Extrusion and expansion

One method of producing hard, amorphous, glassy, starch-based materials is to use an extruder. A starch-based melt at typically 30% moisture can be forced through a die to 

Mechanical measurements of the glass transition are frequently preferred to those of DSC, due to the much higher sensitivity. 

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Two dominant processes have developed for the production of PS foam extrusion and expansion of foamable beads. For polystyrene, the polymerization process is endothermic and, therefore, requires external heat. This requirement essentially eliminates the in situ application of insulation as is possible with the exothermic PU foams. 

Seker M, Sadikoglu H, Ozdemir M, Hanna MA. 2003. Cross-linking of starch with reactive extrusion and expansion of extrudates. Int J Food Prop 6 473 80. 

Foamed polystyrene - which is also known as expanded polystyrene - is used extensively in a variety of applications, ranging from packaging peanuts to insulation board and single-use cups and plates. We produce it by two processes foam extrusion and bead expansion. Both types of expanded polystyrene consist of closed cells, i.e., bubbles with continuous walls. We can visually distinguish the two types of foam by the fact that products made by the expanded bead process consist of discrete beads that are welded together... 

On the other hand, small-ring alkenes such as diphenylcyclopropene derivatives (125) may serve as substrates for the preparation of six-membered heterocycles by way of the cycloaddition-extrusion-ring-expansion reaction. Thus, thd reaction of (9) with (125a) leads to formation of (127a) via the primary adduct (126), whereas the reaction of (9) with (125b) yields (127b) and the tricyclic derivative (128) (75JCS(P1)632). 

Puffed extrudates and other expanded foods ean exhibit different mechanical properties if tested axially or transversaUy, that is, in the extrusion s direction or perpendicular to it. An example is shown in Figure 10.15. This is a manifestation of the oriented structure formed during the materials shear and expansion. Although the differences can be easily picked up by a testing machine, it is unclear whether they can also be perceived sensorily by humans. 

It has been demonstrated that molecular orientation can be achieved starting with a low molecular weight species which is oriented in an elongational flow and subsequently cured under UV-irradiation. The orientation of the monomer is frozen-in by the ultra-fast process of polymerization and crosslinking. Both extrusion and stretching can be carried out at relatively low temperatures and pressures. Polymer filaments produced in this way are definitely anisotropic as is evidenced by their birefringence and by a strong increase of the tensile modulus and a decrease of the thermal expansion coefficient in the axial direction. 

Methods for stabilization of rice bran have been reviewed (37). These include dry heating, wet heating, and extrusion. The most practical method has been the use of extrusion or expansion methods. 

Effect on Energy The energy fraction of the diet can be broken into two parts carbohydrate and fat. First, the carbohydrate fraction, which is primarily starch, is greatly affected by extrusion or heat and expansion. 

Effect on Fat Extmsion, or heat and expansion, effects fat in two ways. First, fat or oil is encapsulated within the cells of oilseeds. When a raw oilseed is ground, the resulting product wiU be dry. During extrusion, the oil is released from the cells making the product oily. The extent to which cells are rupmred in a dry extruder has not been measured. 

Cycloaddition-extrusion-ring expansion reactions of five-membered mesoionic oxazolones and thiazolones with 2,3-diphenylcyclopropenethione produced pyridine-4(l//)-thiones... 

Further examples including extrusion and ring expansion reactions <75JCS(Pi)632> as well as intramolecular [3 -I- 2] cycloadditions have been reported <81LA347>. In addition, the mesoionic 1,3-dithiolones (124) react with formaldehyde regiospecifically in a [3 -i- 2] cycloaddition reaction with formation of the 2-oxa-6,7-dithiabicyclo[2.2.1]heptanone derivative (125) (Equation (17)) <78CB3l7l>. Furthermore, upon reaction with the N=N bond of dimethyl azodicarboxylate, (126) is obtained (Equation (18)) <78CB3171>. 

Refractory oxides are an important class of materials that enable processes to exploit extreme environments. A wide variety of unary, binary, and ternary oxides can be considered refractory, based on their melting temperatures. Refractory oxides are generally prepared from powdered precursors using standard ceramic forming techniques such as casting, pressing, or extrusion, and subsequently sintered to achieve final density. In addition to chemical compatibility, the physical properties of refractory oxides such as thermal expansion coefficient, thermal conductivity, modulus of elasticity, and heat capacity must be considered when selecting an oxide for a specific application. 

Hoses and expansion joints Paste extrusion, melt extrusion PTFE, PFA, FEP, ETFE... 

The dipolar cycloaddition of sydnones (l,2,3-oxadiazolidin-5-one derivatives) (108) with benzocyclobutene (109) has been used to synthesize 3 f-2,3-benzodiazepines (110). This synthesis involves a cycloaddition-extrusion-ring-expansion sequence, and with other mesionic compounds, for example the thiazolium-4-olate (111), primary cydoadducts (112) were isolated (Scheme 13)... 

Fig. 14 Combined de-airing extrusion unit with vertical primary pug sealer and expansion barrel...

Dicyanomethylenediphenylcyclopropene and an equimolar amount of mesoionic 3-methyl-2,4-diphenylthiazol-5-one refluxed 8 hrs. in xylene -> product. Y 74%. F. e. s. H. Matsukubo and H. Kato, Soc. Perkin I 1975, 632 4H-l,4-thiazine 1,1-dioxides by cycloaddition-extrusion-ring expansion s. Chem. Lett. 1975, 1153. 

Tubing is used in many industries for the transport of fluids. One of the more interesting applications is heat shrinkable tubing, which is made by extrusion, followed by crosslinking and expansion. Another important use is in the medical industry as catheter tubing. One of the more sophisticated medical devices based on polymeric tubing is the balloon catheter used for percutaneous transluminal coronary angioplasty. 

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