1,721,196 research outputs found
Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage
Full text linkThe peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anionic surfactants can be selectively adsorbed at the inner surface generating inorganic micelles able to solubilize hydrophobic species in a controlled cleaning protocol. We briefly discuss how the natural halloysite nanotubes can be supportive in various conservation processes of cultural heritage and present an outlook for future perspectives
Calori Specifici, Volumi e solubilità del Pentanolo in Soluzioni Acquose di Cloruri di Dodecilammonio, Dodecildimetilammonio e Dodeciltrimetilammonio
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Colloidal stability of halloysite clay nanotubes
Full text linkThe colloidal stability of halloysite clay nanotubes dispersion is reviewed showing the strategy and the mechanism to obtain stable systems in water and apolar solvents. The selective modification of halloysite inner/outer surfaces can be achieved by exploiting electrostatic interactions. The adsorption of anionic surfactants onto the halloysite cavity allows generating inorganic cylindrical micelles that can be separated from the solvent. On the other hand, the functionalization of halloysite shell by positively charged surfactants drives to obtain stable water-in-oil emulsions. The interactions with ionic and nonionic polymers alters the dispersability of halloysite due to electrostatic and steric effects that are strongly dependent on the nanoarchitecture of the hybrid systems. Modified nanotubes by selective interactions lead to the formation of colloidal systems with tuneable surface properties and controlled colloidal stability adjusted to the solvent polarity. These dispersions are perspectives nanocarriers for substances such as antioxidants, biocides, drugs and corrosion inhibitors, to be released in response to external stimuli
Filling of mater-BI with nanoclays to enhance the biofilm rigidity
Full text linkWe investigated the efficacy of several nanoclays (halloysite, sepiolite and laponite) as nanofillers for Mater-Bi, which is a commercial bioplastic extensively used within food packaging applications. The preparation of Mater-Bi/nanoclay nanocomposite films was easily achieved by means of the solvent casting method from dichloroethane. The prepared bio-nanocomposites were characterized by dynamic mechanical analysis (DMA) in order to explore the effect of the addition of the nanoclays on the mechanical behavior of the Mater-Bi-based films. Tensile tests found that filling Mater-Bi with halloysite induced the most significant improvement of the mechanical performances under traction force, while DMA measurements under the oscillatory regime showed that the polymer glass transition was not affected by the addition of the nanoclay. The tensile properties of the Mater-Bi/halloysite nanotube (HNT) films were competitive compared to those of traditional petroleum plastics in terms of the elastic modulus and stress at the breaking point. Both the mechanical response to the temperature and the tensile properties make the bio-nanocomposites appropriate for food packaging and smart coating purposes. Here, we report a preliminary study of the development of sustainable hybrid materials that could be employed in numerous industrial and technological applications within materials science and pharmaceutics
Nanoclays for Conservation
No full textWithin the conservation of artworks materials, this chapter describes innovative strategies based on clay nanoparticles that are promising for protective coating, surface cleaning, and consolidation. We present the preparation of polymer/montmorillonite nanocomposites, which are revealed as efficient protective coatings for highly porous stones, marbles, and bread-made artifacts. Anticorrosive films for metal substrates have been obtained by polymer filling with laponite and halloysite nanotubes (HNTs) containing corrosion inhibitors into their lumen. The dispersion of hydrophobically modified HNTs into chitosan matrix drives to fabricate biofilms with surface cleaning capacity. Rust stains have been removed from marble samples by using laponite/cellulose fibers. Regarding the preservation of lignocellulosic artworks, composite systems based on sustainable polymers (cellulose ethers and beeswax) and HNTs have been successfully employed as consolidants of archaeological woods. Encapsulation of Ca(OH)2 into an HNT cavity has been explored for paper deacidification. In conclusion, we have summarized the nanoclay-based protocols used in conservation issues. © 2019 Copyrigh
Halloysite nanotubes/Keratin composites for wool treatment
Full text linkThe optimization of a consolidation and protection coating for wool-based artefacts is a challenging issue for conservator of cultural heritage. In this study, an aqueous dispersion containing Keratin (K) and Halloysite nanotubes (Hal) was investigated in a coating protocol for wool thread. Colorimetric analysis and optical microscopy revealed the surface characteristic of wool. Scanning electron microscope showed the halloysite nanotubes distribution in the wool fibers. The protection efficacy after UV-irradiation was evaluated and the mechanical analysis gave us direct information on consolidation and protection effect of Hal/K mixtures in treated wool thread samples. The formulation with the optimal performances was used on conservation protocol for a historical yarn. The obtained results indicate that the proposed protocol is promising to generate a reinforcing coating layer onto wool-based yarn also providing protection from deterioration due to UV exposure with a minimal impact on the sample aesthetic aspects
Halloysite nanotubes filled with MgO for paper reinforcement and deacidification
Full text linkA novel material for the deacidification and protection of paper has been designed by using MgO filled halloysite nanotubes (Hal). The ability of MgO loaded nanotubes to control the acidic conditions was evaluated by pH measurements in aqueous solvent. Afterwards, paper was impregnated into hydroxypropyl cellulose dispersions containing the consolidating material. A simulation of strong acidic conditions allowed us to evaluate the deacidification effect of the composite material on the samples. In particular, the paper reaches a pH of 7.7 after 1 h exposition to HNO3 vapours when MgO-Hal nanoparticles are added to the impregnation mixture at a concentration of 10 wt% and it remains still neutral after 12 h. Dynamic mechanical analysis showed that the tensile strength of the consolidated paper is improved, since the stress at breaking increase of ca. 8% for the samples treated with MgO-Hal compared to the untreated paper. Due to the presence of halloysite loaded with the alkaline reservoir, the acidic degradation of cellulose is neutralized as suggested by the stored energy which is similar to the pristine paper without any chemical attack. Therefore, the mechanical performances of the paper are preserved during the aging together with its macroscopic aspect, as suggested by colorimetric analysis. The proposed consolidation protocol represents a further step for the self-healing and long-term protection of cellulose based artworks
Hydrogel based on patch halloysite nanotubes: A rheological investigation
Full text linkThe rheological behaviour of Patch halloysite nanotubes (PT_Hal) was investigated here. Their peculiar morphology shows longer and thinner nanotubes and gives rise to the formation of gel-like systems that are not evidenced in halloysite from other natural sources. According to frequency sweep tests, PT_Hal possesses solid-like characteristics even at low concentrations, suggesting that the material is highly structured. Interestingly, flow ramp analysis evidenced two distinct behaviours based on the clay concentration: a yield stress was detected only from 0.75 wt%, indicating the sample's ability to resist deformation or breaking. Furthermore, the study investigated the influence of ionic strength, revealing that the addition of salt did not significantly affect the gel's properties of this clay. Accordingly, in this work we propose a new hydrogel system based on green nanoclays that can be suitable for industrial and biological applications as well as for cultural heritage
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