Development of a phase change material for vaccine transport without dry ice

Abstract

Certain vaccines that have been developed against COVID‐19 require a storage temperature between around −60 and −70°C. It is challenging for logistics to assure these temperature limits. However, the use of dry ice has to be viewed critically for safety and environmental reasons. Additionally, its use is heavily regulated in air cargo. To preserve the cooling chain during transport and to increase the energy efficiency, special transport containers with an incorporated phase‐change material (PCM) can be used. In the first step, PCM candidates were investigated via differential scanning calorimetry (DSC) and in an ultra‐low freezer with a minimal temperature of −85°C. None of the candidates crystallised reliably without nucleating agents. After the initial tests, the eutectic LiBr·5H2O + H2O with a suitable nucleating agent was identified as favourite PCM. Thermal cycling stability tests showed that this PCM crystallises reliably above −80°C and possesses a melting plateau at −67°C. Further tests in vacuum‐insulated transport boxes of the company va‐Q‐tec show that, depending on the box type, the internal temperature stays below −60°C for over 48 h.