Interface tailoring between flax yarns and epoxy matrix by ZnO nanorods

Abstract

The ideal mechanical performance of a composite is controlled by the level of interfacial adhesion and to overcome the incompatibility issues between plant fibres and polymeric matrices, the surface of flax yarns has been modified by zinc oxide (ZnO) nanostructures. The ZnO nanorods were synthesized through a lowtemperature hydrothermal treatment, and several parameters have been analysed in order to obtain a uniform and homogeneous ZnO interphase, such as the number of the seeding cycles, the growth reaction times and the replacement of the growth solution. The results showed that it is possible to obtain highly oriented and well aligned ZnO nanostructures (by FE-SEM), with an hexagonal wurtzite structure (by XRD) and a high degree of coverage along the whole yarn (by TGA), reducing the number of the seed cycles, with rather long growth times (5 hours) and substituting the growth solution at least once during the synthesis. The experimental conditions preserved the breaking force of the yarns, while Single Fibre Fragmentation Tests (SFFT) highlighted a better interfacial adhesion of ZnO-modified flax yarns with epoxy matrix, which displayed a 29 % reduction in average debonding length relative to untreated yarns.

Functionalization of Commercial Electrospun Veils with Zinc Oxide Nanostructures

“…This confirmed that the removal of MB in the presence of hexagonal ZnO nanorods can be attributed to the ability of such structures to promote the production of radical species such as superoxide anions ( • O 2 − ) and hydroxyl radicals ( • OH) [ 65 ] thanks to the electron-hole pairs mechanism [ 24 ]. No substantial difference between the specimens was observed: in both cases a kinetic of first order (Equation (8)) well describes the MB removal time ( t ) in accordance with other authors [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ...…”

“…In conclusion, the success obtained in the decoration of commercial veils allows introducing possible future application regarding their use as toughening material in composites. Their use in a neat form proved to reduce the extension of delaminated area after low velocity impact test [32] while the presence of ZnO nanorods on fiber surface enhances the adhesion between fibers and polymer matrix [56,57]. The high aspect ratio of ZnO nanorods after 3 h in 250 mL makes the electrospun veils suitable as a composite toughening element.…”

Influence of Adhesive Systems on the Mechanical and Physical Properties of Flax Fiber Reinforced Beech Plywood

“…The difference between flax and glass fiber for epoxy resin indicates that flax is well suitable. One method to improve the bonding performance between flax fiber and epoxy resin is given by Sbardella et al (2021), suggesting the use of zinc oxide (ZnO) nanorods [30]. The decrease in PUR indicates adhesive application problems during the manufacturing process.…”

Development of Bio-Inspired Hierarchical Fibres to Tailor the Fibre/Matrix Interphase in (Bio)composites

“…Sbardella et al (2021) studied the growth of ZnO nanorods on flax yarn surface in order to improve the interfacial adhesion in flax/epoxy matrix biocomposites [ 69 ]. The hydrothermal treatment was provided to obtain highly oriented ZnO nanostructures, that is, hexagonal wurtzite nanorods.…”

“… ( a , b ) FE-SEM micrographs showing fracture surfaces for ZnO-flax/epoxy single yarn composites. Micro-computed tomography observation for the ZnO-modified flax yarn/epoxy matrix with ( c ) high-resolution micro-CT image of the flax embedded in the epoxy resin and ( d ) volumetric reconstruction of the flax yarn and the fracture zone: the flax yarn is represented in dark grey, the fracture zone in blue and the ZnO coating in red (reprinted with permission from Sbardella et al, 2021 [ 69 ]). …”