focus on the use of extruded magnesium sheets as semi-finished products e.g. for subsequent processing by roll forming. Special interest is given by the hcp-structure of magnesium which reduces forming abilities. Extrusion experiments using AZ31 were carried out to investigate the influence of different die geometries (S = sharp-edged and R= radius), billet temperatures (TB= 350°C and 390°C) and extrusion speeds (vext= 2.31 m/min and 9.24 m/min) on mechanical properties, grain structure and texture of said alloy. Two types of sheets with the dimensions of 80 x 1 mm and 80 x 2 mm respectively were produced using the institutes 10 MN extrusion press make SMS MEER. Sheet material with a thickness of 1 mm rolled from cast billets has been used for reference. Microstructural analysis focused on recrystallization behavior and grain size as well as grain distribution within the sheets. Tensile tests in extrusion or rolling direction as well as 45° and 90° to the same showed a strong influence of the specimen orientation on the mechanical properties. Additional Erichsen cupping tests demonstrated the stretch-forming capacity of the different test set-ups.

Melt strengthening of poly (lactic acid) through reactive extrusion with epoxy-functionalized chains

Poly (lactic acid) is an industrially mature, bio-sourced and biodegradable polymer. However, current applications of this eco-friendly material are limited as a result of its brittleness and its poorly melt properties. One of the keys to extend its processing window is to melt strengthen the native material. This paper considers the chain extension as a valuable solution for reaching such an objective. An additive based on epoxy-functionalized PLA was employed during reactive extrusion. The reaction times as a function of chain extender ratios were determined by monitoring the melt pressure during recirculating micro-extrusions. Once residence times were optimized, reactive extrusion experiments were performed on a twin screw extruder. Size exclusion chromatography provided information about the molecular weight distributions (MWD) of the modified PLAs and revealed the creation of a high molecular weight shoulder. The rheological experiments highlighted the enhancement of the melt properties brought about by the chain extension. Shear rheology revealed some enlarged and bimodal relaxation time spectra for the extended materials which are in accordance with the MWD analysis. Such a modification directly amplified the shear sensitivity of modified PLAs. Regarding the rheological temperature sensitivity, it was found to be decreased when the chain extender content is raised as shown from the Arrhenius viscosity fit. The reduction of the polar interactions from neat to highly chain-extended PLAs is here proposed to explain this surprising result. Chain extension was also found to impact on the elongational melt properties where strain hardening occurred for modified PLAs. Investigation of the chain extension architecture was made from the rheological data and revealed a long-chain branched topology for the modified PLAs.

Prediction of pressure required to extrude a wrought magnesium alloy using optimized strain-dependent constitutive parameters

In the present study, the results of uniaxial compression tests were used to predict the pressure required for extruding a wrought magnesium alloy Mg–Al4–Zn1 under different conditions. The breakthrough and steady-state extrusion pressures were calculated using a strain-dependent constitutive equation and verified by laboratory-scale extrusion experiments. A good agreement was achieved between the calculated and measured extrusion pressure at different ram speeds and reduction ratios for different extrudate shapes. A correlation of the peak extrusion pressure with modified reduction ratio and ram speed was established.

Influence of homogenising and extrusion on plasticity of as cast AZ31 magnesium alloy

Forward extrusion experiments of as cast AZ31 magnesium alloy were carried out at different temperatures and different extrusion ratios using the homogenised and non‐homogenised billets. The elongation of pre‐ and post‐extrusion of the two different initial state billets were investigated. Experimental results show that elongation will increase when the as cast AZ31 magnesium alloy is treated by homogenising. Regardless of whether the billets are treated by homogenising, the elongation of post‐extrusion is improved compared with that of pre‐extrusion. The elongation of post‐extrusion using the homogenised billet is higher than that of the non‐homogenised one.

An Investigation into the Deformation Behaviour of AA6061—5% SiCp Composite During and after Hot Extrusion Process

In this study, hot extrusion of AA6061—5% SiCp composite was studied to determine the composite thermo-mechanical behaviour during deformation and the mechanical properties of extruded composite. Hot compression tests were first carried out to obtain the flow stress behaviour of the composite at different temperatures and strain rates. Then a mathematical model was used to estimate the required energy as well as to predict temperature and strain distributions during the process. Finally, hot extrusion experiments were performed in order to verify the predictions and, also, tensile and hardness testing were conducted to evaluate mechanical properties of extruded material. Comparison between the results obtained from the model and the experimental data shows a good agreement. The results indicate that the extrusion speed has a considerable effect on the mechanical properties of the produced material.

