Organo-modified Montmorillonite Research Articles

Effects of different factors on photodefluorination of perfluorinated compounds by hydrated electrons in organo-montmorillonite system

Perfluorinated compounds (PFCs) are considered as the most recalcitrant organic contaminants. Our previous research has shown that PFCs can be completely defluorinated in the UV/organoclay/3-indole acetic acid system, however, the factors that could affect the degradation of PFCs, are still not clear. In this study, we further investigated the effect of different indole derivatives and organo-modified montmorillonite on the degradation of perfluooctanoic acid (PFOA). Based on multiple linear regression analysis, our results clearly indicate that hydrated electron yields of indole derivatives, adsorption of PFOA and indole derivatives on organo-montmorillonite contributed independently to the degradation of PFOA. In addition, the results also show that the presence of humic substance (even at 10 mg C L−1) would not significantly suppress the degradation process due to the strong adsorption of humic substance on the organo-montmorillonite surface. This study would provide more information to design an efficient and environment-friendly system for degradation of PFCs, and this technique will have great potential for treatment of persistent contaminants under mild reaction conditions.

Life Cycle Analysis of Extruded Films Based on Poly(lactic acid)/Cellulose Nanocrystal/Limonene: A Comparative Study with ATBC Plasticized PLA/OMMT Systems

Life cycle analysis (LCA) of limonene plasticized poly(lactic acid) (PLA) films containing cellulose nanocrystals (CNC) extracted, by acid hydrolysis, from Phormium tenax leaf fibres, was assessed and compared with the results of acetyl tributyl citrate (ATBC) plasticized PLA films, having equivalent mechanical properties, containing organo-modified montmorillonite (OMMT). Eco-Indicator 99 tool has been adopted as the main method for life cycle assessment. Results indicated that, despite CNC are biobased fillers obtained by natural sources, the related chemical extraction leads to a large environmental footprint and a relatively relevant energy expense. LCA characterization of these films demonstrated that the environmental impact of PLA/limonene film reinforced with 1% in weight of CNC (PLA/CNC/limonene) is comparable to the environmental impact of polylactic acid films reinforced with OMMT and plasticized with a petroleum based plasticizer (ATBC) (PLA/OMTT/ATBC). A “cradle to gate” approach has been considered for both the film typologies.

Morphology, rheology property, and crystallization behavior of PLLA/OMMT nanocomposites prepared by an innovative eccentric rotor extruder

An innovative eccentric rotor extruder, which can generate continuous elongation flow, was used to fabricate the poly(L‐lactide) (PLLA)/organo‐modified montmorillonite (OMMT) nanocomposites in different OMMT concentrations. The morphology of the nanocomposites was characterized by thermal gravimetric analyzer, X‐ray diffractometer, and transmission electron microscope. The results showed that the OMMT nanoparticles were uniformly dispersed in the PLLA matrix and mainly existed in intercalation mode. The intercalation and exfoliation process of OMMT in the eccentric rotor extruder may be a double‐side exfoliation, which is more effective than the layer‐by‐layer peeling mechanism based on the shear flow. The influence of OMMT on the rheological behavior of PLLA was investigated by dynamic rheological measurements, showing greater improvement of rheological properties for the nanocomposites. The thermo‐mechanical properties analysis indicated that significant enhancement of E′ can be seen for all the nanocomposites. Presence of intercalated OMMT platelets did not lead to a significant shift of the E″ and tan δ curves compared with that of pure PLLA. The crystallization and melting behavior was studied by differential scanning calorimetry, which indicated that the incorporation of OMMT nanoparticles slightly increased the crystallinity of PLLA matrix. The polarizing microscope was further carried out and showed that the dispersed OMMT nanoparticles acted as a heterogeneous nucleating agent to promote the crystallization of PLLA.

Morphology Development and Mechanical Properties Variation during Cold-Drawing of Polyethylene-Clay Nanocomposite Fibers.

