Modified Montmorillonite Nanocomposites Research Articles

Design of mucoadhesive thiomer/organically modified montmorillonite nanocomposites: Evaluation of controlled drug release

This present work introduces a novel thiomer/nanoclay nanocomposite material with mucoadhesive and controlled release properties that has been prepared and evaluated as a potential drug carrier system. This hybrid material is based on thiolated alginate and organically modified montmorillonite (MMT). Alginate thiomer was synthesized by immobilization of l-cysteine on alginate backbone via carbodiimide reaction. Thiol/disulfide groups were identified and quantified by FT-IR, 1H NMR and Ellman's method. Rheological assays as preliminary in vitro mucoadhesion test using mucin show that complex viscosity increases until ∼7-fold compared to unmodified alginate/mucin, and G’ > G″ is present in thiomers, compared with G” > G′ present in unmodified alginate, which indicate strong interactions between thiomer and mucin. Thiomer/nanoclay nanocomposites were prepared by film casting method and characterized by TGA, XRD, TEM and rheometry. Nanocomposites maintain rheological properties showed by thiolated alginate when they are tested with mucin, increasing complex viscosity until ∼8-fold respect a nanocomposite formulation based on unmodified alginate. The release of deltamethrin from nanocomposite films was studied and the impact of the amount of nanoclay (0–7%) and four types of organic modifiers in MMT were evaluated. Different kinetic models were evaluated in order to study the mechanism involved in drug release. Zero, first, Higuchi and Korsmeyer-Peppas model were evaluated, being the last two kinetic models the ones with better fitting and higher values of R2. The presence of nanoclay on the formulation influence significantly (P < 0.001) deltamethrin short-term release showing an anomalous and Case-II transport mechanism. Compared with a Fickian diffusion when nanoclay is absent in the formulation. The diffusion coefficient D could decrease until ∼7-fold compared to a formulation without nanoclay. Long-term release is significantly influenced (P < 0.0001) by the chemical nature of organic modifier used on nanoclay and its interaction with the drug. This thiomer/nanoclay nanocomposite material could be a useful prospect as a mucoadhesive material for drug carrier with controlled drug release properties.

Effects of dioctyl phthalate on the properties of poly(vinyl chloride)/organically modified montmorillonite nanocomposites

The effects of dioctyl phthalate (DOP) loading on morphology and thermal and mechanical properties of the poly(vinyl chloride)/organically modified montmorillonite/DOP (PVC/O-MMT/DOP) nanocomposites are studied in this paper. Results of transmission electron microscope (TEM) indicate that O-MMT is partially intercalated and exfoliated in all PVC/O-MMT/DOP nanocomposites. It shows that the addition of DOP has no obvious influence on the dispersion of O-MMT in the PVC/O-MMT/DOP nanocomposites. Young’s modulus and tensile strength of the PVC/O-MMT/DOP nanocomposites are significantly decreased as the amount of DOP is increased. The thermal degradation onset temperature and glass transition temperature (Tg) of the PVC/O-MMT/DOP nanocomposites are decreased as the amount of DOP is increased. On the other hand, the elongation at break of the PVC/O-MMT/DOP nanocomposites is increased as the amount of DOP is increased. Also, the first thermal degradation weight loss (ΔY) of the PVC/O-MMT/DOP nanocomposites is increased as the amount of DOP is increased. While increasing DOP loading, the PVC/O-MMT/DOP nanocomposites change from a rigid product to a semirigid product and finally into a flexible product.

Structure and properties of Polylactide/Poly(butylene succinate)/Organically Modified Montmorillonite nanocomposites with high-efficiency intercalation and exfoliation effect manufactured via volume pulsating elongation flow

The Polylactide (PLA)/Poly(butylene succinate)(PBS)/Organically Modified Montmorillonite (OMMT) nanocomposites with different ratio were manufactured via intense volume pulsating elongation flow. The nanostructure, microscopic morphology, crystallization property, thermostability, mechanical properties were well investigated. The processing mechanism was well discussed. The OMMT (C30B) was well dispersed, intercalated, and exfoliated in all the nanocomposites. The interlayer spacing doubled in all the nanocomposites. The clay mainly dispersed in PBS and located at the interface of PLA/PBS in all samples, which could be predicted by the interfacial tension, enthalpic interaction, and wettability parameter. Diameter of the in situ formed PBS fiber decreased as the C30B content increased. Nanocomposites with PBS content range from 30% to 70% displayed the co-continuous structure. The Young's modulus and elongation at break of the blend increased significantly by adding the clay.

