Addition Of Halloysite Nanotubes Research Articles

Insight into halloysite nanotubes-loaded gellan gum hydrogels for soft tissue engineering applications

A tri-component hydrogel, based on gellan gum (GG), glycerol (Gly) and halloysite nanotubes (HNT), is proposed in this work for soft tissue engineering applications. The FDA-approved GG polysaccharide has been recently exploited as biomaterial because its biomimetic features. Gly is added as molecular spacer to improve hydrogel viscosity and mechanical properties. HNT incorporation within the hydrogel offers the versatility to improve the GG-Gly biocompatibility with potential incorporation of target biomolecules. In this work, hydrogels with different composition ratios are physically crosslinked for tuning physico-mechanical properties. An accurate physico-chemical characterization is reported. HNT addition leads to a water uptake decrease of 30–35% and tuneable mechanical properties with a compressive Young’s modulus ranging between 20 and 75kPa. Finally, in vitro study with human fibroblasts on GG-Gly hydrogels loaded with 25% HNT offered the higher metabolic activities and cell survival up to 7days of incubation.

Effects of halloysite nanotubes on physical properties and cytocompatibility of alginate composite hydrogels

Sodium alginate (SA)/halloysite nanotubes (HNTs) composite hydrogels were successfully prepared by solution blending and cross-linking with calcium ions. HNTs can improve the physical properties and cytocompatibility of composite hydrogels. The static and shear viscosity of SA/HNTs solution increase by the addition of HNTs. FTIR suggests the presence of hydrogen bond interactions between HNTs and SA. The crystal structure of HNTs is retained in the composites as showed by the X-ray diffraction result. A porous structure with pore size of 100–250μm is found in the hydrogels, which can provide a space for cell growth and migration. The compressive mechanical properties of composite hydrogels significantly increase compared to the pure SA hydrogel. The SA/HNTs composite hydrogels with 80% HNTs loading exhibit the compressive stress at 80% strain of 2.99MPa, while the stress at 80% strain of pure SA hydrogel is only 0.8MPa. The dynamic storage modulus of composite hydrogels also markedly increases with HNTs concentration. The differential scanning calorimetry endothermic peak area and swelling ratios in NaCl solution of the composite hydrogels decrease by the addition of HNTs. Preosteoblast (MC3T3-E1) culture results reveal that the SA/HNTs composites especially at relatively low HNTs loading show a significant increase in cells adhesion and proliferation compared to the pure SA hydrogel. All the results demonstrate that the SA/HNTs composite hydrogels show a promising application in bone tissue engineering.

Structure–property relationship of halloysite nanotubes/ethylene–vinyl acetate–carbon monoxide terpolymer nanocomposites

Poly(ethylene- co-vinyl acetate- co-carbon monoxide) (EVACO)/halloysite nanotube (HNT) nanocomposite films were solution cast. Dispersion of HNTs in the matrix was analyzed by elemental mapping and the role of HNTs on crystallizability, flammability and thermal, mechanical, and electrical properties of the polymer was evaluated. The nature of interaction between the EVACO matrix and HNTs was studied using Fourier transform infrared spectroscopy. The highest tensile strength was observed for the composite with 1% filler loading, whereas the highest crystallinity was observed for that with 3% filler loading. The decay in the tensile properties at higher filler loading was due to agglomeration of HNTs and debonding of polymer–filler interface. The electrical volume resistivity of the composites decreased with HNT loading because of the ionic charge transfer. The direct current electrical resistivity study of the composites proves that the addition of HNT can improve the antistatic properties of the polymer.

