Dry ice is a solidified carbon dioxide (CO2). When dry ice melts, it turns into carbon dioxide gas. (Dry Ice: A Reliable Solution for Ultra-Low Temperature Pharmaceutical Cold Chain Logistics, January 23, 2023) In the Cold Chain packaging industry, dry ice can be used as a super cooling agent with uses which keep payloads including food and medical samples frozen. Dry ice possesses the special property of sublimation, meaning that it turns directly from solid into a gas, bypassing the liquid form. Dry ice can maintain temperatures as low as -78.5 degrees Celsius (-109 degrees F), making it ideal for pharmaceuticals that require extremely cold storage and transport conditions, including certain vaccines, gene therapies, cell therapies, and biological samples. Sublimation creates challenges in packaging design. It creates void spaces, thus allows natural convection, heat transfer to the product. Sublimation reduces dry ice’s mass, therefore its ability to store thermal energy. And, sublimation allows movement inside the package, thus risks product damage and change in temperature distribution. (ISTA) The sublimated CO2 gas needs a way to escape from the packaging (packaging design consideration) to avoid pressure build up, which in extreme cases can lead to an explosion. Dry ice comes in different forms (blocks, chunks, pellets), and due to the forms exposed to the surface area, which influences its rate of sublimation. Pellets sublimate faster than a solid block due to increased surface area exposed for heat transfer. Dry ice and its payload (if liquid) can undergo acidification due to the formation of carbonic acid following diffusion through packaging materials or failed seals. High barrier materials may help to mitigate this. (ISTA)
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