In this work, the influence of composition and cold-drawing on nano- and micro-scale morphology and tensile mechanical properties of PE/organoclay nanocomposite fibers was investigated. Nanocomposites were prepared by melt compounding in a twin-screw extruder, using a maleic anhydride grafted linear low density polyethylene (LLDPE–g–MA) and an organomodified montmorillonite (Dellite 67G) at three different loadings (3, 5 and 10 wt %). Fibers were produced by a single-screw extruder and drawn at five draw ratios (DRs): 7.25, 10, 13.5, 16 and 19. All nanocomposites, characterized by XRD, SEM, TEM, and FT-IR techniques, showed an intercalated/exfoliated morphology. The study evidenced that the nanoclay presence significantly increases both elastic modulus (up to +115% for fibers containing 10 wt % of D67G) and drawability of as-spun nanocomposite fibers. Moreover, at fixed nanocomposite composition, the cold-drawing process increases fibers elastic modulus and tensile strength at increasing DRs. However, at high DRs, “face-to-edge” rearrangement phenomena of clay layers (i.e., clay layers tend to rotate and touch each other) arise in fibers at high nanoclay loadings. Finally, nanocomposite fibers show a lower diameter reduction during drawing, with respect to the plain system, and surface feature of adjustable roughness by controlling the composition and the drawing conditions.

Assessment of kinetic release of thymol from LDPE nanocomposites obtained by supercritical impregnation: Effect of depressurization rate and nanoclay content

LDPE nanocomposites prepared with different concentrations of an organo-modified montmorillonite (OM-MMT) (2.5 and 5.0% (w/w)) were impregnated with thymol using supercritical carbon dioxide, with the aim of obtaining an antimicrobial packaging. Impregnation assays were carried out at 12MPa, 1h, 313K and two depressurization rates, 10.0 and 1.0MPamin−1, with impregnation yields in the range of 0.36–1.19% (w/w).The highest incorporation percentages of thymol were obtained employing the lowest depressurization rate. Moreover, thymol incorporation was favored with the presence of nanoclays. XRD results indicated the improvement of nanocomposites intercalation impregnated with thymol. Simultaneously, a phenomenological mass transfer model has been used to describe the release of thymol from the nanocomposite in ethanol 95% (v/v) solution. From the model, the effective diffusion coefficient of thymol through the nanocomposite seem to be independent of the depressurization rate employed. These values were ranged from 2.7 to 3.5×10−13m2s−1 and are significantly lower than the values obtained for free nanoclay LDPE films, which shows values ranged from 1.0 to 1.3×10−12m2s−1. This result could be explained by the formation of a polymer-nanoclay intercalated structure that slows down the thymol transfer.

Effect of addition of organomodified montmorillonite nanoclay on three-body abrasive wear behavior of maleic anhydride grafted polyethylene compatibilized ethylene-co-vinyl acetate/high density polyethylene nanocomposites

In this experimental study, effect of addition of organomodified montmorillonite (OMMT) nanoclay in increasing quantity, viz. 0, 1, 2, 3, and 4 parts per hundred on three-body abrasive wear behavior of maleic anhydride grafted polyethylene compatibilized ethylene-co-vinyl acetate/high-density polyethylene (EVA/HDPE/MA-g-PE) nanocomposites have been investigated. Experiments were conducted on rubber wheel abrasion tester, which was in-house developed according to ASTM G65-04 standard. Comparative wear volume loss and specific wear rate of polymer nanocomposites were evaluated at different loads and sliding distances with 300 µm sand abrasive size particles. It was observed that both wear volume loss and specific wear rate were increased with increase in loads. Wear volume loss was increased with increase in sliding distance while specific wear rate was decreased. Taguchi (L18) design of experiment and analysis of variance were used to optimize control factors and determine statistical significance and percentage contribution of control factors. Scanning electron microscopic images showed surface fatigue and microploughing wear mechanism on surface matrix. The aim of this study is to establish the prospects of studied polymer nanocomposites in automobile, aerospace, and similar industrial applications, where three-body abrasive wear is dominating. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

Novel thermal stable polymeric nanocomposite based on poly(ethyl vinyl ether‐alt‐maleic anhydride) and organo‐modified montmorillonite

