Surface Of Halloysite Nanotubes Research Articles

An ammonia-sensitive fluorescence sensor based on polyvinyl alcohol-graphene quantum dots/halloysite nanotubes hybrid film for monitoring fish freshness

A fluorescent hybrid film composed of nitrogen-doped graphene quantum dots (N-GQDs) loaded on halloysite nanotubes (HNTs) (N-GQDs/HNTs nanocomposite) as a sensitive element and polyvinyl alcohol (PVA) as a film-forming matrix was designed for freshness detection. The PVA-N-GQDs/HNTs hybrid film exhibited significantly enhanced fluorescence attributed to the loading of N-GQDs onto the surface of HNTs through electrostatic interactions and hydrogen bonding, effectively reducing their aggregation. The fluorescence of the hybrid film could be quenched by ammonia via photoinduced electron transfer (PET), with good linearity in the range of 20 ppm to 500 ppm ammonia and a limit of detection (LOD) of 0.63 ppm. In addition, the hybrid film was applied to monitor the freshness of seawater fish and freshwater fish stored at refrigeration and room temperature to evaluate the practicality of this approach. The developed hybrid film showed promise for nondestructive and on-site monitoring of fish spoilage.

The fabrication of organic-inorganic hybrid structure towards high mechanical property and improved flame retardancy

In order to design UPR composites with high mechanical property and improved flame retardancy, an organic-inorganic hybrid flame retardant (DA-Si-HNT) was fabricated by grafting silane coupling agent (KH560) and the phosphorus-nitrogen containing structure (DOPA-A, the production of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and adenine) on the surface of halloysite nanotube (HNTs). The UPR/DA-Si-HNT15 composites exhibited significant improvements in tensile strength, tensile modulus, and flexural strength, with respective increases of 65.6%, 140.6%, and 80.2% compared to neat UPR. These enhancements can be attributed to the enhanced compatibility and interfacial force between the flame retardants and the polymer matrix. Meanwhile, it passed the UL-94 V-0 rating at a limiting oxygen index (LOI) value of 34.5%. The peak of heat release rate (PHRR) and total heat release (THR) decreased by 49.5% and 43.5% comparing to that of UPR, indicating a sharp decline in the heat hazard. Moreover, an obvious catalytic carbonization effect in the condensed phase accompanied with moderate gas-phase effect jointly improved flame retardancy of the UPR/DA-Si-HNT15 composites.

Metalized Plastic Current Collectors Incorporated with Halloysite Nanotubes toward Highly Safe Lithium‐Ion Batteries

AbstractMetalized plastic current collectors (MPCCs) have shown potential in improving the energy density and safety of lithium‐ion batteries (LIBs). However, the poor mechanical strength, weak interfacial adhesion force, and surface metal corrosion have impeded the practical application of MPCCs. Here, an innovative engineering of MPCCs is proposed by incorporating halloysite nanotubes (HNTs) as fillers into polyimide (PI) polymer layer, which is further coated with two thin copper (Cu) layers. Because of the strong bonding between HNTs surface and the PI precursor, HNTs improve the mechanical strength of PI‐HNTs composite film, reinforce the interfacial adhesion force between the PI‐HNTs film and the coated Cu layer, and suppress the Cu corrosion by electrolyte. The prepared MPCCs exhibit a low mass density and only account about one‐fifth of the density of commercial Cu CCs. Furthermore, the PI‐HNTs‐Cu composite demonstrates significantly enhanced interfacial adhesion force doubled to 4 N cm−1 along with prolonged stability under electrolyte immersion and electrochemical reaction conditions, and delivers a high fracture strength of 125 MPa. LIBs assembled with MPCCs deliver a twice higher discharge capacity compared to battery with Cu CCs and reach a long‐term cycle capacity retention as high as 92.9% at 0.5 C after 500 cycles.

