Halloysite Nanotubes Nanocomposites Research Articles

ZnS/HALLOYSITE NANOCOMPOSITES: SYNTHESIS, CHARACTERIZATION AND ENHANCED PHOTOCATALYTIC ACTIVITY

Zinc sulfide (ZnS) nanoparticles are successfully deposited on the surface of natural halloysite nanotubes (HNTs) to produce ZnS /HNTs nanocomposites. The samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and photoluminescence (PL) analysis. The results indicate that ZnS nanoparticles are uniformly attached on the surface of HNTs with narrow particle size distribution center at ~10 nm, and are prevented from aggregation by HNTs and expose more active sites. ZnS /HNTs show excellent photocatalytic activity for the degradation of eosin B under UV light, better than pure ZnS and HNTs, indicating its potential application in the field of environmental protection. The mechanism for photocatalytic activity enhancement is also investigated.

Highly dispersed polyamide‐11/halloysite nanocomposites: Thermal, rheological, optical, dielectric, and mechanical properties

AbstractBio‐based polyamide 11 and natural halloysite nanotubes (HNTs) were used for the preparation of PA‐11/HNT nanocomposites with varying nanotubes concentrations by melt extrusion using a masterbatch dilution process. The prepared nanocomposites were analyzed for microstructural changes, transparency, thermal stability, rheological behavior, dielectric, and mechanical properties. The HNT nanotubes are well dispersed in PA‐11 matrix in the studied composition range as shown by microscopy and spectrophotometry. Interestingly, good halloysite dispersion in PA‐11 matrix increases the tensile strength and Young modulus of PA‐11 without sacrificing the ductility. Highly dispersed nanotubes also bring favorable changes in the thermal stability, dielectric, and rheological characteristics of PA‐11. Additionally, glass transition temperature, crystallization temperature, and degree of crystallinity of the nanocomposites tend to increase with increase in nanotubes loading. Thus, PA‐11 can become a tailor‐made material with multifunctional characteristics, thanks to the addition of HNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Novel Polyvinyl Alcohol/Styrene Butadiene Rubber Latex/Carboxymethyl Cellulose Nanocomposites Reinforced with Modified Halloysite Nanotubes

Novel polyvinyl alcohol (PVA)/styrene butadiene rubber (SBR) latex/carboxymethyl cellulose (CMC)/halloysite nanotubes (HNTs) nanocomposites were successfully prepared through physical blending. The as‐obtained PVA/SBR/CMC/HNTs nanocomposites were coated on the surface of old corrugated container (OCC)‐based paper in an effort to improve the mechanical properties of paper. To improve the dispersion of HNTs and enhance the compatibility between HNTs and polymer matrix, HNTs were modified with titanate coupling agent (TCA). FT‐IR, together with TGA, confirmed that TCA was grafted onto the surface of HNTs successfully. XRD demonstrated that the crystal structures of HNTs remained almost unchanged. TEM showed that modified HNTs exhibited good dispersion and possessed nanotubular structures with an outer diameter of around 50 nm and an inner diameter of about 20 nm. SEM gave an indication that modified HNTs were dispersed more uniformly than unmodified HNTs within PVA/SBR/CMC matrix. Rheological measurement exhibited that surface modification process enhanced the compatibility between HNTs and polymer matrix, thus resulting in the decreased viscosity of nanocomposites. In comparison with unmodified HNTs, modified HNTs were found to contribute more to the enhancement in mechanical properties, which might be attributed to the better dispersion and compatibility of modified HNTs evidenced by TEM, SEM, and rheological measurement.

Poly(lactic acid)/halloysite nanotubes nanocomposites: Structure, thermal, and mechanical properties as a function of halloysite treatment

AbstractPoly(lactic acid) (PLA)/halloysite nanotubes (HNT) nanocomposites were prepared by melt extrusion using a masterbatch dilution process. Effect of addition of both unmodified halloysites (HNT) and quaternary ammonium salt treated halloysites (m‐HNT) was investigated at different nanofiller contents. A homogeneous distribution/dispersion of halloysites in the PLA matrix is obtained for both unmodified and modified nanotubes within the studied composition range. The nucleating effect of halloysites, resulting in a limited increase of degree of crystallinity, is more pronounced in the case of m‐HNT. Besides, the rigidity, tensile, flexural, and impact resistances of PLA significantly increase on addition of halloysites, the property improvement being higher for m‐HNT than for HNT. Interestingly, there is no significant embrittlement (almost constant elongation at break). Based on micromechanical models, this superior reinforcement efficiency of m‐HNT was ascribed to the better interfacial compatibility induced by the modification of the nanotube surface. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Influence of the Processing Conditions on the Mechanical Properties of PA 6 - Halloysite Nanotubes Nanocomposites for Injection Moulding

