Biodegradable polyester‐based heat management materials of interest in refrigeration and smart packaging coatings

Abstract

In this study, two biodegradable matrices, polycaprolactone (PCL) and polylactide (PLA) were used to encapsulate for the first time a phase changing material (PCM), specifically dodecane (a paraffin which has a transition temperature at 210 C), through the use of the electrospinning technique with the aim of developing coating materials with energy storage capacity for thermal insulation applications. The encapsulation efficiency obtained using both matrices has been studied and the different morphology, thermal properties, and molecular structure of the materials developed were characterized. Results showed that dodecane can be properly encapsulated inside both biopolymers with a submicron drop size, albeit PCL provides better encapsulation performance. A temperature mismatch between melting and crystallization phenomena (the so-called supercooling effect) was observed in the encapsulated paraffin, mainly ascribed to the reduced PCM drop size inside the fibers. Addition of dodecanol was seen to best act as a nucleating agent for the PCL/PCM and PLA/PCM structures, allowing a significant amount of heat storage capacity for these systems without supercooling. These innovative ultrathin structured biomaterials are of interest as energy storage systems to advantageously coat or wrap temperature sensitive products in refrigeration equipment and constitute smart food or medical/pharmaceutical packaging.

Electrospun heat management polymeric materials of interest in food refrigeration and packaging

“…The greater encapsulation efficiency of PCL structures could be related with the greater diameter and internal structure observed in these fibers which could retain a higher amount of the PCM. A similar behavior was also observed by Pérez‐Masiá et al working with PCL/dodecane (porous fibers) and PLA/dodecane hybrid structures (thinner and nonporous fibers).…”

“…These differences between PCL and PS crystallization behavior could be also explained by the different particle size of the PCM droplets, which was greater in PCL fibers. Similar behavior was observed in PCL/dodecane hybrid structures …”

“…The full process of the PCM encapsulation through electrohydrodynamic processing has been previously developed (patent application number: P201131063). Based on previous knowledge, PCL/PCM and PS/PCM solutions were prepared according to Pérez‐Masiá et al, in order to produce fibrillar structures. Thus, PCMs were microencapsulated within two different polymeric matrices (PS and PCL) by means of a Fluidnatek® electrospinning pilot plant tool from Bioinicia S.L.…”

“…One methodology being increasingly used for the microencapsulation of materials is electrohydrodynamic processing. This processing technique has proven to be a suitable method for encapsulation of several components, including biomedical substances, functional food ingredients, PCMs, and others substances within polymer matrices . The electrohydrodynamic processing commonly termed as electrospinning is a technique whereby long nonwoven ultrafine structures, typically fibers with diameters of several tens to several hundreds of nanometers, may be formed by applying a high‐voltage electric field to a solution containing polymers .…”

Development of an encapsulated phase change material via emulsion and coaxial electrospinning

“…In contrast to that previously observed for PLA/PCM and PCL/PCM fibres, it can be observed that the melting temperature of the PVOH/PCM electrospun hybrid structures prepared without Tween 20 did not differ from that of the neat PCM (see Table ), indicating that similar PCM crystals were formed in the encapsulation structures probably due to the low compatibility between the paraffin and the hydrophilic polymer, precluding any interaction between both components. However, Pérez‐Masiá et al ., observed that the melting process of PLA/PCM and PCL/PCM occurred over a broader temperature range in the hybrid structures than in the pure PCM, and the presence of two different melting peaks of the PCM, which was attributed to the formation of two different crystal populations.…”