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

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.

Conducting Shape Memory Polyurethane‐Polypyrrole Composites for an Electroactive Actuator

“…The combination of conventional polymers with conductive polymers or filler allows to create new polymeric materials with unique electrical properties. Li et al [7] prepared conducting shape memory polyurethane incorporating carbon black. They studied the shape memory properties by applying thermal heating but not electrical voltage.…”

Electrical properties and fractal behavior of polyurethane elastomer/polyaniline composites under mechanical deformation

“…In addition, there is a portion of unrecoverable elongation, which is due to mechanical properties and relaxation of deformation for parent PU films used in the study. It has been reported [21] that almost complete recovery (up to 98%) can be reached in pure polyurethane. However, the presence of the conductive filler reduces the recovery rate down to 70% when the load is above the percolation threshold.…”

“…Deformation of the sample causes enhancement of the optical contrast due to interruption of the conductive layer with insulating PU micro-regions. The latter appear Table 1 Theoretical and experimental scaling exponents and fractal dimensions of the system depending on the dimensionality of embedding space, d or type of PU matrix modification with PANI Theoretical predictions [21] Experimental results bright on the images due to optical transparency of the PU elastomer. At 3 ¼ 0.65 PANI regions are still inter-connected and the sample looks electrically percolated, however, its electrical conductivity is about 10 times lower in comparison to the pristine sample.…”

High performance shape memory foams with isocyanate-modified hydroxyapatite nanoparticles for minimally invasive bone regeneration

“…In polyurethane/carbon black system containing 30 wt% of carbon black, the shape recovery ratio of the composite reduced from 98% to 65% [21]. It was also found that clay particles in polyurethane, reducing shape fixity ratio from 78% to 57% at 5 wt% of clay [22].…”