Montmorillonite Nanocomposite Films Research Articles

QbD assisted formulation design and optimization of thiol pectin based Polyethyleneglycol and Montmorillonite(PEG/MMT) nanocomposite films of neomycin sulphate for wound healing

QbD assisted formulation design and optimization of thiol pectin based Polyethyleneglycol and Montmorillonite(PEG/MMT) nanocomposite films of neomycin sulphate for wound healing

Nanoclay assisted ultra-drawing of polypropylene tapes

Isotactic polypropylene (i-PP) – montmorillonite (MMT) nanocomposite films were prepared by melt-compounding and hot-pressing. The influence of organoclays on the mechanical properties and drawability of these isotropic composite films was investigated. Ultimate properties of solid-state drawn PP tapes incorporating 2.5 wt% MMT outperformed those of pure PP tapes. Interestingly, these improvements were found not to be the result of a mechanical reinforcement effect of the nanoclay platelets but merely the result of a more efficient ultra-drawing mechanism with MMT acting as a processing additive that altered initial polymer morphology and drawing behaviour. Hence, the introduction of MMT resulted in higher ultimate draw ratios and subsequently higher ultimate mechanical properties of the oriented nanocomposite tapes.

Enhancing antibacterial properties of polypropylene/Cu‐loaded montmorillonite nanocomposite filaments through sheath–core morphology

AbstractPolypropylene (PP) loaded with copper‐exchanged montmorillonite (Cu‐MMT) nanocomposite filaments and films with excellent antimicrobial activity have been reported for the first time. A sheath–core morphology filament in which only the sheath contains Cu‐MMT was prepared for maximizing bioactivity. Sodium MMT clay was modified to acid‐activated MMT and further to Cu‐MMT via an ion exchange process. The exchange operation was confirmed using wide‐angle X‐ray diffraction and energy‐dispersive X‐ray spectroscopy (EDX) which suggested increased interlayer spacing and confirmed the loading of copper in Cu‐MMT. Further, Cu‐MMT was melt‐mixed in PP in the form of PP/Cu‐MMT nanocomposite filament, film and sheath–core morphology PP/Cu‐MMT nanocomposite filament. The surface morphology and elemental composition of the nanocomposites were studied using scanning electron microscopy coupled with EDX. Transmission electron micrographs were obtained to understand the dispersion characteristics of Cu‐MMT phase in PP. X‐ray diffraction analysis of nanocomposites suggested increased crystallinity at lower loading due to heterogeneous nucleating action of MMT. The PP nanocomposite filaments and films were tested for antimicrobial activity against Gram‐negative bacterium Escherichia coli, which is the main pathogenic bacterium found abundantly in water, and were found to exhibit excellent antimicrobial activity. © 2018 Society of Chemical Industry

Poly(lactic acid)/montmorillonite blown films: Crystallization, mechanics, and permeation

ABSTRACTThe study focuses on the development and characterization of poly(lactic acid) (PLA)/montmorillonite (clay) nanocomposite films. Samples of 0%, 1%, 3%, and 6% (by weight) clay were shear‐mixed, melt‐blended, and blown‐film processed. Afterward, the effects of clay on the kinetics of cold‐crystallization, mechanical properties, and the oxygen barriers are investigated using differential scanning calorimetry, dynamic mechanical analyzer, and permeation tester, respectively. Through the traditional Avrami analysis, clay is found to accelerate the crystallization process with a higher crystallization rate constant. The Avrami exponent obtained for composites is higher than the neat PLA although all samples show a decreased Avrami exponent with increase of the crystallization temperature. At the same time, the clay exhibits reinforcement effects on the glassy modulus of the composites and influences the cold‐crystallization event, similar to the calorimetric results. In addition, the oxygen permeation slightly decreases on adding the clay. With 3% clay concentration, the permeation coefficient is reduced by 24%. The implication of the results is discussed in the article. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45260.

Application of bio-inspired nanocomposites for enhancing impact resistance of cementitious materials

Bio-inspired Polyvinyl Alcohol (PVA)/ Montmorillonite (MMT) nanocomposite films were synthesized and applied to High Performance Concrete (HPC) cylinders as coatings. Drop tower tests were performed to evaluate the effects of nanocomposite films on the impact response of the concrete. The preliminary results show that applying PVA/MMT nanocomposite film with 25vol% MMT as coatings with an approximate thickness of 160µm, demonstrated an improvement on the impact resistance of the concrete for a strain rate (∼102/s). For specimens subjected to the same impact energy, the damage pattern changed from complete fracture of an uncoated concrete cylinder, to only localized surface damage on the coating and the concrete cylinder substrate at the impacted region. Finite element simulations of the impact tests indicate that robust stiffness, tensile strength and toughness of the nanocomposite film, and strong bonding between the film and concrete have induced strong confinement effects to the brittle concrete cylinder substrate. This work demonstrates the potential application of bio-inspired PVA/MMT nanocomposites as protective coatings for cementitious structures.

