Cushioning

Distillation Technique. With all distillations on a semi-micro scale it is essential to heat the liquid so slowly that a cushion of its... 

Flexible foams are used in mattresses, cushions, and safety applications. Rigid and semiflexible foams are used in structural applications and to encapsulate sensitive components to protect them against shock, vibration, and moisture. Foam coatings are tough, hard, flexible, and chemically resistant. 

Cushing s disease Cushing s syndrome Cushioning applications... 

Polyurethane. SmaU quantities of polyurethane film are produced as a tough mbber-like film. Polyurethane is more commonly used to produce foamed sheet, both flexible and rigid. The flexible foam is used as cushioning in furniture and bedding the rigid foam is widely used for architectural insulation because of its outstanding thermal insulation efficiency (see Urethane POLYMERS). 

Resihency provides another opportunity for the mbber functioning as a cushion between stainless steel loop clamps and fuel—hydraulic fluid lines in aircraft. Pratt and Whitney E-lOO military jet engine use (12) provides vibration damping without the clamp abraiding the tube surfaces in normal service as well as at temperatures down to —55°C. 

Unmodified Modified Sheet Standard cushioning Carpet underlay High resilience type PVC b Liquid Sheet ... 

Compressive Behavior. The most kiformative data ki characterising the compressive behavior of a flexible foam are derived from the entire load-deflection curve of 0—75% deflection and its return to 0% deflection at the speed experienced ki the anticipated appHcation. Various methods have been reported (3,161,169—172) for relating the properties of flexible foams to desked behavior ki comfort cushioning. Other methods to characterize package cushioning have been reported. The most important variables affecting compressive behavior are polymer composition, density, and cell stmcture and size. 

Compression Set. The compression set is an important property ki cushioning appHcations. It has been studied for polyurethane foams (185,186), and has been discussed ki reviews (32,60,156). Compression set has been described as flex fatigue and creep as weU. 

Latex foam mbber was initially accepted as a desirable comfort-cushioning material because of its softness to the touch and its resiUence (equal to that of a steel spring alone but with better damping quaUties than the spring). 

Cellular mbber has been used extensively as shoe soles, where its combination of cushioning abiUty and wear resistance, coupled with desirable economics, has led to very wide acceptance. In this case the cushioning properties are of minor importance compared with the abrasion resistance and cost. Other significant cushioning appHcations for cellular mbbers and latex foam mbbers are as carpet underlay and as cushion padding ia athletic equipment. 

Antistatic protection is an important consideration within the electronic industry and various antistatic agents are used commercially to aUeviate this problem in cushion packaging materials. 

Applications. Carpet undedayment as just descdbed is a substantial market. Most furniture cushioning is made from blocks of slab-produced polyurethane foam in the density range of 16 to 29 kg/m (1.0—1.8 lbs /fT). A minor portion of the market, 9—14 thousands of metric tons (20—30 million pounds) uses 40 kg/m (2.5 lbs/fT) high resident (HR) foam for higher pnced furniture cushions. The furniture market for polyurethane foams grew strongly until saturation occurred around 1979. Market use now tends to reflect the current economic trends. 

Their Eperan beads have been used to produce molded articles as cushioning materials, sound iasulating panels, etc. Asahi-Dow and BASE have also been reported to have developed similar products. 

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. 

Fluidization refers to the condition in which soHd materials are given free-flowing, fluid-like behavior (29). As a gas is passed upward through a bed of sohd particles, the flow of gas produces forces which tend to separate the particles from one another. At low gas flows, the particles remain in contact with other soflds and tend to resist movement. This condition is referred to as a fixed bed. As the gas flow is increased, a point is reached at which the forces on the particles are just sufficient to cause separation. The bed then becomes fluidized. The gas cushion between the soflds allows the particles to move freely, giving the bed a Hquid-like characteristic. 

The products from the continuous process (buns) are cut to shape for the particular appflcation, while the molded foams ate formed to shape during the mol ding process. The density of the continuous buns is traditionally between 16-32 kg/m (1-2 Ibs/ft ). Molded foams have densities greater than 32 kg/m. Flexible foams find appHcafions as automotive cushions, carpet underlay, furniture, seating, and bedding. 

Foam Products. Latices are made into foams for use in cushioning appHcations. The latices are frothed with air and then chemically coagulated for thick appHcations, or heated to induce coagulation for thinner appHcations. The latter method allows for infinite pot life during production (see Foamed plastics). 

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