SHOCK ABSORBING PACKAGING

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). 

Polystyrene homopolymer is an optically clear glass. However, it is relatively brittle and weathers badly out of doors. Consequently, toughened versions of polystyrene have been developed (Chapter 4). As an oriented film, it can be used for the electrical insulation of capacitors. When converted into low density foam, it is used for building insulation and shock absorbing packaging. 

Foams have a very low thermal conductivity, and so are used as insulating materials. Since their densities are low and the foam structure moves elastically with an impact, foams are used as shock-absorbing packaging materials. In addition, structural foams have a favorable ratio of rigidity to mass as well as a high strength, and, depending on the polymer component, they also exhibit favorable thermomechanical behavior. 

A steering tool sensor and electronic package is mounted in a housing in Figure 4-238 with a shock absorber and a spring to decrease the value of deceleration when engaging the mule shoe. 

The package has a mass of 2 kg or a weight of 4.415 lb. Assume a downward velocity of about 10 ft/s. The shock absorber develops a constant force (independent of the relative velocity) of 10 lb (44.48 N). The spring stiffness is 57.10 Ib/in. The potential energy due to gravity will be neglected. 

Taking into account only the shock absorber, compute the distance x traveled by the instrument package with respect to the housing when the... 

Some of the key factors that lead us to select polyurethane foam for upholstery are its durability, resilience, and controllable hardness (or softness, depending on your point of view). Vibration dampening and shock absorbance are important attributes in automobile and public transportation seating. Open cell foams are preferred for these applications because they allow for air and moisture transport, which improve the comfort of passengers who may occupy a seat continuously for several hours. This inherent breathability is also a valuable attribute in mattresses. Shock absorbance plays a key role in selecting flexible polyurethane foams for the packaging of fragile items. 

First, sheet corrugated board was shown to perform well in absorbing shock in tests in which three sheets of corrugated board were put into a small case and the cases used as shock absorbers for preventing the propagation of explosion from a detonator. Second, the safety of the new package was shown by applying the United Nations classification tests for explosives. 

ASTM D 1596-91 Standard Test Method for Shock Absorbing Characteristics of Package Cushioning Materials, 6 pp (Comm D-10)... 

The extrusion of starch with relatively low water contents (15 - 25% w/w) was extensively studied by the food industry [43]. One of the first commercial products of starch that achieved very good results was the expanded starch used for protection and as a shock absorber in packages, as a replacement for expanded polystyrene. These materials were patented by the National Starch Chemical Investment Corporation [44]. 

PS is one of the most versatile packaging resins. The amorphous grade, crystal PS, is used to make bottles for pills, tablets, and capsules. High impact PS (HIPS) is commonly used as thermoformed containers for dairy products. PS foam has good shock absorbing and heat insulation characteristics. Applications in food packaging include egg cartons and meat trays. Varieties of styrene-based copolymers have also been developed to exhibit special combinations of properties. Typical PS properties are shown in Table 4.10. 

The cask is a cylindrical packaging, vertically transported, provided with a double closure lid and protected by external shock absorbers. The cask body has a sandwich-like shielded wall stainless steel-lead-stainless steel and metallic gasket seals. An assortment of items necessary for proper cask manipulation, cormection to site services (water, gas, etc ), peruse leakage tests, and tie-down to the transport vehicle, are taken into account in the design. The maximum weight (when loaded) is 101. 

Expandable PS (EPS). Crystal PS is also supplied as partially expanded bead to fabricate foams. EPS foam has good shock absorbing and heat insulation characteristics. Applications in food packaging include egg cartons and meat trays. 

Polystyrene foam has been extensively sulfonated by treatment with one or more of the following reagents oleum, chlorosulfonic acid, fluorosulfonic acid or sulfur trioxide. The polysulfonated polystyrenes were useful as shock absorbers in packaging and formed conductive, antistatic, condensation-inhibiting, fire-resistant coatings. - ... 

Expanded poiystyrene foam (EPS) is usually white and made from expanded PS beads. It is lightweight, absorbs shocks and is a very good sound and heat insuiator. It crumbles easily and burns readily unless flame proofed. Familiar uses include moulded packaging material to cushion fragile items inside boxes and as heat insulation in the construction industry. It is also widely used to make foam cups, plates, food containers, meat trays and egg cartons. 

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