Expanded synthetic plastics have very poor recovery properties and nearly no elasticity. They deform very quickly under load, i.e. they become thinner under compression leads. They can therefore only be used for filling gaps with relatively light loads. In all other cases, they should not be used as a filling material. The same applies for cardboard and corrugated board.
Used tires may to a certain extent be suitable for filling in gaps, but not as has been done here: Ring-shaped point loads may occur. To enable them to fill in a large area, they could be arranged so that they are pressed between two walking boards which each cover a large surface area of the cargo.
Again, we quote the CTU guidelines:
3.2.12 When deciding on packaging and cargo-securing material, it should be borne in mind that some countries enforce a garbage- and litter-avoidance policy. This may lead to limitations on the use of certain materials and imply fees for the recovery of packaging at the reception point as well as similar problems for the shipper of the cargo. In such cases, reusable packaging and securing material should be used. Increasingly, countries are requiring timber dunnage and packaging materials to be debarked.
3.2.4 If airbags are used, the manufacturer's instructions on filling pressure should be scrupulously observed. Allowance should be made for the possibility of a considerable rise in the internal temperature of the CTU above the temperature at the time of packing. This may cause the bags to expand and burst, thereby making them ineffectual as a means of securing the cargo. Airbags should not be used as a means of filling space at the doorway unless precautions are taken to ensure that they cannot cause the door to open violently when the locking bars are released.
The most commonly used form of airbag comprises a multilayer paper bag available in a wide variety of different sizes. This type should only be used if the areas to the left and right of the gap are as smooth as possible and have a high load-bearing capacity. If necessary, walking boards are to be provided to ensure correct distribution of pressure. Special measures are required for working with airbags, in particular with white and brown goods, since the parts of the cartons which are not padded would be pushed in. The minimum inflation pressure should be 200 hPa. For many airbags, this is around 300 hPa. This can still achieve a securing force of 3,000 daN per m². Airbags are inflated using compressors. Special inflation fittings with pressure reducers are required. Special fittings enable the air to be evacuated. This is an advantage if a bag is not seated correctly, as it can quickly be deflated and then inflated again. This fitting facilitates deflation of reusable bags. Since it is time-consuming to have to unscrew valves to let out the air, the recipient will generally deflate single-use bags by puncturing them. When closing gaps, airbags which have already been partially inflated should be placed in the stowage gap and then completely inflated. Suitably large and smooth surfaces are required on the cargo transport units when using them. Only airbags which are capable to a certain extent of withstanding point loadings should be used. One important factor with regard to usability is that their side faces should be as near as possible to parallel. Air bags with a pronounced bulge must not be used.