State Of Nanoclay Dispersion Research Articles

Effect of different blend compositions on properties of low-density polyethylene/ethylene vinyl alcohol/clay toward high oxygen barrier nanocomposite films

In this study, high oxygen barrier nanocomposite films were prepared by melt blending of low-density polyethylene/ethylene vinyl alcohol/nanoclay/polyethylene-grafted-maleic anhydride (LDPE/EVOH/nanoclay/LDPE-g-MA). Effect of each component presence was determined by using Box-Behnken experiment design methodology. For all the responses obtained, R 2 was between 0.956 and 0.981 indicating a very good fitting of the experimental data with the response surface method (RSM) in the models. Oxygen transfer rate (OTR) results shown that the addition of EVOH, compatibilizer, and nanoclay in formulations significantly decreases oxygen permeability. The experimental results showed that addition of 30 wt % EVOH, 4 wt % nanoclay, and 5 wt % LDPE-g-MA to the LDPE matrix gave the best oxygen barrier properties. The crystallization behaviors of the samples and thermal analysis have been characterized by using differential scanning calorimetry (DSC). The addition of nanoclay to the blends has resulted in increased crystallinity of LDPE phase. The state of nanoclay dispersion in the samples was examined by the X-ray diffraction (XRD) tests. The reduction of EVOH and nanoclay content, as well as the increase of LDPE-g-MA, has resulted in the better dispersion of nanoclay in the polymer matrix. The morphology of specimens was observed by using energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM).

Cure kinetics of hot cured unsaturated polyester (UP)/nanoclay nanocomposite including dual initiators

In this work, cure behaviour and cure kinetic parameters of unsaturated polyester (UP) resin containing Na-Montmorillonite (Cloisite 30B) is investigated. The state of nanoclay dispersion is analysed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Addition of 1–5 wt-% nanoclay results in decreasing gel time, exothermic peak and increasing cure rate. Cure kinetic parameters are determined employing Borchardt–Daniels method. The modelling results also prove: decreased curing reaction starting temperature, higher reaction rate and higher conversion ratio. Besides decreased activation energy ratio and shorter curing cycle are also observed as the main results of incorporating Cloisite 30B to neat UP resin.

Influence of fiber surface treatment on the physical and mechanical properties of wood flour-reinforced polypropylene bionanocomposites

In this article, the different chemical modifications of natural fiber on the physical and mechanical properties of polypropylene (PP)/wood flour (WF)/nanoclay hybrid composites were studied. To meet this objective, the chemical treatments on WF, namely alkali, acetylation, and benzoylation, were carried out. Then, the composites were prepared through the melt mixing of WF and PP at 50% weight ratios, with various amounts of nanoclay (0, 3, and 6 per hundred compounds (phc)) in Haake internal mixer and the test specimens were prepared by injection molding. The amount of coupling agent was fixed at 2 phc for all formulations. The tensile strength, impact strength, and water uptake of these composites were analyzed and the reinforcing properties of the chemically treated composites were compared with those of untreated composites. The chemical modification efficiency was verified by Fourier transform infrared (FTIR) analysis, and the dispersion state of nanoclay in the composites was examined using X-ray diffractometer and transmission electron microscopy. The results showed that the tensile modulus, tensile strength, and impact strength of the composites increased by applying chemical treatments. Modified composites had lower water absorption (WA) and thickness swelling than unmodified ones. Furthermore, the highest mechanical properties and the lowest water uptake were observed in the composite modified with acetic anhydride. FTIR spectra show that the intensity of O–H bond at 3444.2 cm–1 and formation of ester bond at 1741.4 cm–1 were indications of changes in the chemical structure of the fibers. The tensile modulus and strength increased with increase of nanoclay up to 3 phc and then decreased. However, the impact strength and WA decreased with increase of nanoclay loading. The morphological findings showed that the samples containing 3 phc of nanoclay had higher order of intercalation and better dispersion.

Preparation of High Performance SPEEK/Cloisite 15A Nanocomposite Membrane via Advanced Membrane Formulation Method

Sulfonated poly (ether ether ketone) (SPEEK)/Cloisite 15A® nanocomposite membranes were prepared via solution intercalation method. For better dispersion of nanoclay in the polymer matrix, the solution intercalation method was modified and a compatibilizer was introduced. The state of nanoclay dispersion was determined by FESEM. The effect of the solution formulation preparation method and compatibilizer on the performance properties such as proton conductivity and methanol permeability of all membranes was studied. FESEM analysis confirmed that SPEEK/Cloisite 15A® nanocomposite membrane prepared via modified solution intercalation method and in the presence of compatibilizer was the best membrane in terms of its morphological structure. Due to its well nanoclay distribution in polymer matrix, this kind of membrane exhibited the highest selectivity owing to its high proton conductivity and low methanol permeability. SPEEK/Cloisite 15A® with compatibilizer prepared via modified solution intercalation method was found to be the best membrane.

