Layered Silicate Nanocomposites Research Articles

Mechanical properties and thermal stability of low-density polyethylene grafted maleic anhydride/montmorillonite nanocomposites

Polymer layered silicate nanocomposites are very prevailing in both basic research and industrial development, among them montmorillonite (MMT) provide the most significant applied value. In this study, structures and properties of various organic/inorganic nanocomposites of low-density polyethylene (LDPE) containing MMT and LDPE grafted maleic anhydride/montmorillonite (LDPE-g-MA/MMT) were investigated. Mechanical properties and thermal stability of LDPE/MMT and LDPE-g-MA/MMT nanocomposites were examined. Samples of LDPE/MMT and LDPE-g-MA/MMT nanocomposites were fabricated with twin-screw extruder and injection molding machine in accordance with the standard test specimens. Furthermore, tensile, impact, bending, hardness, DSC, TGA, and SEM examinations were performed to establish the structure–properties relationships. The mechanical properties significantly improved when the proper amounts of MMT and MA-grafted materials were added to LDPE. This improvement in properties is mainly due to the compatibilizing effect of MA grafts.

Structure‐property relationships in copolyester elastomer‐layered silicate nanocomposites

ABSTRACTWhile the field of polymer–clay nanocomposites is reaching maturity, some parts of the studied systems still present researchers with possibilities for the improvement of material properties. This study entails the understanding of the relationships in copolyester elastomer/organically modified layered silicate nanocomposite and the structure–property relationships within the system of the nanocomposite. A series of these nanocomposites was prepared via twin‐screw extrusion melt compounding. The experiments included the following three types of synthetic organosilicates: high aspect ratio Somasif (ME100) fluoromica and two lower aspect ratio Laponite synthetic hectorites, (WXFN) and (WXFP). These organosilicates were modified with quaternary octadecyltrimethylammonium bromide (ODTMA) and were used to prepare the nanocomposites. The nanocomposite structure on a micro‐ and nanometre scales was evaluated by two techniques, such as X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of the nanocomposites were examined to determine the impact aspect ratio of the nanofiller and wt % loading have on performance. The addition of the 2 wt % high aspect ratio of ME100‐ODTMA, in particular, showed statistically improved tensile strength, tear resistance, creep resistance, and water vapor permeation barrier enhancement. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41742.

Functional Copolymer/Organo-MMT Nanoarchitectures. XXII. Fabrication and Characterization of Antifungal and Antibacterial Poly (Vinyl Alcohol-co-Vinyl Acetate/ODA-MMT/AgNPs Nanofibers and Nanocoatings by e-Spinning and c-Spinning Methods

Nanofibrous films and coatings were fabricated by electrospinning and centrifugal spinning of aqueous solutions of poly(vinyl alcohol-co-vinyl acetate)/octadecyl amine-montmorillonite layered silicate nanocomposites with/without in situ generated silver nanoparticles (AgNPs). Characterization of nanofibers were realized by FTIR, XRD, SEM, and thermal analysis methods. It was found that AgNPs significantly accelerated phase separation process providing fine distribution of nanofibers. Antifungal and antimicrobial activities of nanocomposites investigated by using Candida Spp fungals, G-positive and G-negative microorganisms strongly depended on chemical/physical structural factors, and loading silver species. Observed effective properties of nanomaterials can be employed for many applications (e.g., air filtration, food packaging, biomedical).

Effects of mixing protocols on impact modified poly(lactic acid) layered silicate nanocomposites

ABSTRACTPoly(lactic acid)/2 wt % organomodified montmorillonite (PLA/OMMT) was toughened by an ethylene‐methyl acrylate‐glycidyl methacrylate (E‐MA‐GMA) rubber. The ternary nanocomposites were prepared by melt compounding in a twin screw extruder using four different addition protocols of the components of the nanocomposite and varying the rubber content in the range of 5–20 wt %. It was found that both clay dispersion and morphology were influenced by the blending method as detected by X‐ray diffraction (XRD) and observed by TEM and scanning electron microscopy (SEM). The XRD results, which were also confirmed by TEM observations, demonstrated that the OMMT dispersed better in PLA than in E‐MA‐GMA. All formulations exhibited intercalated/partially exfoliated structure with the best clay dispersion achieved when the clay was first mixed with PLA before the rubber was added. According to SEM, the blends were immiscible and exhibited fine dispersion of the rubber in the PLA with differences in the mean particle sizes that depended on the addition order. Balanced stiffness‐toughness was observed at 10 wt % rubber content in the compounds without significant sacrifice of the strength. High impact toughness was attained when PLA was first mixed with the clay before the rubber was added, and the highest tensile toughness was obtained when PLA was first compounded with the rubber, and then clay was incorporated into the mixture. Thermal characterization by DSC confirmed the immiscibility of the blends, but in general, the thermal parameters and the degree of crystallinity of the PLA were not affected by the preparation procedure. Both the clay and the rubber decreased the crystallization temperature of the PLA by acting as nucleating agents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41518.