Study on dry desulfurization performance of modified HNTs

The production characteristics of coking industry determine that the coke quenching process has the characteristics of complex pollutant composition, high purification difficulty and serious environmental pollution. SO2 is one of the main pollutants in coke dry quenching tail gas, which is easy to cause serious harm. Dry desulfurization process is the use of particles or powder desulfurizer to remove SO2. The hydroxyl groups on the surface of Halloysite nanotubes make the active components of catalytic reaction fixed on the nano-scale surface or in the lumen, which can produce more selective and active catalytic materials with good catalytic performance. In this study, HNTs were modified by molten salt etching method. The functionalized halloysite and chitosan were cured by chemical precipitation method to prepare halloysite chitosan nanospheres desulfurizer, and its application performance and reaction mechanism in SO2 removal were explored.

Charge-Selective Photocatalytic Degradation of Organic Dyes Driven by Naturally Occurring Halloysite Nanotubes

This study explores the use of Halloysite NanoTubes (HNTs) as photocatalysts capable of decomposing organic dyes under exposure to visible or ultraviolet light. Through a systematic series of photocatalytic experiments, we unveil that the photodegradation of Rhodamine B, used as a model cationic dye, is significantly accelerated in the presence of HNTs. We observe that the extent of RhB photocatalytic degradation in 100 min in the presence of the HNTs is ~four times higher compared to that of bare RhB. Moreover, under optimized conditions, the as-extracted photodegradation rate of RhB (~0.0022 min−1) is comparable to that of the previously reported work on the photodegradation of RhB in the presence of tubular nanostructures. A parallel effect is observed for anionic Coumarin photodegradation, albeit less efficiently. Our analysis attributes this discrepancy to the distinct charge states of the two dyes, influencing their attachment sites on HNTs. Cationic Rhodamine B molecules preferentially attach to the outer surface of HNTs, while anionic Coumarin molecules tend to attach to the inner surface. By leveraging the unique properties of HNTs, a family of naturally occurring nanotube structures, this research offers valuable insights for optimizing photocatalytic systems in the pursuit of effective and eco-friendly solutions for environmental remediation.

Bio-derived polyphosphazene modified halloysite nanotubes as eco-friendly flame retardants to significantly reduce smoke release and enhance the fire safety of epoxy resin

At present, designing efficient bio-based flame retardants for epoxy resin (EP) and exploring low-toxicity and sustainable flame retardant strategies is still a great challenge. In this work, a novel bio-based hybrid flame retardant was successfully prepared by constructing a resveratrol-based cyclic cross-linked polyphosphazene (PPZ) shell on the surface of halloysite nanotube (HNT). The enhancement effects of HNT@PPZ on the fire safety of EP composites were investigated by thermal degradation, simulated fire performance (cone calorimeter test), gas-phase product analysis, and condensed-phase char residue analysis. Compared to pure EP, he total heat release (THR), total smoke production (TSP) and the average yield of carbon monoxide (Av-COY) of EP/3HNT@PPZ were reduced by 47.8 %, 46.5 % and 48.8 % respectively. Furthermore, the EP composites containing HNT@PPZ had a stable flame retardancy even after 6 months of natural aging. It was found the barrier effect of HNT@PPZ in condensed phase was further strengthened by the formation of new product aluminum phosphate, which formed a multiple protective char layer. Additionally, PPZ shell improved compatibility and dispersion of HNT in EP matrix, the mechanical properties of the composite with HNT@PPZ were improved significantly. This work proposed a feasible solution for the preparation of highly efficient bio-based flame retardants with excellent heat reduction and smoke toxicity reduction ability, which could be expected to broaden the application of biomass resources in the development of highly efficient flame retardants.

Protecting Mg-sites from hydration by embedding magnesium-aluminium layered double hydroxide in halloysite and using as pickering catalysts in Baeyer-Villiger oxidation

A facile strategy was developed via thermal treatment to get hierarchically structured magnesium-aluminium layered double hydroxide (MgAl-LDH) selectively loaded on the inner and external surfaces of halloysite nanotubes, respectively. The loaded MgAl-LDH was found to have active centers for Baeyer-Villiger (BV) oxidation that was protected from hydration by embedding in halloysite lumens. The BV oxidation of cyclohexanone was observed to have better performance by using the halloysite impregnated MgAl-LDH (MgAl-LDH@Hal) as catalysts than that of external surface modified MgAl-LDH (MgAl-LDH@Hal600). A conversion 57.0% of cyclohexanone was achieved, and the yield of ε-caprolactone was 22.0% when the MgAl-LDH@Hal was used as catalysts. Density Functional Theory (DFT) calculations as well as high-resolution of X-ray photoelectron spectrum (XPS) measurements revealed the charge depletion occurred in the Mg-sites of sample MgAl-LDH@Hal in comparison with MgAl-LDH@Hal600, which benefited the activation of H2O2 oxidants, and thus assisting the BV reaction. The prepared composites were able to work as phase-transfer catalysts as Pickering emulsions in oxidation of cyclohexanone.

