Polyurethane/conducting carbon black composites: Structure, electric conductivity, strain recovery behavior, and their relationships

Abstract

ABSTRACT:The polyurethane composites with conducting carbon black (CB) were prepared by a solution-precipitation process, which was followed by melt compression molding. The polyurethane used has good shape memory effect. The morphology of CB fillers in polyurethane matrix and the resulting conductivity of the composites were investigated. It has been found that CB fillers exist in the forms of aggregates. The percolation threshold is achieved at the CB concentration of 20 wt %. The presence of CB fillers decreases the degree of crystallinity of polycaprolactone (PCL) soft segments of the polyurethane. However, the composites still have enough soft-segment crystals of polyurethane to fulfil the necessary condition for the shape memory properties. Dynamic mechanical data show that CB is an effective filler for the reinforcement of the polyurethane matrix, but does not deteriorate the stable physical cross-link structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory materials. Addition of CB reinforcement in the polyurethane has influenced the strain recovery properties, especially for those samples with CB concentrations above the percolation threshold. The response temperature of the shape memory effect T r has not been affected too much. Strain fixation S f , which expresses the ability of the specimens to fix their strain, has been improved in the presence of the CB fillers. The final recovery rates R f and strain recovery speeds V r of the shape memory measurements, however, have decreased evidently. It is expectedly ascribed to the increased bulk viscosity as well as the impeding effect of the inter-connective structure of CB fillers in the polymer matrix.

Infrared-Triggered Actuators from Graphene-Based Nanocomposites

“…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.…”

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers

“…Another example for shape-memory polymers with T trans being a T m are block copolymers from poly(ethylene terephthalate) and poly(ethylene oxide) (5). Compounds from shape-memory polymers and inorganic particles, including SiC particles (6, 7), carbon black (8,9), and nanotubes (10,11), were prepared. The incorporation of particles leads to enhanced mechanical properties (6,8) or electric conductivity (7,9).…”

Electroactive shape memory performance of polyurethane composite having homogeneously dispersed and covalently crosslinked carbon nanotubes

“…From the TEM images ( figure 2(a)), in-situ and cross-linking polymerized composites have more black dots and lines, indicating the homogeneous dispersion of carbon nanotubes, while the conventionally blended composite has aggregated tubes due to poorly dispersed tubes. These results can be explained by the interaction between the nanotubes and the polyurethane molecules [16,21]. We also confirmed the enhanced dispersion structure of the tubes in cross-linking polymerized composites, based on the presence of bright spots from the topographical AFM mapping images( figure 2(b)) and current AFM images (figure 2(c)) [22].…”

“…For example, carbon nanotubes have been utilized as highly conductive routes for the purpose of increasing the electrical conductivity of various composites. In the case of materials possessing conductive shape memory [16,21], the variation of the surface temperature due to electric heating caused by the application of voltage is closely related to the dispersion structure of the tubes within the polymer matrix. In this regard, we compared the electroactive shape memory of composites prepared by conventional blending, in-situ and cross-linking polymerization ( figure 3(b) and 3(c)).…”