Effect of HNT on the Microstructure, Thermal and Mechanical Properties of Al/FACS-HNT Composites Produced by GPI

To develop an optimised manufacturing method of fly ash-reinforced metal matrix composites, the preliminary tests were performed on the cenospheres selected from fly ash (FACS) with halloysite nanotubes (HNTs) addition. The preform made out of FACS with and without the addition of HNT (with 5 and 10 wt.%) has been infiltrated by the pure aluminium (Al) via adapted gas pressure infiltration process. This paper reveals the influence of HNT addition on the microstructure (analysis was done by computed tomography and scanning electron microscopy combined with energy-dispersive x-ray spectroscopy), thermal properties (thermal expansion coefficient, thermal conductivity and specific heat) and the mechanical properties (hardness and compression test) of manufactured composites. The analysis of structure-property relationships for Al/FACS-HNT composites produced shows that the addition of 5 wt.% of HNT to FACS preform contributes to receiving of the best mechanical and structural properties of investigated composites.

Preparation and property of ultrahigh molecular weight polyethylene/halloysite nanotube fiber

In this research, halloysite nanotubes (HNTs) were incorporated into ultra-high molecular weight polyethylene (UHMWPE) in order to prepare the nanocomposite fibers by a gel-spun and hot drawing process. The HNTs were treated with oleic acid to improve the dispersion in the UHMWPE fibers. Both the crystallinity tested by differential scanning calorimetry (DSC) and mechanical properties increased with a low loading of HNTs, and decreased with a high loading. The thermal gravimetric analysis (TGA) test showed the thermal stability to improve with the incorporation of HNT. The addition of HNT did not change the crystal type, according to the X-ray diffraction (XRD) study.

Fabrication and characterization of biodegradable poly(butylene succinate-co-adipate) nanocomposites with halloysite nanotube and organo-montmorillonite as nanofillers

Biodegradable poly(butylene succinate-co-adipate) (PBSA)-based nanocomposites were successfully prepared. A commercial halloysite nanotube (HNT) and an organo-montmorillonite (denoted as 15A) served as reinforcing fillers. Scanning electron microscopy and transmission electron microscopy results confirmed the nano-scale dispersion of HNT and 15A in the composites. Differential scanning calorimetry results showed that 15A served as nucleating agent for PBSA crystallization, but HNT hardly affected the nucleation of PBSA. Both nanofillers assisted the isothermal crystallization of PBSA, with 15A demonstrating superior efficiency. Melting behavior study suggests that the presence of HNT or 15A hampered the melting-recrystallization process of the originally less stable crystals during heating scans. Thermogravimetric analyses revealed that 15A enhanced the thermal stability of PBSA in air environment, but HNT caused a decline at high loadings. The rigidity of PBSA, including Young’s/flexural moduli, evidently increased after the addition of HNT or 15A, with 15A showing higher enhancing efficiency than HNT at similar loadings. The flexural modulus increased up to 94% with 20 wt% in HNT and up to 48% with 5 wt% 15A loading. The rheological property measurements confirmed the achievement of pseudo-network structure at 5 wt% 15A loading, whereas the HNT-included system did not develop a network structure.

Anti‐Infective and Histogenic Bioscaffold for Bone Defect Repair

The objective of this study was to develop a stable drug delivery platform that is biocompatible, biodegradable and would provide sustained combinatorial drug release for the control of bone infection while simultaneously supporting bone tissue regeneration. Chitosan has been widely used in tissue engineering and in a variety of biomedical applications due to its eco‐friendly and biodegradable properties and it possesses a physiochemistry similar to the extracellular matrix of bone. However, the application of chitosan has been limited by its inherent mechanical weakness. Halloysite nanotubes (HNTs) are a naturally‐occurring aluminosilicate clay with a hollow tubular structure. HNTs are widely used as a bulk filler to materially reinforce a variety of polymer materials from bone cement to rubber. They have also been shown to be a potent nanocontainer for the sustained release of varied bioactive factors. In this study, chitosan and HNTs and chitosan and HNTs, doped with gentamicin and BMP‐2, were combined in different wt./wt. ratios and cross‐linked with tripolyphosphate. The biodegradability, mechanical properties, and surface structure of the hybrid nanocomposites were tested. The ability of the nanocomposites to control bacterial growth while supporting bone tissue formation was also evaluated. Gentamicin was selected as a model drug to evaluate the drug release capability of the chitosan‐HNTs nanocomposites and with release, its effectiveness against E. coli was analyzed through growth inhibition studies. Results indicate that the addition of HNTs to the chitosan hydrogel significantly improved the gels’ mechanical properties, permitting an extended period of drug release, and without a negative affect on drug efficacy. The coatings were capable of inhibiting bacterial growth and osteoblasts cultured on the hydrogel surfaces showed enhanced growth and functionality. Our doped clay/chitosan nanocomposite may overcome the limitations of traditional anti‐bacterial hydrogels and its ability to support bone tissue formation may enable its use in bone defect repair results from osteomyelitis.Support or Funding InformationFunding for this project was provided by the Louisiana Governor's Biotechnology Initiative and Louisiana Board of Regents OPT‐IN program.

