Evaluation of energy storage potential within shape memory rubber nanocomposite films

Shape memory rubber (SMR) is a type of smart rubber capable of undergoing reversible transformations when exposed to external factors such as temperature. Lightly crosslinked natural rubber (NR) exhibits shape memory behaviour without requiring preliminary heat treatment making it a unique smart material. This study aims to develop rubber nanocomposite films reinforced with starch nanocrystals (SNC) for improvement of mechanical properties. To this end, the focus is on evaluating the shape memory effect (SME) and quantifying the energy storage potential of the SNC reinforced rubber composite films. Natural rubber latex (NRL) and SNC synthesized by acid hydrolysis were used as raw materials to fabricate the green shape memory natural rubber latex (SMNRL) films. It was found that the incorporation of SNC into NRL effectively enhanced the mechanical properties and SME of the rubber nanocomposite films. The tensile strength of the rubber nanocomposite film was increased by up to 206% upon addition of SNC while having no detrimental effect on the elasticity of the material. The excellent SME is demonstrated through high shape fixity (S_f) and shape recovery (S_r) achieving 93.3% and 100%, respectively. As a result of its shape fixing capability, the SMNRL film can store part of the applied energy showcasing its energy storage potential. The calculated stored energy is 20.6 MJ/m³ with a storage efficiency of 61.5%. In summary, SNC is an effective reinforcing filler showed through the increase in tensile strength. Moreover, addition of 8% SNC improved the S_f by 35% while having a positive impact on the energy storage potential of the rubber nanocomposite films.