Investigation on the Thermal Degradation Kinetics of Polypropylene/Organically Modified Montmorillonite Nanocomposites with Different Levels of Compatibilizer

AbstractPolypropylene/organically modified montmorillonite (OMMT) nanocomposites are prepared with different levels of compatibilizer (maleic anhydride functionalized polypropylene) and OMMT. A specially designed polymer nanocomposite injection molding compounder with a hyperbolic nozzle is used to prepare the nanocomposites. The thermal kinetic parameters, the activation energy, pre‐exponential factor, and the reaction model are estimated using isoconversional methods. The activation energy of virgin polypropylene is slightly higher than the polypropylene/OMMT nanocomposites. However, the presence of the compatibilizer is the vital reason for the lower activation energy in the polypropylene/OMMT nanocomposites. The reaction model explains the complexity of the reaction in the presence of OMMT and its influence on the accelerated charring in the later stages of degradation. The optimum working temperature of the prepared polypropylene/clay nanocomposites is significantly higher thus proving that OMMT improves the thermal stability of the nanocomposites. The polypropylene with 5% OMMT and 10% compatibilizer in its weight proportion has the optimum working temperature of 198 °C for 20 000 h before losing its integrity.

Development of Poly(L-lactic acid)/Organically Modified Montmorillonite Nanocomposites for the Fabrication of Orthodontic Anchoring Screws

Development of Poly(L-lactic acid)/Organically Modified Montmorillonite Nanocomposites for the Fabrication of Orthodontic Anchoring Screws

Organoclay nanocomposites of post-industrial waste poly(butylene terephthalate) from automotive parts.

Polymeric nanocomposites are novel materials of huge interest owing to their favourable cost/performance ratio with low amount of nanofillers, improved thermal resistance, flame retardancy and mechanical properties in relation to their matrices. In this work, composites based on post-industrial waste or primary recycled poly(butylene terephthalate) and 5 wt.% of organic modified montmorillonite clays were melt compounded using a twin-screw extruder. A 2(2) factorial experimental design was used to study the compounding and processing variables: Organic modified montmorillonite with one or two hydrogenated tallow (initial basal spacing) and screw speed of the extruder. X-ray diffraction and transmission electron microscopy suggest that a partial exfoliation of the organoclay in the recycled poly(butylene terephthalate) matrix was achieved for organic modified montmorillonite with lower initial basal spacing. On the other hand, formulations containing organic modified montmorillonite with higher initial basal spacing showed only intercalated structure. The recycled poly(butylene terephthalate)-organic modified montmorillonite nanocomposites did not drip flaming material during burning tests. Storage of dynamic-mechanical, tensile and flexural moduli of the recycled poly(butylene terephthalate)-organic modified montmorillonite were improved when compared with both virgin and recycled poly(butylene terephthalate)s, mainly for nanocomposites formulated at a lower initial basal spacing organoclay. This could be related to a better diffusion of polymer into organic modified montmorillonite layers compared with the higher initial basal spacing organoclay. The improvements on the physical properties of recycled poly(butylene terephthalate) showed the feasibility to add value to primary recycled engineering thermoplastics with a very small amount of organic modified montmorillonite.

Modified rapeseed oil/silane coupling agent-montmorillonite nanocomposites prepared by in-situ method: Synthesis and properties

The environmentally friendly flame retardant fatliquoring agent has aroused the attention of tannery industry. In this study, rapeseed oil and montmorillonite were used to prepare flame retardant fatliquoring agent. Firstly, silane coupling agent modified montmorillonite was prepared from Na-montmorillonite (Na-MMT) and silane coupling agent γ-aminopropyltriethoxysilane. Then the modified rapeseed oil/silane coupling agent modified montmorillonite nanocomposites was obtained by using silane coupling agent modified montmorillonite and rapeseed oil through in-situ method. The as-prepared modified rapeseed oil/silane coupling agent modified montmorillonite was applied in fatliquoring process of goatskin garment leather. Flame retardancy, softness and mechanical properties of the fatliquored leather were tested. Compared with those of the leather fatliquored by modified rapeseed oil (MRO), flame retardancy, softness and tear strength of the leather treated by modified rapeseed oil/silane coupling agent modified montmorillonite were improved. The results of environmental impact assessments indicated that the modified rapeseed oil/silane coupling agent modified montmorillonite nanocomposites did not increase the pollution to the environment.