Facile synthesis of ZnO/halloysite nanotube composite with greatly enhanced photocatalytic performance

ZnO/halloysite nanotube composites (ZH-X, X = 10, 30, 40, 50, 70), with different mass ratio of ZnO to halloysite nanotubes (HNTs), were fabricated successfully via a facile wet chemical technique in anhydrous ethanol under a mild reaction condition. ZnO nanoparticles about 9 nm in size were inhibited from agglomeration and loaded homogeneously on the surface of HNTs. The microstructure, specific surface area, light absorption ability, photocatalytic performance, etc. of the ZH-X composites varied with the mass ratio of ZnO to HNTs. All ZH-X composites displayed better photocatalytic performance than pure ZnO sample did. With the increasing of ZnO content, the photocatalytic activity of ZH-X composite toward degrading methylene blue (MB) solution strengthened gradually and reached the maximum by ZH-40 composite (with ZnO content of 28.57 wt%), then decreased step by step. ZH-40 (0.05 g) removed 99.88% of MB (100 mL, 15 mg/L) after adsorption in dark and then photocatalytic degradation for 60 min, and whose photocatalytic reaction rate constant was 5.73 times that of pure ZnO. The enhanced photocatalytic efficiency of ZH-40 composite was attributed to the interfacial effect of ZnO and HNTs as well as the dispersed ZnO nanoparticles, which maintained the adsorption ability of HNTs and improved the separation and migration of photo-generated electron and hole pairs. This work provides a feasible method for loading photocatalyst on clay mineral to realize efficient photocatalysis.

Fabrication and characterization of Halloysite–Fe3O4–Ag nanocomposite as efficient catalyst for metronidazole degradation by using sodium borohydride: Artificial neural network modeling

In this work, halloysite–Fe3O4–Ag nanocomposite produced by doping Fe3O4 and Ag nanoparticles on the surface of halloysite nanotube after activation with HCl by co-precipitation method was used as a catalyst for the catalytic degradation of metronidazole antibiotic with sodium borohydride. The physical and chemical structure of synthesized nanocomposite were characterized by pHpzc, FTIR, XRD, SEM/EDX and TGA. The degradation process of metronidazole antibiotic with sodium borohydride in the presence of nanocomposite catalyst was investigated. According to this, metronidazole removal efficiency was determined as %93.1 (as 0.069 in terms of Ct/C0) at the end of 120-min contact time under determined optimum conditions (pH 7, 10 mM NaBH4 concentration, 2 g/L catalyst dosage, 25 °C temperature) for 30 ppm metronidazole solution. In the pH range in which the process is applied, metronidazole is in anionic form in solution. The used nanocomposite was efficiently recycled and it was determined that it could be reused at least 6 times as a catalyst. Moreover, the process was modeled with Artificial Neural Networks approach. Finally, it was revealed with HPLC analysis that metronidazole was converted into different products as a result of applied process.

Design of Etched- and Functionalized-Halloysite/Meloxicam Hybrids: A Tool for Enhancing Drug Solubility and Dissolution Rate.

