Characterization of nanocellulose‐ reinforced shape memory polyurethanes

Abstract

BACKGROUND: Shape memory polymers are capable of fixing a transient shape and of recovering their original dimensions by the application of an external stimulus. Their major drawback is their low stiffness compared to smart materials based on metals and ceramics. To overcome this disadvantage, nanocellulose was utilized as reinforcement. RESULTS: Composites were prepared by casting stable nanocellulose/segmented polyurethane suspensions. The heat of melting of the polyurethane soft segment phase increased on cellulose addition. Composites showed higher tensile modulus and strength than unfilled films (53% modulus increase at 1 wt% nanocellulose), with higher elongation at break. Creep deformation decreased as cellulose concentration increased (36% decrease in 60‐minute creep by addition of 1 wt% nanocellulose). The nanocomposites displayed shape memory properties equivalent to those of the neat polyurethane, with recoveries of the order of 95% (referred to second and further cycles). CONCLUSIONS: It is possible to markedly improve the rigidity of shape memory polymers by adding small amounts of well‐dispersed nanocellulose. However, this improvement did not have substantial effects on the material shape fixity or recovery. Shape memory behavior seems to continue to be controlled by the polymer properties. Copyright © 2007 Society of Chemical Industry

Infrared-Triggered Actuators from Graphene-Based Nanocomposites

“…It is well-known that the agglomeration and poor dispersion of fillers in nanocomposites cause crack initiation and propagation, which would result in decrease of tensile strength for the materials. 18 Thus, the observed increased tensile strength with increasing concentration of sulfonatedgraphene could be considered as indirect evidence of the homogeneous dispersion of sulfonated-graphene in the TPU matrix. Moreover, the noticeable increase of Young's modulus with such low loading of fillers, which is comparable or even rather larger than related studies, 1,18,41 makes these nanocomposites highly promising in the realm of multifunctional materials.…”

“…650%, measured at a crosshead speed of 100 mm/min). 18 The hard-segment crystallites provide the reversible physical cross-links that render polyurethane a thermoplastic elastomer. Strain-induced crystallization of the soft segments enhances mechanical performance under extreme deformation by increasing physical cross-link density and by providing reinforcement.…”

“…With this strategy, the addition of distinctly different nanofillers to polymeric actuator matrix may exploit synergism between the nanofillers and the polymers and may impart a novel and prominent actuation behavior as well as superb enhancement of overall performance. 1,2,15,16 Thermoplastic polyurethane (TPU), which possesses the ability to store and efficiently recover large strains by application of prearranged thermal stimuli because of its two-phase structure: a thermally reversible phase responsible for fixing a transient shape and a frozen phase responsible for recovering the original shape, 1,6,7,17,18 is one of the most widely used polymeric thermal-induced actuator materials. Unfortunately, TPU, which is essentially infrared (IR) transparent, does not show IR-induced actuation.…”

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

“…Further possibilities are opened by the addition of composite reinforcement materials, such as nanocellulose [78] or CNTs [79,80] although it should be noted that composite reinforcement is far from a magic bullet and may in fact degrade SMP performance [81]. The reader is referred to a number of excellent general reviews of SMPs and their composites [82][83][84][85] for more exhaustive assessments of previously studied polymers and their properties.…”

Investigation of Nanofibrillated Cellulose for Hydrophobic Packaging Material: Examining Alternatives to Solvent Exchange and Lyophilization

“…Many previous studies have shown the ability of nanocellulose to form aerogels, which are low-density foams derived from a gel-state material (Jin et al 2004). Additionally, many recent studies have investigated the possibility of improving polyurethane foam properties through the addition of nanocellulose (Auad et al 2007;Wik et al 2011;Faruk et al 2013;Amin et al 2016;Lee et al 2016;Ivdre et al 2016;Zhou et al 2016).…”