What Insulation Thickness of Insulated Boxes Is Suitable for Ice Cream Transportation?
Toughest Logistics of All: Ice Cream Shipping
In Temperature-controlled logistics, there's nothing more challenging than ice cream shipping. Most perishable, chilled goods don’t have this same problem. Ice cream has a very low tolerance temperature range that needs to be adhered to. This range is between minus 18 and minus 22 degrees celsius. Any slight increase in temperature can be detrimental and lead to a partial melting. This melting can then lead to a re-freezing cycle that destroys the cellular structure and airiness, creating icy, unpalatable products. This is bad news, leading to unsatisfied customers. The Insulated Boxes used to temporarily store this ice cream as it is shipped is the primary line of defense to this thermal betrayal. The boxes maintain the deep freeze, and it mostly depends on one engineering choice: insulation. Insulation thickness and quality is key. This thickness is not chosen randomly, however. It is a decision based on physics, material science, and the length of the delivery.
What Determines How Thick An Insulation Should Be!
Considering insulation thickness is about weighing how much insulation is too much insulation and how much insulation is too little insulation. These interdependent factors must be considered first. How long is the delivery? Is it a quick last mile delivery of 2-4 hours or a longer 24-48 hours long regional shipment? With longer delivery times, insulation becomes a must-have since it will be needed to mitigate heat ingress over the long delivery period. Next, is the external ambient temperature the box will be exposed to. A box being transported in a mild 20°c climate will not be exposed to as aggressive of a heat thermal attack as one being transported in a 35°c summer heat. These differential ambient temperature insulations work together to heat the box from the outside, which is where more efficient insulation is needed.
As previously mentioned, each shipment is unique, and, therefore, will each have unique requirements when it comes to the insulation material chosen for the product compared to the insulation material thickness. Insulation material thickness is not equal across the board. For example, Expanded Polystyrene foam is cheap to buy and is the most common insulation material on the market, but only has a moderate R-value. A higher R-value is good for compact design boxes, and an example is polyurethane foam, or PU foam, which is standard in more competitive Insulated Boxes. PU foam has more R-value than EPS foam, allowing for thinner insulation to pack more tightly while still preserving cold for a longer time. The thickness of insulation is a prime factor for material selection and thickness to retain the same thermal hold.
Thickness Material and Choice Guidelines
There are no absolute thickness guidelines since each shipment is unique. However, some recommendations can frame the decision. For example, local delivery in moderate temperatures with a delivery time of under six hours can use a box thickness of approximately 25-40 mm (1 to 1.5 inches) of EPS or PU foam, along with a sufficient amount of gel packs or dry ice, on average 5-15 pounds of ice. This time length delivery is frequently seen in direct-to-consumer e-commerce ice cream pints.
To meet the 24-hour shipment standard for the industry and take major steps towards improving their regional distribution, the building walls require 2 to 3 inches (50 to 75 mm) of high density PU foam, which provides the thermal inertia needed to maintain sub-zero temperatures for 24 hours from the external variable temperature. For 48-hour shipment extremes, or exposure to extreme heat, other options are available, like increased thickness to over 75mm. More costly, but high value options are available when using Vacuum Insulated Panels (VIPs) that offer great R-value insulation.
Looking at the Entire Set-Up: More than Walls
The insulation layer in the walls is one of the components of a thermal system, and a common mistake is to focus only on the thickness of the walls. Insulated Boxes performance can be negatively impacted by the other elements of the system as well. Management of the cold source is the most critical of these other components. Ice cream, for example, can't be kept frozen for very long without one of the frozen phase-change materials (PCMs) like specialized frozen gel packs or dry ice... which act as the heat absorbing "battery." For a shipment, the type of PCM and the amount must be properly calculated.
Second, we'll move on to the integrity of the box. It's a common misconception that a box can have walls that are three inches thick. However, if the lid on the box doesn't seal off properly or if the box seams have major gaps, cold air can escape rapidly in a process referred to as "short-circuiting." Features like interlocking, gasketed lids are absolutely necessary. The quality of a box's construction is as equally important as the thickness of the box, specifically insulation. A box that is thinner but well-sealed and properly constructed is likely to outperform the competition over a thicker, poorly made box.
Lastly, we have operational handling. A box that's in direct sunlight for a period of an hour before it's loaded will need to overcome a large heat burden that will significantly hinder the insulation on the box for the entirety of its journey. Training staff to reduce the box's exposure to any heat during the rest of the ambient air during packing and staging is a simple, effective method to support enhanced performance.
That is why it is most helpful to partner with packaging suppliers who understand this entire ecosystem. A packaging partner such as Zhuoyue Printing wouldn’t just randomly hand you a box with some thickness; they consider the product (the ice cream is delicate), the necessary transit time and weather conditions, and what cold source is needed to help bring a solution to the table. This is how they ensure the required insulation thickness is accurately set to the box’s true purpose: to arrive with ice cream, frozen and creamy, to perfection, every time.