Halloysite Nanotubes Content Research Articles

Characterization of polylactic acid/halloysite nanotubes bionanocomposite films for food packaging

Abstract The application of biopolymers as food packaging materials is limited because they exhibit low mechanical, thermal, and barrier properties. However, this limitation can be countered by adding nano-sized fillers to the biopolymers to prepare bionanocomposites. In this work, polylactic acid (PLA)/halloysite nanotubes (HNTs) bionanocomposite films were prepared by the casting method using different concentrations (0, 1.5, 3.0, 4.5, and 6.0 wt.%) of HNTs. The effects of HNTs concentrations on the dispersion, chemical bonding, and the average molecular weights of the PLA/HNTs bionanocomposite films for improvements of their mechanical, thermal, and barrier properties were investigated. The optimum concentration of HNTs that resulted in the optimum properties of the films was found to be 3.0 wt.%. The PLA/HNTs bionanocomposite films were demonstrated to have the potential to extend the shelf life of packaged cherry tomatoes. The results of this study opened a window for improving the mechanical, thermal, and barrier properties of biopolymers for potential food packaging applications.

Soy protein and halloysite nanotubes-assisted preparation of environmentally friendly intumescent flame retardant for poly(butylene succinate)

Ammonium polyphosphate (APP) and soy protein (SP) were used to form biodegradable intumescent flame retardants (BIFR) and further combined with halloysite nanotubes (HNTs) to prepare environmentally friendly intumescent flame retardants (EIFR) to enhance the flame retardancy of poly(butylene succinate) (PBS). Thermogravimetric analysis (TGA), cone calorimeter test and the observation of char residue showed that SP acted as both char source and gas source in BIFR. BIFR with APP/SP (2/1) had the best char-forming capability for PBS, significantly increasing the limiting oxygen index (LOI), reducing peak heat release rate (PHRR) and total heat release (THR), but increasing the total smoke release (TSR). HNTs had a synergistic effect with BIFR to improve the flame retardancy of PBS when at an appropriate content. Addition of 1.0 wt% HNTs increased the LOI, and reduced the PHRR and THR, especially the TSR. However, the synergistic effect became week or diminished when the content of HNTs increased to 1.5 wt% and 3.0 wt%. The possible flame retardant mechanism of EIFR for PBS was proposed. Mechanical test showed that HNTs improved the tensile strength and impact strength of PBS/EIFR composites. The result of soil burial test indicated that BIFR accelerated the biodegradation of PBS. This work may offer a strategy for providing environmentally friendly flame retardants for biodegradable polymers such as PBS, and also addressing the environmental harmfulness of traditional intumescent flame retardants.

The Effect of Halloysite Addition on the Material Properties of Chitosan-Halloysite Hydrogel Composites.

Chitosan-based hydrogels are being widely used in biomedical applications due to their eco-friendly, biodegradable, and biocompatible properties, and their ability to mimic the extracellular matrix of many tissues. However, the application of chitosan hydrogels has been limited due to their inherent mechanical weakness. Halloysite nanotubes (HNTs) are naturally occurring aluminosilicate clay minerals and are widely used as a bulk filler to improve the performance characteristics of many polymeric materials. HNTs have also been shown to be a viable nanocontainer able to provide the sustained release of antibiotics, chemicals, and growth factors. This study’s objective was to develop a stable drug delivery chitosan/HNT nanocomposite hydrogel that is biocompatible, biodegradable, and provides sustained drug release. In this study, chitosan/HNTs hydrogels containing undoped or gentamicin-doped HNTs were combined in different wt./wt. ratios and cross-linked with tripolyphosphate. The effects of chitosan and HNTs concentration and combination ratios on the hydrogel surface morphology, degradability, and mechanical properties, as well as its drug release capability, were analyzed. The results clearly showed that the addition of HNTs improved chitosan mechanical properties, but only within a narrow range. The nanocomposite hydrogels provided a sustained pattern of drug release and inhibited bacterial growth, and the live/dead assay showed excellent cytocompatibility.