Polymer/Layered Silicate Nanocomposite as Matrix for Bioinsecticide Formulation

SummaryDue to current encouragement to the use of bioinsecticides for pest control and the susceptibility of biological agents to external factors, we investigated the use of a polymer nanocomposite (PLN, polymer/ layered silicate nanocomposite) as matrix to encapsulate an entomopathogenic fungus active against pest insects of palm trees. The beads were formed by extrusion and the following variables were assessed: fungus conidial concentration (series 1: 107; series 2: 108 and series 3: 109 conidia/mL) and nanolayered silicate concentration (0; 0.5; 1; 2 and 4%). The matrix was evaluated by X‐ray powder diffraction and Fourier transform infrared spectroscopy and the following characteristics of the products were assessed: percent of encapsulated conidia, size distribution and polydispersity index, swelling index, formulation's in vitro ability to release conidia and stability under different storage temperatures. PLN, whose interactions could be visualized by FTIR, proved to be a potential matrix for this fungus, because, while composed by natural substances non‐toxic to the environment, it succeeded to encapsulate high amounts of conidia (series 2). A barrier effect with bentonite increase was also demonstrated by increased fungus germination time and thermal stability.

Functional organo-Mt/copolymer nanoarchitectures. XXII. Interlamellar graft copolymerisation of l-lactic acid onto poly(maleic anhydride-alt-1-octadecene) in the presence of different clays as catalyst-nanofillers

In this work, novel functional copolymer-g-biopolymer layered silicate nanocomposites were prepared by in situ graft copolymerisation of l-lactic acid (LA) onto poly(maleic anhydride-alt-1-octadecene) in the presence of Na+-montmorillonite (Mt), Ag+-Mt and octadecyl amine-Mt (ODA) nanofillers using a specially constructed vacuum micro-reactor with Dean-Stark unit at 80°C. It was observed that inorganic and organic clays executed the dual functions as catalyst of interlamellar graft copolymerisation and nano-filler in formation of clay polymer nanocomposites (CPNs). This new approach allow us to realise the grafting and graft copolymerisation without use of hazardous tin(oct)2 catalyst. The surfactant matrix copolymer provides the first step of grafting via ring opening monoesterification of anhydride units with LA monomer. The catalytic activity of the positively charged clays and their LA preintercalated complexes as a function of phase separation time, strongly depends on the particle parameters (zeta-size and zeta-potential) of the used clay systems and changed in the following range: organoclay<Na+-Mt<Ag+-Mt. The obtained graft copolymer/clay nanohybrids were characterised by FTIR, 1H and 13C NMR, DSC-TGA-DTG, XRD and SEM-TEM analysis methods. These observed that type of the clays significantly influences the chemical and physical structures, thermal properties, surface and internal core–shell morphology of the copolymer-g-PLA layered silicate nanocomposites. Better results were obtained for the copolymer-g-biopolymer/reactive organoclay nanocomposites. It was concluded that this versatile and green synthetic method can utilise for a wide range of anhydride-containing alternating, random, graft and block functional copolymers as matrix polymers and their silicate layered nanocomposites.

Epoxy Layered-Silicates Filled with Fly Ash Based Geopolymer: Compressive Properties

The effect of fly ash based geopolymer in epoxy layered silicates nanocomposites was studied using a compressive test. A series of nanocomposites with fly ash based geopolymer 1-7phr content was prepared. Qualitative evaluation of the three-dimensional shape of a fly ash based geopolymer surface and the origin was characterized using scanning electron microscopy. It was found that the addition of fly ash at the beginning with lower content are showing lower compressive strength than nanocomposites without fly ash filled. However, compressive properties suddenly increased at 3phr of fly ash geopolymer content compared to nanocomposites without fly ash. This indicated the blending of fly ash geopolymer in nanocomposites system have the ability for further studies.

