A new bio-based, renewable phase change material is used
to keep blood and pharmaceuticals cool during shipping.
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.
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
"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
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.