The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na‐MMT, the surface of Na‐MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion‐exchange and adsorption technique. Both Fourier transform infrared and X‐ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt‐blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co‐modified MMT (C‐MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C‐MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C‐MMT nanocomposites with 5.0 wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C‐MMT. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Application of design of experiments, response surface methodology and partial least squares regression on nanocomposites synthesis

We present an integral chemometric treatment for characterization and synthesis of low-density poly(ethylene)/organically modified montmorillonite nanocomposites using direct melt processing method, complementing design of experiment (DOE), response surface methodology (RSM) and partial least squares (PLS) regression. A central composite circumscribed DOE was used to study the influence of four processing parameters—concentration of clay (Clay%), concentration of compatibilizer (Comp%), mixing temperature (T mix) and mixing time (t mix)—on six nanocomposites properties: interlayer distance, decomposition temperature, melting temperature, Young’s modulus, loss modulus and storage modulus. PLS-regression was used to simultaneously correlate parameters and responses. RSM was used to explore interactions among parameters and predict nanocomposite properties on the experimental region. The six responses were simultaneously PLS-modeled with R 2 = 0.768 (p ≤ 0.05) being Clay% and Comp% the most important parameters and t mix the least influential. Moreover, significant (p ≤ 0.05) and complex interactions among Clay%, Comp% and t mix were found. A complementary interpretation of score and loading plots, coefficient plots, variable importance plots and response surface plots are explained to show how to find the optimal combination of processing parameters according the desired nanocomposite properties.

Effect of montmorillonoite modification and maleic anhydride‐grafted polypropylene on the microstructure and mechanical properties of polypropylene/montmorillonoite nanocomposites

ABSTRACTTwo types of modified montmorillonite (MMT) were achieved using octadecylamine as the modifying agent by the methods of dry process and wet route. Polypropylene (PP)/MMT nanocomposites were prepared using the melt mixing technique and employing maleic anhydride‐grafted polypropylene (PP‐MA) as the compatibilizer. The modification of montmorillonite was characterized by fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscope (SEM). The effect of MMT modification and PP‐MA on the microstructure and properties of PP/MMT nanocomposites was investigated by SEM, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and polarizing microscopy. The results show that organic montmorillonite modified by wet process (WOMMT) has a large d‐spacing increment; whereas montmorillonite modified by dry process (DOMMT) shows little d‐spacing increment. Furthermore, the mechanical properties of composites incorporating WOMMT are better than that containing DOMMT. As a third component, the addition of PP‐MA benefits the formation of exfoliated structure and the dispersion of MMT in PP matrix, and hence, enhances the physical properties of the nanocomposite. With the presence of PP‐MA, the highly dispersed MMT increases the number of spherulite crystals, enhances the melting enthalpy, improves the thermal stability, and induces the desired tiny crazes more effectively. MMT increases the storage modulus (E′) and glass‐transition temperature (Tg) of PP because of the stiffness of MMT layers, but PP‐MA decreases them owing to its high melt flow index, both of which were in favor of improving the physical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3952–3960, 2013

Transport of organic solvents through natural rubber/nitrile rubber/organically modified montmorillonite nanocomposites

The article describes the transport phenomenon of some commonly used laboratory organic solvents which differ in their solubility parameter value through polymer blend nanocomposites membrane prepared by melt mixing. The three solvents that were used are hexane, toluene and xylene which differed widely in their solubility parameter values. The motivation for the study was to know the effect of solubility parameter on the diffusion transport properties of NR/NBR (natural rubber/nitrile rubber) blends. The solvent uptake, diffusion, sorption and permeation constants were investigated and were found to decrease with organically modified montmorillonite (OMt) content at lower loading. The mode of transport through NR/NBR nanocomposites was found to be anomalous. The difference in solubility parameter value greatly influenced the transport properties. The dependence of various properties on OMt content was supported by morphological analysis data. The effect of blend ratio, solvent size and OMt loading on the diffusion of aromatic and aliphatic solvents through NR/NBR blend systems were investigated. The swelling coefficient values also decreased upon the addition of fillers indicating the presence of hindered path for solvents to diffuse into the polymer matrix. The better reinforcement at lower filler loading was confirmed from the cross-link density values and mechanical properties. The transport data obtained were applied to mathematical models for predicting the diffusion behaviour through nanocomposite membranes and to elucidate the physical mechanism of transport. .

