The Cold In Cold Chain Packaging

Let’s delve into all the options Cold Chain shippers have for maintaining the “Cold” in their packages.

 

The Cold component is often called the coolant.  Coolant is available in a variety of types, and it is vitally important to understand each type as you consider what coolant to integrate into your cold chain package.

 

Coolant types include:

 

• Gel Packs in standard and moisture absorbing type bag films – H2O based gel.
• Brick type packs with hydrated (H20) phenolic foam cores that hold dimensional shape
• Hard-shell packs with molded plastic enclosure for the gel or liquid coolant
• PCM (phase change material) packs in soft, brick, and hard-shell forms
• Dry Ice – CO2 in pellet and block forms
• Wet Ice – straight H2O/water in various forms. Rarely used.

 

Today’s issue is about Gel Packs and Dry Ice.

 

Gel Packs

 

Gel packs have been the standard coolant for chilled cold chain packages for many decades.  Frozen gel packs are used for fresh, chilled foods and pharma/biological materials typically requiring stable temperatures between 2-8C.  Often gel packs are referred to as ice packs, but the better descriptor is what they are made of prior to freezing.  In this case, gel material.  Most gel packs on the market are water-based formulations that freeze to ice at sub-32F freezer temperatures.  Once removed from the freezer conditions, the gel/ice packs will stabilize near 32F to match their freezing (phase change) temperature.  I mentioned above that gel/ice packs are the standard for “chilled” packages.  I was careful not to designate them for frozen products.  Gel packs will work to hold chilled/refrigerated temperatures in the package.  They will not protect frozen items from thawing.  At best they will slow the thaw.  Only dry ice and PCMs (Phase-Change-Materials to be discussed later) will properly keep frozen payloads below 32F. In my 33 years of cold chain package consulting, I typically have 2-3 conversations per week correcting the misconception that ice packs keep frozen items frozen.  They simply do not.  Gel packs are the most economical coolant available and easily sourced.  The primary downside to gel packs is related to their soft, pliable form which often results in irregular frozen ice pack shapes that can make them difficult to load into the cooler package.  Where irregular shaped ice packs is a concern, we direct clients to our Ice Bricks as a solution.  We will discuss ice bricks in a future blog.

 

Dry Ice

 

Now let's pivot to dry ice which has been the coolant of choice for many, many decades to keep frozen products frozen during shipment.  Since the 1950s dry ice has been primarily used in EPS foam molded coolers for shipping frozen foods and other materials.  Dry ice offers unparalleled cooling performance with a temperature of -109F keeping all package payload safely frozen.  Dry ice is available in block and pellet form primarily.  Block dry ice offers the best extended protection pound for pound compared to pellet form.  Dry ice sublimates from a solid to a gas with the super cooled CO2 gas flowing around the package payload keeping everything well frozen.  Sublimation occurs on the surface of the dry ice resulting in pelletized dry ice quickly converting to a gas and losing its cooling power much quicker than an equal mass of block dry ice.  As an example, where a five-pound block of dry ice protects a package for 24hrs, you would need 10 pounds of pellet dry ice for that same transit period.  Pellet dry ice is more economically priced than block dry ice.  Many clients prefer the pellets because their packing personnel can simply scoop up the pellets and dump them into the package filling in around the product for very efficient cooling early in the transit period.  Shippers should consider the effect of extra pellet weight on their UPS and FedEx rates when deciding between block ice versus pellets.  Block dry ice can be problematic for integration into cold chain package design based on available block dimensions offered by regional dry ice manufacturers.  The standard block dimensions may not be a good fit for a particular package and product thus making pellet dry ice the only option.