The success of exporting perishable products by air is to a great extent dependent on adequate and appropriate insulation.

The Air Freight Council of Queensland Ltd has worked with industry to develop and introduce a cost-effective airline container insulation system for temperature-sensitive products. Currently varying types of insulation material/systems are used by industry with varying degrees of success.

 
  • Many exporters forego insulation due to additional costs — or the materials are of dubious benefit.
  • Queenland DPI Centre for Food Technology has analysed the thermal characteristics of a metallised polyester foil-backed bubble wrap manufactured by Polycell International Ltd — a summary of their report follows.
  • Container interior roof surface temperature differential between insulated and non-insulated containers was in excess of 13°C and internal air temperature 8°C.
  • Trial loadings have been completed and inspected by various airlines and cargo terminal operators who have approved this new system.
  • Your specialist freight forwarder can supply and fit the material which is extremely cost effective eg approx $55-60 per standard airline pallet or less than 1.5c per kg.

Queensland DPI - Executive Summary

A trial was conducted to comparatively assess the effectiveness of utilising single-sided 10 millimetre bubble film laminated with metallised P.E.T foil ** (P10Sfoil1) as an insulative cover over standard airline ULDs in maintaining cooler internal temperatures under fairly extreme external conditions. The first unit consisted of the standard airline ULD currently being used by freight forwarders. The second unit was a standard airline ULD with one layer of P10Sfoil1 applied externally with foil side out.

Both ULDs were filled with identical loads of refrigerated mass simulating chilled product. For this trial, the mass consisted of 16 X 25L containers of water pre-chilled to 3-5°C per ULD. No other refrigerant was present in the ULD. Air and surface temperatures were monitored throughout the recording period (up to 26 hours) in each of the ULDs. The trial was replicated 4 days later, to eliminate any possible anomalies.

The most significant finding from the trial is illustrated by the internal air temperatures of the ULDs. The internal air temperature exhibiting an 8°C difference when exposed to an external ambient temperature of 31°C and a tarmac temperature of 45°C.

Another significant outcome, shows the ability of the single-side laminated P.E.T foil to inhibit heat transfer to the internal roof surface of the ULDs. During the most extreme times of the day the uninsulated ULD exhibited an internal roof surface temperature in excess of 45°C, while the insulated ULD obtained only 31°C, a difference of over 13°C.

External roof surface temperatures: the uninsulated ULD experienced in excess of 57°C - the insulated ULD displayed only 34°C, a differential around 23°C.

The temperatures monitored on either side of the P10Sfoil1 on the roof of the ULD, during the most extreme times of the day shows that temperatures between the foil side and the bubble side were 50°C and 34°C respectively, a differential of 16°C.

 





It is clear from these results that the external application of single-sided laminated P.E.T foil to an airline ULD greatly reduces the internal air and surface temperatures. The overall effect upon temperature sensitive product transported within ULDs could probably be enhanced by utilising some further form of refrigerant eg. dry ice or chill packs, dependant on product requirements.

** Single-sided 10 millimetre bubble film laminated with metallised P.E.T foil (P10Sfoil1) as manufactured and supplied by POLYCELL INTERNATIONAL Pty Ltd.