High-Pressure Water Intrusion Investigation of Pure Silica RUB-41 and S-SOD Zeolite Materials

The energetic performance of two microporous siliceous materials, RUB-41 (RRO structure type) and S-SOD (SOD structure type) possessing medium-sized and very small pore openings, respectively, were studied using high-pressure water intrusion−extrusion experiments at room temperature. The pressure−volume diagrams of the RUB-41 material indicate a partly reversible phenomenon showing a slight hysteresis at the extrusion stage, which reveals that the water− RUB-41 system displays a shock-absorber behavior. Moreover, a shift toward the low pressure range was detected between the first cycle of water intrusion and the second one, indicating the creation of new defect sites in the inorganic framework after the intrusion process. Several investigations, mainly by 29Si solid-state NMR spectroscopy, confirm this observation. For the S-SOD material, no water intrusion was observed after three water intrusion−extrusion cycles. The highly hydrophobic character of the S-SOD material with its small pore opening or the ...

Shape Complexity, Metal Flow, and Dead Metal Zone in Cold Extrusion

Nonhomogeneous metal flow through an extrusion die can directly affect product quality, productivity, and die life. The complexity of a die profile is an indicator of how difficult it is to extrude the profile. Some investigations about the effect of die complexity on extrusion pressure, product quality, and die life can be found in the published literature. However, the effect of profile complexity on metal flow through the extrusion die has not been explored much. Such a study can directly contribute toward die design improvement and reduction of extrusion defects related to metal flow. This article investigates the effect of shape complexity on the dead metal zone (DMZ) and metal flow through cold extrusion experiments and finite element simulations on some solid profiles. Experiments were performed using flat-face dies of different complexities and different billet materials. 2D and 3D finite element simulations were carried out. One significant conclusion is that currently existing definitions of extrusion shape complexity cannot satisfactorily explain the variations in DMZ size under different conditions. Factors such as die profile symmetry and extrusion ratio may play significant roles in the formation of DMZ and distortion of metal flow through the die.

A Maxwell-pulse constitutive model of Zr 55Cu 30Al 10Ni 5 bulk metallic glasses in supercooled liquid region

Stress overshoot related to the variation in free volume is an important phenomenon in cylinder compression tests of bulk metallic glasses (BMGs). A Maxwell-pulse constitutive model was proposed according to the overshoot of Zr 55Cu 30Al 10Ni 5 BMG in the supercooled liquid region (SCLR). Compression experiments and the constitutive model showed good agreement, especially with regard to the stress overshoot phenomenon. Furthermore, micro-backward extrusion experiments and numerical simulation were conducted in SCLR. The results showed that the constitutive model describes the mechanical behavior of the BMG well.

An experimental study of single‐screw extrusion of HDPE–wood composites

AbstractSingle‐screw extrusion experiments were carried out to study the extrusion characteristics of HDPE–wood composites. Three screw geometries (A, B, and C) were used, and the effects of screw speed on output, melting, and pressure profile were studied. Screw A had a much higher compression ratio than screws B and C, which directly affected the melting behavior of the polymers. Screws B and C had the same compression ratio; however, screw C had the same metering capacity as screw A. Therefore, by comparing screws B and C, the effect of feed depth on the solid conveying capacity was investigated. It was found that while screw B had higher outputs than both screws A and C as expected, screw C had a much lower output than screw A for highly filled resins even though they had the same metering capacity. For HDPE, screws A and C showed the same output as expected. Further examinations of the pressure profiles and melting profiles from screw extraction experiments confirmed that screw C showed a severely starved solids conveying capacity for wood‐filled resins, which limited the total outputs. Comparing the outputs and pressure generations between theoretical predictions and actual experimental results, it was evident that due to the inaccurate assumption of fully filled channels common in single screw extrusion, both outputs and pressure generations in the extruders were overpredicted. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:197–218, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20190

