TPC PRODUCTS - TECHNICAL OVERVIEW
FOUR REFRIGERANTS CURRENTLY AVAILABLE
A general explanation of the properties of available refrigerants follows to explain how ThermaFreeze™ outperforms older products.
Water Ice has been used to protect foods since mankind came out of the cave. As ice thaws, it melts into a puddle, and then evaporates to add to humidity. This process includes multiple heat stages, reducing efficiency. If used to ship perishables, the puddle stage produces a watery mess that damages many perishable products.
Dry Ice (frozen carbon dioxide) was developed in the 19th Century. It does not melt; it “sublimes” when it goes from a frozen solid to a carbon dioxide vapor with no puddle. Its other main property is a deep cold, which is both asset and liability. The surface of dry ice is -109o F which is fine for a few foods and biotech products but it freezer burns most foods and can destroy pharmaceuticals. Dry ice is expensive to use since about 30% of the mass will “sublime” before use. Five pounds in a box lasts 18 hours; ten pounds, only 22 hours. Most important, dry ice is a hazardous material that rapidly burns to the bone if held. There are confirmed instances of people being sickened or even dying from carbon dioxide vapor concentration. Most current dry ice applications do not need such deep cold. Customers are looking for alternative shipping refrigerant methods.
Sample comments from commercial carrier regulations regarding dry ice:
• FedEx states: “We do not offer refrigeration service. If the shipment contains dry ice, consult the Dangerous Goods section for dry ice requirements. All dry ice shipments require package marking and labeling. FedEx is not required to add dry ice to packages in its system. Prior to shipments call … to connect to the Dangerous Goods Hotline for assistance.”
• UPS states: “UPS transports hazardous materials only within and between the 50 United States and Puerto Rico … For each hazardous materials package requiring shipping papers under 49 CFR Section 172.200, an additional charge … will be assessed.” Currently, the additional charge is $25.00 per package with over 5 pounds of dry ice.
• IATA (International Air Transport Association) requires dry ice shipments to be labeled as Class 9 (Miscellaneous) hazards. “The Miscellaneous label is always a primary risk. This means if another label is shown on the package, there is more than hazardous product inside. The most common example of this is when Dry Ice, i.e. solid carbon dioxide, is being used as a refrigerant.”
Gel Packs and Bricks were developed in the 20th Century to perform between the previous two items. They function like water ice scientifically but because they are sealed, they do not puddle after thawing. The downsides of gel products are several: (1) they are shipped filled with water raising inbound freight. (2) There is no cooling value after the product thaws. (3) Whether used in a Styrofoam chest, box, or pouch, gel packs are frozen lumps that do not distribute cold temperatures efficiently over the full transit time.
ThermaFreeze™ is the refrigerant product of the 21st Century. It is an open product with fabric on one side but water does not exit the hydrated product; rather it is held in gel suspension by the active polymer for six to eight days. The water “sublimes” via the fabric providing evaporative cooling, even when thawed. ThermaFreeze™ is flexible when frozen and its flat, flexible properties