Nowadays polymer based nanocomposites are very interesting to manufacture products of less weight and higher mechanical properties and specific performance depending on the morphology of nanoscaled reinforcement. Most of these potential improvements are focused to the challenges newer products require like HEV (hybrid or electrical vehicles) for example. The development of these new products requires the full characterization of the rheological and mechanical behavior of the materials and the correct preparation of the raw material for further processing. As an example two nanocomposite blends were prepared letting down a masterbach of PA6+30% HNT (Halloysite nanotubes) to 3% and 6% of HNT content in a PA6 matrix of (BADADUR). The letting down process was developed in an extrusion-compounding machine (COPERION ZSK 26) and the rheological behavior was determined in a capillar rheometer obtaining the viscosity curves of the material needed for injection molding simulation. The products obtained were used for injection molding of test specimens in an electrical injection machine (JSW EL II 85). In addition, the letting down process was done directly in the injection machine in order to establish the relevance of the previous extrusion process. The probes obtained were analyzed by DSC and FTIR to determine the functional groups of the resultant product and SEM and TEM to determine the quality of the dispersion of the nanotubes. The probes were finally tested to determine its stiffness and tensile properties. The results showed the feasibility to develop parts made of nanocomposite with improved performance with scaled industry equipment with natural reinforcements..

Influence of the Processing Conditions on the Mechanical Properties of PA 6 - Halloysite Nanotubes Nanocomposites for Injection Moulding

Nowadays polymer based nanocomposites are very interesting to manufacture products of less weight and higher mechanical properties and specific performance depending on the morphology of nanoscaled reinforcement. Most of these potential improvements are focused to the challenges newer products require like HEV (hybrid or electrical vehicles) for example. The development of these new products requires the full characterization of the rheological and mechanical behavior of the materials and the correct preparation of the raw material for further processing. As an example two nanocomposite blends were prepared letting down a masterbach of PA6+30% HNT (Halloysite nanotubes) to 3% and 6% of HNT content in a PA6 matrix of (BADADUR). The letting down process was developed in an extrusion-compounding machine (COPERION ZSK 26) and the rheological behavior was determined in a capillar rheometer obtaining the viscosity curves of the material needed for injection molding simulation. The products obtained were used for injection molding of test specimens in an electrical injection machine (JSW EL II 85). In addition, the letting down process was done directly in the injection machine in order to establish the relevance of the previous extrusion process. The probes obtained were analyzed by DSC and FTIR to determine the functional groups of the resultant product and SEM and TEM to determine the quality of the dispersion of the nanotubes. The probes were finally tested to determine its stiffness and tensile properties. The results showed the feasibility to develop parts made of nanocomposite with improved performance with scaled industry equipment with natural reinforcements..

Water-assisted extrusion as a novel processing route to prepare polypropylene/halloysite nanotube nanocomposites: Structure and properties

Naturally occurring halloysite nanotubes (HNTs) are used to prepare Polypropylene (PP)/HNTs nanocomposites using a novel “one step” water-assisted extrusion process with and without the use of a PP-graft-maleic anhydride (PP-g-MA) as compatibilizer. In order to analyze the influence of PP-g-MA and/or water injection on the HNTs dispersion and therefore on nanocomposite properties, structural analysis (SEM and TEM) is combined with rheological and thermo-mechanical experiments. The best clay dispersion is obtained when compatibilizer and water injection are combined together (synergistic effect). As a consequence, the linear viscoelastic properties and the dynamic storage modulus are dramatically enhanced for this system. A mechanism explaining the interaction between HNTs and PP-g-MA in presence of water is proposed. The thermal stability and flame retardant property are also investigated. Thermal analyses reveal two opposite effects of HNTs on the thermal behaviour of PP. A surface catalytic action of the halloysite speeds up thermal degradation of PP. However, this effect is reduced with improved HNTs dispersion, presumably via an entrapment mechanism of the decomposition products inside the lumens. Finally, cone calorimeter results show that low flammability of nanocomposites is only achieved when combining water injection and PP-g-MA. In view of these results, PP/HNTs nanocomposites prepared using this novel processing route are promising candidates for flame retardant applications.