Optimization of processing parameters for the synthesis of low‐density polyethylene/organically modified montmorillonite nanocomposites using X‐ray diffraction with experimental design

AbstractThe influence of the processing parameters on the synthesis of low‐density polyethylene (LDPE)/organically modified montmorillonite (OMM) nanocomposite films was studied using experimental design. Intercalation in the nanocomposites was analysed using X‐ray diffraction and verified using atomic force microscopy. Four direct melt processing parameters were studied to obtain surface maps of intercalation in the nanocomposites: concentration of OMM (clay‐%), concentration of Polybond® 3149 (compatibilizer‐%), mixing temperature (Tmix) and mixing time. An ANOVA validated the polynomial function, and intercalation maps from response surface methodology (RSM) were obtained. The clay‐% parameter had the most significant effect, and Tmix showed no significant effect on intercalation (p &lt; 0.05). A strong synergic interaction between clay‐% and compatibilizer‐% was observed, which is not possible to detect using univariate experiments. RSM provides a powerful tool for choosing the best processing conditions that lead to formulations with the highest intercalations by considering the main factors and their interactions. © 2013 Society of Chemical Industry

Featured structures of fire residue of high‐impact polystyrene/organically modified montmorillonite nanocomposites during burning

SUMMARYThe structures and constituents of fire residue of high‐impact polystyrene/organically modified montmorillonite (HIPS/OMMT) nanocomposite during burning was investigated using scanning electron microscopy, thermogravimetric analysis, X‐ray diffraction analysis, and elementary analysis techniques and based on quenched samples obtained during the cone calorimeter test. It was found that during burning the HIPS/OMMT nanocomposite tends to form a two‐layer structure of fire residue on the surface of material. This two‐layer structure contains a thin and condensed skin layer at the top and a loose and expanded cellular layer under the skin layer. The skin structure contains many small sizes of voids, while the cellular structure includes a large number of large‐size voids. Both the skin and cellular layers are composed of mainly montmorillonite platelets, which are aggregated to form a nanoscale network structure, in which certain amounts of carbonaceous char components are trapped during burning but decompose above approximately 550°C in the presence of oxygen. Finally, an idealized model was put forward to explain the featured structures of fire residues for the nanocomposite studied. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Structural, thermal and morphological properties of aqueous hybrid emulsion of silylated poly (urethane)/organic modified montmorillonite nanocomposites based on a new silicone and imide ring containing vinylic macromonomer

A new silicone and imide ring containing vinylic macromonomer, N-trimethylsiloxyethyltrimellitilimidomethacrylate (TMSETMIM), has been synthesized for the formulation of waterborne polyurethane (PU). A vinyl group containing silicone, the (3-methacryloyloxypropyl) trimethoxysilane (MPTMS) was used for comparison of the effects of silicone type with TMSETMIM on the PU. Then, a series of new siliconized PU hybrid nanocomposites, were successfully synthesized by the emulsion polymerization in the presence of organic modified montmorillonite (OMMT) and an aqueous PU dispersion using ammonium peroxodisulfate (APS) as an initiator. The PU dispersion was synthesized by a polyaddition reaction of hexamethylene diisocyanate (HMDI), on polypropylene glycol (PPG-1000) and dimethylol propionic acid (DMPA) as a chain extender. The obtained NCO chain ends reacted with water (which acts as a further chain extender producing some urea bonds). The structural elucidation of monomer was carried out by FTIR, 1H-NMR, and 13C-NMR spectroscopic techniques. The copolymers were also characterized by using FTIR. Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphologies of the copolymers were characterized with scanning electron microscopy (SEM) and transition electron microscopy (TEM) and then the effects of silicone concentrations on the water absorption ratio was examined. The formed film from the hybrid emulsion containing TMSETMIM could provide obviously higher water-resistance property in comparison with MPTMS. Also, the heat stability increases while the Tg decreased.

