An Insulated Shipping Packaging Solution Perfectly Stable for 240 Hours

The most commonly used insulations in manufacturing insulated shipping packaging solutions are polyurethane, expanded or extruded polystyrene and polyethylene. With thermal conductivity at 20 and 25mW/m.K, PU produces the best thermal performance in traditional insulation. Combined with eutectic gel panels at 0°C, PU boxes provide up to 5 days autonomy between +2 and +8°C, compared to only 3 days for others. A privileged insulation material can offer greater insulation at reduced thickness. This material is capable of maintaining a perfectly stable internal temperature inside the packaging for up to 10 days, and to secure the cold chain shipping of pharmaceutical products even in extreme temperatures. A 240-hour conservation packaging, it is 3 to 5 times more than traditional insulated packaging systems. What is this insulating material? How is it used and what are its advantages and disadvantages?

Staring material: the VIP - Vacuum Insulated Panel The VIP gets its name from the Vacuum Insulated Panel. It has a minimal thermal conductivity (between 3 and 7 mW/m.K). In other words, for the same source of cold, VIP provides an autonomy of 7 to 10 days, or 2 to 3 times that of a classic insulation material. VIP therefore meets the specific needs of long haul shipping, especially in intense heat. This insulation material has been used since the beginning of the 2000s in the aeronautical, marine, construction, refrigeration etc. industries. Daniel Quenard, head of the materials division in the official French building materials organisation) tells us more:

"To create heat insulation, gas is trapped in small, more or less closed cavities, with a minimum quantity of material or a very high porosity (< 90 %). In insulating material the main contributor to heat transfer is therefore the trapped gas, usually air, which has a thermal conductivity of 25 MW / mK. To reduce this contribution the most efficient solution is therefore to "eliminate" this gas by creating a vacuum, or at least by applying low pressure.

A VIP vacuum insulated panel is therefore composed of a porous, open cavity "core" material (fibrous mats, foams, grains etc.) packed in a sealed film. The film is usually a multi-layered polymer-aluminium-polymer that guarantees the VIP's service life. In fact, it must prevent the components of air, mainly nitrogen, oxygen and especially water vapour, from penetrating the material. The main core materials used are open celled cellular foams and "pyrogenated" silicons that have the advantage of having a certain volume of nanometric pores, which makes it possible to increase the service life of the vacuum inside the panel. VIP thermal conductivity is in the order of 10 mW/mK for a vacuum of about 1 mbar."

The different types of VIP panels VIP vacuum insulated panels provide better insulation and a reduced thickness. They have considerably progressed over the past 10 years: better quality core materials, improved availability of barrier films.

"The vacuum is a core material enveloped in a metallic multi-layer barrier that resists to oxygen and water vapour for long life VIPs, or a polymer barrier for shorter lived applications, such as heat insulated packing used in the cold chain. The core materials can be composed of open celled polymer foam, glass fibre and silicon based material. Compared to other core materials, silicon does not require a very high vacuum, this gives performance stability over time without needing the use of gas traps or very high vacuums. " explains Quentin Shrimpton from NanoPore Insulation.

With thinner walls than traditional insulating materials, a VIP insulated shipping packaging system provides good performances for a reduced volume and transport cost.

The VIP vacuum insulated panel has a thermal conductivity of between 3 and 7 mW/m.K, or a ratio of 3 to 7 compared to traditional insulating materials. These values, provided by the main VIP manufacturers, depend on the type of core material, the vacuum level and the quality of the film used. The Vacuum Insulated Panel is combined with other materials, often a traditional insulating material used to protect it, which increases the heat transfer coefficient. It also has specific thermal bridges during assembly which reduce the actual heat efficiency ratio of the boxes to a value between 2 and 3.

Advantages and disadvantages of an insulated packaging in VIP

VIP is vacuum based insulation known for its high thermal conductivity. It is ideal for the transport of heat sensitive products in extreme conditions (prolonged periods, intense heat, etc.). It is used in insulated shipping packaging boxes for its many advantages :

• Performance: Its thermal conductivity of about 5 mW/m.K makes VIP more efficient than other insulating materials, even if performances are reduced by thermal bridges. • Temperature maintenance time: For the same source of cold, VIP provides an autonomy of 7 to 10 days. This duration is 2 to 3 times more than what can be achieved using the best classic insulation, thus fulfilling a specific need. VIP caters for needs in excess of 5 days, which are not guaranteed by other insulation materials. Used without a cold source, the VIP heat insulated box increases the temperature maintenance time. • Thermal resistance: The VIP heat insulated box has better resistance to hot segments and extreme profiles. •Thickness: The use of VIP can reduce the thickness of the sides, and therefore the volume of the box, or the weight of the cold source used.

When used in insulated or cooling packaging solutions, the VIP can have some weaknesses. Below are some of its disadvantages:

•Fragility: VIP is usually protected by another material which is often classic insulation (PU, PSE, etc.), this increases the total thickness and results in another disadvantage. • Cost: Despite efforts to lower its cost, VIP remains expensive. •Shape: The panel shape is not perfectly square, this complicates box assembly and creates thermal bridges. • Weight: It has a density of 150 to 250 kg/m3, making it heavier than other insulation materials.