Polyurethanes Open cell

AMS 3570D-89 Foam, Flexible Polyurethane, Open Cell, Medium Flexibility, 7 pp (DOD Adopted) (FSC 9330) (AS)... 

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. 

The most common methods for trapping pesticide vapors from air use adsorbents. Common air sampling adsorbents include charcoal (derived from petroleum or coconut) and synthetic polymeric materials, such as cross-linked polystyrene and open-cell polyurethane foam. Charcoal has been used for the cumulative sampling of volatile... 

Some of the key factors that lead us to select polyurethane foam for upholstery are its durability, resilience, and controllable hardness (or softness, depending on your point of view). Vibration dampening and shock absorbance are important attributes in automobile and public transportation seating. Open cell foams are preferred for these applications because they allow for air and moisture transport, which improve the comfort of passengers who may occupy a seat continuously for several hours. This inherent breathability is also a valuable attribute in mattresses. Shock absorbance plays a key role in selecting flexible polyurethane foams for the packaging of fragile items. 

Materials. The flexible polyurethane (polyether) foam, formulated from a polyol, tolylene diisocyanate, emulsifier, catalyst, and blowing agent, was obtained from the Nopco Chemical Co. It had a density of about 1.5 pounds per cubic foot (0.02 gram per cc.) and contained approximately 40 open cells per linear inch. The foam samples were washed in detergent, dried, and weighed before being irradiated. 

In recent years, we have become integrated into the much larger world of polyurethanes, but we have always begun our investigations with a focus on the surface chemistry. While our studies have been on the full range of polyurethane chemistries and the full range in which polyurethanes are produced, the chemical aspects in which we are most interested are foams (the bulk of polyurethane production), specifically open-celled foams, and more specifically products known in the industry as reticulated foams. 

This chapter introduces readers to the versatility of polyurethane polymers without spending too much time on the chemistry. The next chapter will discuss a more classical view of the molecule and how it is developed. Our point, however, is to present a functional view of this system. We have examined its physical characteristics, focusing our attention on the uniqueness of reticulated foams. All the chemical points we have made apply to all polyurethane polymers, whether they are open-celled foams, closed-cell foams, or thermoplastic elastomers. 

The production of an open-cell foam by the techniques described above only partially covers the polyurethanes considered most useful in the context of this book. Open-cell foams are converted to reticulated foams by a postprocessing technique. Two techniques are used in the U.S. The oldest involves immersing the foam in a... 

This study was reported with another set of experiments that confirmed the growth of fibroblasts in connection with an experimental bum dressing. " While our work was positive enough to warrant further research, a technical problem prevented continued work. While we felt the surface chemistry was a necessary component of a successful artificial liver, it was not sufficient. In order to build a successful device, fluids must be able to enter and exit the environment freely. We discussed the differences in structure between open-celled polyurethanes and reticulated foam earlier. 

Until the late 1980s trichlorofluoromethane (CFC 11) was also used to blow flexible, open-celled polyurethane foams used in furniture upholstery however, the rapid loss of the blowing agent to the atmosphere meant that this CFC application was one of the first to be eliminated when concern over the possible effects of CFCs on stratospheric ozone increased. Similarly, dichlorodifluoromethane (CFC 12) in the relatively minor application of polystyrene hot-food containers was also rapidly replaced by hydrocarbon-blowing agents. 

Polyurethane sponge foam. One fabricator offers a coalescer design employing an open-celled polvure-thane foam in a horizontal tank (Fig 4). 

Flexible Polyurethane. 1 hcse foams are produced from long-chain, lightly branched polyols reacting wilh a diisocyanale. usually toluene diisocyanale (TDI), to form an open-celled structure wilh free air flow during flexure. During manufacture these foams arc closely controlled for proper density, ranging from 17 to 80 kg/ml (0.8-5 Ibs/ft ). to achieve the desired physical properties and cost. 

A polishing pad has a significant impact on the performance of the CMP process. It transports the slurry to the pad-wafer interface, impacts the polishing nonuniformity, and affects the global wafer and device planarity. Pads may consist of thin porous closed cell [28], open cell [29], or noncell [30] polyurethane material. The properties of polishing pad can be studied in detail... 