A novel clay‐based polymeric nanocomposite was synthesized using alternative copolymer of ethyl vinyl ether and maleic anhydride. To this aim, first, montmorillonite (MMt) was modified by cetyltrimethyl ammonium bromide (CTAB) surfactant, and then in situ intercalative radical‐initiated copolymerization was performed. Different amounts of organo‐modified clay were used to determine its optimum amount in nanocomposite. The results showed that 2 wt% is the optimum amount of organo‐modified montmorillonite (OMMt) for nanocomposite preparation. Different characterization techniques including FT‐IR, XRD, SEM, UV‐Vis, DSC and TGA were used for characterization of prepared nanocomposites. The thermal behavior of nanocomposites measured by DSC and TGA techniques showed distinct increase in Tg and Tm of nanocomposites compared with pure copolymer. POLYM. COMPOS., 39:3889–3895, 2018. © 2017 Society of Plastics Engineers

Effect of an Organo-Modified Montmorillonite on the Barrier Properties of PET Nanocomposites Using a Polyester Ionomer as a Compatibilizing Agent

Poly(ethylene terephthalate)/organically modified montmorillonite (PET/o-Mt) nanocomposites were prepared via melt intercalation in a twin-screw extruder using a polyester ionomer (PETi) as compatibilizer. The o-Mt content used was 0, 1, 3 or 5 wt% and the compatibilizer/o-Mt mass ratio was 0/1, 1/1 or 3/1. The main objective was to study the effects of the addition of o-Mt and compatibilizer on the barrier properties of PET/o-Mt nanocomposites. The nanocomposites showed a significant reduction in CO2 permeability of up to 50% when compared to the neat PET, without significant change in the CO2 solubility revealing the importance of the diffusional path imputed by the organoclay on the overall permeation process. Water vapor permeability was reduced for all nanocomposites, achieving up to 30% reduction for the nanocomposite containing a compatibilizer/o-Mt mass ratio of 1/1. Overall, the nanocomposite containing 5 wt% of organoclay and compatibilizer/o-Mt mass ratio of 1/1 showed the best barrier properties.

Effects of Organo-Modified Clay Addition and Temperature on the Water Vapor Barrier Properties of Polyhydroxy Butyrate Homo and Copolymer Nanocomposite Films for Packaging Applications

Polymer nanocomposites, based on bacterial biodegradable thermoplastic polyester, poly(hydroxy-butyrate) (PHB), poly(hydroxyl-butyrate-co-hydroxy-valerate) (PHBHV), and commercial organo-modified montmorillonite (OMMT-Cloisite 10A) were prepared by solution casting method. This work aims to investigate the effect of Cloisite 10A type clay addition on the water vapour permeability properties of PHB/OMMT, and PHBHV/OMMT nanobiocomposite films. Temperature dependence of water vapor permeabilities of the films were also evaluated at various temperatures, and semi empirical permeability models were used to predict the permeability of polymer systems as a function of clay concentration and aspect ratio of nanoplates. Moreover, thermal, optical, and mechanical properties of the composites were examined by using varieties of techniques including differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), scanning electron microscope (SEM), and thin-film X-ray diffractometer (TF-XRD) respectively. Test results indicated that addition of highly intergallery swollen Cloisite 10A to the PHB/PHBHV, reduced the water vapor permeability up to 41 and 25% compared to native PHB and PHBHV films, respectively. Regarding the all mechanical properties measured, the maximum improvement was achieved for 3 wt% clay loaded samples for both PHB and PHBHV polymer composites. An increase of about 152 and 73% in tensile strength and of 77 and 18% in strain at break was achieved for PHB and PHBHV polymers, respectively. As a result of X-ray diffraction analysis, exfoliated structure was achieved at low clay loaded sample (1% w/w), however at higher concentration (3% w/w) the structure found as intercalated. Therefore, it is an evident that enhancement of characteristic properties highly depend on the dispersion level of clay particles in polymer matrix. The results obtained in this study show the feasibility of improvement of the properties of PHB based polymers with incorporation of nanoclay.

