High Performance Shape Memory Polyurethane Synthesized with High Molecular Weight Polyol as the Soft Segment

Abstract

Shape memory polyurethanes (SMPUs) are typically synthesized using polyols of low molecular weight (M W~2 ,000 g/mol) as it is believed that the high density of cross-links in these low molecular weight polyols are essential for high mechanical strength and good shape memory effect. In this study, polyethylene glycol (PEG-6000) with M W ~6000 g/mol as the soft segment and diisocyanate as the hard segment were used to synthesize SMPUs, and the results were compared with the SMPUs with polycaprolactone PCL-2000. The study revealed that although the PEG-6000-based SMPUs have lower maximum elongations at break (425%) and recovery stresses than those of PCL-based SMPUs, they have much better recovery ratios (up to 98%) and shape fixity (up to 95%), hence better shape memory effect. Furthermore, PEG-based SMPUs showed a much shorter actuation time of <10 s for up to 90% shape recovery compared to typical actuation times of tens of seconds to a few minutes for common SMPUs, demonstrated their great potential for applications in microsystems and other engineering components. OPEN ACCESSAppl. Sci. 2012, 2 536

Triple‐shape‐memory polymer films created by forced‐assembly multilayer coextrusion

“…The fixity ratio ( R f ) and the recovery ratio ( R r ) for each deformation step and the overall deformation were calculated by eqs. and , respectively:: where x and y stand for two different shapes, respectively; ε x , load is the maximum strain under load; ε x and ε y represent fixed strains after cooling and unloading; and ε x, rec is the strain after recovery.…”

“…The characteristics of PU, EVA, and PVAc, therefore, fulfilled the requirements of producing a multilayered triple‐shape‐memory material. In addition, PU as a material capable of 100% recovery has been largely used as a shape‐memory material . PVAc, with it sharp morphology/property change at its T g , has also been used to make SMPs through the formation of a blend or a network of PVAc and other polymers .…”

Palm kernel oil polyol based shape memory polyurethane: effect of polycaprolactone and polyethylene glycol as soft segment

“…As the MW increases, from 2000 g mol −1 to 4000 g mol −1 , the melting point and the percentage of crystallinity increase from 48°C to 54°C, and 15.4% to 30.4%, respectively. The MW of polyol is proportional to the length of the SS, and the higher the MW the higher the chain flexibility of SS, which makes the molecular chain of SS easier to pack into ordered arrangement and formed lamellae [19,49].…”

“…The degree of crystallinity of PEG4000 played a vital role to provide stiffness to the material. However, when the crystallinity of the material is too high (0.6 PEG molar ratio), failure occurs at lower stress level as the crystalline portion acted as the stress concentrator [19]. Therefore, with further increasing of the amount of PEG4000, the brittleness of the material increased due to the increase in soft segment crystallinity, as well as decrease of the chain flexibility provided by the PCL fragments, hence resulted in the decline of tensile strength.…”

“…According to Ahmad et al [19] and Firdaus et al [20], polyethylene glycol (PEG) based SMPU exhibited good SME but the mechanical properties was limited due to its brittleness. In contrary, polycaprolactone diol (PCL) is known as a flexible polyol, consequently PCL-based SMPU possesses good elastomeric mechanical properties [19,21]. Hence, the combination of PEG and PCL as the soft segment can be lucrative and the variation of PEG/ PCL molar ratio may be the key to optimize the properties of SMPU in terms of shape memory and mechanical properties.…”