Manufacturing and Characterization of Functionalized Aliphatic Polyester from Poly(lactic acid) with Halloysite Nanotubes.

This work reports the potential of poly(lactic acid)—PLA composites with different halloysite nanotube (HNTs) loading (3, 6 and 9 wt%) for further uses in advanced applications as HNTs could be used as carriers for active compounds for medicine, packaging and other sectors. This work focuses on the effect of HNTs on mechanical, thermal, thermomechanical and degradation of PLA composites with HNTs. These composites can be manufactured by conventional extrusion-compounding followed by injection molding. The obtained results indicate a slight decrease in tensile and flexural strength as well as in elongation at break, both properties related to material cohesion. On the contrary, the stiffness increases with the HNTs content. The tensile strength and modulus change from 64.6 MPa/2.1 GPa (neat PLA) to 57.7/2.3 GPa MPa for the composite with 9 wt% HNTs. The elongation at break decreases from 6.1% (neat PLA) down to a half for composites with 9 wt% HNTs. Regarding flexural properties, the flexural strength and modulus change from 116.1 MPa and 3.6 GPa respectively for neat PLA to values of 107.6 MPa and 3.9 GPa for the composite with 9 wt% HNTs. HNTs do not affect the glass transition temperature with invariable values of about 64 °C, or the melt peak temperature, while they move the cold crystallization process towards lower values, from 112.4 °C for neat PLA down to 105.4 °C for the composite containing 9 wt% HNTs. The water uptake has been assessed to study the influence of HNTs on the water saturation. HNTs contribute to increased hydrophilicity with a change in the asymptotic water uptake from 0.95% (neat PLA) up to 1.67% (PLA with 9 wt % HNTs) and the effect of HNTs on disintegration in controlled compost soil has been carried out to see the influence of HNTs on this process, which is a slight delay on it. These PLA-HNT composites show good balanced properties and could represent an interesting solution to develop active materials.

Water and gas barrier properties of polyvinyl alcohol (PVA)/starch (ST)/ glycerol (GL)/halloysite nanotube (HNT) bionanocomposite films: Experimental characterisation and modelling approach

In this study, ecofriendly polyvinyl alcohol (PVA)/starch (ST)/glycerol (GL)/halloysite nanotube (HNT) bionanocomposite at HNT contents of 0.25, 0.5, 1, 3 and 5 wt% were prepared in a solution casting process. Barrier properties against water vapour and gases of such bionanocomposite films were detected to consistently improve with increasing the HNT content when compared with those of PVA/ST/GL blends owing to tortuous paths generated at different HNT dispersion levels. Water vapour permeabilities of such blends and corresponding bionanocomposites increased in a linear manner when the temperature and relative humidity gradient increased from 25 to 55 °C and 10%-70%, respectively. Nonetheless, such permeabilities of bionanocomposites appeared to be less dependent of temperature and relative humidity gradient with increasing the HNT content. An accurate measurement of HNT aspect ratios with the aid of atomic force microscopy (AFM) yielded better agreement between experimental data and Nielsen model with respect to relative permeability of bionanocomposites. Overall, our fabricated bionanocomposites demonstrated good water and gas barrier properties to prolong the shelf life of avocados and peaches with great potential of being used as effective food packaging materials.

Polyethylene-Matrix Composites with Halloysite Nanotubes with Enhanced Physical/Thermal Properties.

The aim of the present work is to investigate the effect of halloysite nanotubes (HNT) on the mechanical properties of low-density polyethylene composites modified by maleic anhydride-grafted PE (PE-graft-MA). Polyethylene nanocomposites were prepared using an injection molding machine, Arburg Allrounder 320 C 500–170; the HNT content was varied at 0 wt %, 2 wt %, 4 wt % and 6 wt %, and the PE-graft-MA content was varied at 5 wt %. The composites were examined for their ultimate tensile stress, strain at ultimate stress, hardness, impact strength, melt flow rate, heat deflection temperature, Vicat softening temperature, crystallinity degree and phase transition temperature. It was found that the addition of halloysite nanotubes to low-density polyethylene (LDPE) led to an increased heat deflection temperature (HDT, up to 47 °C) and ultimate tensile strength (up to 16.00 MPa) while the Vicat softening temperature, strain at ultimate stress, impact strength and hardness of examined specimens slightly decreased. Processing properties of the materials specified by the melt flow rate (MFR) deteriorated almost twice. The results have demonstrated that the nanoparticles can reinforce enhance LDPE at low filler content without any considerable loss of its ductility, but only when halloysite nanotubes are superbly distributed in the polyethylene matrix.