The properties of polyethylene nanocomposites based on organo-modified montmorillonite

The properties of polyethylene nanocomposites based on organo-modified montmorillonite

Effects of OMMT on the aging behaviors of halogen-antimony flame-retarded LGFPA6 composites: Flammability and thermal degradation kinetics

After a long-term thermo-oxidative exposure, compared to the long-glass-fiber reinforced polyamide 6 composite containing halogen-antimony flame retardants (FR/LGFPA6), substitution of a certain content of flame retardants with organo-modified montmorillonite (OMMT) was found to positively affect the FR/LGFPA6 composite in some cases (i.e. flammability and thermal degradation kinetics). The aged OMMT/FR/LGFPA6 composite not only was less flammable but also behaved better in the formation of char residues. All the calculated apparent activation energy obtained by the methods of Friedman, Flynn-Wall-Ozawa and Coats-Redfern in a dynamic measurement showed an obvious increase for the OMMT/FR/LGFPA6 composite after aging, a theoretical evidence for its improved flame retardancy.

Tailored montmorillonite nanoparticles and their behaviour in the alkaline cement environment

This is the first time an analytical protocol is proposed to investigate and live-monitor the behaviour of montmorillonite nanoparticles, of different natures, in alkaline cement environment (pH of 12–13). In this study inorganic and organomodified montmorillonite nanoparticles were characterised via TEM, XRD, SEM-EDX and TGA. The inorganic montmorillonite used consisted of a purified montmorillonite commercially available as HPS-clay, and an organomodified montmorillonite, namely XDB-organoclay, consisted of purified montmorillonite modified with Noramonium MB2HT salt. Both montmorillonite nanoparticles were tailored to increase their compatibility with the hydrating cement environment. This gave rise to three different slurries: (i) reference-slurry, (ii) inorganic-slurry, and (iii) organic-slurry. The slurries were characterised and investigated through UV/vis, to measure suspension quality in terms of physical stability and rheological properties, and by AFM and FTIR to determine the chemical stability. The results indicated that the organic-slurry can offer a good stability, preventing aggregation of the clay particles at the targeted pH (13). The inorganic-slurry showed a reduction in surface charge and increased double layer repulsion. At pH13 it was possible to obtain dispersion of the reference slurry although it underwent gelation and became viscous. The research findings informed that the inorganic slurry favours miscibility of the montmorillonite nanoparticles with cement particles and offers additional nucleation sites for CSH. Therefore it can be considered an alternative to organomodified montmorillonite as an addition in cement based materials.

Two-dimensional growth of crystalline nanofiber fabricated from Gemini-type amphiphilic diamide derivative inducing the thixotropic property.

The formation of a nanofiber morphology at the mesoscopic scale and the molecular-level packing of a gemini-type amphiphilic diamide derivative with two hydrocarbons were investigated from two perspectives. First, it was confirmed that a diamide derivative with two hydrocarbons forms crystalline nanofibers even in a monomolecular layer. The height, thickness, and lattice spacing of the two-dimensional orthorhombic system of this crystalline nanofiber in the monolayer of a diamide derivative with two hydrocarbons are 5, 30, and 0.4nm, respectively. Next, it was determined that the fibrous growth of the diamide derivative with two hydrocarbons, which contributes to the thixotropic ability, can be achieved by the addition of a quaternary ammonium cation with long chains, modified with montmorillonite. Here, the interlayer spacing was about 3.8nm for the organo-modified montmorillonite and was consistent with the layer spacing of the diamide derivative having two hydrocarbons. The surface pressure-area isotherms of the mixed monolayers suggest that there is miscibility between these materials. From "the affinity due to the van der Waals interaction between the terminal groups of the alkyl chains" and the "similarity of layer spacing," epitaxial growth is expected.