The study focuses on the synthesis and characterization of Meloxicam-halloysite nanotube (HNT) composites as a viable approach to enhance the solubility and dissolution rate of meloxicam, a poorly water-soluble drug (BCS class II). Meloxicam is loaded on commercial and modified halloysite (acidic and alkaline etching, or APTES and chitosan functionalization) via a solution method. Several techniques (XRPD, FT-IR, 13C solid-state NMR, SEM, EDS, TEM, DSC, TGA) are applied to characterize both HNTs and meloxicam-HNT systems. In all the investigated drug-clay hybrids, a high meloxicam loading of about 40 wt% is detected. The halloysite modification processes and the drug loading do not alter the structure and morphology of both meloxicam and halloysite nanotubes, which are in intimate contact in the composites. Weak drug-clay and drug-functionalizing agent interactions occur, involving the meloxicam amidic functional group. All the meloxicam-halloysite composites exhibit enhanced dissolution rates, as compared to meloxicam. The meloxicam-halloysite composite, functionalized with chitosan, showed the best performance both in water and in buffer at pH 7.5. The drug is completely released in 4-5 h in water and in less than 1 h in phosphate buffer. Notably, an equilibrium solubility of 13.7 ± 4.2 mg/L in distilled water at 21 °C is detected, and wettability dramatically increases, compared to the raw meloxicam. These promising results can be explained by the chitosan grafting on the outer surface of halloysite nanotubes, which provides increased specific surface area (100 m2/g) disposable for drug adsorption/desorption.

Quantitative XPS analysis of amine-terminated dendritic functionalized halloysite nanotubes decorated on PAN nanofibrous membrane and adsorption/filtration of Cr(VI)

Quantitative XPS analysis of the active functional groups on the surface of nanofiber membranes is an important issue for evaluating the potential efficiency of the membranes in removing heavy metals from aqueous solutions. This research is developing a novel composite nanofiber for accessibility adsorption groups on the surface of the electrospun membrane for effective removal of Cr(VI). For this purpose, three generations (G1, G2, and G3) of poly(amidoamine) dendrimers (PAMAM) were grafted onto the surface of halloysite nanotubes (HNTs). Functionalized HNTs (F-HNTs) were decorated on the surface of polyacrylonitrile (PAN) nanofiber layers in different ratios by simultaneous electrospinning and electrospraying techniques. The results showed that the decoration with F-HNTs made the surface of the membranes superhydrophilic. The removal efficiency of the optimal sample with 10 % third-generation F-HNTs (PAN/HNTs-G3-10 %) reached 96 % within 5 min. The mechanism for the removal of Cr(VI) ions in the PAN/HNTs-G3-10 % membrane was electrostatic interaction, chelation, and reduction. X-ray photoelectron spectrometer (XPS) analysis was used to characterize the quantitative and qualitative correlation dependencies between the removal of Cr(VI) and the amine functional groups of different generations decorated onto the electrospun layer. Quantitative analysis of the amine-terminated dendritic groups has revealed that the percentage of Cr(VI) removal is proportional to the number of terminal amine groups. Furthermore, PAN/HNTs-G2 and PAN/HNTs-G3 composite nanofiber membranes showed significantly lower leachability of nanoparticles and higher mechanical strength compared to other membranes due to the formation of ionic bonds between the amine-terminated dendritic of HNTs-G2 and HNTs-G3 and the cyanide groups of PAN. Effects of competing heavy metal ions on Cr(VI) adsorption follow the order of Zn(II) > Cu(II) > Ni(II).

Towards promoting wound healing: A near-infrared light-triggered persistently antibacterial, synergistically hemostatic nanoarchitecture-integrated chitosan hydrogel

The skin, the primary barrier of the body, is inevitably broken. However, the development of materials that facilitate wound healing with sustained antimicrobial, hemostatic, and biocompatible properties remains a formidable challenge. In this article, we prepared a photopolymerizable composite hydrogel consisting of a hydrogel matrix, a hemostatic/antibacterial agent, and a photothermal therapy agent. The photopolymerizable hydrogel matrix was prepared by grafting the photoinitiator and polymerizable active monomer onto the chitosan chain segment, which exhibits excellent biocompatibility. Furthermore, linalool is adsorbed on the surface of halloysite nanotubes (HNTs) to form a hemostatic and antibacterial. Meanwhile, dopamine is employed as a coating material for hollow glass microsphere (HGM), which enables them to function as photothermal therapy agents. Upon exposure to near-infrared radiation, the PHA hydrogel releases linalool molecules from the surface of the HNTs, which diffuse into the hydrogel matrix, resulting in a sustained antimicrobial effect. At the same time, rapid curing of the photopolymerizable hydrogel under UV light forms a physical barrier that synergistically enhances the hemostatic properties of the HNTs. From the above, the results pave the way to develop a potential hemostatic antimicrobial dressing for clinical use in wound healing.

