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.

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This study deals with the development and optimization of hybrid composites integrating microcrystalline cellulose and short basalt fibers in a polypropylene (PP) matrix to maximize the mechanical properties of resulting composites. To this aim, the effects of two different coupling agents, endowed with maleic anhydride (MA-g(grafted)-PP) and acrylic acid (AA-g-PP) functionalities, on the composite properties were investigated as a function of their amount. Tensile, flexural, impact and heat deflection temperature tests highlighted the lower reactivity and effectiveness of AA-g-PP, regardless of reinforcement type. Hybrid formulations with basalt/cellulose (15/15) and with 5 wt. % of MA-g-PP displayed remarkable increases in tensile strength and modulus, flexural strength and modulus, and notched Charpy impact strength, of 45% and 284%, 97% and 263%, and 13%, in comparison with neat PP, respectively. At the same time, the thermo-mechanical stability was enhanced by 65% compared to neat PP. The results of this study, if compared with the ones available in the literature, reveal the ability of such a combination of reinforcements to provide materials suitable for automotive applications with environmental benefits.

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The present research is focused on the synthesis of hexagonal ZnO wurtzite nanorods for the decoration of commercially available electrospun nylon nanofibers. The growth of ZnO was performed by a hydrothermal technique and for the first time on commercial electrospun veils. The growth step was optimized by adopting a procedure with the refresh of growing solution each hour of treatment (Method 1) and with the maintenance of a specific growth solution volume for the entire duration of the treatment (Method 2). The overall treatment time and volume of solution were also optimized by analyzing the morphology of ZnO nanostructures, the coverage degree, the thermal and mechanical stability of the obtained decorated electrospun nanofibers. In the optimal synthesis conditions (Method 2), hexagonal ZnO nanorods with a diameter and length of 53.5 nm ± 5.7 nm and 375.4 nm ± 37.8 nm, respectively, were obtained with a homogeneous and complete coverage of the veils. This easily scalable procedure did not damage the veils that could be potentially used as toughening elements in composites to prevent delamination onset and propagation. The presence of photoreactive species makes these materials ideal also as environmentally friendly photocatalysts for wastewater treatment. In this regard, photocatalytic tests were performed using methylene blue (MB) as model compound. Under UV light irradiation, the degradation of MB followed a first kinetic order data fitting and after 3 h of treatment a MB degradation of 91.0% ± 5.1% was achieved. The reusability of decorated veils was evaluated and a decrease in photocatalysis efficiency was detected after the third cycle of use.