Biodegradable and Water Resistant Poly(vinyl) Alcohol (PVA)/Starch (ST)/Glycerol (GL)/Halloysite Nanotube (HNT) Nanocomposite Films for Sustainable Food Packaging

As a novel biodegradable material, poly (vinyl) alcohol (PVA)/starch (ST)/ glycerol (GL)/ halloysite nanotube (HNT) nanocomposite films were prepared by solution casting at the HNT contents of 0.25, 0.5, 1, 3 and 5 wt%. Water absorption capacity and water solubility of nanocomposite films were decreased remarkably by 44.24 and 48.05%, respectively, with increasing the HNT content from 0 to 5 wt% when compared with those of biopolymer matrices. Moreover, the water contact angle of nanocomposite films increased by 21.36o with the incorporation of HNTs. The presence of HNTs appeared to reduce the overall migration rates for PVA/ST/GL/HNT nanocomposite films when interacting with either hydrophilic or lipophilic food simulants. However, the migration rates of HNTs alone were enhanced with increasing the HNT contents in hydrophilic, lipophilic and acidic food simulants. On the other hand, the biodegradation rate and light transmittance of nanocomposite films were reduced linearly by 18.56 and 26.90% with increasing the HNT content from 0 to 5 wt%. Overall, novel PVA/ST/GL/HNT nanocomposite films in this study offer highly competitive material with excellent water resistance, good biodegradability and acceptable transparency to be potentially used for sustainable food packaging particularly targeting lipophilic and acidic foodstuffs.

Investigations on the Properties and Performance of Mixed-Matrix Polyethersulfone Membranes Modified with Halloysite Nanotubes.

Ultrafiltration (UF) polyethersulfone (PES) membranes were prepared by wet phase inversion method. Commercial halloysite nanotubes (HNTs) in the amount of 0.5–4 wt % vs PES (15 wt %) were introduced into the casting solution containing the polymer and N,N-dimethylformamide as a solvent. The morphology, physicochemical properties and performance of the membranes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), zeta potential, porosity and contact angle analyses, as well as permeability measurements. Moreover, the antifouling properties of the membranes were evaluated during UF of a model solution of bovine serum albumin (BSA). The research revealed a positive influence of modification with HNTs on hydrophilicity, water permeability and antifouling properties of the PES membranes. The most significant improvement of permeability was obtained in case of the membrane containing 2 wt % of HNTs, whereas the highest fouling resistance was observed for 0.5 wt % HNTs content. It was found that a good dispersion of HNTs can be obtained only at loadings below 2 wt %. Based on the results a relation between severity of membrane fouling and surface roughness was proved. Moreover, an increase of the roughness of the modified membranes was found to be accompanied by an increase of isoelectric point values.

Mechanical and Thermal Properties of Ternary System Based on Starch-Grafted-Polyethylene/High Density Polyethylene/Halloysite Nanocomposites

In this paper, the effect of unmodified halloysite nanotubes (HNTs) content on the chemical structure and the thermal and mechanical properties of blends based on starch-grafted-polyethylene (SgP) and high density polyethylene (HDPE) (70/30 w/w) nanocomposites was investigated at various filler content ratios, i.e. 1.5, 3 and 5 wt.%. The study showed the occurrence of chemical interactions between the polymer matrix and HNTs through OH bonding. Further, the addition of HNTs to the polymer blend led to an increase in the crystallization temperature of the nanocomposite samples, in particular at higher filler contents i.e. 3 and 5 wt.%, while the melting temperature remained almost unchanged. Tensile and flexural properties of the nanocomposite samples were however improved compared to the virgin blend with respect to the HNTs content ratio.

