Polystyrene foams physical properties

Expandable polystyrene with improved properties has been obtained by copolymerization, postreaction, additives, or by physical means. Improvements have been achieved particularly in resistance to premature fusion of particles during expansion, in reducing cell size, in self-extin-guishability, in attractive coloration, in resistance of foams to attack by gasoline and in dimensional stability of foams at elevated temperatures. 

It is evident that polystyrene foams have a broad range of physical properties (Table 10.1) [22,23] the manufacturer should be consulted for the properties of... 

Table 10.1 Physical properties of commercial extruded polystyrene foams ASTM C578 - Standard for Rigid, Cellular Polystyrene Thermal Insulation... 

In foundation insulation, rigid plastic foams are widely used. A covering over the foam provides protection against ultraviolet light and physical damage. The properties of extruded polystyrene foam make it a desirable insulation for foundation applications. 

The materials employed for making hollow microspheres include inorganic materials such as glass and silica, and polymeric materials such as epoxy resin, unsaturated polyester resin, silicone resin, phenolics, polyvinyl alcohol, polyvinyl chloride, polyjM-opylene and polystyrene, among others, commercial jx oducts available are glass, silica, phenolics, epoxy resin, silicones, etc. Table 36 shows low-density hollow spheres. Table 37 shows physical properties of glass microspheres, and Table 38 shows comparison of some fillers on the physical properties of resulting foams (10). 

Table 52 Comparison of Physical Properties of Thermax and Polystyrene Foams (35)...

A variety of foams can be produced from various types of polyethylenes and cross-linked systems having a very wide range of physical properties, and foams can be tailor-made to a specific application. Polypropylene has a higher thermostability than polyethylene. The production volume of polyolefin foams is not as high as that of polystyrene, polyurethane, or PVC foams. This is due to the higher cost of production and some technical difficulties in the production of polyolefin foams. The structural foam injection molding process, described previously for polystyrene, is also used for polyethylene and polypropylene structural foams (see Figure 2.61). 

Expanded polystyrene foam (EPS) has different applications, because of its physical form (beads) and properties (higher permeability to water and less effective adhesion to facing materials than polyurethane). The expansion gases, pentane and steam, escape fairly rapidly from the foam, so the thermal conductivity of the foam filled with air is about twice that of the best polyurethane foam—a 50 mm thick slab of foam has a U-value of 0.5-0.6 Wm K . EPS mouldings can be used as shutters (formwork) for pouring concrete in a composite wall. The two EPS layers are connected at intervals to fix the thickness of the concrete. Extruded polystyrene foam (XPS) is used in plank form for insulation imder the concrete floor of houses, and in roofing panels. 

The relationship between chemical structures and their physical performance is one of the central topics of polymer physics. lUPAC has recommended a whole set of names to describe the detailed chemical structures of polymer chains and their derivatives. However, in our daily communication, people prefer to use the popular names of polymers reflecting their characteristic physical performances, such as high-density polyethylene (HOPE), foamed polystyrene, thermoplastic elastomers, liquid crystal polymers, conductive polymers, and polyelectrolyte. Such terminology allows us to comprehend quickly the basic characteristics of chemical structures responsible for their specific physical properties. 

The main physical properties of expanded polystyrene foam are dependent on the density as is seen in Table 8. Unlike the thermoset rigid polyurethanes, thermoplastic poly-... 

The resultant cured product will have a density of approximately 112 kg/m (7 Ib/ft ), with a compressive strength of 0.69 MPa (100 psi). The polystyrene microspheres have about the same physical and electrical properties as those obtained with other organic syntactic foam fillers. 

Cellular solids are a class of materials with low densities and novel physical, mechanical, thermal, electrical, and acoustic properties. Low-density cellular metals can feature a wide variety of topologies to include open-cell foam, closed-cell foam, hollow-sphere foam, periodic/optimized truss structures, and honeycomb. Metallic foams consist of air dispersed in a solid matrix, similar to polymer foams such as polystyrene or food foams such as whipped cream. Closed-cell foams feature solid faces such that each cell is independently sealed from its neighboring cells, whereas open-cell foams (also known as porous metals, metal sponges and truss-type materials) do not contain cell walls they only have cell edges. Hollow-sphere foams consist of an assembly of individual hollow spheres. 

Styrene butadiene copolymers come in a wide variety of types, with a similar wide variety of properties. As discussed in Section 4.6, HIPS (High Impact PS), is partially a graft copolymer and partially a physical blend of polystyrene and polybutadiene. HIPS, which is opaque, typically contains 2 to 15 weight % polybutadiene. In addition to significantly decreased brittleness, it has a broad processing window and is easy to thermoform, either as sheet or as extruded foam. 

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