Alkyd‐clay nanocomposites for improved anticorrosion and mechanical performance of coating

Exfoliated nanoclays in polymers are a class of inorganic composite which provides reinforcement along with barrier properties to polymer films owning to their high aspect ratios. Despite of having good adhesion to the substrate, alkyd polymers generally shows poor performance in corrosion resistance. Herein, we have explored the role of exfoliated organo‐modified montmorillonite (O‐MMT) clays in alkyd resins for improved barrier and mechanical properties. The exfoliation of nanoclay in alkyd polymer was performed in two steps—first intercalation of long chain amine in Na‐montmorillonite via ion exchange and secondly, their subsequent exfoliation in polymer by applying high shear and ultrasonication. O‐MMT clays and their composites were thoroughly characterized by Fourier transform infrared (FT‐IR), Thermogravimetric analysis and X‐ray diffraction analysis. Paint was formulated using polymer clay composite for evaluation of their performance in real coating formulation. Anticorrosion performance of coating is assessed by salt spray analysis whereas dynamic mechanical analysis and universal testing machine analysis carry out to measure the mechanical strength of coating. POLYM. COMPOS., 39:2922–2931, 2018. © 2017 Society of Plastics Engineers

Water Transport Properties of Poly(butylene succinate) and Poly[(butylene succinate)-co-(butylene adipate)] Nanocomposite Films: Influence of the Water-Assisted Extrusion Process

Poly(butylene succinate) (PBS) and poly[(butylene succinate)-co-(butylene adipate)] (PBSA)-based composite films loaded with 5 wt % of fillers (native or organo-modified montmorillonites) were extruded using a standard protocol or assisted by water injection. In the resulting composite films, the filler morphology was altered, as evidenced by TEM images. The CNa aggregates were broken with the help of water injection, and the exfoliation/dispersion levels of C30B were dependent on the matrix. By considering the degree of crystallinity of the polymer matrix, the nature of the fillers, and also the processing conditions, the film (micro)structure was successfully correlated to the water (liquid and vapor) behavior of the PBS- and PBSA-based films, studied by means of sorption and permeation measurements. The water permeability and diffusivity were significantly reduced even with an increased water sorption, depending on the matrix and the clay morphology or nature. Specifically, concomitant effects such as ...

Nanoclays for Lipase Immobilization: Biocatalyst Characterization and Activity in Polyester Synthesis.

The immobilization of Candida antarctica lipase B (CALB) was performed by physical adsorption on both neat and organo-modified forms of sepiolite and montmorillonite. The influence of different parameters, e.g., solvent, enzyme loading, cross-linking, and type of clay support, on immobilization efficiency and catalyst hydrolytic activity has been investigated. The highest hydrolytic activities were obtained for CALB immobilized on organo-modified clay minerals, highlighting the beneficial effect of organo-modification. The esterification activity of these CALB/organoclay catalysts was also tested in the ring-opening polymerization of ε-caprolactone. The polymerization kinetics observed for clay-immobilized catalysts confirmed that CALB adsorbed on organo-modified montmorillonite (CALB/MMTMOD) was the highest-performing catalytic system.

Enhancement of thermal and mechanical properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites by ultrasound-assisted in-situ emulsion polymerization

This study reports synthesis and characterization of poly(MMA-co-BA)/Cloisite 30B (organo-modified montmorillonite clay) nanocomposites by ultrasound-assisted in-situ emulsion polymerization. Copolymers have been synthesized with MMA:BA monomer ratio of 4:1, and varying clay loading (1–5wt% monomer). The poly(MMA-co-BA)/Cloisite 30B nanocomposites have been characterized for their thermal and mechanical properties. Ultrasonically synthesized nanocomposites have been revealed to possess higher thermal degradation resistance and mechanical strength than the nanocomposites synthesized using conventional techniques. These properties, however, show an optimum (or maxima) with clay loading. The maximum values of thermal and mechanical properties of the nanocomposites with optimum clay loading are as follows. Thermal degradation temperatures: T10%=320°C (4wt%), T50=373°C (4wt%), maximum degradation temperature=384°C (4wt%); glass transition temperature=64.8°C (4wt%); tensile strength=20MPa (2wt%), Young’s modulus=1.31GPa (2wt%), Percentage elongation=17.5% (1wt%). Enhanced properties of poly(MMA-co-BA)/Cloisite 30B nanocomposites are attributed to effective exfoliation and dispersion of clay nanoparticles in copolymer matrix due to intense micro-convection induced by ultrasound and cavitation. Clay platelets help in effective heat absorption with maximum surface interaction/adhesion that results in increased thermal resistivity of nanocomposites. Hindered motion of the copolymer chains due to clay platelets results in enhancement of tensile strength and Young’s modulus of nanocomposite. Rheological (liquid) study of the nanocomposites reveals that nanocomposites have higher yield stress and infinite shear viscosity than neat copolymer. Nonetheless, nanocomposites still display shear thinning behavior – which is typical of the neat copolymer.

