Ceramic nanoparticles and carbon nanotubes reinforced thermoplastic materials for piezocapacitive sensing applications

This work reports on the development of polymer composites for load sensing applications. Three thermoplastic polymers, one with elastomeric behaviour, namely poly(styrene-butadiene-styrene) and poly(styrene–ethylene/butylene-styrene), and a semi-crystalline fluorinated polymer, poly(vinylidene fluoride), were selected as hosting matrices. In order to improve the sensing capacity, both ceramic nanoparticles (barium titanate, BT) and carbon nanotubes (CNTs) have been incorporated through solvent mixing followed by spreading the solution onto a glass substrate and subsequent solvent evaporation. Scanning electron microscopy results show that nanoparticles remain uniformly distributed through the nanocomposite at concentrations as high as 50% by weight. Polymer-filler interactions and thermal stability of the nanocomposites were assessed by Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively, in which these nanocomposites present physical interaction between constituents rather than chemical interaction and thermal stability increases slightly for larger filler contents. The mechanical properties are dependent on the matrix, filler type and amount in which the incorporation of both fillers in the elastomeric matrices increases the initial modulus of the nanocomposites up to 3-times. Electrically insulating BT increases dielectric properties and electrically conducting CNTs increase the dc conductivity of nanocomposites, respectively, and the combination of both fillers results in a synergetic effect. Finally, the changes induced by applied static loads on the capacitance variation (ΔC) of the nanocomposites were evaluated, showing a marked enhancement on the ΔC upon the incorporation of both fillers due to the synergetic effect provided by electrically insulating BT together with electrically conducting CNTs.The authors thank the FCT (Fundação para a Ciência e Tecnologia) for financial support under the framework of Strategic Funding grants UID/FIS/04650/2019, UID/EEA/04436/2013 and UID/QUI/0686/2016; and projects no. PTDC/EEI-SII/5582/2014 and PTDC/FIS-MAC/28157/2017. The authors also thank the FCT for financial support under grants SFRH/BD/140242/2018 (T.M.), SFRH/BPD/110914/2015 (P.C.). SFRH/BPD/112547/2015 (C.M.C.) as well POCH and European Union. Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including FEDER financial support) and from the Basque Government Industry and Education Departments under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively, is also acknowledged. The authors also thank to Dynasol Elastómeros for supplying the TPE polymer

Highly tunable interfacial adhesion of glass fiber by hybrid multilayers of graphene oxide and aramid nanofiber

The performance of fiber-reinforced composites is governed not only by the nature of each individual component comprising the composite but also by the interfacial properties between the fiber and the matrix. We present a novel layer-by-layer (LbL) assembly for the surface modification of a glass fiber to enhance the interfacial properties between the glass fiber and the epoxy matrix. Solution-processable graphene oxide (GO) and an aramid nanofiber (ANF) were employed as active components for the LbL assembly onto the glass fiber, owing to their abundant functional groups and mechanical properties. We found that the interfacial properties of the glass fibers uniformly coated with GO and ANF multilayers, such as surface free energy and interfacial shear strength, were improved by 23.6% and 39.2%, respectively, compared with those of the bare glass fiber. In addition, the interfacial adhesion interactions between the glass fiber and the epoxy matrix were highly tunable simply by changing the composition and the architecture of layers, taking advantage of the versatility of the LbL assemblyclose0