An integrated experimental and theoretical approach to probe Cr(vi) uptake using decorated halloysite nanotubes for efficient water treatment.

Halloysite nanotubes (HNTs) were surface functionalized using four distinct chemical moieties (amidoxime, hydrazone, ethylenediamine (EDA), and diethylenetriamine (DETA)), producing modified HNTs (H1-H4) capable of binding with Cr(vi) ions. Advanced techniques like FTIR, XRD, SEM, and EDX provided evidence of the successful functionalization of these HNTs. Notably, the functionalization occurred on the surface of HNTs, rather than within the interlayer or lumen. These decorated HNTs were effective in capturing Cr(vi) ions at optimized sorption parameters, with adsorption rates ranging between 58-94%, as confirmed by atomic absorption spectroscopy (AAS). The mechanism of adsorption was further scrutinized through the Freundlich and Langmuir isotherms. Langmuir isotherms revealed the nearest fit to the data suggesting the monolayer adsorption of Cr(vi) ions onto the nanotubes, indicating a favorable adsorption process. It was hypothesized that Cr(vi) ions are primarily attracted to the amine groups on the modified nanotubes. Quantum chemical calculations further revealed that HNTs functionalized with hydrazone structures (H2) demonstrated a higher affinity (interaction energy -26.33 kcal mol-1) for the Cr(vi) ions. This can be explained by the formation of stronger hydrogen bonds with the NH moieties of the hydrazone moiety, than those established by the OH of oxime (H1) and longer amine chains (H3 and H4), respectively. Overall, the findings suggest that these decorated HNTs could serve as an effective and cost-efficient solution for treating water pollution.

Assessing the effect of acid and alkali treatment on a halloysite-based catalyst for dry reforming of methane.

Dry reforming of methane (DRM) has recently received wide attention owing to its outstanding performance in the reduction and conversion of CH4 and CO2 to syngas (H2 and CO). From an industrial perspective, nickel (Ni)-supported catalysts have been deemed among the most suitable catalysts for DRM owing to their low cost and high activity compared to noble metals. However, a downside of nickel catalysts is their high susceptibility to deactivation due to coke formation and sintering at high temperatures. Using appropriate supports and preparation methods plays a major role in improving the activity and stability of Ni-supported catalysts. Halloysite nanotubes (HNTs) are largely utilized in catalysis as a support for Ni owing to their abundance, low cost, and ease of preparation. The treatment of HNTs (chemical or physical) prior to doping with Ni is considered a suitable method for increasing the overall performance of the catalyst. In this study, the surface of HNTs was activated with acids (HNO3 and H2SO4) and alkalis (NaOH and Na2CO3 + NaNO3) prior to Ni doping to assess the effects of support treatment on the stability, activity, and longevity of the catalyst. Nickel catalysts on raw HNT, acid-treated HNT, and alkali-treated HNT supports were prepared via wet impregnation. A detailed characterization of the catalysts was conducted using X-ray diffraction (XRD), BET surface area analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (ssNMR), H2-temperature programmed reduction, (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), and Ni-dispersion via H2-pulse chemisorption. Our results reveal a clear alteration in the structure of HNTs after treatment, while elemental mapping shows a uniform distribution of Ni throughout all the different supports. Moreover, the supports treated with a molten salt method resulted in the overall highest CO2 and CH4 conversion among the studied catalysts and exhibited high stability over 24 hours testing.

Thermally stable, mechanically strong, easily biodegradable and water-resistant Poly(vinyl alcohol) composites crosslinked by supported crosslinker

Water-resistant Poly(vinyl alcohol) (PVA) materials integrated with excellent mechanical strength and simultaneously high thermal stability would be of great use in many fields, however their fabrication has been proven to be a big challenge. Here, the concept of supported crosslinker for PVA crosslinking was proposed and prepared by using halloysite nanotubes (HNTs) as supporter and reactive 3-glycidyloxypropyltrimethoxysilane (KH560) grafted on HNTs surface as crosslinker. The resultant PVA composites (c-PVA/HNTs-s-560) crosslinked with supported crosslinker (HNTs-s-560) shows high tensile strength (which is 20% higher than PVA composites with physically blended HNTs-s-560 (PVA/HNTs-s-560) and 40% higher than pure PVA) and excellent thermal stability (the maximum decomposition temperature is 21 °C higher than that of PVA/HNTs-s-560). Moreover, c-PVA/HNTs-s-560 has higher weight loss after soil burial tests for 90 days and higher tensile strength (110%) after immersion in water at room temperature for 15 days than that of PVA/HNTs-s-560, indicating the easy biodegradability and excellent water resistance of c-PVA/HNTs-s-560. The smart design of making mechanically strong and thermally stable inorganic nanofiller as building blocks of the crosslinked PVA network using a supported crosslinker is responsible for the excellent comprehensive performance of c-PVA/HNTs-s-560 and this work may open an avenue toward the development of PVA-based smart materials.