Impact, Thermal, and Morphological Properties of Poly(Lactic Acid)/Poly(Methyl Methacrylate)/Halloysite Nanotube Nanocomposites

ABSTRACTPoly(lactic acid)/poly(methyl methacrylate) blends containing halloysite nanotube (2 and 5 phr) and epoxidized natural rubber (5–15 phr) were prepared by melt mixing. The impact strength of poly(lactic acid)/poly(methyl methacrylate) blend was slightly improved by the addition of halloysite nanotube. Adding epoxidized natural rubber further increased the impact strength of poly(lactic acid)/poly(methyl methacrylate)/halloysite nanotube nanocomposite. Single Tg of poly(lactic acid)/poly(methyl methacrylate) is observed and this indicates that poly(lactic acid)/poly(methyl methacrylate) blend is miscible. The addition of halloysite nanotube into poly(lactic acid)/poly(methyl methacrylate) slightly increased the Tg of the blends. The epoxidized natural rubber could encapsulate some of the halloysite nanotube and prevent the halloysite nanotube from breaking into shorter length tube during the melt shearing process.

Electrospun poly(vinyl alcohol) composite nanofibers with halloysite nanotubes for the sustained release of sodiumd‐pantothenate

ABSTRACTPoly(vinyl alcohol) (PVA) nanofibers containing halloysite nanotubes (HNTs) loaded with sodiumd‐pantothenate (SDP) were successfully fabricated via simple blend‐electrospinning. SDP was efficiently loaded into the innate HNT lumen with an SDP/HNT mass ratio of 1.5:1 via vacuum treatment. The SDP‐loaded HNT‐inclusion complex was evaluated with drug‐loading efficiency testing, Fourier transform infrared (FTIR) spectroscopy, and X‐ray diffraction. The morphologies of the nanofibers were observed by scanning electron microscopy, which revealed uniform and smooth surfaces of the nanofibers. The addition of HNTs to the composite nanofibers increased the viscosity of the polymer solution, and this suggested shorter fiber diameters. FTIR spectroscopy verified the good compatibility of the SDP and HNTs with PVA. Moreover, the swelling properties were found to quantitatively correlate with weight loss.In vitrodrug‐release testing revealed that the HNTs and crosslinking reaction most dramatically affected the sustained release of SDP from the PVA and SDP‐loaded HNT complex. In the drug‐release kinetics model, SDP release depended on the diffusion caused by the deformation of the polymer‐based structures in the medium; it followed Fickian diffusion with acceptable coefficient of determination (r2) values between 0.88 and 0.94. Most importantly, the HNTs as natural biocontainers effectively modulated the release profile by loading the active compound in harmony with the electrospun nanofibers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 42900.