소형 헬리컬 기어 제조를 위한 분말 압출 금형 제작 및 실험

Extrusion process in the bulk material for fabrication of miniature helical gears has problems such as a high forming load and short tool life because the cross-section is complex and asymmetry. To overcome these problems, in this study, miniature helical gears were fabricated by Zn-22Al powder hot extrusion. The included die angle for minimum extrusion load and improving die filling was determined by FE-simulation. The Zn-22Al spheroidal powder produced by gasatomization were compacted and sintered for extrusion experiment. The dimension of helical-gear is 0.3mm in module, 3.35mm in pitch diameter, <TEX>$15^{\circ}$</TEX> in helix angle and the number of teeth is 12. All of the extrusion experiments were performed with internal helical gear die which was machined by precision electric discharge machining using the electrode. The experiment was conducted at <TEX>$190^{\circ}C$</TEX> to <TEX>$310^{\circ}C$</TEX> to obtain extrusive and mechanical properties. The extruded helical gears were analyzed through extrusion load, Vickers hardness and SEM images for each extrusion temperature. The powder hot extrusion process was successfully applied to fabricate a miniature helical gear.

Influence of homogenizing on mechanical properties of as-cast AZ31 magnesium alloy

Forward extrusion experiments of as-cast AZ31 magnesium alloy were conducted at different temperatures and different extrusion ratios using the as-cast billets with and without homogenizing treatment. The mechanical properties of pre- and post-extrusion of the two kinds of billets were investigated. Experimental results show that the mechanical properties of post-extrusion of the two kinds of billets all are obviously improved compared with those of pre-extrusion. The elongation of post-extrusion using the billet with homogenizing is higher than that without homogenizing, but the tensile strength is lower than that without homogenizing. When the extrusion ratio increases, the elongation and tensile strength of post-extrusion of two kinds of billets all will increase obviously. When the extrusion temperature of billet without homogenizing increases, the tensile strength of post-extrusion will decrease obviously and the elongation of post-extrusion will change to a small extent. For the billet with homogenizing, the tensile strength of post-extrusion will decrease in some sort when extrusion temperature increases.

Grain Refinement and Texture Evolution during Equal Channel Angular Extrusion of Pure Cu and Cu-Zn Alloys

Equal channel angular extrusion (ECAE) experiments were conducted on as-cast pure Cu, Cu–10%Zn, and Cu–30%Zn, using a 90 die for up to 4 passes. The stacking fault energies (SFEs) of the three materials decrease with increasing Zn content. The microstructures and textures of the processed billets were analyzed using optical microscope and X-ray diffraction, respectively. The results show that the structures of the three materials were all significantly refined after ECAE and a lower SFE led to a finer microstructure with a higher density of shear bands. The textures were considerably weakened after 4 passes, more apparent in the material with a lower SFE. It is concluded that the SFE has significant influences on both the grain refinement and texture evolution during ECAE deformation.

Influence of plasticizer type and level on the properties of Eudragit® S100 matrix pellets prepared by hot-melt extrusion

Matrix-type pellets with controlled-release properties may be prepared by hot-melt extrusion applying a single-step, continuous process. However, the manufacture of gastric-resistant pellets is challenging due to the high glass transition temperature of most enteric polymers and an unacceptably high, diffusion-controlled drug release from the matrix during the acidic phase. The objective was to investigate the influence of three plasticizers (triethyl citrate, methylparaben and polyethylene glycol 8000) at two levels (10% or 20%) on the properties of hot-melt extruded Eudragit® S100 matrix pellets. Extrusion experiments showed that all plasticizers produced similar reductions in polymer melt viscosity. Differential scanning calorimetry and powder X-ray diffraction demonstrated that the solid state plasticizers were present in the amorphous state. The drug release in acidic medium was influenced by the aqueous solubility of the plasticizer. Less than 10% drug was released after 2 h at pH 1.2 when triethyl citrate or methylparaben was used, independent of the plasticizer level. Drug release at pH 7.4 resulted from polymer dissolution and was not influenced by low levels of plasticizer, but increased significantly at the 20% level. Mechanical testing by diametral compression demonstrated the high tensile strength of the hot-melt extruded pellets that decreased when plasticizers were present.

