Expandable polystyrene mechanical properties

The insulating value and mechanical properties of rigid plastic foams have led to the development of several novel methods of buUding constmction. Polyurethane foam panels may be used as unit stmctural components (220) and expanded polystyrene is employed as a concrete base in thin-sheU constmction (221). 

Flame-retardant polystyrene is used primarily in expanded foam for building insulation. Rubber-modified styrenic polymers are flame retarded for use in a number of applications, such as enclosures for electronics and business equipment. By far the largest volume flame-retardant HIPS application is television enclosures (Figure 29.1) these are made primarily from flame-retardant HIPS [3]. Flame-retardant HIPS has an attractive balance of mechanical properties, processability and cost. Flame-retardant styrenic blends such as HIPS-PPO and PC-ABS also find utility in a number of electrical applications such as printers, computers and monitors. These blends have received increasing attention recently because of their ability to be flame retarded with nonhalogen flame retardants (see Section 7). 

B. Chen, J. Liu Mechanical properties of polymer-modified concretes containing expanded polystyrene beads. Construction and Building Materials 21, (2007), p. 7-11. 

Styrenics. A large percentage of expanded polystyrene, EPS, is being recycled. Also laminated trays of EPS, with such a barrier polymer as ethylene vinyl alcohol, EVAl, are re-granulated and re-extruded with virgin PS at least 20 times. The re-extrusion generated PS VAc/EVAl blends that, after foaming, produced articles with excellent mechanical properties [23]. 

An especially severe case of thermal stresses in expanded plastic insulation occurs when the insulation is bonded to a more rigid member of the structure, A theoretical analysis of thermal stresses has been made for cylindrical geometry in which the boundary conditions approximate the case of insulation bonded to the inner surface of the warm outer shell of a low temperature storage vessel, From this analysis a prediction of the low temperature performance of such insulations can be made if they are isotropic and if their mechanical properties are known. The properties that must be known as functions of temperature are the modulus of elasticity in tension and Poisson s ratio. In addition to these properties, the tensile strength and the modulus of rigidity have been obtained at selected temperatures down to 20 K for two densities of expanded polystyrene and an expanded epoxy resin. 

Some patents have reported that the introduction of fibers and/or inorganic fillers is interesting for improving mechanical properties of starch materials (Andersen et al., 1998 Andersen and Hodson, 1995, 2001). Other studies have shown that it is possible to obtain food packaging from mixtures of starch, fibers, water, and other additives by thermopressing or baking (Carr et al., 2006 Schmidt and Laurindo, 2010), and these products could be an alternative to the use of expanded polystyrene foams (Vercelheze et al 2012). 

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