Preparation and Characterization of Halloysite Nanocomposites by Rapid Prototyping Technology

Rapid prototyping (RP) is a new technology to fabricate a prototype part layer-by-layer. This technique has been achieved in many industrial sectors, but parts fabricated using this technique exhibit low mechanical properties, this makes it difficult to apply to fast growing applications. This technology can not only effectively save production time and cost of the prototypes, but also produce complicated product. In this study, we investigate the effect of the addition of halloysite nanotubes on mechanical properties of nanocomposites made by the RP process. Test specimens were fabricated using tetrafunctional polyester acrylate (TPA) and 1, 6 hexanediol diacrylate (HDDA) photopolymer as a matrix material and halloysite nanotubes as a reinforcing material. The adhesion between TPA/HDDA and halloysite nanotubes has been improved by using surface modification of a silane coupling agent. When compared with neat photopolymer, the tensile strength of nanocomposites decreased by about 22%, because the halloysites had poor interfacial adhesion. Silane treatment of halloysites using 3-aminopropyl triethoxysilane was succeeded to improve tensile strength of nanocomposites (2 phr halloysite nanotubes) by 31%.

Halloysite nanotube reinforced polylactic acid composite

Polylactic acid (PLA) has a long history in medical applications. Reinforced PLA has the potential to be used in the medical applications that require high mechanical strength such as coronary stents and bone fixation devices. Halloysite nanotube (HNT) has received considerable attention recently due to its tubular structure, high aspect ratio, high mechanical strength, thermal stability, biocompatibility and sustained drug releasing properties. Halloysite has been investigated in compounding with many polymers. However, the research in compounding halloysite with biodegradable materials for use in biological applications is sparse. In this study various weight fractions of HNT was compounded with the biodegradable polymer PLA using a melt compounding method. Tensile test, Fourier infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), contact angle test, scanning electron microscopy (SEM), void content and thermogravimetric analysis (TGA) were carried out to study the PLA/HNT composite. Tensile test results indicated that Young's modulus and stiffness of PLA were enhanced with the addition of HNT; FTIR spectra showed the interaction between the PLA and HNT; whereas contact angle measurements indicated that the wettability of the PLA/HNT composite was not affected by the addition of HNT. However, the thermal stability of PLA was adversely effected by the addition of HNT which may be related to the presence of voids between the polymer and matrix. Nevertheless, the reinforced PLA/HNT composite, which maintains the surface characteristics, may prove beneficial for use in biological applications. POLYM. COMPOS., 38:2166–2173, 2017. © 2015 Society of Plastics Engineers

Preparation of biodegradable poly(butylene succinate)/halloysite nanotube nanocomposite foams using supercritical CO2 as blowing agent

Biodegradable poly(butylene succinate) (PBS) was melt compounded with halloysite nanotube (HNT) to prepare PBS/HNT nanocomposites, and both pure PBS and PBS/HNT nanocomposites were foamed successfully using supercritical carbon dioxide as a physical blowing agent. The cell morphologiesshowed that the cell size decreased, and both cell density and volume expansion ratio increased with the addition of HNT. Within the HNT content used in this work (1, 3, 5, and 7 wt.%), the content of 5 wt.% was found to be the one that lead to the smallest cell size and highest cell density and volume expansion ratio. In addition to the HNT content, both saturation temperature and saturation pressure were found to significantly influence the cell morphology. Higher saturation pressure led to smaller cell size and higher volume expansion ratio. Interestingly, a close-celled to interconnect open-celled morphology transition occurred for PBS/HNT nanocomposites at a saturation temperature of 120 °C. The formation of interconnect open-celled morphology was mainly attributed to the stress induced by the HNT in the cell solidification process. With the increase of HNT content, saturation temperature and saturation pressure, the enthalpy of fusion of the foamed samples increased.

Thermal and dynamic mechanical properties of beeswax-halloysite nanocomposites for consolidating waterlogged archaeological woods

Thermal and mechanical properties were determined for the halloysite nanotubes (HNT)/beeswax composites at various compositions. The beeswax degradation temperatures and time course, provided by thermogravimetry (TG), evidenced the improvement of the thermal properties operated by HNT. Differential scanning calorimetry (DSC) allowed us to determine the enthalpy of melting as well as the time course of the melting process for beeswax. A slight loss of beeswax crystallinity was observed upon HNT addition. The dynamical mechanical analysis (DMA) provided the loss and the storage modulus for the nanocomposites upon heating and it was shown that the nanoclays create an inorganic framework which enhances the mechanical properties keeping unaltered the beeswax shape even above the melting temperature. To the light of these insights, samples of waterlogged archaeological wood were consolidated with the HNT/beeswax nanomaterial. The amount of HNT entrapped into the pores as well as the shrinkage volume of wood samples were determined. The HNT/beeswax mixtures can be considered a promising consolidant material for archaeological wood.

