Mechanical Properties Of Extrudates Research Articles

High-moisture extrusion of soy protein: Effects of insoluble dietary fiber on anisotropic extrudates

Insoluble dietary fiber (IDF) was commonly present in feedings during extrusion for preparing plant protein-based meat analogs. The aim of this study was to investigate the feasibility of using IDF to improve the fibrous structure of high-moisture extrudates (HME) produced from soybean protein isolate (SPI). The structures of extrudates were analyzed visually and using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The mechanical properties of extrudates were determined by a texture analyzer. The CLSM and SEM images of SPI-IDF extrudates presented a clear interface between the SPI and IDF domains, which indicated that the IDF phase dispersed within the SPI phase reduce the mutual cross-linking between SPI. The substitution of 10%–20 wt% IDF promoted the formation of an SPI matrix/IDF filler mesh structure, which could contribute to the fibrous appearance and higher mechanical anisotropy. Substitution of more IDF in SPI resulted in a collapsed structure, possibly due to macroscopic phase separation during extrusion. It can be concluded that the partial substitution of SPI with IDF can promote the formation of a fibrous structure with enhanced mechanical anisotropy.

Rheology and processing of polytetrafluoroethylene (PTFE) paste

AbstractThis is a review article on the paste extrusion of polytetrafluoroethylene (PTFE). The article begins with an overall presentation of the process. Important aspects related to this process are the physical properties of PTFE, its rheology, the morphological changes occurring during flow (fibrillation) that play a critical role on the dimensional stability of the final products, the geometrical characteristics, and types of dies used and temperature. PTFE is a compressible, zero Poisson's ratio material, and the mechanical properties of extrudates after extrusion are also discussed in view of fibrillation and Poisson's ratio.

Factors affecting structural properties and in vitro starch digestibility of extruded starchy foams containing bran

Rye bran of two different particle sizes (coarse: 440 μm and fine: 28 μm) were prepared by milling of commercial rye bran. Coarse and fine rye bran was added into a blend of rye endosperm flour and corn starch (70:30) to achieve two bran levels, 15 or 30%, to produce directly puffed extrudates. A co-rotating twin screw extruder was used with a screw speed of 500 rpm, barrel temperature profile: 40-70-75-90-95-110-110 °C and constant feed rate of 67 g/min. Feed moisture content of 17% was used either as in barrel-water feed or as preconditioning. Fine bran addition effectively improved macrostructural properties as compared to coarse bran through increasing expansion by 3.3–11.7% and piece density by 3.8–10.5%. Reduction of bran particle size significantly (P < 0.05) increased crispiness by 66.7–203.3%. Particle size reduction of bran had only minor influences on cell wall thickness, cell area and hydrolysis index of the extrudates. Extrudates made with 30% fine bran at in barrel-water feed provided the crispiest extrudates with lower in vitro hydrolysis index. The results demonstrated that the macrostructural and mechanical properties of extrudates containing rye bran can be improved by reducing bran particle size.

Extrusion of Solid Wood Impregnated with Phenol Formaldehyde (PF) Resin: Effect of Resin Content and Moisture Content on Extrudability and Mechanical Properties of Extrudate

A new deformation technique of wood flow forming is promising for industrial uses of solid wood. Flow deformability, size stability, and good mechanical properties were obtained by using wood impregnated with low molecular weight phenol formaldehyde (PF) resin. In this study, to clarify the effect of the PF resin and moisture contents in wood on the flow deformability (extrudability) and the mechanical properties of the product (extrudate), a lateral extrusion was conducted by using wood impregnated with various contents of PF resin and three levels of moisture content. The results indicated that the extrudability of wood impregnated with PF resin improved with an increase in both PF resin and moisture content. The mechanical properties of the extrudate worsened with increases in the moisture content of the wood impregnated with PF resin. Because most of the water in the wood remained in the mold during the extrusion process, chemical changes of the wood substance and PF resin occurred due to steam forming under the high temperature and pressure of the extrusion. The steam worsened the mechanical properties of the extrudate.

Improvement of mechanical properties of Al6061 extrudate by die cooling with N2 gas during hot extrusion

In this study, the mechanical properties of the extrudate are improved by correcting the defects such as abnormal grain growth (AGG). Die cooling with N2 gas is conducted to control the extrusion temperature during the hot extrusion of Al6061 in order to obtain fine grains of the extrudate. Computational fluid dynamics (CFD) is conducted to evaluate the effect of die cooling with N2 gas and to determine the relationship between AGG and the extrusion temperature. The optimal cooling channel with a high cooling effect is designed by using the design of experiment (DOE) method, and thermo-mechanical analysis is performed to predict the extrusion temperature. A hot extrusion experiment is also carried out to measure the extrusion temperature and to observe the microstructure of the extrudate. The extrusion temperature predicted from the thermo mechanical analysis is found to be in good agreement with the measured extrusion temperature. The process condition required to reduce the AGG is determined on the basis of the distribution of the evolved microstructure in the hot extrusion experiment. The results confirm the relationship between the distribution of AGG and the mechanical properties of the extrudate. It is confirmed that the mechanical properties of Al6061 can be improved by the application of die cooling with N2 gas during the hot extrusion process.

