By Sofrigam S.A
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Vacuum Insulated Panel (VIP)
Following a decade of research and development, Sofrigam is able to introduce VIP (vacuum insulated panel) insulation for cold chain shipping.
VIP revolutionizes temperature-controlled logistics and long-haul cool chain distribution by offering record-beating heat conductivity resistance and autonomy records. VIP insulated packages retain cool temperatures for up to ten days, almost three times the duration offered by previous insulation technologies.
Superior VIP performance
Classic insulating materials used to manufacture heat-insulated packaging include polyurethane, expanded or extruded polystyrene and polyethylene. With heat conductivity of 20 to 25 milliwatts per meter Kelvin (mW/m.K.), polyurethane has hitherto been the most efficient insulating material. Associated with 0°C gel packs, polyurethane boxes provide an autonomy of up to five days between +2°C/+8°C, compared to less than three days for other materials.
The VIP vacuum insulated panel offers thermal conductivity between 3 and 7 mW/m.K. Thus, for the same cooling source (gel pack, etc.) The VIP insulated package provides autonomy of seven to 10 days or between twice and three times that of the polystyrene and polyethylene insulated package.
VIP (Vacuum Insulated Panel) 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 and other industries but is only now being introduced to cool chain distribution.
VIP technology and design
Insulation performance is measured in R-values, which quantify the thermal conductivity resistance of a packaging material. R-values are a product of mass and thickness. High-density materials such as metals, hard plastics and solid wood have low R-values and so form poor insulators.
Still air or trapped gases have very high R-values and low thermal conductivity (<25 MW /m.K) so bulky materials (such as a feather or fiber duvet) that can trap pockets of still air can reduce the ability for heat to be transferred by conduction.
Therefore the traditional basis for ideal thermal insulation has been to trap dry air in lightweight, bulky materials that consist of many small cavities of trapped air rather than a large, contiguous volume of air.
Daniel Quenard, head of the materials division in the ‘Centre Scientific et Technique du Bâtiment’ (CSTB, or official French building materials organisation) explains: “To reduce heat transfer even further, it is necessary to eliminate gas or trapped air altogether by creating a vacuum, or at least by creating low pressure.”
A VIP vacuum insulated panel is therefore composed of a porous, open cavity “core” material such as fibrous mats, foams, or grains, packed in a sealed film. The film is usually a multi-layered polymer-aluminium-polymer that guarantees the VIP’s service life.
“In fact, the VIP must prevent the components of air, mainly nitrogen, oxygen and especially water vapor, from penetrating the material,” says M. Quenard.
“The main core materials used are open celled cellular foams and “pyrogenated” silicones 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,” M. Quenard explains.
Types of VIP panel
VIP vacuum insulated panels provide superior insulation and reduced bulk and thickness compared with traditional insulations. Over the past ten year, VIP technology has considerably progressed thanks to higher quality core materials and improved availability of barrier films.
A leading manufacturer of core materials is NanoPore Insulation LLC of Albuquerque, New Mexico.
Quentin Shrimpton from NanoPore says: “The vacuum is a core material enveloped in a metallic multi-layer barrier that resists oxygen and water vapor 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 fiber 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. “Mr. Shrimpton explains.
With thinner walls than traditional insulating materials a VIP insulated shipping system provides higher thermal insulation 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 that reduce the actual heat efficiency ratio of the boxes to a value between 2 and 3.
Applications for VIP insulated shipping packaging
VIP can be s built into heat-insulated packaging to provide the following user benefits:
- For the same source of cold, VIP provides autonomy of 7 to 10 days, or 2 to 3 times that of a classic insulation material, thus fulfilling a specific need for long haul distribution or distribution in under developed regions
- Used without a cold source, the VIP heat insulated box increases the temperature maintenance time
- The VIP heat insulated box has better resistance to hot segments and extreme profiles