Organically Modified MMT Research Articles

Thermo-oxidative stability and flammability properties of bamboo/kenaf/nanoclay/epoxy hybrid nanocomposites.

In this study, three types of nanoclay [halloysite nanotube (HNT), montmorillonite (MMT) and organically modified MMT (OMMT)] were incorporated into bamboo/kenaf (B/K) reinforced epoxy hybrid composites to compare their thermo-oxidative (TOD) stability and flammability properties. B/K (50 : 50) hybrid nanocomposites were fabricated by adding 1% loading (by weight) nanoclay through a hand lay-up technique. Wide angle X-ray scattering (WAXS) and field emission scanning electron microscopy (FESEM) were used to study the morphology of the nanoclay–epoxy mixture. The TOD stability of the hybrid nanocomposites was studied with a thermogravimetry analyzer (TGA) under oxygen atmosphere. The flammability properties were evaluated using the Underwriters Laboratories 94 horizontal burning test (UL-94HB), limiting oxygen index (LOI), cone calorimetry and smoke density test. The morphological study reveals that MMT/epoxy and HNT/epoxy are highly agglomerated while OMMT/epoxy reveals a more uniform distribution morphology. The obtained results reveal that B/K/HNT shows better TOD stability below 300 °C, but B/K/MMT and B/K/OMMT show high residue content and decomposition temperatures above 300 °C. The flame retardancy of the hybrid nanocomposites improved with the loading of all types of nanoclay, but B/K/OMMT shows higher flame retardancy than B/K/MMT and B/K/HNT hybrid nanocomposites. Hybrid nanocomposites show improvement in flame properties in terms of peak heat release rate (pHRR), total heat release, fire growth rate index (FIGRA) and maximum average rate of heat emission (MARHE) and smoke growth rate index (SMOGRA) indicators. The findings from this work can be utilized to prepare high-performance fire retardant natural fiber reinforced epoxy hybrid composites for automotive and construction applications to save human lives.

Compatibilization of clays and hydrophobic polymers: the case of montmorillonite and polyetheretherketone

In the last three decades, nanoclay fillers have been increasingly used to improve the mechanical, thermal, barrier and biological properties of the polymers. Nevertheless, incorporation of clays into the hydrophobic polymer matrices leads to the formation of the microcomposites with the minimal improvement in properties. To overcome the intrinsic incompatibility between the clays and the hydrophobic polymers, clay particles are organophilized using organic modifiers. The organic modifier should be thermodynamically miscible with the polymer. In the case of the composites prepared at high temperatures, the organic modifier should also have a high thermal stability to withstand the processing temperature. Taking into account these requisites, this study proposes a novel procedure for screening the diverse sets of the ionic liquids to find the most appropriate organic modifiers for compatibilization of the clays and any given hydrophobic polymers. The proposed procedure has been used to find the appropriate organic modifier to compatibilize montmorillonite clay (MMT) and polyetheretherketone (PEEK). Composites of PEEK filled with MMT and the organically modified MMT (OMMT) were synthesized via melt compounding. Then, they were characterized by FTIR, XRD and TEM. The results showed that the selected organic modifier satisfied both the processing requirements and the thermodynamic considerations and improved the dispersion of MMT particles within the PEEK matrix. The XRD patterns and TEM micrographs confirmed the formation of the PEEK/OMMT nanocomposite with intercalated/exfoliated morphology. The findings of this study provide a practical means for compatibilization of immiscible clays and polymers.

Oil palm waste based hybrid nanocomposites: Fire performance and structural analysis

This study presents an investigation of the flame retardant (FR) tendency of modified and chemically treated nano oil palm empty fruit bunch (OPEFB) filler to improve the fire properties of highly combustible kenaf/epoxies. In this work hybrid nanocomposites were fabricated by adding nano OPEFB filler at 3% loading (by weight) through a hand lay-up technique. Fabricated hybrid nanocomposites were then compared to and analyzed with pure kenaf/epoxy, montmorillonite (MMT) and organically modified MMT (OMMT) hybrid nanocomposites. Flammability performance and functional group analysis of composites and hybrid nanocomposites are evaluated through limiting oxygen index (LOI), Underwriters Laboratories vertical burning test (UL-94V) burning test and Fourier transform infra-red (FTIR) spectroscopy. The obtained results revealed that all kenaf/epoxy hybrid nanocomposites possess better (and satisfactory) flame retardancy properties in comparison to kenaf/epoxy composites, relatively little flame dripping or ignition. The superior flame retardancy of nano OPEFB hybrid nanocomposites are attributed to an intense synergistic flame retardation effect in the gaseous phase between tin and bromine elements that promote the free radical mechanisms to suppress the combustion. Flame tests show that MMT and OMMT hybrid nanocomposites display flame retardancy through physical barrier (char) formation at the composite surface in condensed phase. FTIR spectra displayed the presence of a specific functional group of added nano fillers in their respective hybrid nanocomposites.

