Mechanical reinforcement of electrospun poly(vinyl alcohol) by α‐FeOOH nanowires

The authors kindly acknowledge the financial support of the Estonian Research Council for the post-doctoral research grants of personal research funding in projects PUT1096 and PUTJD578 as well as Institutional Research Funding Projects, IUT20-17, and IUT23-7.We report the mechanical performance of α‐FeOOH nanowire reinforced poly(vinyl alcohol) (PVA) composite nanofiber mat, fabricated using straightforward aqueous processing methods. Goethite (α‐FeOOH) nanocrystals have a high elastic modulus and –OH rich surface, ensuring strong interactions with hydrophilic polymers and effective reinforcement. Needle‐less electrospinning resulted in alignment of the nanowires along fibre axis, as confirmed by transmittance electron microscopy studies. Produced composite PVA nanofibers containing 10 wt% goethite nanoparticles exhibited an outstanding fivefold increase in Young's modulus and 2.5‐fold improvement of tensile strength compared to mats of neat PVA. The addition of α‐FeOOH had a significant influence on glass transition temperature indicating formation of interphase regions around nanowire inclusions. Observed properties are explained by nanowire grafting in the precursor solution, extensive interactions between the adsorbed PVA chains and the matrix and percolation of interphase regions at 10 wt% α‐FeOOH.Estonian Research Council PUT1096 and PUTJD578; Institutional Research Funding Projects, IUT20-17, and IUT23-7; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Electrospinning of Poly(Vinyl Alcohol) Nanofiber Mats Reinforced by Lignocellulose Nanowhiskers

This article reports on electrospun poly(vinyl alcohol) (PVA) modification with lignocellulose nanowhiskers (LCNWs) produced from hemp shives without using harsh preparation steps. LCNWs were obtained by using steam explosion (SE) pretreatment, ball milling, and ultrasonication. Formation of LCNWs was confirmed by atomic force microscopy. Obtained LCNWs were used to modify the mechanical properties of electrospun PVA nanofibers. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy analyses provided clear evidence of the presence of cellulose nanowhiskers in the PVA/LCNW electrospun mats. It was found that tensile stress at break increases more than fivefold for PVA nanofiber mats reinforced with LCNWs

Multifunctional Materials from Hemp Fibres Treated with Steam Explosion Technology

Multifunctional materials include properties of smart material systems (e.g. smart textiles) as well as biologically synthesized materials (case of biomimetic). Natural wood, flax and hemp fibres are examples of such multifunctional materials – polymer composite systems. In current research attempt has been made to analyse hemp fibres treated with steam explosion (SE) technology. Disintegration of hemp fibres separated from non-retted, dew-retted and dried stems of hemp (‘Purini’) by alkali treatment and steam explosion (SE) were investigated. An average intensive SE in combination with the hydro-thermal and alkali after-treatment allows decreasing the diameter of hemp fibres and reduce the concentration of non-celluloses components, among them hemicelluloses, lignin, pectin, waxes and water

UV radiācijas absorbētāju ietekme uz UV aizsardzības efektivitāti

Pētījumā apkopota sistematizēta informācija par ultraviaoleto (UV) starojumu un siltumstarojuma iedarbību un progresīvām metodēm aizsardzības nodrošināšanai pret UV un siltumstarojumu gan uzturoties ārvidē, gan regulējot mikroklimatu telpās, kā arī apzinātas iespējas izmantot metālus un to oksīdus aizsargpārklājumu veidošanai, sniegti to raksturojumi, kā arī metodikas ZnO iegūšanai un auduma apstrādei. Eksperimenti veikti uznesot vakuumā termoiztvaicēšanas procesā dažāda biezuma Zn pārklājumus uz kokvilnas un kokvilnas ķemdzijas auduma, kā arī linu auduma, kas ir biežāk lietotie tekstilmateriāli ekovides veidošanai. Eksperimenta gaitā salīdzinātas dažādu materiālu paraugu ar atšķirīgu pārklājuma biezumu starojuma caurlaidības, kā arī virsmu mikrogrāfijas, kas ļauj secināt, ka vakuuma termoiztvaicēšanas procesā iespējams iegūt pat 0,12 μm vienmērīgu gludu Zn pārklājumu uz kokvilnas auduma, palielinot pārklājuma biezumu līdz 0,21 μm caurejošās starojuma plūsma samazinās par 35 %. Uz linu auduma pavedieniem uznestā Zn kārtiņas struktūra ir graudaina, jo lielāks ir kārtiņas biezums, jo Zn klasteri kļūst rupjāki, līdz ar to pārklājums ekspluatācijā mazāk noturīgs. Tā kā aplūkotā fizikālā metode ultraplānu metālpārklājumu uznešanai uz tekstilmateriāliem atšķirībā no ķīmiskajām apstrādēm nerada vides piesārņojumus, ir mērķtiecīgi turpināt pētījumus adhēzijas uzlabošanai, kā arī meklēt veidus, kā piešķirt metālpārklātajai virsmai papildnetīrumus nepiesaistošas īpašība

Electrospun Herbal Extract Derived Polymer Nanocomposites for Medical Applications

Herbal plants have been used in medicine since ancient times due to their health benefits. The research in this field continues to reveal advantages of these plants such as antibacterial activity against multidrug-resistant bacteria and possibility to integrate extracts in fibers by electrospinning. Electrospinning is a simple, yet versatile method of creating polymer-based nanofiber web, which can be used for wound dressings, tissue engineering and drug delivery systems. In production of electrospun nanofibers a solution of biocompatible polymer and a plant extract is needed. Therefore exploration of such composition ingredients is importan

STEX Treated and Untreated Hemp Fiber Comparative Structural Analysis

In this article, the architecture of hemp fibres as a source of high strength cellulose is analyzed. In the experimental part, steam explosion technology is applied to disintegrate technical hemp fibres to elementary fibres with the aim to find out the best procedure, without resort to environmentally harmful chemical pre-treatments, to solving the problems on further nano-level environmentally friendly hemp cellulose disintegration. Influence of pre-treatment intensity, steam explosion process temperature and pressure are investigated on disintegration level of fibres of hemp variety Bialobrzeskie, and the acquired results are discussed