Mechanical and Physical Properties of Sago Starch/Halloysite Nanocomposite Film

The incorporation of unmodified halloysite nanotube (HNT) in a thermoplastic sago starch (TPSS) film to form a nanocomposite material was investigated. The TPSS/HNT nanocomposite was fabricated through solvent casting method at varying HNT loading of 0, 0.25, 0.5, 1.0, 3.0, and 5.0 wt.%. Evaluation on mechanical and physical properties (tensile test, water absorption, thickness and density) was made to study the effect of HNT loading on the TPSS properties. Tensile strength achieved an optimum value at 0.25 wt.% of HNT loading and decreased with higher addition of HNT. Meanwhile higher amount of HNT in the nanocomposite film exhibited brittleness with the reduced tensile strain. Water absorption decreased with the addition of HNT due to the difficulty of water molecules to pass through the tortuous path of HNT structure. Thickness and density of the nanocomposite film, however, increased at higher HNT contents. FESEM (field emission scanning electron microscope) which examined the surface morphology of the TPSS/HNT nanocomposite displayed uniformly dispersed HNT in the plasticized starch matrix.

Effects of Halloysite Nanotubes on Mechanical and Thermal Stability of Poly(Ethylene Terephthalate)/Polycarbonate Nanocomposites

The objective of this study is to investigate the effect of halloysite nanotubes (HNTs) loading on mechanical and thermal properties of poly(ethylene terephthalate)/polycarbonate (PET/PC) nanocomposites. Nanocomposites containing 70PET/30PC and 2-8 phr HNTs were prepared by twin screw extruder followed by injection moulding. As the percentage of HNTs increased, the flexural modulus increased. However, the flexural strength decreased with increasing HNTs content. The impact strength also decreased when HNTs increased. Thermogravimetry analysis of PET/PC/HNTs nanocomposites showed higher thermal stability at high HNTs content. However, on further addition of HNTs up to 8 phr, thermal stability of the nanocomposites decreased due to the poor dispersion of HNTs.

Preparation and characterization of ethylene-vinyl acetate/halloysite nanotube nanocomposites

Ethylene-vinyl acetate (EVA) nanocomposites based on halloysite nanotubes (HNT) were prepared by solution casting method. The thermal, mechanical, water uptake, as well as oxygen permeability properties of the nanocomposites were examined. X-ray diffraction (XRD) and field emission scanning electron microscopy showed that HNTs were dispersed well into the EVA matrix. XRD data also suggested that HNT frustrates chain ordering and reduced total crystallinity percentage. The thermal and mechanical properties of the nanocomposites were improved with HNT loading, up to 3 wt%. Both ductility and toughness were enhanced by incorporation of up to 3 wt% of HNT, implicitly confirming that HNT has been dispersed in EVA homogeneously. The addition of HNT also enhanced the water resistance and oxygen permeability of the prepared nanocomposites.