Augmentin loaded functionalized halloysite nanotubes: A sustainable emerging nanocarriers for biomedical applications

Clay minerals such as Halloysite nanotubes (HNTs), abundantly available green nanomaterial, exhibit a significant advantage in biomedical applications such as drug delivery, antibacterial and antimicrobials, tissue engineering or regeneration, etc. Because of the mesoporous structure and high absorbability, HNTs exhibit great potential as a nanocarrier in drug delivery applications. The sulfuric acid treatment enhances the surface area of the HNTs and thereby improves their drug-loading capacity by enlarging their lumen space/inner diameter. In the present investigation, based on the literature that supports the efficacy of drug loading after acid treatment, a dual treatment was performed to functionalize the HNTs surface. First, the HNTs were etched and functionalized using sulfuric acid. The acid-functionalized HNTs underwent another treatment using (3-aminopropyl) triethoxysilane (APTES) to better interact the drug molecules with the HNTs surfaces for efficient drug loading. Augmentin, a potential drug molecule of the penicillin group, was used for HNTs loading, and their antibacterial properties, cytotoxicity, and cumulative drug release (%) were evaluated. Different characterization techniques, such as X-ray diffractometer (XRD) and Fourier Transform Infra-Red (FT-IR), confirm the loading of Augmentin to the APTES@Acid HNTs. TEM images confirm the effective loading of the drug molecule with the HNTs. The drug encapsulation efficiency shows 40.89%, as confirmed by the Thermogravimetric Analysis (TGA). Also, the Augmentin-loaded APTES@Acid HNTs exhibited good antibacterial properties against E. coli and S. aureus and low cytotoxicity, as confirmed by the MTT assay. The drug release studies confirmed the sustainable release of Augmentin from the APTES@Acid HNTs. Hence, the treated HNTs can be considered as a potential nanocarrier for effectively delivering Augmentin and promoting enhanced therapeutic benefits.

Control of halloysite nanotubes localization into a LLDPE/EVA (70/30) blend through specific chemical modifications and sequence of mixing during extrusion

ABSTRACT The control of the localization of halloysite nanotubes (HNT) in a linear low-density polyethylene/ethylene-vinyl acetate copolymer (LLDPE/EVA, 70/30) blend was studied through three approaches: i) Functionalization of the filler, ii) Addition of a compatibilizer and iii) Modification of the processing sequence. First, the HNT surface modification was carried out with three different organosilanes (3-aminopropyltriethoxysilane (APTES), dodecyltricholosilane (DTCS) and triacontyltrichlorosilane (C30)). Grafting amounts about 0.10 mmol/g were reached whatever the nature of the organosilane. Then, the unmodified and modified HNT were mixed with a LLDPE/EVA (70/30) polymer blend using a microextruder and the localization of the fillers were scrutinized by scanning electron microscopy (SEM) analysis. It was observed that both the neat HNT and modified HNT were mostly localized in the EVA phase. These observations were also discussed according to the wettability coefficient determined for neat HNT and modified HNT thanks to contact angle measurements. The addition of PE-g-MA as a compatibilizer to the blend containing the HNT-APTES allowed to localize the HNT in the LLDPE phase. Finally, the influence of the mixing sequence of the different components was evaluated by using a twin-screw extruder, and it was successfully used to localize the modified HNT into the LLDPE phase.