Effect of two types of layered silicate on mechanical and barrier properties of hydrogenated acrylonitrile butadiene rubber (HNBR)/layered silicate nanocomposites

The role of the type of layered silicate platelets, OMMT and rectorite on the mechanical properties, aging resistance and oxygen permeation properties of HNBR/layered silicate nanocomposites was investigated. The effect of peroxide vulcanising agent on the dispersion of layered silicate in the HNBR matrix was also studied. HNBR was mechanically mixed with layered silicate via melt blending method. The results of the test show remarkable improvement in tensile strength, tear strength, aging resistance and oxygen permeation properties of HNBR nanocomposites than that of unfilled HNBR. It is obvious that the OMMT filled nanocomposites have far better properties than that of rectorite filled HNBR.

Aging of EVA/organically modified clay: Effect on dispersion, distribution and combustion behavior

Abstract Heating of polymer layered silicates nanocomposites, under air, promotes lamellas migration toward the surface. In this communication we show that aging a poly[ethylene-co-(vinylacetate)] (EVA)-organically modified clay (Cloisite 20A) nanocomposite, at temperature close to the melting point, strongly affects its combustion behavior. The thermal treatment leads to lamella exfoliation which allows an easier migration of the clay toward the surface during the early stage of combustion. This promotes the formation of a thin film, made of lamellas and polymer matrix, that traps the volatile degradation products and enormously delay the time to ignition. At the end of the combustion the film is, however, preserved.

Comparison of the Nanostructure and Mechanical Performance of Highly Exfoliated Epoxy-Clay Nanocomposites Prepared by Three Different Protocols.

Three different protocols for the preparation of polymer layered silicate nanocomposites based upon a tri-functional epoxy resin, triglycidyl para-amino phenol (TGAP), have been compared in respect of the cure kinetics, the nanostructure and their mechanical properties. The three preparation procedures involve 2 wt% and 5 wt% of organically modified montmorillonite (MMT), and are: isothermal cure at selected temperatures; pre-conditioning of the resin-clay mixture before isothermal cure; incorporation of an initiator of cationic homopolymerisation, a boron tri-fluoride methyl amine complex, BF3·MEA, within the clay galleries. It was found that features of the cure kinetics and of the nanostructure correlate with the measured impact strength of the cured nanocomposites, which increases as the degree of exfoliation of the MMT is improved. The best protocol for toughening the TGAP/MMT nanocomposites is by the incorporation of 1 wt% BF3·MEA into the clay galleries of nanocomposites containing 2 wt% MMT.

Characterization of Polymer Layered Silicate Nanocomposites by Rheology and Permeability Methods: Impact of the Interface Quality

Polymer clay nanocomposites are mostly described as materials with improved properties. However, many studies are not concluding about the possible benefits. This work reports permeability measurements on different polyolefins nanocomposites. Clay exfoliation has been proved by various techniques. Unfortunately, the nanocomposite does not exhibit good barrier properties. Hence, permeability coefficients were found to increase. A poor quality of the interface between filler and medium is likely to be responsible for this degradation. Insufficient interactions between silicate layers and the surrounding polymer lead to preferential pathways for diffusion. Organoclay exfoliation does not necessarily lead to better barrier properties. A good quality of the interface between polymer and filler is required to reach a high performance level. The standard techniques used to characterize exfoliation degree do not permit to highlight this kind of phenomena.

Functional copolymer/organo-MMT nanoarchitectures. XIX. Nanofabrication and characterization of poly(MA-alt -1-octadecene)-g -PLA layered silicate nanocomposites with nanoporous core-shell morphology

Novel bioengineering functional copolymer-g-biopolymer-based layered silicate nanocomposites were fabricated by catalytic interlamellar bulk graft copolymerization of L-lactic acid (LA) monomer onto alternating copolymer of maleic anhydride (MA) with 1-octadecene as a reactive matrix polymer in the presence of preintercalated LA…organo-MMT clay (reactive ODA-MMT and non-reactive DMDA-MMT) complexes as nanofillers and tin(oct)2 as a catalyst under vacuum at 80°C. To characterize the functional copolymer layered silicate nanocomposites and understand the mechanism of in situ processing, interfacial interactions and nanostructure formation in these nanosystems, we have utilized a combination of variuous methods such as FT-IR spectroscopy, X-ray diffraction (XRD), dynamic mechanical (DMA), thermal (DSC and TGA-DTG), SEM and TEM morphology. It was found that in situ graft copolymerization occurred through the following steps: (i) esterification of anhydride units of copolymer with LA; (ii) intercalation of LA between silicate galleries; (iii) intercalation of matrix copolymer into silicate layers through in situ amidization of anhydride units with octadecyl amine intercalant; and (iv) interlamellar graft copolymerization via in situ intercalating/exfoliating processing. The main properties and observed micro- and nanoporous surface and internal core–shell morphology of the nanocomposites significantly depend on the origin of MMT clays and type of in situ processing (ion exchanging, amidization reaction, strong H-bonding and self-organized hydrophobic/hydrophilic interfacial interactions). This developed approach can be applied to a wide range of anhydride-containing copolymers such as random, alternating and graft copolymers of MA to synthesize new generation of polymer-g-biopolymer silicate layered nanocomposites and nanofibers for nanoengineering and nanomedicine applications. Copyright © 2014 John Wiley & Sons, Ltd.

