A new bio-based, renewable phase change material is used
to keep blood and pharmaceuticals cool during shipping.
Called "Greenbox", the innovative technology received the top prize in the 22nd Annual DuPont Awards for Packaging Innovation.
Paraffin-based phase change materials have been used to control temperatures in buildings for many years. But development of the new, more pure technology, combined with application to packaging, is new.
Entropy Solutions of Eden Prairie, MN, was awarded a U.S. patent in 2008 for use of the phase change materials in packaging.
According to Entropy Solutions, traditional methods of shipping pharmaceuticals are energy intensive or may not work adequately.
"When pharmaceutical products are removed from a refrigeration storage unit and transported for use (e.g., to hospitals) they are often transported in an insulated container overnight which may or may not contain, for example, ice (i.e., frozen H2O) or dry ice (i.e., frozen CO2)," says the patent. Ice, however, melts at 0C, which is not adequate to maintain blood. Other approaches use electric power for refrigeration.
"It is desired to have a lightweight, highly reliable, portable container that maintains the temperature of pharmaceutical products or other temperature sensitive materials over a relatively long or given period of time," says the patent.
A material (paraffin or eutectic salt) may be designed to change phase (melt or solidify) in a range around 4C, which is described as an ideal temperature for storing bags of human blood.
In the Greenbox, phase change materials are placed within open areas of corrugated panels, which may be made of fiber or plastic. An agent may also be injected to trigger temperature movements by the phase change material. For example, the agent may be used to initiate solidification when a liquid exists at a temperature that is lower than the normal solidification temperature.
The amount of heat needed to convert a kilogram of solid to a kilogram of liquid via melting is defined as the latent heat of melting. Entropy Solutions says that the magnitude of the latent heat of melting explains the effectiveness of melting as a cooling process. When a kilogram of ice melts, it absorbs about 330 kJ (kilojoules) of heat. To melt a kilogram of a typical paraffin, about 232 kJ are needed.
Paraffins are highly engineered to achieve the exact heat-blocking required. Paraffins melt at a different temperature based on the number of carbon atoms. For example, the Astor brand of paraffins produced by Honeywell may be designed to store pharmaceutical products within a specific temperature range around 8C.
Their sharp melting profiles allow controlled energy release and absorption. They are also stable and inert, making them suitable for use in the Greenbox. Paraffins, which are relatively low in cost, can also be blended to achieve a specific temperature goal.
The DuPont judges lauded the Greenbox for dramatically reducing freight costs and packaging waste, in addition to its role in preserving temperature-sensitive products. Companies such as Walmart Specialty Pharmacy, Abbott Laboratories, Amgen, American Red Cross and Medtronic use the system to ship pharmaceuticals, biologics and blood supplies.
"PureTemp and its packaging applications like Greenbox are changing the way life science companies do business, and we are honored to receive this recognition from one of the world's pioneers in sustainable packaging," Entropy CEO Eric Lindquist said.
The Greenbox can be engineered to provide cooling at very specific temperatures.