Thermal aging and accelerated weathering of PVC/MMT nanocomposites: Structural and morphological studies

ABSTRACTThis work focuses on the influence of weathering factors—UV radiation, humidity, and temperature on the structure and morphology of poly(vinyl chloride)/montmorillonite (PVC/MMT) nanocomposites obtained by melt blending. It has been observed that organically modified MMT (OMMT) deteriorates the weathering resistance, the thermal behavior, as well as the long‐term stability of PVC. Decomposition of the organic modifier of MMT causes substantial color changes in the PVC nanocomposites as it facilitates the dehydrochlorination process of the polymer. However, the nonmodified MMT provides some stabilization during PVC weathering. The nanocomposites after annealing are characterized by higher glass transition temperature. The increase in heat capacity step (Δcp) during glass transition suggests that in the PVC composites with nonmodified MMT stronger molecular interactions between the polymer and clay platelets occur than in PVC/OMMT nanocomposites. The scanning electron microscopy images on the surface and the cross section show that thermal aging and weathering proceed by different mechanisms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42090.

Organically modified montmorillonite and chitosan–phosphotungstic acid complex nanocomposites as high performance membranes for fuel cell applications

Nanocomposite membranes based on polyelectrolyte complex (PEC) of chitosan/phosphotungstic acid (PWA) and different types of montmorillonite (MMT) were prepared as alternative membranes to Nafion for direct methanol fuel cell (DMFC) applications. Fourier transform infrared spectroscopy (FTIR) revealed an electrostatically fixed PWA within the PEC membranes, which avoids a decrease in proton conductivity at practical condition. Various amounts of pristine as well as organically modified MMT (OMMT) (MMT: Cloisite Na, OMMT: Cloisite 15A, and Cloisite 30B) were introduced to the PEC membranes to decrease in methanol permeability and, thus, enhance efficiency and power density of the cells. X-ray diffraction patterns of the nanocomposite membranes proved that MMT (or OMMT) layers were exfoliated in the membranes at loading weights of lower than 3 wt.%. Moreover, the proton conductivity and the methanol permeability as well as the water uptake behavior of the manufactured nanocomposite membranes were studied. According to the selectivity parameter, ratio of proton conductivity to methanol permeability, the PEC/2 wt.% MMT 30B was identified as the optimum composition. The DMFC performance tests were carried out at 70 °C and 5 M methanol feed and the optimum membrane showed higher maximum power density as well as acceptable durability compared to Nafion 117. The obtained results indicated that owing to the relatively high selectivity and power density, the optimum nanocomposite membrane could be considered as a promising polyelectrolyte membrane (PEM) for DMFC applications.

PVC/MMT nanocomposites

Poly(vinyl chloride) (PVC) nanocomposites with sodium montmorillonite (Na-MMT) and organically modified MMT (O-MMT) have been prepared by melt processing using mixing and extrusion techniques. The differential scanning calorimetry (DSC) with stochastic temperature modulation (TOPEM™) results show that the glass transition temperature (T g) of PVC is slightly higher than T g of PVC/Na-MMT and PVC/O-MMT which would indicate that MMT plays a role of an internal plasticizer that increases the distance between the PVC macrochains. The DSC TOPEM non-reversing heat flow profiles show enthalpy relaxation effects, and the lowest value has been found for pristine PVC—the presence of MMT (both Na+ and ammonium salt modified) may generate a certain orientation level of PVC macrochains during the extrusion process. Specific heat vs temperature dependencies at different frequencies revealed that the best fit to the single profile was found for PVC/Na-MMT nanocomposite, and this observation may be related to internal stability of the composite material as confirmed by analysis of the change in the specific heat (Δc p).