Influence of Forward Extrusion on the Mechanical Properties and Microstructure of Homogenized AZ80 Magnesium Alloy

The forward extrusion experiments of homogenized AZ80 magnesium alloy were conducted in the extrusion temperature range of 300°C to 420°C and extrusion ratios between 15 and 75 to study the effect of plastic deformation on the mechanical properties and microstructure. The microstructure and mechanical properties of extrudate were measured by tensile tests and optical microscopy. The results demonstrated that the alloy grains were small, and small amounts of black hard and brittle second-phase precipitated at 330°C. When the extrusion temperature was up to 390°C, the grain size increased significantly, but the second phase precipitation became continuous. And then, in the case of the extrusion ratio of 60, the tensile strength of the alloy reached the peak value of 390 MPa. Inhomogeneous precipitation of the second-phase increased with the increasing of extrusion temperature. At the same temperature, the tensile strength increased firstly and then decreased with increasing extrusion ratio. With the gradual increase of the grain refinement, the dispersed precipitates increased and the tensile strength and plasticity reached their peaks when the extrusion temperature was 390°C. As the grain grew, the second phase distribution became inhomogeneous, and the strength and plasticity gradually decreased.

Microstructure and mechanical properties of ternary intermetallic compound dispersed P/M Al-Mn-X-Zr (x=Cu,Ni) alloys

Heat-resistant aluminum alloys are generally developed by dispersing stable intermetallic compounds by adding transition metals (TM) whose diffusion coefficient in aluminum alloys is low even at high temperatures. Commonly used intermetallic compounds include Al-TM binary intermetallic compounds, for example, Al6Fe, Al3Ti and Al3Ni. By contrast, multicomponent intermetallic compounds are hardly used. The present study focuses on Al-Mn-Cu and Al-Mn-Ni ternary intermetallic compounds, and by finely dispersing these intermetallic compounds, attempts to develop heat-resistant alloys. Through the atomization method, Al-(4.96–5.96)Mn-(6.82–7.53)Cu-0.4Zr and Al-(5.48–8.76)Mn-(2.23–4.32)Ni-0.4Zr (in mass%) powders were fabricated, and by degassing these powders at 773 K, intermetallic compounds were precipitated. These powders were then solidified into extrudates by hot extrusion at 773 K. The microstructural characterization of powders and exrudates was carried out by XRD analysis, SEM/EDX and TEM. The mechanical properties of extrudates were determined at room temperature, 523 K and 573 K. In Al-Mn-Cu alloys, while a small amount of Al2Cu was crystallized, precipitated Al20Mn3Cu2 intermetallic compounds were mainly dispersed. In Al-Mn-Ni alloys, while a small amount of Al6Mn intermetallic compounds was precipitated, the precipitated A60Mn11Ni4 intermetallic compounds were mainly dispersed. Both ternary intermetallic compounds were about 200 nm in size. The compounds were elliptical, and their longitudinal direction was oriented along the extrusion direction. In the Al-Mn-Cu alloys, since the work hardening at room temperature was high, the tensile strength became 569 MPa. At elevated temperatures, since hardly any work hardening was observed, the tensile strength decreased markedly. However, in Al-Mn-Ni alloys, since the work hardening is low even at room temperature, the roomtemperature strength is not high. Thus, the decrease in tensile strength at elevated temperatures is relatively small and a high strength was obtained at 523 K and 573 K: 276 MPa and 207 MPa, respectively.

Wood–PVC composites: formulation optimisation

A standard rigid PVC profile formulation has been optimised to better accept the wood fibre presence in terms of compatibility, dispersion level, rheology, extrusion output, physical and mechanical properties of extrudates. Several different additives have been evaluated at different use levels. Process aids and lubricants appear to be the most critical ones. The effects of wood flour type and content, PVC resin K value, as well as specific wood–PVC compatibilisers have also been investigated. It is concluded that PVC is the most suitable polymer matrix for wood–plastic composites applications.

Paste extrusion of polytetrafluoroethylene (PTFE): Surface tension and viscosity effects

The effects of the lubricant physical properties on the processing of polytetrafluoroethylene (PTFE) fine powder resins are studied. Lubricants having different surface tension and viscosity were used; the two properties changed independently. These effects were studied by using dies of various contraction angle and reduction ratio for resins having a variety of molecular architecture. It was found that the wettability (surface tension) of the lubricant strongly affects the pressure needed to extrude the PTFE pastes. The viscosity of the lubricant was also found to play a significant role in the process since a lubricant with a low viscosity causes the paste to be extruded at a lower pressure. These effects of the physical properties on the extrusion pressure influence significantly the mechanical properties of the final extrudates. The latter are functions of the degree of fibrillation, which is significantly influenced by the wettability and viscosity of lubricants. Finally, the effects of die geometry on extrusion pressure and mechanical properties of extrudates were also assessed in order to determine the geometrical characteristics and operation conditions for the optimization of the process.

