Closed-cell

Now using a hydrocarbon component, say ethane, as an example, let us consider the other parameter, volume, using a plot of pressure versus specific volume (i.e. volume per unit mass of the component, the inverse of the density). The process to be described could be performed physically by placing the liquid sample into a closed cell (PVT cell), and then reducing the pressure of the sample by withdrawing the piston of the cell and increasing the volume contained by the sample. 

The fraction of open cells expresses the extent to which the gas phase of one cell is in communication with other cells. When a large portion of cells are intercoimected by gas phase, the foam has a large fraction of open cells, or is an open-ceUed foam. Conversely, a large proportion of noninterconnecting cells results in a large fraction of closed cells, or a closed-ceUed foam. 

The Dynamit-Nobel extmsion process (252) utilizes a volatile plasticizer such as acetone which is injected into the decompression section of a two-stage screw and is uniformly dispersed in the vinyl resin containing a stabilizer. The resulting PVC foam has low density and closed cells. 

Fig. 25.8. Poly meric foams, showing the polyhedral cells. Some foams hove closed cells, others hove cells which ore open.

Whilst rigid closed-cell polyurethanes are excellent thermal insulators they do suffer from a limited and often unsatisfactory level of fire resistance, even in the presence of phosphorus-containing and halogen-containing fire retardants. Considerable promise is now being shown by the polyisocyanurates, which are also based on isocyanate chemistry. 

Clamping plate Closed-cell foam Cohesion Cold flow... 

Closed-cell foam Cellular plastic that is composed predominantly of noninterconnecting cells. 

A high-performance, closed-cell adiabatic calorimeter. 

Closed-cell flange protectors are much less expensive than stainl bands. However, if not installed properly they can actually accelerate c msion if a path is created through the material to allow moisture to en... 

Thermal insulation is available over a wide range of temperatures, from near absolute zero (-273 C) ( 59.4°F) to perhaps 3,(1()0°C (5,432°F). Applications include residential and commercial buildings, high- or low-temperature industrial processes, ground and air vehicles, and shipping containers. The materials and systems in use can be broadly characterized as air-filled fibrous or porous, cellular solids, closed-cell polymer foams containing a gas other than air, evacuated powder-filled panels, or reflective foil systems. 

The R s of a fibrous or cellular insulation like those in Table 2 generally decrease as the temperature increases. In the case of closed-cell polymeric foams like polyurethane nr pnlyisncyanurate board, the R may decrease if the insulation temperature drops below the condensation temperature of the blowing agent in the cells. This is because of changes in the gas- phase composition and therefore the gas-phase thermal conductivity. The R of insulations also depends on density when all other factors are constant. The relationship bett een R and density... 

Its closed-cell structure makes cellular glass particularly suitable for refrigeration applications on pipes and cold stores. High load-bearing capacity enables it to be used under rooftop car parks. 

One example is the use of rigid selfexpanding closed cell polyurethane foams as a method to inhibit corrosion of the interior surfaces of metal (steel, etc.) structural cavities exposed to seawater and moisture is one of many example of plastic providing corrosion protection. Unfilled metal cavities are a general feature of various structures or products used in the marine, building, electronics,... 

Property ASTM Test Phenolics Foamedin Syntactic Place Castable Polyvinyl Chloride Rigid Closed Cell Phenylene Oxide Foamable Resin Polycarbonate Polystyrene Medium-Density Foam Polystyrene Molded Extruded Polyurethane Rigid Closed Cell... 

Most rigid polyurethane foams have a closed cell structure. Closed cells form when the plastic cell walls remain intact during the expansion process and are not ruptured by the increasing cell pressure. Depending on the blowing process a small fraction (5-10%) of the cells remain open. Closed cell structures provide rigidity and obstruct gaseous or fluid diffusional processes. 

Fig. 8-53 Example of how a closed-cell PE foam density affects both its cushioning and its loading.

Fig. 8-54 A closed-cell PE foam at different densities compared to its cushioning efficiency.

Bulk microstructure Continuous channels Between fibers Complex foam to vertically oriented channels Closed cell to open cell foam None... 

During construction, all possible penetrations between the crawlspace and the house should be sealed to simply prevent the passage of radon up into the living areas. Attempts to seal penetrations can be made by using expandable closed-cell foam sealants and urethane caulk. Sealing these areas can be difficult because of limited access even during construction. Areas of particular concern include9... 

Poly(aryloxyphosphazene) elastomers can be cured with peroxides, sulfur and radiation. The resulting vulcanizates are resistant to attack by moisture and oils and have been found to have desirable characteristics for electrical insulation applications where fire safety is a concern (Table II) (12). Fire resistant, low smoke, closed cell foams with excellent properties (Table III) have also been developed from poly(aryloxyphosphazene) elastomers (13). Applications for these foams, which can be produced as either slabstock or tube stock, are being developed for military, aerospace and commercial uses. (See Table II and III.)... 

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... 

Rigid polyurethane foams can be made from either polyester or polyether prepolymers, which are crosslinked with polyfunctional isocyanates. The resulting foams are largely closed cell, with only about 5 to 10% of cells being open. Rigid polyurethane foams are widely used as insulation in commercial, residential, and industrial settings. 

Foamed polymeric materials can have either a closed or open cellular structure. Closed cells tend to be favoured when the pressure is maintained during the expansion. Both types are used for different applications, e.g., closed for thermal and sound insulation, open cell for soaking up liquids by capillary... 

---