Polymer Clay Nanocomposites Research Articles

Novel vinyl-modified sepiolite-based polymer nanocomposites: synthesis and characterization

An environmental-friendly synthesis of polymer clay nanocomposites (PCNs) was carried out by incorporation of nanoclay into polymer matrix for their potential application as sorbent of metals present in aqueous media. Polyacrylonitrile was chemically grafted onto 77% vinyl triethoxysilane-modified sepiolite. The polymerization was carried out with benzoyl peroxide (BPO, C14H10O4) initiator in three different weight ratios of 1.0, 2.0, and 3.0%. The maximum polymer grafting of about 83% was obtained in nanocomposite initiated by 2.0% ratio of BPO. The surface modification of nanocomposites was carried out using hydroxyl amine hydrochloride (NH2OH·HCl). The prepared nanocomposites were characterized by Fourier transform infrared spectroscopy, X-ray diffractometry, thermogravimetric analysis, and Brunauer–Emmett–Teller technique. The copper removal tendency of nanocomposites was studied by atomic absorption spectroscopy. The maximum adsorption of copper was 86%, which could be achieved by nanocomposites synthesized with 2% initiator. The results have revealed the practical potential of the prepared PCN as efficient adsorbents.

Recent advances in starch–clay nanocomposites

ABSTRACTBiological nanocomposites are a valuable addition to the existing nanocomposite materials and eventually can substitute petroleum-based composite materials in numerous applications due to their inherent advantages such as biodegradability, eco-friendliness, low cost, and easy availability to name a few. Recently, polymer–clay nanocomposites have achieved much more attention due to their enhanced properties such as size dispersion and significant enhancement in physicochemical and mechanical properties in comparison to the pure polymer systems. Among various biopolymers, starch is one of the most abundant natural polymers on the earth and is highly valuable due to its chemical and physical properties. Starch polymer has highly increased potential as an alternative to petroleum-based materials. However, starch cannot be used alone and starch–clay nanocomposite has emerged as a new potential green sustainable material. This article focuses on recent progress in starch-based nanocomposites with particular emphasis on starch–clay nanocomposite preparation, properties, and applications.

Synthetic talc as a new platform for producing fluorescent clay polyurethane nanocomposites

As a non-swelling clay, talc generally interacts very weakly with organic molecules. However, two new nanometric synthetic talcs that incorporate berberine chloride were successfully used as fluorescent fillers in clay polyurethane nanocomposites obtained by the blending method. A micrometric natural talc filler was also used for comparison. The clay polymer nanocomposites (CPN) were characterized by FTIR, molar mass analysis and XRD. All talc fillers were well dispersed into the polyurethane matrix even at high filler content of 5 wt%, as supported by TEM and SEM analyses. Morphological changes were confirmed by AFM. The optical properties of the fluorescent talcs, dye-doped polymer and CPN were compared. While the dye-doped polymer suffered from conventional fluorescence quenching due to dye aggregation, the emission quantum yield of the CPN was increased with increasing the filler content. The best emission efficiency was observed for the CPN that contains the smallest talc-berberine hybrid particles. The use of fluorescent synthetic talc resulted in materials with good thermal and mechanical properties, and can be considered as a new method to produce fluorescent CPN in view of multiple applications.

Molecular dynamics simulations of montmorillonite reinforcing amylose plasticized by Brazilian Cerrado oils: polymer-clay nanocomposite

Abstract

The Effects of Clay Platelets Orientation Achieved via a Dry Lamination Process on the Barrier Properties of Clay Polymer Nanocomposites

Clay platelets have been used to make clay polymer nanocomposite (CPN) in order to enhance the barrier properties of plastic substrates and sputtered barrier films. Clay platelets tend to be randomly dispersed and should be oriented in the film direction to achieve effective barrier properties. In this work, well-oriented nanocomposites were prepared on substrates by adopting a dry lamination process between two heated rubber rolls during the curing step. Dry lamination enabled the clay platelets to be oriented upon application before the sample was completely cured, and the final curing step froze the structure to maintain the orientation. The dry lamination time was optimized at a maximum peak of isothermal curing reaction using DSC. Through characterization via XRD and TEM, it was confirmed that clay platelets are well dispersed and exfoliated in the CPN. The CPN with highly oriented clay platelets enhanced the barrier properties to reach a water vapor transmittance rate of 5.5×10-4 g/m2/day, while maintaining optical properties.