EPDM/silicone blend layered silicate nanocomposite by solution intercalation method: Morphology and properties

Ethylene–propylene–diene terpolymer (EPDM)/silicone blend nanocomposites are prepared by solution method for the first time. EPDM and silicone rubber in their 50:50 (by weight) blend is intercalated within the silicate sheets of organically modified montmorillonite. Organic modification to the pristine sodium montmorillonite (Na‐MMT) surfaces is carried out by ion‐exchange reaction using hexadecyl ammonium chloride. The incorporation of such organic functional group makes Na‐MMT hydrophobic and expands the interlayer spacing between silicate sheets. The intercalated structure of EPDM/silicone blend nanocomposites is characterized by the X‐ray diffraction. Transmission electron microscopic characterization visualized the presence of both exfoliated and intercalated layered silicate in the polymer nanocomposites. The mechanical properties of the nanocomposites show a maximum improvement in tensile strength and elongation at break of 23 and 68%, respectively, compared with EPDM/silicone blend. The dielectric measurement demonstrates the increase in relative permittivity for the nanocomposite than the pure blend. The increase in the onset temperature of the thermal degradation of nanocomposites (∼52°C) corresponding to 1 wt% decomposition indicates the enhancement of thermal stability of (EPDM)/silicone blend due to interaction with silicates. POLYM. COMPOS., 35:1834–1841, 2014. © 2014 Society of Plastics Engineers

Unsaturated Polyesters / Layered Silicate Nanocomposites: Synthesis and Characterization

Unsaturated polyester (PEs) / Egyptian bentonite nanocomposites were prepared. The bentonites used were chemically modified by cation exchange reactions with surfactant (quaternary ammonium salt). The prepared nanocomposites were characterized by morphology analysis using X-ray diffraction, transmition electron microscope, thermal analysis, mechanical analysis and electrical analysis. The results reported in this study revealed the improvement of the thermal and mechanical properties of the prepared nanocomposites. All modified clay-polyester nanocomposites displayed improved mechanical properties with organoclay content up to 7 wt % as compared with PEs filled with micrometer clay (40 wt %).Also the prepared nanocomposites show improvement of thermal stability and electrical conductivity .

Some Studies on Poly (vinyl chloride)/Layered Silicate Nanocomposites: Electrical, Antibacterial and Oxygen Barrier Properties

The influence of 1.31PS organoclay content relative to PGV grade on the properties of PVC compounds was analyzed. Dielectric properties (i.e. permittivity ' & dielectric loss  ) of the PVC nanocomposites were investigated in the frequency range 10 2 - 10 5 Hz at room temperature  25 o C. In addition to the dielectric properties the experimental data of conductivity term  were also detected. The initial results show that nanoparticles of 1.31PS clay can improve electrical insulation properties of PVC by lowering (at 2.5 phr) and  (at 4 phr). The nano 1.31PS shows a significant influence on the electrical resistivity of PVC by enhancing it up to 1.4 x 10 -11 ohm.cm. Biodegradation percentage (BD%) and optical density (OD) of tested samples have been screened in testes against both Gram-positive bacteria such as Micrococcus luteus RM1 and Gram-negative bacteria such as Pseudomonas aeruginosa HR1.The particle size and morphology of PVC/1.31PS was found to play a significant role in indicating the antimicrobial efficiency. The results indicate a remarkable and significant resistance of PVC/1.31PS (2.5phr) to both kinds of microorganism, as compared with PVC containing 1.31PS (10phr). The oxygen permeability was measured at 23 o C and 50% relative humidity. With increasing 1.31PS content up to 6 phr the oxygen permeability of the PVC matrix is reduced based on the tortuous path formation.

