Development of polystyrene-based films with temperature buffering capacity for smart food packaging

• Heat storage multilayer films containing PS/PCM electrospun coatings were developed.
• The heat storage capacity was affected by the storage time and temperature.
• The heat storage capacity decreased in PS-multilayer systems stored at 25 °C.
• The greatest efficiency was achieved for those coated with PCL/PCM and PCL electrospun layers.

One of the main factors affecting the quality of perishable products is represented by temperature variations during storage and distribution stages. This can be attained through the incorporation of phase change materials (PCMs) into the packaging structures. PCMs are able to absorb or release a great amount of energy during their melting/crystallization process and, thus, they could provide thermal protection to the packaged food. Thus, the objective of this research was to develop polystyrene (PS)-based multilayer heat storage structures with energy storage and hence temperature buffering capacity for their application in refrigerated foods. To this end, polycaprolactone (PCL) was used as the encapsulating matrix of a phase change material (PCM) called RT5 (a commercial blend of paraffins with a transition temperature at 5 °C), by using high throughput electrohydrodynamic processing. The PCL/PCM fibrous mats were directly electrospun onto PS films and an additional PCL electrospun layer (without PCM) was also deposited in some experiments to improve the overall functionality of the PCM. The attained morphology, thickness, deposition time, temperature and multilayer structure played an important role on the energy storage capacity of the developed PS-based multilayer structures. Results obtained from a differential scanning calorimeter (DSC) show that RT5 can be properly encapsulated inside the PCL matrix and the encapsulation efficiency and, thus, the heat storage capacity was affected not only by the multilayer structure, but also by the storage time and temperature. The thermal energy storage/release capacity was of about 88–119 J/g. As a result, this work demonstrates the potential of these materials for an efficient temperature buffering effect of relevance in food packaging applications, in order to preserve the quality of refrigerated packaged food products.