Elastic foams

This low pressure process, also known as elastic reservoir molding, consists of making basically a sandwich of plastic-impregnated open-celled flexible polyurethane foam between the face layers of fibrous reinforcements. When this plastic composite is placed in a mold and squeezed, the foam is compressed, forcing the plastic outward and into the reinforcement. The elastic foam exerts sufficient pressure to force the plastic-impregnated reinforcement into contact with the heated mold surface. Other plastics are used. 

Foam formation in a boiler is primarily a surface active phenomena, whereby a discontinuous gaseous phase of steam, carbon dioxide, and other gas bubbles is dispersed in a continuous liquid phase of BW. Because the largest component of the foam is usually gas, the bubbles generally are separated only by a thin, liquid film composed of several layers of molecules that can slide over each other to provide considerable elasticity. Foaming occurs when these bubbles arrive at a steam-water interface at a rate faster than that at which they can collapse or decay into steam vapor. 

The properties of polyurethanes can be tailored by prudent selection of their constituent monomers. They can be converted into elastic foams, which are widely used in upholstery, and are used as covers for the handles of various tools and implements, such as the soft touch grips on bail-point pens and power tools. 

Units for producing slabs of expanded (foamed) polyurethane are also equipped with a conveyer belt with side walls. The initial mixture is continuously fed onto the line, then foamed, and finally passed into a solidification chamber, where it is heated under IR lamps. Commercial lines for making slabs of elastic foamed polyurethane are up to 125 m long. The items produced can be up to 2 m wide and 1.5 m high. 

These differences in sulfonate and carhoxylate associations are believed to be important factors in potential applications involving these ionomers, such as thermoplastic elastomers (8), elastic foams (14), solution applications (13), and related uses (6). 

The composition of the foam was studied by the use of renewable raw materials, including new HUM. As a result, hard and elastic foams were obtained with properties not inferior to polyurethane foams. The foams were produced in the laboratory only (Table 4.9). 

At present, the elastic foams hold the greatest interest. They are made by reacting hydroxyl-terminated resins like castor oil, polyether glycols, or polyesters with a diisocyanate and water in the presence of a catalyst. Two simultaneous reactions occur. The first is the reaction of the diisocyanate with the hydroxyl groups in the resin, and the second is the reaction of the diispeyanate with water, liberating carbon dioxide. As the elasto-... 

Hard, scanihard and soft elastic foams Closed-cell, open-cell and mixed-cell... 

Polyurethane foam synthesis can be modified by additions of PEG in such a way that an open-cell, very flexible, highly elastic foam is produced, for example, for upholstery. 

The creep behavior and mechanism of several visco-elastic foams were analyzed in this paper to understand the stmcture property relationship. The creep behavior and recoverability of these foams were characterized by the compression set, short time creep test, as well as hysteresis with an optical extensometer. The creep mechanism was analyzed and explained based on foam cell structure (cell orientation and uniformity) and material properly. Material parameters and cell stmcture that possibly control the creep and recoverability of visco-elastic foams are also discussed. 

Two visco-elastic foam samples were selected for this investigation and were designated as VE foam 1 and 2. VE foam 1 is a toluene diisocyanate (TDI) based and VE foam 2 is a methylene diphenyl diisocyanate (MDI) based viscoelastic foam. Some basic material characterizations were run to characterize these two foams such as density, air flow, compression set (90%) according to the ASTM 395 B standard, resiUency (ball rebound), and resiliency (BASF recovery). 

The results of meehanieal analysis of two viseo-elastic foams analyzed in this paper show clearly differentiation in stress strain behavior, ereep and eompression srt, and recoverabihty. It was known that mechanical property of foam depends on material chemieal structure, phase morphology, strut dimension, eell structure, and cell orientation and imiformity. The question is why these two visco-elastic foams have different eonqjressive stress strain behavior and compression set. For foam 1 we observed an elastomeric behavior under the compressive stress up to 60% of strain. The foam shows visco-elastic behavior when it was loaded and unloaded at different strain levels. However, for foam sample 2 under the compressive loading we observed elastic deformation, plateau due to possible localized buckling, and densification. 

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