Whole sorghum kernels were directly processed into whole grain snacks with acceptable texture. Extrudates made from whole sorghum had a harder gritty texture than those made from decorticated materials. Extrusion of whole sorghum provides significant savings in processing: there are no dry matter losses; no equipment or energy is required for decortication or milling; the extruder consumes less power and processes more material per time unit. In addition, the extruder utilized is a simple adiabiatic, friction extruder of relatively low cost. Grinding whole sorghum and removing fines did not improve product expansion during extrusion but altered the gritty pieces in the extrudates. The best products were obtained when whole sorghum (ground or un-ground) was extruded at 14% moisture. The whole sorghum extrudates had larger bubbles with thick cell walls, which made extrudates more crunchy. Decortication of sorghum improved extrusion performance and products by allowing adequate formation and retention of air cells. Decortication to remove 20% of the original sorghum weight was enough to produce extrudates with characteristics comparable to those made from commercial yellow corn meal. Sorghum milled fractions with composition and particle size distribution similar to corn meal produced extrudates with higher expansion, lower bulk density and similar texture. In addition, sorghum extrudates were rated equal to corn meal extrudates by a taste panel for appearance, flavor, texture and overall characteristics. Extrudates made from polished rice were less expanded and whiter than extrudates made from sorghum. When processed under similar conditions, sorghum extrusion required more energy than corn meal extrusion. However, whole sorghum extrusion required less energy than corn meal extrusion. Unground sorghum samples (decorticated or non-decorticated) produced harder extrudates compared to those made from ground raw material. White sorghum is a feasible option for snack extrusion because of its versatility, product characteristics, cost and processing properties.

The objective of this project is to design a tool for moderate cross section reduction of bars that are deformed within a channel slider tool that is used for equal channel angular extrusion (ECAE). The bars that are deformed via ECAE have an initial square cross section with a nominal value of 1.00 in2 and aspect ratios (length/width) ranging between 4 and 6. A systems engineering design methodology is used to generate a topbottom approach in the development of the tool's design. This includes defining a need statement, which is the "Need for an area reduction extrusion tool to replace the current practices of machining ECAE processed billets". The system functions and requirements are defined next and used to generate three concepts that are compared to select the winning concept for further refinement. Major components of the selected tool are: a container, ram, base plate, punch plate, four die-inserts, four wedges and four flange locks. For materials, such as copper (C10100) and aluminum (Al6061-T6), that can be processed by this tool, the upper bound extrusion pressure, which is derived by limit analysis, is set at 192 ksi. The upper bound extrusion pressure is constrained by the buckling limit of the ram, which is 202 ksi. The maximum wall stress experienced by the container is 113 ksi. For materials with the same cross section and dimensions, fixed end conditions of the Ram support larger bucking loads when compared to other end conditions such as rounded ends or rounded-fixed ends. With the application of the upper bound method, an increase in the extrusion ratio of the tool causes a corresponding rise in the optimal cone angle of the die further translating to a rise in the extrusion pressure.

Reproduction de : Thèse de doctorat : Sciences pour l'ingénieur: génie des procédés : Reims : 2005. / Titre provenant du cadre-titre. Bibliogr. f. 191-200.

Reproduction de : Thèse de doctorat : Sciences de l'ingénieur : Mécanique des matériaux : Metz : 2004. / Titre provenant de l'écran-titre. Notes bibliographiques.

Reproduction de : Thèse de doctorat : Chimie macromoléculaire : Lyon 1 : 2005. / Titre provenant de l'écran titre. 173 réf. bibliogr.

We present a platform that allows homogeneous and heterogeneous 3-D soft materials to be continuously defined in a single step. Biopolymer solutions are introduced to a microfluidic device and radially distributed to feed to a common outlet at the device center. This forms concentric sheaths of complex fluids and upon crosslinking, a hydrogel tube at the exit. This approach allows for the controlled and continuous extrusion of tubes with tailored diameters of 500 μm to 1500 μm, wall thicknesses of 20 μm to 120 μm, and compositions, as well as predictable mechanical and chemical properties. Using the same platform, single and multi-walled hydrogel tubes with defined heterogeneities and patterns of discrete spots of secondary biopolymer materials can be continuously extruded. A tube-hosting device is presented which can independently perfuse and superfuse isolated tube segments, allowing precise microenvironmental control without cannulation for up to an hour.

We present a platform that allows homogeneous and heterogeneous 3-D soft materials to be continuously defined in a single step. Biopolymer solutions are introduced to a microfluidic device and radially distributed to feed to a common outlet at the device center. This forms concentric sheaths of complex fluids and upon crosslinking, a hydrogel tube at the exit. This approach allows for the controlled and continuous extrusion of tubes with tailored diameters of 500 μm to 1500 μm, wall thicknesses of 20 μm to 120 μm, and compositions, as well as predictable mechanical and chemical properties. Using the same platform, single and multi-walled hydrogel tubes with defined heterogeneities and patterns of discrete spots of secondary biopolymer materials can be continuously extruded. A tube-hosting device is presented which can independently perfuse and superfuse isolated tube segments, allowing precise microenvironmental control without cannulation for up to an hour.

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This creative project has investigated the engineering principles relative to the design and construction of a blown tubular film take-off system. The study has also made a careful analysis of the equipment necessary to construct a blown tubular film extrusion line.In addition, the creative project has discussed alternate methods of producing polyolefin filets, it has suggested possible solutions for troubleshooting which can provide valuable assistance in the successful production of quality blown tubular film.

The effect of molecular weight on polypropylene (PP) extrusion foaming was investigated and the process to make soft touch, largely expanded, high cell density non-crosslinked PP foam using environmental friendly CO2 is presented. In previous research, when the cell density was high, cell opening was dominant and large expansion could not be achieved even in HMS PP materials. The effects of processing and material parameters on the foam morphologies of PP materials with three different melt flow rate (MFR) were studied using single-screw tandem foam extrusion system. By selecting proper material and die, and by tailoring the processing conditions, large expansion (25 fold) and high cell density (>109 cells/cm3) was successfully achieved in the high MFR PP without any additives. The mechanism of locally induced crystallization was found to be significantly affecting the foaming behavior of PP and was successfully verified using SEM, DSC, HPDSC, shear viscosity and solubility measurements.