Preparation and Characterization of Polydopamine-Modified Halloysite Nanotubes and Their Effect on a Natural Rubber, Chloroprene Rubber and Chloro-Isobutylene-Isoprene Rubber Blend

The superior physical and mechanical performances of halloysite nanotubes (HNTs) make them ideal fillers for rubber reinforcement. However, due to the abundant hydroxyl groups on their surface, they are highly polar and have poor compatibility with polymers, making it difficult for them to disperse uniformly in polymers, thus limiting their application in rubber composites to a certain extent. In this paper, noncovalently modified HNTs filled with a natural rubber/chloroprene rubber/chloro-isobutylene-isoprene rubber (NR/CR/CIIR) blend system, using polydopamine(PDA) as a surface modifier, was investigated. and a green and high-performance PDA/HNTs/NR/CR/CIIR composite was prepared by mechanical blending. Transmission electron microscopy (TEM) showed that the original HNTs had a hollow, multi-walled nanotube structure, and the outer surface of the PDA-modified halloysite nanotubes(PDA/HNTs)showed an obvious cladding layer. X-ray diffraction indicated that the modification experiments did not damage the halloysite crystal structure; the modifier only interacted on the outer surface of the HNTs. Zeta potential and thermogravimetric analysis (TGA) further indicated the presence of interfacial interactions between PDA and HNTs, suggesting that PDA was successfully grafted to the surface of HNTs. In addition, the effects of PDA/HNTs on the mechanical properties, vulcanization properties and Rubber Process Analyzer (RPA analysis) of the NR/CR/CIIR blend were also investigated. The dispersion of HNTs in the NR/CR/CIIR blend was enhanced by the adsorption of PDA on the HNTs surface by non-covalent bonds, and the comprehensive properties of the composites were improved.

Electro-deposited halloysite nanotube/polyaniline nanocomposites for energy storage applications

A nanocomposite (nanoclay/conductive polymer) was prepared by a template-free method for supercapacitor applications. Halloysite Nanotubes (HNTs) were used as a nanoclay material, and synthesized polyaniline (PANI) by ammonium persulfate-initiated polymerization was used as a conductive polymer. The HNTs/PANI nanocomposite was deposited on an indium tin oxide (ITO) coated glass to obtain a working electrode by an electrochemical deposition method. Morphological and structural examination of the HNTs/PANI nanocomposite proved that the PANI nanoparticles were attached to the HNTs surface. The structural analysis demonstrated that the PANI and HNTs crystal size significantly decreased in the HNTs/PANI as a result of the composition of PANI molecules with HNTs structure. The main characteristic bonds and functional groups of HNT, PANI, and HNTs/PANI nanocomposites were determined by FT-IR analysis. Using cyclic voltammetry (CV), the electrochemical performance of the HNTs//PANI nanocomposite electrode was investigated. The specific capacitance values were reported via the CV curves as 264, 230.22, 175.2, and 154.8 F/g at scan rates of 50, 100, 200, and 300 mV/s respectively. The results showed that the specific capacitance at the slow scan rates revealed higher maximum specific capacitance values.

Preparation of zinc oxide/halloysite compound and their reinforcement for styrene butadiene rubber composite

This study investigated the surface treatment of halloysite nanotubes (HNTs) with zinc oxide (ZnO) and used to enhance the mechanical properties of butyl rubber (SBR) composites. The prepared ZnO-modified HNTs (ZnO/HNTs) was characterized by X-ray diffraction (XRD), Fourier infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results indicated that ZnO particles were successfully loaded on the surface of HNTs and interacted with hydroxyl groups. The outer surface of HNTs became rough due to the loading of ZnO. The effects of ZnO/HNTs on the processing and mechanical properties of filled SBR composites were evaluated. The results showed that the ZnO/HNTs particles displayed a fine dispersion in the matrix system and have a strong interaction compatibility with rubber matrix chains. The tensile strength reached at the maximum of 9.35 MPa at a filler content of 60 phr, which was 405% and 31.69% higher than those of pure SBR and the HNTs/SBR composites, respectively. The enhancement of the mechanical properties of filled SBR composites is attributed to the fine dispersion of the ZnO/HNTs particles in the SBR matrix and the improved incorporation between the rubber molecules and the filler particles due to the loading of ZnO on the surface of HNTs, which restricts the movement of the rubber chains by entrapping molecules when the composites is subjected to stress loading.