Processing methods foaming

There are many solutions according to the materials, output and processing methods, for example rigid beam, damping foam and skin with various thermoplastic versions such as ... 

All molten-state processing methods are usable extrusion, injection, compression, blown film, blow moulding, thermoforming, foam, co-extrusion, machining for high hardness grades, welding. 

All the molten-state processing methods can be used, mainly extrusion, injection, blow moulding, co-extrusion, foaming, welding, crosslinking. 

Foamed plastics can be classified in different ways, for instance by their nature (flexible vs. rigid), chemical composition of the matrix, density, cell size, cell structure (open-celled vs. closed-celled), processing method, and dimensions. It is the aimed combination of these properties that determines the final application of the cellular polymer. As an example, open-celled ultra-low density foams are highly desirable for acoustical insulation, while rigid foams with closed-cells and elevated densities are preferred as load-carrying core materials in composite materials. 

The objective of this paper Is to describe the United Merchants and Manufacturers continuous foam processing method for the finishing and coloring of textiles. The term "continuous Is used to distinguish It from the batch foam dyeing process known as the Sancowad process developed and commercialized by the Sandoz Colors and Chemicals Co. (j6). 

Eqs. (5.34-5.36), (5.38), (5.42), (5.44) and (5.46) describe the process of foam drainage at complete immobility of border surfaces. Calculation of drainage rate with the correction p being a function of surface viscosity is possible only by numerical methods. 

A method of parallel plate mode was used to estimate the shear stress and viscosity of a foam [35], The lower plate was fixed and the upper one was rotated. In order to exclude the slip of the foam on the walls the plate was covered with a sand paper. To diminish the drainage and coalescence processes, the foam was produced from a solution with a high concentration of the foaming agent to which dodecyl alcohol was added. Proper linear... 

High expansion ratio foam can be produced by stream generators or by any other modes and then dried by creating reduced pressure from one side of the porous plate, the other side being in contact with the foam (see Section 1.2). This method of foam drying proves to be the only one used in industry [9-12]. The process of foam centrifugation in order to reach a... 

The lower concentration limit of the applicability of the foam separation method is determined by the lowest residual concentration and depends on the surface activity of the substances, the rate of establishing of the adsorption equilibrium, foam stability and the apparatus used in the process. During foam accumulation the surfactant is extracted from the solution, thus leading to a decrease in foam stability and expansion ratio. Finally, a concentration is reached at which the foam cannot be withdrawn from the apparatus and the accumulation ratio becomes close to 1. 

The particular case of polymer-oligomeric compositions creates new technological possibilities such as the preparation of foamed articles directly at the place of utilization by foaming solutions or pastes at room temperature or sl tly elevated temperatures. It als) leads to a considerable reduction of enei consumption as cOTii ed to traditional processing methods (extrusion, casting and pressing). 

There are various secondary processing methods permitting the finished closed-cell foams to be converted to open-cell foams by breaking the cell walls. This is achieved by hydrolysis, oxidation, application of elevated or reduced pressure, heat or mechanical treatment By such a modification an original macrostructure... 

Important processing methods injection molding, blow molding, rotational molding, extrusion, foam molding, compression molding, transfer molding... 

The seventh trend is the increasing use of novel processing methods. For example, there is growing use of supercritical fluids (e.g., supercritical carbon dioxide and nitrogen gases) to foam polyolefin blends for density reduction. There is use of ultrasound to, for example, devulcanize cross-linked rubber. There is use of solid-state shear mechanical processing to break the polyolefin blend material into submicron particles to make environment friendly (water-based) polyolefin dispersions. There is use of electrospinning technique to make polyolefin fibers and in particular nanofibers. 

Several processing methods use foaming as a part of the manufacturing process. These methods and their products are included here, with the exception of coated fabrics, which also contain a foamed layer. Coated fabrics are discussed in the section on web coating. 

Certain methods for making PI foams utilize solutions of diamines and dianhydrides or dianhydride derivatives in a low-molecular-weight alkyl alcohol solvent. The precursor solutions or powders are then processed into foams through the expulsion of water and alcohol during a thermal imidization process. Some processes require the application of microwave radiation to initiate the foaming process. 

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