The piezoresistive effect in polypropylene—carbon nanofibre composites obtained by shear extrusion

Abstract

The piezoresistive effect on poly(propylene) (PP)-carbon nanofibre (CNF) composites fabricated by twin-screw extrusion and compression moulding has been investigated. The electrical and mechanical properties of PP/CNF composites have been obtained as a function of CNF concentration. Electrical conductivity exhibited low thresholds and values close to the required levels for EMI shielding applications at 2.4 vol%. Meanwhile the elastic modulus showed an enhancement with a maximum up to 130% for one of the composites at 0.9 vol% loading. Further, the piezoresistive response has been evaluated in four-point bending. Positive gauge factors between 2 and 2.5 have been obtained. The highest gauge factors are found within the percolation threshold. The characteristics of the materials and the production technique make them suitable for large scale applications.

Piezoresistive polypropylene–carbon nanofiber composites as mechanical transducers

“…As it was demonstrated in Paleo et al (2010), the highest gauge factor (GF = 2.4) was found just below the percolation threshold (0.9 vol. % loading).…”

“…Surface and cross section images were taken after coating the samples with a gold layer by magnetron sputtering. A more detailed description of the fabrication of fibers and their mechanical response is presented in Paleo et al (2010).…”

“…Some other studies report on the variations of the resistivity of the composites in the presence of external deformations (Park et al 2003;Pham et al 2008;Li et al 2008;Paleo et al 2010), effect reported as piezoresistivity.…”

Surface coatings of silver nanowires lead to effective, high conductivity, high-strain, ultrathin sensors

“…However, recently flexible, low stiffness, highly sensitive, cost-efficient sensors made from polymer based nanocomposites have been shown to be ideal for use in next generation wearable smart materials and flexible electronics. [6][7][8] Nanocomposite sensing materials consisting of an elastic polymer matrix loaded with conductive carbon-based nanomaterials [9][10][11][12][13][14][15][16][17][18][19][20][21][22] have been utilized to try and meet the above criteria. In such nanocomposites, when strain is applied the distance between conductive fillers inside the polymer matrix changes, causing large resistive changes, resulting in sensitivities much larger than that of commercial strain sensors.…”

Temperature Dependent Electrical Resistivity in Epoxy—Multiwall Carbon Nanotube Nanocomposites

“…In addition, the sensitivity of electrical conductivity to mechanical strain is significantly altered, resulting in the possibility of developing lighter and cheaper multifunctional polymer/CNT devices. Carbon nanotubes change their electrical conductivity under mechanical stress; consequently they can be used for in situ monitoring of stress distribution and to actively control the composite structures [1][2][3][4], for strain sensing [5][6][7][8][9][10][11][12], and as sensors and actuators [13]. The strain sensing properties of carbon nanotubes and polymer composites has in the past decade been investigated with special focus on sensitivity, linearity and nonlinearity of the strain response [14], dominant mechanisms [9], effect of fabrication processes [15] and effect of carbon nanotube type and morphology.…”