Structural characterization of high-density polyethylene nanocomposites: effect of compatibilizer type and high aspect ratio organoclay platelets

This research focuses on the possibility of improving properties of high-density polyethylene-based nanocomposite films for packaging applications, using a high aspect ratio layered silicate named fluoromica. Three different compatibilizers [ethylene vinyl acetate copolymer and two grades of maleic anhydride grafted high-density polyethylene (HDPE-g-MA) with different melt flow indices] were examined to explore the effects of compatibilizer polarity and molecular weight on the state of nanoclay dispersion. Owing to the direct correlation between nanocomposites morphology and rheological behavior, a quite extensive survey of the role of different material variables was carried out via measuring rheological properties in linear viscoelastic region. Percolation threshold ( $$\phi_{\text{p}}$$ ) were determined by analyzing the improvement in dynamic viscosity in low-frequency region and also, by means of a predicted mathematical model obtained from experimental design. It was found that the HDPE-g-MA compatibilizers result in lower $$\phi_{\text{p}}$$ and better clay dispersion, particularly in the case of high MFI resin. Microstructural characterization of the samples was studied by X-ray diffraction and transmission electron microscopy as well.

Dispersion Characterization of Nanoclay in Molded Epoxy Disks by Combined Image Analysis and Wavelength Dispersive Spectrometry

The state of nanoclay dispersion in a molded epoxy disk and its effects on the thermomechanical properties of the resulting nanocomposite are analyzed. A commercially available nanoclay, Cloisite® 25A, is mechanically mixed at 2wt% with EPON 815C epoxy resin. The epoxy∕clay compound is then mixed with EPI-CURE 3282 curing agent by a custom made molding setup and injected into a disk shaped mold cavity. Upon completion of curing, nanoclay dispersion is quantified on a sample cut along the radius of the composite disk. Dispersion of nanoclay clusters larger than 1.5μm are analyzed by digital image processing of scanning electron micrographs taken radially along the sample, whereas dispersion at smaller scales is quantified by compositional analysis of clay via wavelength dispersive spectrometry (WDS). Digital images of the microstructure indicate that amount of nanoclay clusters that are larger than 1.5μm remain approximately constant along the radius. However, size analysis of nanoclay clusters revealed that they are broken down into finer clusters along the radius, possibly due to the high shear deformation induced through the thickness during mold filling. Compositional analysis by WDS signified that approximately 0.4wt% of the nanoclay is dispersed to particles smaller than 1.5μm, which are not visible in micrographs. Tensile and three-point bending tests are conducted on additional samples cut from the molded disks. Except for slight reduction in flexural strength, up to 9.5% increase in tensile strength, stiffness, and flexural modulus are observed. Glass transition temperature is determined under oscillatory torsion and observed to increase by 4.5% by the addition of nanoclay.

Gas barrier properties of PP/EPDM blend nanocomposites

Abstract Nanocomposites of polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) blend with montmorillonite-based organoclay were prepared in a solvent blending method. Solvent blending of PP and EPDM in a composition of 50:50 formed a two phase morphology in which EPDM appeared as dispersed phase with irregular shape. The size of dispersed phase reduced significantly to almost spherical domains by addition of the nanoclay. For better dispersion of nanoclay in the PP/EPDM blend, an antioxidant was used as compatibilizer. State of nanoclay dispersion was evaluated by X-ray diffraction (XRD), and also, by a novel method using permeability measurements data in a permeability model. The measured d-spacing data proved a good dispersion of nanoclay at low clay contents along with compatibilizer. The permeability model for flake-filled polymers was used to estimate the aspect ratio of nanoclay platelets in the blend nanocomposites. Oxygen and carbon dioxide barrier property of the PP/EPDM blend improved about two-fold by adding only 1.5 vol% organoclay. Differential scanning calorimetry measurements indicated a decrease in crystallinity up to 27% suggesting a reduction in spherulites growth. However, the melting temperature remained unchanged. The increase in barrier property of the blend, despite a decrease in crystallinity, indicated the dominant role of organoclay platelets in barrier improvement. According to the permeability model, very high barrier property could be obtained if the aspect ratio of the flakes or platelets of the organoclay could be significantly increased in the blend. Scanning electron micrographs of fracture surface of nanocomposite membranes broken at very low temperatures, exhibited a very ductile surface indicating a good compatibility of PP and EPDM rubber and also, a possible contribution of nanoparticles to deformation mechanisms, such as extensive shear yielding in the polymer blend.