A Permeability Model for Polymer-Clay Nanocomposites with Varying Clay Platelets Thickness

Polymer-clay nanocomposites (PCNC), are characterized by the high ratio of surface area to volume of the clay nanoparticles which are in the form of clay platelets with very high aspect ratio. This feature provides superior gas barrier properties at very low volume fraction of the nanofiller. Clay platelets introduce discontinuity to flows through the bulk polymer matrix material. The extent of this improvement depends on the success of separation of clay layers during processing which would produce single-layer particles (exfoliation) or several-layer particles (intercalation) through the bulk polymer matrix. This paper discusses the common permeability models used to capture the effects of the clay nanofillers in PCNC. Since these models assume a state of full exfoliation of clay platelets; that is a single phase of the nanofiller, they fall short of representing the actual state as evidenced by experimental works, which confirm the presence of both the intercalated phase and the exfoliated phase. A model that incorporates clay inclusions with different sizes (different thicknesses) is proposed and its implications are assessed.

Preparation of nanocomposites for the removal of phenolic compounds from aqueous solutions

Abstract Alginate beads, with and without different types of organo-modified clays, were obtained using a calcium chloride (CaCl2) solution. Firstly, raw clays were organo-modified with a cationic surfactant, hexadecyl trimethylammonium (HDTMA). Then, their cationic exchange capacities (CEC) were calculated and they also were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Afterwards, the obtained polymers and clay polymer nanocomposites (CPN) were carefully characterized by means of the same techniques. Later, different phenol and 4-chlorophenol (4CF) aqueous solutions were prepared and put in contact, for different periods of time, with the synthesized CPN. Phenol and 4CF concentrations were measured by means of UV–vis spectroscopy. Results indicated a successful modification of the raw clay with this cationic surfactant and its incorporation into the alginate polymer matrix. Finally, the maximum removal capacities for both phenolic compounds, 4CF and phenol, were found at qe = 0.334 mg·g−1 and qe = 0.118 mg·g−1, respectively.

Influence of sepiolite on thermal, mechanical and biodegradation properties of poly-3-hydroxybutyrate- co -3-hydroxyvalerate nanocomposites

Abstract The clay polymer nanocomposites comprising of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and vinyl triethoxy silane grafted sepiolite (VTES-g-SEP) were prepared by the solution casting. Scanning electron micrographs revealed the absence of voids and high interfacial interaction between polymer and VTES-g-SEP. Thermal and mechanical properties of the clay polymer nanocomposites were significantly enhanced as compared to the PHBV. The scanning electron micrographs of clay polymer nanocomposite films subjected to soil burial showed formation of pits and agglomerates. Additionally, Fourier transform infrared spectra of clay polymer nanocomposite films buried in soil demonstrated a sharp decline in the intensities of IR peaks was found at 3617–3019 cm− 1 (OH stretching), 1710 cm− 1 (carbonyl stretching), 1365 cm− 1 (symmetric bending of C H vibrations), 1265 cm− 1 (C O stretching), 1165 cm− 1 (asymmetric stretching of C-O-C group) and 978 cm− 1 (C H bending) after 90 days of soil burial. In a nutshell, the clay polymer nanocomposite films can be used in packaging applications.

Preliminary Molecular Dynamics Studies of the Montmorillonite, Amylose, Fatty Acids and Water for Polymer-Clay Nanocomposite Modeling