Influence of heat treatment on the structure and properties of polyamide 6/ halloysite nanocomposites

Abstract The nanocomposites of polyamide 6 (PA6) with halloysite nanotubes (HNT) were prepared by extrusion using co-rotating twin-screw extruder and then the standard test specimens were injected using a screw injection moulding machine. The content of HNT in the nanocomposites was 5 or 10 weight percent. The heat treatment of unmodified PA6 and nanocomposites was carried out in silicone oil in temp. 150±2°C. The samples were annealed for 3 hours and then cooled at a rate of 4 K/min. Differential scanning calorimetry (DSC) causes annealing to increase the crystallinity of the polyamide matrix. After an annealing treatment a nanocomposite with better mechanical properties was obtained. Halloysite nanotubes in polyamide matrix play the role of a nucleating agent.

Thermal properties of carboxymethyl cellulose (CMC) filled halloysite nanotube (HNT) bio-nanocomposite films

Abstract This paper covered the effect of halloysite nanotube (HNT) content on thermal properties and moisture content of carboxymethyl cellulose (CMC)/halloysite nanotube (HNT) bio-nanocomposite films. The CMC/HNT bio-nanocomposite films were prepared by solvent casting method. The thermogravimetric analysis (TGA) shows that the addition of HNT nanofiller enhanced the thermal stability of CMC/HNT bio-nanocomposites. The results showed the thermal degradation temperature (Td1 and Td2) and residue remaining (char yields) at 800°C increased with increasing HNT filler. This indicated the effective dispersion of HNT nanofiller in CMC matrix in bio-nanocomposites. Meanwhile, the moisture content of CMC/HNT bio-nanocomposite films decreased with increasing HNT content.

Toughening an epoxy network by the addition of an acrylic triblock copolymer and halloysite nanotubes

Abstract A hybrid epoxy composite was synthesized by adding halloysite nanotubes (HNTs) to an epoxy matrix toughened by an acrylic triblock copolymer (MAM). The morphology generated was composed of spherical MAM domains with sizes in the range of hundreds of nanometers and micron-size clusters of HNTs. The addition of HNTs produced an additional toughening effect with respect to the one generated by MAM. The critical stress intensity factor attained a maximum and then decreased due to the presence of defects generated when increasing the concentration of HNTs. An unexpected result was the decrease of the glass transition temperature produced when increasing the concentration of HNTs. This was ascribed to the different partition of starting monomers inside the cavities of nanotubes, generating a stoichiometric imbalance in the formulation.

Effect of halloysite nanotubes on shape stabilities of polyethylene glycol-based composite phase change materials

A series of shape-stabilized phase change materials (PCMs), composed of polyethylene glycol (PEG) and halloysite nanotube (HNT) (PEG/HNT), were prepared using a melt-extrusion technique. Chemical and morphological structures, shape-stabilities, thermal properties, and thermal stabilities of the PEG/HNT composites were investigated. The composite properties were strongly dependent on the weight ratio of HNT to PEG. Transmission electron microscopy and Brunauer–Emmett–Teller analyses showed that PEG was perfectly adsorbed into the HNT pores and covered the surfaces of HNT, which helped prevent leakage of melted PEG during a phase change from solid to liquid. Among the various PEG/HNT composites, the PEG/HNT composites with HNT contents in the range 30–50% exhibited good shape-stabilities. Moreover, the rate of heat transfer increased with the HNT content. Based on these results, we expect that the PEG/HNT composites can be used in food packaging materials to counteract the negative effects such as migration induced by unwanted temperature changes.