Chain orientation in poly(glycolic acid)/halloysite nanotube hybrid electrospun fibers

Chain orientation of poly(glycolic acid) (PGA) induced by halloysite nanotubes (HNTs) in hybrid electrospun fibers was investigated. The well-aligned PGA/HNTs hybrid fibers were prepared by electrospinning. The influence of HNTs loading (0, 1, 5, 10 wt%) on the PGA molecular chain and crystallite orientation was characterized by polarized Fourier transform infrared spectroscopy (FT-IR) and wide angle X-ray diffraction (WAXD). The effect of HNTs loading to the thermal properties of PGA fibers was investigated by differential scanning calorimetry (DSC), and the reinforcement effect of HNTs for PGA fibers was evaluated by tensile test. High temperature FT-IR measurement revealed the presence of hydrogen bonding between PGA carbonyl groups and HNTs surface silanol groups, which induces the alignment of PGA crystallite along the HNTs long axis. At low HNTs loading, HNTs distributed and aligned along the fiber axis during electrospinning process, whereas at high HNTs loading, the aggregation and anisotropic alignment of HNTs in PGA fibers lead disordered PGA chain orientation. The PGA molecular chain and crystallite orientation achieved the highest orientation degree at 5 wt% HNT loading. Furthermore, DSC results indicated that HNTs act as nucleating agent for PGA fibers and further increase the crystallinity of PGA fibers. Besides, young's modulus of PGA fibers was enhanced significantly with the addition of HNTs, which indicates a high reinforcement effect of HNTs to PGA fibers.

Toughening of poly(lactic acid) without sacrificing stiffness and strength by melt-blending with polyamide 11 and selective localization of halloysite nanotubes

This paper aims at improving the mechanical behavior of biobased brittle amorphous polylactide (PLA) by extrusion melt-blending with biobased semi-crystalline polyamide 11 (PA 11) and addition of natural halloysite nanotubes (HNT). The structure and properties of PLA/PA11/HNT blends were studied in terms of morphological, thermal and mechanical properties. The morphological analysis of the PLA/PA11/HNT blends shows a strong interface between the two polymeric phases due to hydrogen bonding, and the migration of HNTs towards PA 11 phase inducing their selective localization in one of the polymeric phases of the blend. A “salami-like” structure is formed revealing a HNTs-rich tubular-like (fibrillar) PA11 phase. Moreover, HNTs localized in the dispersed phase acts as nucleating agents for PA11. Blending PLA (80 wt.%) and PA11 (20 wt.%) increases PLA ductility (elongation at break, ɛr, is multiplied by more than 20), however at the slight expense of strength and stiffness. Further addition of HNTs (2 wt.%) further increases ductility (ɛr reaches 155 %, i.e. it is multiplied by more than 40) whereas tensile strength and modulus of PLA are unchanged and impact strength is more than doubled. The toughening mechanism is discussed based on the combined effect of resistance to crack propagation and nanotubes load bearing capacity due to the existence of the fibrillar structure. Thus, blending brittle PLA with PA11 and HNT nanotubes results in tailor-made PLA-based compounds with enhanced ductility without sacrificing stiffness and strength.

Long-lasting antibacterial behavior of a novel mixed matrix water purification membrane

Formation of water permeable microflow channels between graphene sheets with the addition of halloysite nanotubes.

Influences of halloysite nanotubes on crystallisation behaviour of polylactide

The aim of this study was to investigate influences of halloysite nanotubes (HNTs) on the (i) isothermal and (ii) non-isothermal crystallisation kinetics of polylactide (PLA) by differential scanning calorimetry (DSC) analyses, and (iii) crystallinity of injection moulded and then annealed specimens by DSC and X-ray diffraction (XRD) analyses. Nanocomposites were compounded using melt mixing technique via twin screw extrusion. Owing to basically very effective heterogeneous nucleation effect, addition of HNTs resulted in significant increases in the crystallinity of PLA under all three cases. Crystallisation time parameters and Avrami rate constants indicated that crystallisation rate increased under isothermal crystallisation, while it decreased under non-isothermal crystallisation due to the delayed conformational mobility of PLA chains by the physical barrier actions of HNTs. Avrami exponent also revealed that two-dimensional growth mechanism of crystallites transformed into three-dimensional growth during non-isothermal crystallisation, while there was no change during isothermal crystallisation. Crystallinity determinations of the injection moulded and then annealed specimens indicated that, the highest crystallinity degree of PLA, i.e. 47%, could be reached by the addition of only 1 wt-% HNT.