The crystalline and mechanical properties of PLA/layered silicate degradable composites

The poly(lactic acid) (PLA)/montmorillonite (MMT) composites were prepared by melt blending in an internal mixer. The effect of MMT and organically modified MMT (OMMT) addition on crystallization and mechanical preferences has been studied. The DSC results show that the crystallization ability of PLA is improved by MMT or OMMT. The addition of MMT and OMMT increase the crystallinity of PLA from 27.3 to 32.8%, and the cold crystallization temperature (TCC) of PLA decreases from 93.1 to 88.9°C with the MMT. However, the nucleating effect of MMT is better than that of OMMT due to the velvety surface resulted from the organic modification. The average size of the spherulites in PLA/MMT is smaller than that in PLA/OMMT. The addition of MMT or OMMT increases the tensile strength of PLA from 29.6 to 34.7 MPa and decrease the elongation at break of PLA. The modulus of PLA composites is enhanced rapidly from 338 to 660 MPa by the addition of MMT.

Sol–gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings

Sol–gel silica/nanoclay composites were prepared through sol–gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K + and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si–O–Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38 °C. From DSC thermograms, we observed that the Δ H value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2 θ = 8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate.

An in situ matrix functionalization approach to structure stability enhancement in polyethylene/montmorillonite nanocomposites prepared by intercalative polymerization

This paper discusses a strategy of enhancing the structure stability of polyethylene/montmorillonite (PE/MMT) nanocomposites prepared by intercalative polymerization technique. The chemistry centers on an in situ, controlled PE matrix functionalization that is made possible by engaging a reactive comonomer in the intercalative polymerization process to intentionally anchor in the formed PE matrix ready-to-functionalize reactive groups. Thus, ethylene polymerization was conducted in the presence of p-methylstyrene ( p-MS) using an OMMT (organically modified MMT)-intercalated metallocene catalyst (Et[Ind] 2ZrCl 2 in combination with MAO), resulting in p-MS-containing PE/OMMT nanocomposites. Subsequent functionalization of the PE matrix then facilely and selectively occurred on the benzyl group in the p-MS unit, including a free radical maleation reaction and a butyllithium-initiated metallation reaction which was followed by an anionic graft-from polymerization of methyl methacrylate (MMA), under very mild reaction conditions. The in situ-incorporated functional groups, including the pendant maleic anhydride groups and the polar poly(methyl methacrylate) (PMMA) side chains, significantly improved miscibility between the PE matrix and laminated silicate layers of MMT, leading to effective stabilization of the nanocomposite structure against processing.

Preparation and characterization of rigid poly(vinyl chloride)/MMT nanocomposites. II. XRD, morphological and mechanical characteristics

AbstractA Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na+‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na+‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na+‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na+‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na+‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na+‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

AbstractIn this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na+‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na+‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na+‐MMT nanocomposites are decreased with increasing the amount of Na+‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na+‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na+‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na+‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005

Preparation and properties of montmorillonite‐based polyimide nanocomposites

AbstractMontmorillonite (MMT)‐based polyimide (PI) nanocomposites were prepared via two‐stage polymerization of PI using polyamic acid (PAA). The clay was organically modified using various alkylammonium ions to examine the effect of changes in alkyl length on the intercalation spacing of both the treated clays and their hybrids with PAA and PI. The intercalation behavior of clay in the PI matrix and its thermal and mechanical properties were investigated as a function of clay concentration. The d‐spacing of organically modified MMT (O‐MMT) increased with increasing length of the alkylammonium chain. PI/O‐MMT hybrids form exfoliated nanocomposites at clay concentrations below 2 wt%, while they form intercalated nanocomposites together with some exfoliated ones at clay contents exceeding 4 wt%. Young's modulus increased rapidly to a clay loading of 2 wt%, and leveled off with further increases in clay loading. The tensile strength at break increased rapidly up to a clay loading of 1 wt%, and then decreased sharply, while the strain at break showed a monotonic decrease with increasing clay loading from 0 to 8 wt%. The storage modulus, E′, in the temperature range below the glass transition temperature Tg, generally increased with increasing clay content, except at the highest clay content of 8 wt%. Copyright © 2004 Society of Chemical Industry