Curing epoxy resin with anhydride in the presence of halloysite nanotubes: the contradictory effects of filler concentration

Epoxy resins can be cured with a wide variety of curing agents such as amines and anhydrides, but anhydride curing would be more favorable for research purpose because of epoxy-anhydride curing taking place slowly at room temperature. Incorporation of natural nanosized minerals into epoxy is of environmental importance. Halloysite nanotubes (HNTs) display chemical properties similar to those of silica and alumina, and hydroxyl groups positioned somewhere in between or at the edge of HNTs layers give them potential to participate in epoxy ring-opening. Curing epoxy/anhydride systems containing HNTs at various concentrations (0.5, 1 and 2 wt.% based on 100 parts by weight of epoxy) via nonisothermal differential scanning calorimetry at three heating rates (5, 10 and 15 °C.min−1) is discussed here to study the effect of HNTs concentration on epoxy-anhydride curing reactions. The extent of crosslinking reaction was promoted at 0.5 and 1 wt.% of HNTs as a result of participation of hydroxyl groups of HNTs in epoxide ring-opening, while at 2 wt.% of HNTs a hindered curing was the case, which has been speculated on account of probable deactivation of anhydride curing agent by the internal surface of HNTs pursued by anhydride molecules diffusion into the lumen of HNTs.

Fabrication and Characterization of Electrospun Polysulfone (PSf) / Halloysite (HAL) Nanocomposite Membrane

Polysulfone (PSf) is one of the commonly used polymeric membrane materials due to its excellent properties. One of the major concern however is that PSf membranes are mostly hydrophobic in nature. The presence of fillers like halloysite nanotubes (HNTs) into the polymer matrix can decrease this hydrophobicity and may also alter some of its important properties. This study focused on the fabrication of nanofibrous membranes by electrospinning method and characterization using SEM, UTM and contact angle goniometer to determine the effect of HNT concentration to the membrane’s surface morphology, mechanical properties and wettability. Results showed that samples subjected at the highest voltage produced finer fibers. The initial addition of HNTs also creates fiber strands with smaller diameters until beading in the fibers due to perturbation of the polymer jet caused by the increased viscosity of the solution and particle agglomeration was observed at higher concentrations. In terms of response to mechanical load, the tensile strength was higher upon HNT integration showing an effective transfer of stress to the dispersed phase despite the morphological imperfections. The contact angle results showed a decrease in hydrophobicity at the highest HNT concentration reflecting the water-loving character of the filler. The overall data gathered showed that the addition of nanoclay improved the properties of PSf matrix making them a suitable material for different filtration applications particularly in water treatment systems.

Performance of halloysite nanotube/poly(styrene-co-methylmethacrylate) nanocomposite coatings for the protection of soda-lime glass

Polymer-based coatings for the protection of glass surfaces are used considerably in the construction and automotive industries. This research article focuses on the potential use of halloysite nanotubes (HNT)/Poly(Styrene-co-Methylmethacrylate) (PS-co-PMMA) nanocomposites as coatings for the protection of soda-lime glass. The effect of HNT content and coating thickness on the spectral properties of the glass, morphology, surface-wettability, and thermo-mechanical properties of the nanocomposite coatings were investigated and reported. The inherent spectral behavior of glass was not altered significantly by the coatings when the content of HNTs in coatings was ≤ 5 wt %. The coated glasses also exhibited a slight increase in the solar skin protection factor (SSPF), but notable improvement in the solar material protection factor (SMPF) when the HNT content was high in coatings. Thermogravimetric analysis (TGA) revealed that the HNT/PS-co-PMMA nanocomposite coatings possess excellent thermal stability compared to the neat copolymer. The surface wettability of coated glasses by water droplets decreased substantially due to coatings as evident from contact angle measurements. The HNT/PS-co-PMMA nanocomposites also displayed enhanced tensile strength and scratch resistance with increasing HNT content of coatings up to 5 wt%. Overall, the performance of the coated glass was enhanced by the coatings.