ABSTRACT:This work shows a part of a theoretical study of Polymer-Clay Nanocomposites (PCN) formed by an acetylated amylose segment and fatty acids present in the Pequi oil, a fruit from the Brazilian Cerrado, in aqueous medium, including or not, organophilized montmorillonite (MMT-O). The simulated systems aim to provide qualitative information about the molecular movement among diverse chemical species; their structural and behavioral correlations and essential intermolecular forces. The calculations were carried out by Molecular Mechanics and Dynamics methods with the Polymer Consistent Force Field-interface. Simulation results had shown behavioral differences between systems. Without MMT-O, the acetyl amylose residues quickly became coiled, most of the fatty acids cover its surface, and water molecules are stabilized over the polysaccharide portions free of fatty acids. With MMT-O the fatty acids show a potential plasticizing effect due to the greater compatibility between the components of the studied system, since the organic assemblage is strongly attracted by the electrostatic force of the clay. Besides, water molecules flow to the clay layer, while the non polar portion of fatty acids increase their flexibility, in spite to stay attached to acetyl amylose, progressively coiled, through hydrogen bonds. This behavior is interpreted as an improvement in the miscibility of the oil. The new knowledge acquired about these molecular systems encourages us to increase the models complexity, and undertake further studies in the design of PCNs with biopolymers.

A Novel Bioresidue to Compatibilize Sodium Montmorillonite and Linear Low Density Polyethylene

Despite the improved thermal stability and mechanical properties of polymer–clay nanocomposites compared to pure polymeric materials, creating nanocomposites with enhanced thermomechanical properties requires a good compatibility and dispersion of the clay within the polymeric matrix. This paper introduces a bioresidue extracted from waste biomass to modify montmorillonite clay to compatibilize it with linear low density polyethylene (LLDPE). The biomodified clay was compounded, melt blended, and injection molded with LLDPE, and the thermomechanical properties of the resulting nanocomposites were investigated with oscillatory rheometry, thermogravimetric analysis, X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, and transmission electron microscopy to assess the compatibility of the biomodified clay and the polymer. The structure of the biomodified clay ranged from partially intercalated to fully exfoliated. Hansen solubility parameters indicate that almost all of the identified compounds in the bioresidue are soluble with polyethylene. Density functional-based modeling showed a trade-off between electrostatic screening and dispersion interactions affecting the overall interlayer spacing in polymer–clay nanocomposites.

Synthesis and Characterization of Magnetized Clay Polymer Nanocomposites and its Adsorptive Behaviour in Removal of Chromium(VI) from Aqueous Phase

Synthesis and Characterization of Magnetized Clay Polymer Nanocomposites and its Adsorptive Behaviour in Removal of Chromium(VI) from Aqueous Phase

Effect of Thermal Aging on Mechanical Properties and Fatigue Behavior of PP/HDPE Thermoplastic Polymer Nanoclay Composites

Effect of Thermal Aging on Mechanical Properties and Fatigue Behavior of PP/HDPE Thermoplastic Polymer Nanoclay Composites

Preparation and Characterization of Tubular Composite Membranes and their Application in Water Flow Measurements

The latest technologies require materials with combination of properties that are not usually found in conventional materials. Organic-inorganic hybrid materials emerge as alternatives to the synthesis of low cost new functional materials. The constituent polymer-clay nanocomposites are intended effectively for the treatment of oily effluents. The removal of oily effluents was evaluated using composite membranes with different nanocomposite percentages, consisting of a mineral clay BrasgelTM smaller than 2 μm and ultra high molecular weight polyethylene. The sample of clay was characterized by X-Ray Diffraction (XRD) and Cation Exchange Capacity (CEC), while the membranes by scanning electron microscope (SEM). The produced composite membranes efficiencies were evaluated by continuous flow for 1 hour. The results clearly confirmed that membranes incorporated with a higher percentage of nanocomposites achieved greater stability and less time as assessed in water flow.

Silane functionalization of sodium montmorillonite nanoclay: The effect of dispersing media on intercalation and chemical grafting