Structure and Properties of Poly(vinyl chloride)/Halloysite Nanotubes Nanocomposites

Poly(vinyl chloride)(PVC)/halloysite nanotubes (HNTs) nanocomposites were prepared by melt blending. The effects of HNT content on the mechanical properties, morphology, and rheological properties of the nanocomposites were investigated. The results showed that HNTs were effective in toughening and reinforcing PVC nanocomposites. The notched impact, tensile and flexural strength, and flexural modulus of the nanocomposites were remarkably increased compared with those for the pure PVC. Scanning electron microscopy (SEM) results illustrated the ductile behavior of the nanocomposites, with a possible cavitation mechanism. Transmission electron microscopy (TEM) results showed that HNTs were uniformly dispersed in the PVC matrix. Interfacial interaction of hydrogen bonding between the HNTs and PVC matrix was substantiated. The plasticization times of PVC/HNTs nanocomposites were found to be shorter and the equilibrium torque was higher than that for the pure PVC.

Enhancement of mechanical properties of poly(vinyl chloride) with polymethyl methacrylate-grafted halloysite nanotube

Halloysite nanotubes(HNTs) grafted with Polymethyl methacrylate(PMMA) were synthesized via radical poly- merization. The properties of PMMA-grafted HNTs were characterized by transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The results showed that PMMA grafted to the surfaces of HNTs successfully. Then, PVC/PMMA-grafted HNTs nanocomposites were prepared by melt compounding. The morphology, mechanical properties and thermal properties of the nanocomposites were investigated. PMMA-grafted HNTs can effectively improve the toughness, strength and modulus of PVC. The glass transition and thermal decomposition temperatures of PVC phase in PVC/PMMA-grafted HNTs nanocomposites are shifted toward slightly higher temperatures. The grafted HNTs were uniformly dispersed in PVC matrix as revealed by TEM photos. The fracture surfaces of the nanocomposites exhibited plastic deformation feature indi- cating ductile fracture behaviors. The improvement of toughness of PVC by PMMA-grafted HNTs was attributed to the improved interfacial bonding by grafting and the toughening mechanism was explained according to the cavitation mecha- nism.

Effects of halloysite nanotubes on kinetics and activation energy of non-isothermal crystallization of polypropylene

Halloysite nanotubes (HNTs), a kind of naturally occurring silicates possessing typical fibular structure, were introduced to fabricate polypropylene (PP)/HNTs nanocomposites. The non-isothermal crystallization behaviors were investigated by differential scanning calorimetry (DSC) method according to different treatments. The results suggest, with the inclusion of HNTs in PP matrix, the nanocomposites crystallize at higher temperature regime, which are correlated with the heterogeneous nucleating effects of HNTs during the crystallization process of PP. The kinetics studies of crystallization show that PP nanocomposites possess faster crystallization process and higher activation energy due to the nucleating effect and hindrance effect of HNTs to the motion of PP chains. The polarized light microscopy (PLM) observations further show that HNTs serve as nucleation sites and accelerate the crystallization process.

Structure and Performance of Polyamide 6/Halloysite Nanotubes Nanocomposites

Halloysite nanotubes (HNTs) are chemically modified via silylation with 3-(trimethoxysilyl)propyl methacrylate. The modified HNTs (m-HNTs) are characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, solid state 13C NMR spectroscopy, thermogravimetric analysis (TGA) and extraction experiment. It is showed that the silane has been effectively grafted onto HNTs surface and renders the hydrophobicity to m-HNTs. The nanocomposites consisting of polyamide 6 (PA6) and m-HNTs show significantly improved mechanical properties and heat distortion temperature, which are attributed to the covalent interfacial bonding and the excellent dispersion state of m-HNTs. M-HNTs are found to disperse individually into PA6 matrix. The nucleation effect by m-HNTs is verified by the lowered fold-surface free energy of PA6/ HNTs nanocomposites and the observation of polarized optical microscopy (POM). Both high cooling rate and high m-HNTs loading are beneficial to the formation of gamma-crystals of PA6. The polymorphism could be correlated to the heterogeneous nucleation effects of m-HNTs and the interfacial interactions between m-HNTs and PA6 matrix.