Investigation of the Energetic Performance of Pure Silica ITQ-4 (IFR) Zeolite under High Pressure Water Intrusion

To study the energetic performance of the 1D 12-membred-ring pure silica ITQ-4 zeolite (IFR topology), a high-pressure water intrusion−extrusion isotherm at room temperature was performed. The pressure−volume diagram indicates an irreversible phenomenon, water molecules remaining confined in ITQ-4 micropores. Therefore, the “water−ITQ-4” system appears to behave as a bumper. The water intrusion pressure and intruded volume are of 42 MPa and 0.136 mL/g, respectively. Investigations on the ITQ-4 samples by 29Si and 1H solid-state NMR spectroscopy and powder X-ray diffraction have confirmed the existence of a small amount of silanol defects in the nonintruded sample and an increase of these defects after the water intrusion−extrusion experiment. It appears clearly that one of the crystallographic silicon sites of the porous framework is particularly affected after such a treatment, leading to the creation of Si−OH groups by the breaking of siloxane bonds, these silanols being strongly hydrogen bonded with wa...

Analyses of Plastic Flow and Die Design during Hot Extrusion of Magnesium Alloy Strips

This study involves analyses and experiments of hot extrusion of magnesium alloy strips. Hot compression tests were firstly conducted to obtain the magnesium alloy’s plastic flow stresses at high temperatures. These data are used in the finite element simulations of the thin strip extrusion process. Using the FE simulations, the flow pattern of the magnesium alloy billet within the die, the temperature variation and the thickness distribution at the die exit were analyzed. The effects of different die bearing height design, initial billet temperatures and ram speed on the extrusion load, the temperature at the die exit and the product thickness distribution were also discussed. Finally, hot extrusion experiments were conducted and the experimental values of the extrusion load and dimensions of the products were compared with the analytical values to validate the analytical model. Sound products were obtained using the best designed bearing heights and other appropriate extrusion conditions.

Effect of ECAE conditions on the microstructure, texture and mechanical properties of an extruded Mg–Zn–Y–Zr alloy

Abstract Equal channel angular extrusion (ECAE) experiments of an extruded Mg–Zn–Y–Zr alloy with an intense basal texture were performed up to 8 passes at 250 and 350 °C through route Bc (billets with a rotation of 90° in the same direction between passes) and route A (without rotation between passes). It was found that under these ECAE conditions significant grain refinement was achieved. The initial texture of the alloy gradually altered as the number of ECAE passes increased. The ductility of the alloy was improved in all the cases after eight passes. The yield strength of the alloy ECAEed through route Bc considerably decreased with the passes increasing, as a result of the formation of the texture component with the basal planes inclined at about 45° to the ECAE direction. The yield strength of the material ECAEed at 250 °C with a finer grain structure was considerably lower than that at 350 °C with a coarser grain structure. This abnormal phenomenon was attributed to more crystals in the former being oriented to be more favorable for basal slip.

Modeling of L‐lactide Polymerization by Reactive Extrusion

AbstractThe kinetics of L‐lactide ring‐opening polymerization initiated by stannous octoate and triphenylphosphine was investigated in a batch apparatus (Haake Rheocord Mixer). Based on the experimental data, a kinetic model is developed, considering a coordination‐insertion mechanism. Reactive extrusion experiments were further conducted for the same polymerization process, on a co‐rotating twin screw extruder. The melted material flow and mixing was described by using the Ludovic® commercial simulator. Based on the developed kinetic model and simulated flow of L‐lactide polymerization mixture, a mathematical model of reactive extrusion process is formulated, describing the evolutions of monomer conversion and average molecular weight along the extruder. The model is predicting with a reasonable good accuracy the experimental data.

Experimental Study on Viscosity and Phase Segregation of Al–Si Powders in Microsemisolid Powder Forming

Semisolid powder forming is a promising approach for near-net shape forming of features in macro-/microscale. In this paper, viscosity and phase segregation behavior of Al–Si powders in the semisolid state were studied with back extrusion experiments. The effects of process parameters including shear rate, extrusion ratio, heating time, and precompaction pressure were analyzed using the design of experiments method. The results showed that the effects of shear rate, extrusion, ratio and heating time were statistically significant factors influencing the viscosity. The semisolid state powders showed a shear thinning behavior. Moreover, microstructure analysis of extruded parts indicated severe phase segregation during the forming process. As the extrusion opening became small (∼400 μm), the phase segregation increased. This study expanded the semisolid processing technology by exploring the use of powdered materials instead of typical bulk materials for applications in micro-/mesomanufacturing. Replacing bulk materials with powdered materials may add a new dimension to the technique by allowing tailoring of material properties.