Abstract This study investigated the effect of various dispersing media on the silane functionalization of sodium montmorillonite nanoclay (Na Mt) to evaluate each medium's effectiveness on the intercalation and chemical grafting of silane coupling agent. The amount of intercalation was estimated using the equation that was developed in our previous work based on thermogravimetric analysis. The results showed that the amount of silane intercalation was the greatest for water and glycerol media (≈1.582 mmol/g clay and ≈1.480 mmol/g clay, respectively), which was in agreement with the d001-values calculated by the XRD analysis (≈19.6 A and ≈14.4 A, respectively). 29Si NMR results showed a new T site in addition to Q peaks for all modified nanoclays in different dispersing media, indicating the occurrence of silane chemical grafting at the surface of the nanolayers. The A T 3 A Q 3 in NMR spectra was used to compare the amount of chemically grafted silane in different dispersing media, a new approach for Mt material. Hydrogen-bonding solvents (water, glycerol and ethanol), and polar solvents (DMF and THF) showed greater T3 peak intensities compared to other dispersing media, indicating higher amounts of chemical grafting of silane molecules. This observation was in agreement with the broadening of FTIR peak at 1130–1000 cm− 1, which is explained by the formation of extra Si O Si bonds; that is, in turn, due to silane chemical grafting at the surfaces of the nanolayers. The silane-nanofiller interactions were correlated with the Hansen solubility parameters of different dispersing media used for the modification. This research has potential to help design and improve the nanoclay modification processes, which are used in the fabrication of clay-polymer nanocomposites.

Structural characterization of sepiolite/polyamide6,6 nanocomposites by means of static and dynamic thermal methods

Abstract Clay Polymer Nanocomposites (CPN) are hybrid materials with improved technical characteristics with respect to the counterparts. Polyamide6,6 (PA66) is one of the most widely used as matrix. The α structure (triclinic) undergoes into the γ structure (pseudohexagonal) in a solid-to-solid transition when exposed to high temperatures. In recent years, sepiolite (Sep) has been used as reinforcing agent in polymer matrix as it enhances thermal properties of the nanocomposites without modification in the hydrogen bonds between PA66 chains. In this work we provide information about the structural changes occurring in neat PA66 and Sep/PA66 nanocomposites after the degradation process through a thermo-dynamic study combined with X-ray diffraction methods. In injection molded Sep/PA66 nanocomposites the sepiolite fibres locate between the polymer lamellae in a sloping suitable position, without involving large distortions in the lattice of PA66. Due to organophilization, no changes are induced by the sepiolite in the nanocomposite structure. The PA66…Sep contact promotes the occurrence of the C H…O hydrogen bonds in the typical reticulated structure between the sepiolite fibres and the polyamide chains, which renders thermal sability to the polymer crystals up to 150 °C.

Computational Study of the Effects of Processing Parameters on the Nonlinear Elastoplastic Behavior of Polymer Nanoclay Composites

Processing parameters (e.g., exfoliation extent and volume fraction) of clay particles in polymeric resins play a crucial role in the mechanical properties of polymer nanoclay composites (PNCs). This paper is aimed to investigate the effects of clay aspect ratio and volume fraction on the global mechanical properties (e.g., effective stiffness, yield strength, and ultimate tensile strength) of PNCs. During the process, computational micromechanics models are adopted to simulate the nonlinear elastoplastic behavior of the PNCs of varying clay particle volume fractions and aspect ratios subjected to uniaxial tension. A representative volume element (RVE) of the PNCs is employed for the finite-element-method (FEM) based computational simulations. The polymeric matrix is treated as an idealized elastoplastic solid with isotropic hardening behavior, and the clay particles are treated as stiff elastic platelets distributed evenly in the stack and stagger configurations in the matrix. Seven volume fractions (Vf = 0.5%, 1%, 2%, 5%, 7.5%, 10%, and 15%) and seven aspect ratios (the ratio of platelet length over thickness ρ = 1, 2, 5, 10, 20, 50 and 100) of the reinforcing clay particles are utilized. Numerical experiments show that the effective modulus of the PNCs at small strains increases with the increase of either the clay volume fraction or the platelet aspect ratio largely following those predicted by classic micromechanics models. However, at the low particle aspect ratios (e.g., ρ = 1, 2, 5 and 10), the ultimate tensile strength of the clay composite is nearly independent of the clay volume fraction up to 5% in the present study, i.e., the polymeric matrix governs the PNC strength; at the large particle aspect ratios (e.g., ρ = 20 and 50), the ultimate tensile strength is significantly enhanced with growing clay volume fraction higher than 5% and reaches ~150% of that of the polymeric matrix at ρ = 50 and Vf = 10%. A comparative study is conducted for stack and stagger models for the prediction of the mechanical properties of PNCs. It shows that the stack model predicts slightly larger values of the effective stiffness and tensile strength than the stagger model. The numerical study shows that a large platelet aspect ratio through full exfoliation of the clay particles in matrix is crucial to achieving the preferable mechanical properties of PNCs as evidenced in experiments. The present results can be utilized to quantitatively explain the mechanical properties of clay particle-reinforced composites and PNCs within the framework of classic micromechanics, and provide guidelines for computer-aided nanocomposites design for processing property-tailorable PNCs.