Effects of Selected Process Parameters on Expansion and Mechanical Properties of Wheat Flour and Whole Cornmeal Extrudates

Mechanical properties of cereal extrudates are recognized by consumers as quality criteria. These properties are affected by process variables. The effect of process variables, such as water injection rate, barrel temperature, and screw speed on the expansion and selected mechanical properties of wheat flour and whole cornmeal extrudates was determined. A laboratory-scale twin-screw extruder with an L/D ratio of 25.0 was used. The cross-sectional expansion, the specific length, and the elastic moduli and breaking strength in bending and compression were measured. Water injection rate and barrel temperature significantly affected the cross-sectional expansion index (SEI) (P < 0.01), specific length (P < 0.01), elastic modulus in compression (P < 0.05), and breaking strength in bending (P < 0.05). The SEI was increased with a decrease in water injection rate and/or an increase in barrel temperature. The elastic modulus and breaking strength in bending decreased with the decrease in water injection rate. The SME input, which was dependent on the process variables tested, also influenced the expansion and mechanical properties of extrudates. The higher the SME input was, the lower the elastic moduli and breaking strength were. This result confirmed that the texture of extruded product was controlled by changing the SME input.

Ａｌ‐３％Ｆｅ‐３％Ｎｉ‐３％Ｃｒ‐０．７％Ｚｒ Ｐ／Ｍ合金のメカニカルグラインデング処理による高強度化

Mechanical grinding (MG) of air atomized Al–3Fe–3Ni–3Cr–0.7Zr (in mass%) alloy powder was performed with a vibrational ball mill for various times up to 154.8 ks in an argon atmosphere. Subsequently, MG powders as well as atomized powder were hot extruded to rectangular bar shapes (20 mm in width and 3.5 mm in thickness) at 673 K. The effect of MG time on the mechanical properties of extrudates up to 673 K and on the microstructures of MG powders and extrudates was investigated. Vickers hardness of MG powders increased to about 300 with increasing of MG time up to about 30 ks. The results of DSC, XRD and TEM revealed that the primary intermetallic compounds in atomized powder were finely ground and dispersed by MG. The results also suggest that elements consisting of the compounds were dissolved in the matrix beyond their equilibrium solubility by prolongation of MG time. MG and subsequent hot extrusion processes at 673 K resulted in giving extremely fine sub-grains. On boundaries or interior of the sub-grains, the transition elements dissolved in the matrix by MA were precipitated finely as Al3Fe, Al3Ni and Al13Cr2 phase particles. The tensile strength at ambient temperature and at 573 K were about 431.9 MPa and 208.7 MPa for extrusion specimen from atomized powder, and 675.7 MPa and 281 MPa for extrusion specimen from 154.8 ks-MG powder, respectively. However, the ductility was poor in MG materials. Improvements in the mechanical strength are mainly attributed to the presence of extremely fine sub-structure and finely dispersed particles which were introduced during MG and extrusion process.

Phase heterogeneity of melts of a liquid crystalline copolyester and its effect on the rheology and also the structure and mechanical properties of extrudates

The kinetics of change in the viscous properties of LC melts of a copolyester containing units of phenyl hydroquinone and terephthalic and p-hydroxybenzoic acids has been studied. Two temperature regions were found in which the rheological properties of the coppolyester significantly differ: at low temperatures continuous rise in viscosity is observed and at high ones viscosity remains constant with time. The copolyesters in the low temperature region are characterized by a viscosity anomaly. The DSC data indicate that the rheological behaviour of the copolyesters at low temperatures is determined by the recrystallization process. The thermal and mechanical prehistory influences the rate of recrystallization. The physicomechanical characteristics of the extrudates of the copolyester improve on passing from the low to the high temperature region of formation. Electron microscopic and X-ray structural investigations point to an improvement in the molecular orientation of the extrudates with rise in temperature. The presence of a crystalline phase in the copolyester melt hampers the orientation and worsens the mechanical characteristics.

Twin-screw extrusion cooking of starches: Flow behaviour of starch pastes, expansion and mechanical properties of extrudates

Several starches, corn and durum wheat semolina, and wheat flour were extruded with a twin-screw, pilot-scale machine (Creusot-Loire BC 45). After grinding, pastes of the extruded samples were made and flow curves were obtained at 60°C with a coaxial-cylinder viscometer: a power law can be used to describe them from about 20 to 2600 s −1. Apparent Young's moduli and rupture strengths of extrudates were evaluated with an Instron, and their diametral and longitudinal expansion measured. The following variables were studied: corn semolina water content, barrel temperature and the corn starch amylose/amylopectin ratio. When water content and barrel temperature vary within certain limits, the values of the constants in the power law equation describe a characteristic line which depends on the amylose and lipid contents of the starch. The formation of an amylose-lipid complex during extrusion is suggested as a key factor in the flow properties of pastes and probably also in the rupture strength of extrudates. There is generally a negative correlation between longitudinal and diametral expansion. It is considered that volume expansion phenomena are mainly dependent on viscous and elastic properties of melted starch.