Effect of electron beam irradiation on the mechanical and thermal properties of intumescent flame retarded ethylene-vinyl acetate copolymer/organically modified montmorillonite nanocomposites

Ethylene-vinyl acetate copolymer (EVA) flame retarded by a combination of intumescent flame retardants (IFR) and organically modified montmorillonite (OMMT) have been crosslinked by high-energy electron beam irradiation. The structure was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of electron beam irradiation on the thermal, mechanical and dynamic mechanical properties of the irradiated EVA nanocomposites were investigated. The XRD and TEM results demonstrated that the OMMT was well dispersed in the EVA nanocomposites. The LOI and UL-94 results showed that a synergistic effect on the flame retardancy of EVA nanocomposite existed between the IFR and OMMT. With the addition of 1 wt% OMMT and 24 wt% IFR, the LOI value of EVA/IFR/OMMT nanocomposite increased from 30.5 % to 33.5 %. The mechanical properties of the irradiated EVA nanocomposite were evidently improved at 160 kGy dosage with the increase in the tensile strength to 18.5 MPa. Thermal oxidative degradation of the flame-retardant EVA/IFR/OMMT nanocomposites was characterized by thermogravimetric analysis/infrared spectrometry (TG–IR) and real-time Fourier transformed infrared spectroscopy (RT-FTIR).

Poly(vinyl chloride)/metallic oxides/organically modified montmorillonite nanocomposites: Preparation, morphological characterization, and modeling of the mechanical properties

AbstractPoly(vinyl chloride), metallic oxides (from copper, molybdenum, and zinc), and organically modified montmorillonite (O‐MMT) nanocomposites were prepared in a melt‐blending or intercalation‐in‐the‐molten‐state process. The morphology of the nanocomposites was evaluated with X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Properties, such as the mechanical, thermal, and electrical properties, and the dynamic thermal stability against dehydrochlorination were also evaluated. Nanocomposites with a hybrid intercalated/exfoliated structure were obtained in all of the situations considered, as demonstrated by the XRD and TEM results and indirectly by the increment of Young's modulus of the formulations with increasing amount of O‐MMT incorporated. The modeling of Young's modulus by the Halpin–Tsai, Hui–Shia, and Lewis–Nielsen theories showed that the process of nanocomposite preparation allowed the aspect ratio of the clay particles to increase; these values were comparable to those nanocomposites obtained by other researchers with different polymeric matrices and methodologies. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Isothermal degradation of poly(3‐hydroxybutyrate)/organically modified montmorillonite nanocomposites

AbstractPolymer nanocomposites consisted of biodegradable poly(3‐hydroxybutyrate) (PHB) and organically modified montmorillonite Cloisite25A (OMMT), prepared by the solution‐casting method, were isothermally degraded for 120 min at 230, 235, 240, and 245°C in the nitrogen atmosphere. The addition of OMMT increases the thermal stability of PHB, and the most pronounced effect has the addition of 7 wt% of OMMT. Kinetic analysis was performed using reduced time plots and model‐free isoconversional methods. The empirical kinetic triplets (E, A, and g(α)) for the isothermal degradation of pure PHB and PHB/OMMT nanocomposites were determined. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Kinetic analysis of the non-isothermal degradation of poly(3-hydroxybutyrate) nanocomposites

Poly(3-hydroxybutyrate)/organically modified montmorillonite nanocomposites (PHB/25A) were prepared by the solution-intercalation method. The non-isothermal degradation of pure PHB and PHB/25A nanocomposites was investigated in the temperature range 50–500 °C at four heating rates (2.5, 5, 10 and 20 °C min −1). Kinetic analysis of the non-isothermal degradation of pure PHB and PHB/25A nanocomposites was performed using isoconversional (Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose and Friedman) methods and the invariant kinetic parameters method. The true kinetic triplets ( E, A, and f( α)) were determined.

Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization

AbstractTwo series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (Tcm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (Tm) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the Tcm and Tm peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (Tg) irrespective of clay content, and a noticeable decrease in Tg with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Thermotropic liquid crystalline polyester nanocomposites via in situ intercalation polycondensation

AbstractA thermotropic liquid crystalline polyester (TLCP)/organoclay nanocomposite was synthesized via in situ intercalation polycondensation of diethyl‐2,5‐dihexyloxyterephthalic acid and 4,4′‐biphenol in the presence of organically modified montmorillonite (MMT). The organoclay, C18‐MMT, was prepared by the ion exchange of Na+‐MMT with octadecylamine chloride (C18‐Cl−). TLCP/C18‐MMT nanocomposites were prepared to examine the variations of the thermal properties, morphology, and liquid crystalline phases of the nanocomposites with clay content in the range of 0–7 wt%. It was found that the addition of only a small amount of organoclay was sufficient to improve the thermal behavior of the TLCP hybrids, with maximum enhancement being observed at 1 wt% C18‐MMT. Copyright © 2008 John Wiley &amp; Sons, Ltd.