Influence of Organically Modified Nanoclay on Thermal and Combustion Properties of Bagasse Reinforced HDPE Nanocomposites

The nanocomposites of high density polyethylene (HDPE)/bagasse flour (BF) with different contents of the organomodified montmorillonite (OMMT) were produced by melt blending process. The thermal stability and combustion behavior of nanocomposites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry, and cone calorimeter tests. The results of TGA data of the nanocomposites indicated that the OMMT greatly enhanced the thermal stability, and char residues of the HDPE/BF blends gradually increased with increasing the OMMT content. The activation energy was determined to describe the energy consumption of the initiation of the thermal degradation process. The composites produced with the 6 phc OMMT had the highest activation energy values among the evaluated composites (106 kJ/mol), whereas composites without nanoclay exhibited the lowest one. Furthermore, as the OMMT was incorporated into the nanocomposites, the melting temperature (Tm), crystallization temperature (Tc) melting enthalpy (∆Hm) and crystallinity (Xc) of HDPE/BF blends increased. The findings showed that the OMMT effectively boosted the flame retardancy of nanocomposites due to the formation of the carbonaceous silicate char shields delayed time to ignition and the combustion process was remarkably hindered.

Complete Defluorination of Perfluorinated Compounds by Hydrated Electrons Generated from 3-Indole-acetic-acid in Organomodified Montmorillonite.

Here we describe a unique process that achieves complete defluorination and decomposition of perfluorinated compounds (PFCs) which comprise one of the most recalcitrant and widely distributed classes of toxic pollutant chemicals found in natural environments. Photogenerated hydrated electrons derived from 3-indole-acetic-acid within an organomodified clay induce the reductive defluorination of co-sorbed PFCs. The process proceeds to completion within a few hours under mild reaction conditions. The organomontmorillonite clay promotes the formation of highly reactive hydrated electrons by stabilizing indole radical cations formed upon photolysis, and prevents their deactivation by reaction with protons or oxygen. In the constrained interlayer regions of the clay, hydrated electrons and co-sorbed PFCs are brought in close proximity thereby increasing the probability of reaction. This novel green chemistry provides the basis for in situ and ex situ technologies to treat one of the most troublesome, recalcitrant and ubiquitous classes of environmental contaminants, i.e., PFCs, utilizing innocuous reagents, naturally occurring materials and mild reaction conditions.

Transient materials from thermally-sensitive polycarbonates and polycarbonate nanocomposites

Transient materials, or materials with designed short lifetimes, are of great interest in many fields of research. This work describes the development of polycarbonates as a thermally-triggered vaporizable substrate platform. Good mechanical properties over operational temperature ranges in combination with fast and clean decomposition at slightly higher temperatures create an effective transient substrate. Therefore, characterization of the thermal and mechanical properties of vaporizable polycarbonates (VPC) and their composites are indispensable for creating such materials systems. A tailor-made VPC and its blends with a commercially available poly(propylene carbonate) were investigated. Both polycarbonates have acid sensitive backbones; therefore, when combined with an acid source, catalyzed decomposition was observed within minutes, achieving a range of decomposition temperatures between 160 °C and 250 °C. Polymer with organo-modified montmorillonite nanocomposites were investigated to provide structural support. These nanocomposites resulted in Young's moduli ranging from 4 MPa to ∼2 GPa. Their tunable nature allows for designer control over the substrate's properties based on application needs.