Preparation, Characterization and Drug Release Studies from Poly(D,L-lactic acid)/organoclay Nanocomposite Films

Biocompatible/biodegradable poly(D,L-lactic acid)/layered silicate nanocomposites were prepared by the solution-intercalation film casting technique. The obtained nanocomposites present a shift of glass transition temperature (Tg) to higher values. An increase in the onset temperature of thermal degradation (Tonset) was also observed by TGA. Hydrolytic degradation of PLA nanocomposites becomes apparent after the first 3 months of immersion of specimens into deionized water. Drug release studies from PLA/organoclay nanocomposite membranes showed slightly faster release behavior in comparison with unreinforced specimens containing 5 phr guaifenesin (GFN), whereas the different organic clay modifications studied in this work, did not seem to have any effect in the release profile of GFN.

Thermal and flexural properties of room-temperature cured PMMA grafted natural rubber toughened epoxy layered silicate nanocomposite

Thermal and flexural properties of ternary system containing epoxy, poly(methyl methacrylate) (PMMA) grafted natural rubber, and organic chemically modified montmorillonite clay (Cloisite 30B) were studied. The results of TEM, SEM, XRD, FTIR, DSC, TGA and flexural tests were discussed. The rates of glass transition and decomposition process were introduced as relevant parameters to evaluate glass transition and thermal stability. It was observed that the addition of 5 phr Cloisite 30B in epoxy contributed to significant improvement in thermal properties and flexural modulus of nanocomposites. The intercalated structure of silicate clay may help to introduce tortuous path for volatiles to escape the epoxy network, hence retarding the decomposition process. The high char yield content for epoxy/clay and rubber toughened epoxy/clay nanocomposite show that they can be used as adhesive and coating materials with good thermal stability properties.

Modification of ibuprofen drug release from poly(ethylene glycol) layered silicate nanocomposites prepared by hot‐melt extrusion

ABSTRACTComposites of the poorly water soluble drug ibuprofen, a nonsteroidal anti‐inflammatory commonly used for pain relief, with layered silicates (nanoclays) and a poly(ethylene glycol) (PEG) were prepared by hot melt extrusion. A highly intercalated and partially exfoliated morphology was determined using wide‐angle x‐ray diffraction, field emission scanning electron microscopy, and high‐resolution transmission electron microscopy. The crystalline content of PEG was significantly reduced, as shown by differential scanning calorimetry studies, as a consequence of the large surface area of clay platelets physically hindering polymer chain dynamics and, in the case of montmorillonite, by tethering of PEG via hydrogen bonding. Addition of layered silicate retarded the release of ibuprofen from the PEG matrix, even though the crystalline content of PEG was reduced. This study therefore indicates that drug release in solid dispersion systems may be modified or indeed tailored by the inclusion of layered silicates. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40284.

Polyolefin Layered Silicates Nanocomposites – A Review

A review is given of polyolefins layered silicates nanocomposites. This group of commodity thermoplastic is widely used and gain a great attention among researcher now days for nanocomposite preparation with layered silicates as inorganic filler. Herein, the structure and properties of layered silicates, compatibilzations of polyolefins, the syhthesise preparative method are discussed in general.

Swift heavy ion irradiation induced enhancement in electrochemical properties of ionic liquid based PVdF-HFP-layered silicate nanocomposite electrolyte membranes

In the present work, effects of 100MeV Si9+ ion irradiation of different fluences on poly(vinylidene fluoride-co-hexafluoro propylene) (PVdF-HFP)-layered silicate nanocomposite electrolyte membranes based on ionic liquid, 1-butyl-3-methylimidazolium bromide have been investigated. With increasing ion fluence, intercalation of PVdF-HFP into the interlayers of layered silicate increases eventually leading to exfoliation of silicate layers at the fluence of 5×1011ionscm−2. Swift heavy ion (SHI) irradiation induces chain scissions in the polymer leading to increase in amorphicity due to which room temperature ionic conductivity increases with increasing ion fluence. Highest room temperature ionic conductivity of 4.96×10–2Scm−1 has been obtained at the highest fluence of 1×1012ionscm−2 employed in the present work. SHI irradiation increases the porosity of the nanocomposite electrolyte membranes as confirmed from scanning electron microscopy results. Contact angle measurements reveal that upon SHI irradiation the hydrophilic electrolyte membranes turn hydrophobic. High electrochemical stability window of −3.9V to 6.5 has been achieved at the highest ion fluence of 1×1012ionscm−2. Upon SHI irradiation the rate of decrease of ionic conductivity becomes slower indicating enhancement in interfacial stability.