The following materials that are relevant for the shipping process will be discussed:
- Air bags
- Bubble films
- Rubberized fiber cushioning
- Vibration- and shock-absorbing elements
5.4.1 Air bags
Air bags consist of closed chambers made from an elastic film and filled with air. When at rest, only the static load generated by the weight of the package contents bears upon the cushioning. When dynamic loads occur, these are absorbed by compression of the cushion.
The quantity of inflation air may be varied in accordance with the particular properties and requirements of the package contents. Air bags are commercially available in various sizes and designs, ranging from spheres, standard cushions to corner and edge cushioning and tubular cushioning.
Figure 35: Air bags
Advantages of air bags:
- ease of handling
- highly versatile
- largely insensitive to extreme climatic conditions (heat, cold)
- elevated recovery and ideal shock absorption characteristics
Disadvantage of air bags:
- susceptible to pointed and sharp articles, such as nails or the like
5.4.2 Bubble films
Bubble films function in essentially the same way as air bags. They consist of two plastic films, one of which is completely flat and the other has small, dish-shaped, round indentations, which, once the two film webs have been heat sealed together, contain the necessary air. Bubble films are mainly used inside packaging containers, for instance film covers, where they are placed over sharp-edged components (see Figure 9, section 4.1). The advantages and disadvantages are largely the same as for air bags.
Figure 36: Bubble film
5.4.3 Rubberized fiber cushioning
Rubberized fiber cushioning provides high quality protection for demanding items. This cushioning is made from animal hair or coconut fiber, which is cleaned, converted into nonwoven mats, coated with rubber and vulcanized to form solidly bonded sheets.
Rubberized fiber cushioning is relatively insensitive to the effects of moisture and high or low temperatures and exhibits very good long-term recovery even on extended exposure to loads.
Figure 37: Rubberized fiber cushioning
Foam cushioning materials are manufactured primarily from polystyrene (PS), polyurethane (PU) and polyethylene (PE). Plastic foams are available in flexible, semirigid and rigid forms. Their cushioning characteristics are determined not only by their specific weight but also by their cell structure.
Properties of foams:
- PS: nonhygroscopic, closed-cell, soft elastic, limited recovery
- PU: soft, semi-hard and hard, open-cell, better cushioning with increasing hardness but with reduced recovery and elasticity
- PE: excellent cushioning properties, closed-cell, not weather-resistant
Figure 38: Various foams
5.4.5 Vibration- and shock-absorbing elements
Elements such as these are used with machines and plant equipment in consultation with the manufacturer of such packaged items. Calculations are used to match them to the sensitivity of the packaged goods.
Figure 39: Vibration- and shock-absorbing elements