According to Thomas elastic polymers often produce open-cell foamed plastics, whereas rigid polymers generally form closed-cell materials. However, there are many exceptions to this rule, owing to the variety of blowing techniques. Closed-cell structures are more likely to be produced from polyurethanes, epoxy resins, silicones, poly(vinyl chloride), polystyrene, etc., whereas open-cell materials mainly result from phenolic and carbamide foamed plastics. 

We should now consider the factor 6 in the numerator of the pre-exponential in Eq. (14) which has the physical meaning of either a form factor, packing factor or coordination number of the closest spherical (cubic) sphere packing. The points of Fig. 3 are somewhat scattered probably because of the equal proportions of open cells (9J in samples of different volume weights. Eq. (14) has a maximum when 9(,/9p = 1 (Fig. 3), i.e. when the volume ratio of polymer in a sample is equal to that in a plastic foam with closest spherical packing the gas phase volume is then 74% which, for polyurethane foam, corresponds to a volumetric weight of 315 kg/m. ... 

Foaming the polymer creates small, open cells that are able to hold fluids and the cell size may be controlled during the foaming process. The most common polymer used is polyurethane. Their structure and softness also provide a cushion that protects and contributes to thermal insulation of the wound. They also may be tailored for particular applications such as tracheostomy dressing without particle loss to the wound and with the retention of their conformable characteristics. The non-adhesive foams will require a secondary dressing. 

Braun, T., Faiag, A. B. Plasticized open-cell polyurethane foam as a universal matrix for organic reagents in trace element preconcentration I. Collection of silver traces on dithizone foam. Anal Chim. Acta 69, 85 (1974)... 

Surfactants. A surfactant is a major raw material for polyurethane foams. Surfactants play an important role in obtaining required cell structures, e.g., fine cells, coarse cells, closed cells, and open cells, and these cell structures then influence foam properties. 

Classification. Flexibie urethane foams have the largest market of all polyurethane products. The production properties and applications of various flexible urethane foams are described in the following sections. Flexible urethane foams are defined as open-cell urethane foams having the property of complete recovery immediately after compression. They can be classified into two kinds, i.e., polyether foams and polyester foams. Polyether foams are further classified as follows conventional flexible foams, high-resilience flexible foams (HR foams), cold-molded foams, super-soft foams, and viscoelastic foams. 

It is clear from Figure 12 that open-cell foams can be obtained only by a good balance between two reactions, i.e., polyurethane formation and gas generation. When gas generation is too fast, the rising foam may collapse like beer bubbles, because the foam is not stable. 

This book describes the chemistry, manufacture and use of the wide range of flexible polyurethane foams, from low-density open-cell upholstery foams to microcellular and reaction- injection-molded and reinforeed-reaction-injection-molded materials. The related effects of varying the raw-material chemistry and the production process and machinery on the properties and service performance of the final product are indicated. 

Type I is closed-cell polyethylene and Type II is open-cell polyurethane. 

This Navy specification covers a single class of foam, nominal density 2.0 Ib/ft rigid unicellular polyurethane foam, and the materials required for preparation by the foam-in-place technique. Requirements cover density, compressive strength, volume change after heat aging, humidity aging, compressive set, unicellularity (% open cells, max.), oil resistance, and fire resistance. 

M1L-F-81334B(AS) Foam, Plastic, Flexible, Open Cell, Polyester Type, Polyurethane, 5 July 1977, 16 pp (FSC 5340) (AS)... 

A solid chelating material, l-nitroso-2-naphthol supported on silica gel, provides a rapid and highly selective mean of separating traces of Co(II) from natural waters [19]. Open-cell polyurethane foam loaded with PAN azo reagent [20], and organic resins modified with nitroso-R salt have been used similarly [21,22]. 

Polypropylene (G/F)/nylon 6,6 Polyurethane open/closed cell foam Polypropylene (mica filled/glass filled/mineral filled) Aluminum tube AA4343/AA3003 base Aluminum tube AA4343/AA3003 base Nylon 6,6/nylon 6/polypropylene Nylon 6,6/nylon 6 Polypropylene (GF)... 

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