Insulation, polystyrene

If we assume there is a layer of insulation (polystyrene 0.05 m thick) on the floor, then the heat resistance ... 

The product of this polymerization is polystyrene a clear, brittle plastic that is often used for inexpensive lenses, transparent containers, and styrofoam insulation. Polystyrene is also the major component of the resin beads that are used to make synthetic proteins. (See Section 24-11). 

About 65% of styrene is used to produce polystyrene. Polystyrene is used in the manufacture of many commonly used products such as toys, household and kitchen appliances, plastic drinking cups, housings for computers and electronics, foam packaging, and insulation. Polystyrene finds such widespread use because it is relatively inexpensive to produce and is easy to polymerize and copolymerize, resulting in plastics with a broad range of characteristics. In addition to polystyrene, styrene is used to produce acrylonitiile-butadiene-styrene polymer, styrene-acrylonitrile polymer, and styrene-butadiene synthetic rubber (SBR). 

Thermoplastic Foam Extrusion. Foamed plastics find applications as rigid profiles, pipe, sheet, packaging material, and thermal insulation. Polystyrene (PS) finds the widest application in foamed products while poly(vinyl chloride) PVC, low-density polyethylene (LDPE), and acrylonitrile-butadiene-styrene (ABS) (21) are also used in large quantities. All common thermoplastics can be foamed by various techniques as described hereafter. 

The largest markets for foamed plastics are in home insulation (polystyrene, polyurethane, phenol formaldehyde) and in packaging, including various disposable food and drink containers. Also refers to the occurrence of frothy mixture of air and a slurry that can reduce the effectiveness of the product, and cause sluggish hydraulic operation, air binding of oil pumps, and overflow of tanks or sumps. 

Applications of expanded polystyrene Insulation Polystyrene foam at densities below llOkg/m exhibits a thermal conductivity X (u) of 0.037 W/m.K (k = 0.26 Btu.in/ft h°F). As a general rule, therefore, polystyrene foam insulation must be 70% thicker than a urethane foam to provide equivalent heat loss characteristics, but since material costs are substantially lower for polystyrene both foams are used depending upon requirements. 

Eoamed polystyrene sheet has exceUent strength, thermal resistance, formabUity, and shock resistance, as weU as low density. It is widely known for its use in beverage cups, food containers, building insulation panels, and shock absorbent packaging. Polystyrene products can be recycled if suitable coUection methods are estabUshed. Eoamed polystyrene sheet can also be easily therm oformed (see Styrene plastics). 

The use of CFCs as foam blowing agents has decreased 35% from 1986 levels. Polyurethanes, phenoHcs, extmded polystyrenes, and polyolefins are blown with CFCs, and in 1990 the building and appHance insulation markets represented about 88% of the 174,000 t of CFCs used in foams (see Foamed plastics). 

In a study (206) of the moisture gain of foamed plastic roof insulations under controlled thermal gradients the apparent permeabiUty values were greater than those predicted by regular wet-cup permeabiUty measurements. The moisture gains found in polyurethane are greater than those of bead polystyrene and much greater than those of extmded polystyrene. 

Commercial Construction. The same attributes desirable on residential constmction appHcations hold for commercial constmction as weU but insulation quaHty, permanence, moisture insensitivity, and resistance to free2e—thaw cycling in the presence of water are of greater significance. For this reason ceUular plastics have greater appHcation here. Both polystyrene and polyurethane foams are highly desirable roof insulations in commercial as in residential constmction. 

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). 

Steam-Chest Expansion. In steam-chest expansion the resin beads in which gas is already present are poured into molds into which steam is injected. The steam increases the temperature close to the melting point and expands within the stmcture to create beads with food cushioning and insulating properties. Expanded polystyrene is widely used in this process for thermal insulation of frozen food packaging. 

Polyurethane, PVC, and extruded polystyrene provide the bulk of the cellular plastics used for low and cryogenic temperature appHcations. In some cases, eg, the insulation of Hquid hydrogen tanks on space systems, foams have been reinforced with continuous glass fibers throughout the matrix. This improves strength without affecting thermal performance significantly. 

In the mid-to-late 1980s, growth estimates of the use of polystyrene and polyurethane ceUular plastic insulation materials and products were a healthy 10% per year and greater for phenoHc (40,41). The principal appHcation where strongest growth was forecast for these types was for roofing, especially single-membrane systems (42). 

In modem PMR constmction, thermal iasulation that is unaffected by water or that can be kept dry ia some manner is required. Extmded polystyrene (XEPS) foam iasulation boards ate commonly employed (see Insulation, thermal). They ate placed on top of the waterproofing roof membrane, which is next to the deck. The iasulation should not be adhered to the membrane. Ballast at the rate of >48.8 kg/m (1000 lb/100 ft ) holds the iasulation ia place and offers protection from the sun. The iasulation joiats ate open and drainage must be provided. Various other materials, eg, patio blocks and concrete slabs, ate also used as sutfaciags and ballast. The extra weight imposes mote exacting requirements on constmction. 

Polystyrene (PS). Common appHcations include packaging, food containers, and disposable tableware toys furniture, appHances, television cabinets, and sports goods and audio and video cassettes. For some of these appHcations, PS is modified by blending or graft polymerization with SBR to form impact polystyrene, which is less sensitive to breakage. Expandable polystyrene is widely used in constmction for thermal insulation. 

General-Purpose Polystyrene. Polystyrene is a high molecular weight M = 2 — 3 x 10 ), crystal-clear thermoplastic that is hard, rigid, and free of odor and taste. Its ease of heat fabrication, thermal stabiUty, low specific gravity, and low cost result in mol dings, extmsions, and films of very low unit cost. In addition, PS materials have excellent thermal and electrical properties that make them useful as low cost insulating materials (see Insulation, ELECTRIC Insulation, thermal). 

Polystyrene. Polystyrene [9003-53-6] is a thermoplastic prepared by the polymerization of styrene, primarily the suspension or bulk processes. Polystyrene is a linear polymer that is atactic, amorphous, inert to acids and alkahes, but attacked by aromatic solvents and chlorinated hydrocarbons such as dry cleaning fluids. It is clear but yellows and crazes on outdoor exposure when attacked by uv light. It is britde and does not accept plasticizers, though mbber can be compounded with it to raise the impact strength, ie, high impact polystyrene (HIPS). Its principal use in building products is as a foamed plastic (see Eoamed plastics). The foams are used for interior trim, door and window frames, cabinetry, and, in the low density expanded form, for insulation (see Styrene plastics). 

Polyurethane. Polyurethanes (pu) are predominantly thermosets. The preparation processes for polyurethane foams have several steps (see Urethane polymers) and many variations that lead to products of widely differing properties. Polyurethane foams can have quite low thermal conductivity values, among the lowest of all types of thermal insulation, and have replaced polystyrene and glass fiber as insulation in refrigeration. The sprayed-on foam can be appHed to walls, roofs, tanks, and pipes, and between walls or surfacing materials directly. The slabs can be used as insulation in the usual ways. 

Thermal Insulation. Foamed plastics (qv) are used as thermal insulation for aU types of constmction because of their low heat- and moisture-transmission values. Polystyrene is used either as foamed board or expandable beads. The foam may be faced with a stmctural surfacing material, eg, a kraft liner-board, to form a panel for insulating mobile homes. These foams can dupHcate the appearance of wood and be used as trim. Foams can also be used as backing, for example, on aluminum siding, to provide heat and sound insulation. Foamed beads can be incorporated in concrete to reduce its density and provide some thermal insulation. 

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