High performance liquid crystalline bionanocomposite ionogels prepared by in situ crosslinking of cellulose/halloysite nanotubes/ionic liquid dispersions and its application in supercapacitors

A high performance halloysite nanotubes (HNTs)-doped liquid crystalline bionanocomposite ionogels has been synthesized by in situ crosslinking of cellulose/ionic liquid solutions using bisphenol A epoxy resin via ring opening reactions with cerium ammonium nitrate, and HNTs as the ionic conducting promoter. These ionogels with HNTs demonstrate significantly improved ionic conductivity compared with that of pure ionogel without the addition of HNTs, due to the liquid crystal phases induced by the assembly of anisotropic HNTs nanoparticles generated ionic channels for ion transport. The ionic conductivity of the ionogels increases with increasing HNTs concentration, and shearing can improve the room temperature ionic conductivities, which are on the order of 1 mS/cm. The mechanical properties and thermal stability of the nanocomposite ionogels were significantly improved compared with those of the pure ionogel without HNTs. The ionogel was tested as a flexible gel electrolyte for supercapacitor device and the measured specific capacitance was maintained for up to 5000 charge-discharge cycles. Such novel liquid crystalline bionanocomposite ionogels with high ionic conductivity, high mechanical strength, and flexibility are desirable for use in flexible electrochemical devices.

Removal of methylene blue from aqueous solution by electrophoretically deposited titania‐halloysite nanotubes coatings

AbstractTwo‐component suspensions of titania and halloysite nanotubes (HNTs) were prepared in ethanol with 0.5 g/L (optimum concentration) of polyethyleneimine (PEI) and different wt% of HNTs. Kinetics of Electrophoretic deposition (EPD) decreased with increasing the HNTs content in suspensions due to their less mobility compared with titania particles. HNTs reinforced the microstructure of coatings and reduced or completely prevented from cracking during drying and heat‐treatment steps. Removal of methylene blue (MB) via adsorption by HNTs coatings was faster than its photocatalytic degradation by titania coating. Dispersion of HNTs (up to ≈30 wt%) in the matrix of titania resulted in the synergistic catalytic effect in MB removal. The synergistic effect was because of the shorter traveling distance of MB molecules adsorbed on HNTs toward the photocatalytic active site of titania particles in composite coatings. However, the synergistic effect was destroyed with increasing the HNTs content in coating. Difference between the amount of MB removed by titania and composite coatings increased at longer times (≥60 minutes). Mass transfer of MB adsorbed on HNTs toward the photocatalytic active sites of adjacent titania particles can compensate the decline in the mass transfer from solution at longer times.

Effect of halloysite nanotube structure on physical, chemical, structural and biological properties of elastic polycaprolactone/gelatin nanofibers for wound healing applications

Nanofibrous elastic material based on the blend of hydrophobic poly(ε-caprolactone) (PCL) and hydrophilic gelatin (Gel) reinforced with halloysite nanotubes (HNTs) was prepared by electrospinning process by respecting principles of “green chemistry” required for tissue engineering and drug delivery carriers. Three different kinds of HNTs with similar aspect ratio, but different length and inner diameter were examined to explain the effect of HNT concentration and geometry on a structure, morphology, chemical composition, mechanical properties and biocompatibility of nanostructured materials. Reinforcing effect of each type of HNTs has been confirmed up to 6 wt%. However, the highest improvement of mechanical properties was exhibited by addition just 0.5 wt% of HNTs. All HNT modified nanofibers have been confirmed as non-cytotoxic based on the interaction with mouse fibroblasts NIH-3T3 cells and therefore suitable for biomedical applications, e.g. as wound healing coverings with controlled drug delivery.

Thermal Stability and Surface Wettability Studies of Polylactic Acid/Halloysite Nanotube Nanocomposite Scaffold for Tissue Engineering Studies

This paper reports the preliminary study about the incorporation of halloysite nanotubes (HNT) into polylactic acid (PLA) scaffold to improve the thermal resistance and surface wettability properties. The fabrication of the porous scaffold requires a simple yet effective technique with low-cost materials within freeze extraction method. The thermal stability of PLA/HNT scaffold compared to neat PLA scaffold achieved with increased content of HNT by 5 wt%. Moreover, the surface wettability of the scaffold also shows a positive impact with high content of HNT by 5 wt%. This new nanocomposite scaffold may have high potential as a suitable template for tissue regeneration.