Stochastic analysis of interphase effects on elastic modulus and yield strength of nylon 6/clay nanocomposites

The multifunctional properties of polymer clay nanocomposites (PCNs) can be related to the interaction of clays, polymer and interphase region. Several experimental, analytical and numerical studies have been conducted to characterize the mechanical behavior of PCNs. The elastic behavior of PCNs is well documented in the literature but their other material properties like yield strength are rather vague. On the other hand, the variation of material parameters and the stochastic nature of interphase region hinder the use of deterministic methods. In this study, a stochastic analysis along with a hierarchical multiscale method is used to analyze the effect of interphase properties on the macroscopic properties of PCNs. Since the interphase layer is expected to be weaker than the polymer matrix, a weakening coefficient is defined to describe the interphase properties based on the matrix properties. This weakening coefficient and the interphase thickness are considered as the stochastic inputs. The elastic modulus and yield strength of nylon 6/clay nanocomposites are calculated using the stochastic multiscale framework. The uncertainty propagation and sobol sensitivity analysis are performed to study the effect of random inputs on the elastic modulus and yield strength of PCNs. Despite the wide range of input variations, the accuracy of the proposed stochastic multiscale framework for the prediction of the PCNs properties is estimated by validating our results against the available experimental data in the literature.

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations, CEC, and Chain Length

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na+, K+, Ca2+), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.

Sodium montmorillonite/ureasil-poly(oxyethylene) nanocomposite as potential adsorbent of cationic dye

A sodium montmorillonite/ureasil-poly(oxyethylene) clay-polymer nanocomposite was prepared using the sol-gel reaction of a U-PEO hybrid precursor/clay mineral suspension, with the aim of developing a sorbent for the removal of cationic dyes from aqueous media. The structural characteristics of the nanocomposite were studied by FTIR, XRD, UV–Vis spectroscopy, and SAXS. The XRD results revealed intercalation of the U-PEO in the silicate interlayer spaces. FTIR spectra indicated the existence of strong interactions between methylene blue (MB) dye and the clay mineral silicate layers. Time-resolved SAXS measurements during MB adsorption showed a decrease of the montmorillonite (Mt) peak area and an increase of the half-height width of the peak, indicating that water uptake during dye adsorption caused a reduction of the Mt. crystallite size. UV–Vis adsorption experiments showed that the kinetics of MB adsorption followed a pseudo-first order process and that the steady state equilibrium adsorption capacity followed the Langmuir model. The results showed that the nanocomposite is potentially applicable as an adsorbent of dyes present in contaminated waters.

Effect of nanoclay localization on the peel performance of PE based blend nanocomposite sealants

Polyethylene (PE) based clay polymer nanocomposites (CPN) are of great importance to generate peelable seals in packaging industry. This study shows the significant effect of organoclay (OC) localization in PE-based blend sealants on their peel properties, for the first time. Two different immiscible blends composed of PE/ethylene-methyl acrylate copolymer (EMA) and PE/ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EMA-GMA) were examined for their potential to generate peelable seals upon addition of organo-modified montmorillonite (OMt). WAXD results and TEM observations reveal that OC is localized at the interface of PE/EMA phases while it is localized within the dispersed EMA-GMA phase in the PE/EMA-GMA blend, which is in agreement with the thermodynamic predictions. The incorporation of 4 phr OC converts the lock seal behavior of the PE/EMA blend seal to a peelable behavior over a wide peelable heat seal temperature range (over 35°C). In contrast, the OC/PE/EMA-GMA nanocomposite sealant, in which OC is mostly located within the EMA-GMA phase, shows lock seal performance similar to the PE/EMA-GMA neat blend.