Cyanate esters as a high performing shape memory polymer: A review

Cyanate Ester (CE) based Shape memory polymers (SMPs) are one of the emerging SMPs with a considerable potential for space applications. As a thermoset polymer with excellent mechanical and thermal properties due to its 3D polycyanurate network, CEs have an added qualification with its shape memory property. From the perspective of shape memory characteristics, by co-curing with epoxies and modifiers, several properties of CEs including toughness, glass transition temperature (55 0C to 178 0C), durability (up to 30 shape memory cycles) can be tailored to achieve desired properties for a particular application. Herein the effects of using modifiers such as Polyethylene glycol (PEG), Polybutadiene epoxy (PBEP) were reviewed. While readily available chemicals such as PEG and PBEP has shown shape fixity (Rf) and recovery ratios (Rr) over 95%. Most of the reviewed CE SMPs have retained more than 90% Rf & Rr even after 30 shape memory cycles. Many fundamental research work has used fillers and reinforcements such as carbon clack, graphene and carbon fibres for the electro-activation of SMPs. It has been reported that carbon black and short carbon fibre reinforced CE SMPs are very effective for rapid activation of SMPs. Also, it has been reported that, Graphene can effectively substitute carbon black with much lower quantities and reduce the weight of the components significantly. Furthermore, it has been revealed that the effect on CE based SMPs by space mimicking conditions such as high vacuum, ultraviolet (UV), gamma and atomic oxygen were insignificant on the shape memory properties of CE SMPs.