Development of long-term antimicrobial poly (ε-caprolactone)/silver exchanged montmorillonite nanocomposite films with silver ion release property for active packaging use

Poly (e-caprolactone)/silver exchanged montmorillonite (PCL/Ag–MMT) nanocomposites with a strong antibacterial activity and a slow release property were successfully prepared via solvent casting method, for active packaging use. The PCL/Ag–MMT nanocomposites containing different Ag–MMT loadings were characterized by several techniques. X-Ray Diffraction (XRD), UV–visible Spectroscopy and Transmission Electron Microscopy (TEM) results revealed that the MMT layers were exfoliated and spherical Ag nanoparticles were randomly distributed in the polymer matrix. Differential scanning calorimetry (DSC) showed that glass transition and melting temperatures of PCL/Ag–MMT nanocomposites were unaffected by clay contents compared to neat PCL. Nevertheless, the crystallization temperatures were increased due to the incorporation of effective nucleation agent Ag–MMT and its satisfactory dispersion into the PCL matrix. The positive effect of the Ag–MMT addition on the PCL barrier properties was confirmed by the reduction in the water permeability (WVP). Tensile results also displayed an improvement of mechanical properties for the PCL/Ag–MMT nanocomposites due to the insertion of clay particles into the PCL matrix. The potential of the silver ion release from the PCL/Ag–MMT films to a slightly acidified water medium was measured by atomic absorption spectroscopy. The results exhibited a gradual increase of the amount of silver ions released up to 30 days of immersion. The kinetic study of the ions release showed that the release’s mechanism is governed by the diffusion process. The apparent diffusivity coefficient values calculated using the diffusion model were in the range of 3.8 × 10−10 to 5.8 × 10−10 cm2/s. Furthermore, the PCL/Ag–MMT films exhibited a strong antibacterial efficiency against S. aureus, E. coli, salmonella and P. aeruginosa due to the presence of the long-lasting biocidal silver nanoparticles.

Polymer/clay nanocomposite films as active packaging material: Modeling of antimicrobial release

An integral combination of design of experiments (DoE), partial least squares regression (PLSR) and response surface methodology (RSM) was applied to model the release of carvacrol into a food simulant from an antimicrobial material based on low-density polyethylene/organically-modified montmorillonite (LDPE/OMM) nanocomposite films. Using a D-optimal design, one qualitative-multi-level x-variable and two quantitative x-variables of the nanocomposite formulation were studied: type of OMM, concentration of OMM and concentration of a compatibilizer agent. Eight y-responses were simultaneously modeled using PLSR, including four kinetic/diffusion properties of carvacrol release toward food simulant (initial rate of release, overall kinetic rate constant, diffusion coefficient and diffusion rate constant), and four packaging properties (Young’s modulus, intercalation, decomposition and melting temperature). An ANOVA-validated (p<0.05) PLS model was obtained with R2=0.923 and Q2=0.453, modeling the all x-variables with all y-responses simultaneously. A formulation that maximizes packaging properties and minimizes carvacrol release was calculated by using RSM.

The synergistic antimicrobial effect of carvacrol and thymol in clay/polymer nanocomposite films over strawberry gray mold

The in vivo synergistic antimicrobial effect of the essential oils constituents (EOCs) carvacrol (CRV) and thymol (TML) included in low-density polyethylene/organically modified montmorillonite (LDPE/OMM) nanocomposite films were evaluated using strawberries inoculated with Botrytis cinerea. XRD analysis of an LDPE/OMM nanocomposite showed an increase in the interlayer distance with respect to the original nanoclay, indicating an intercalated morphology. Improved packaging properties, such as mechanical, thermal and rheological properties, with respect to the neat LDPE were achieved. An approximately 15% decrease in the release rate of the EOCs compared to neat LDPE was observed, indicating the potential of the films to function as controlled-release food packaging material. A synergistic antimicrobial effect was observed for the CRV:TML mixture against B. cinerea compared to a film containing only CRV, when the films were applied by indirect contact with the strawberries. The IC50 of the EOCs in the film was reduced from 40.4 mg g−1 (CRV only) to 13.2 mg g−1 (CRV:TML 50:50). Therefore, with only one third of the total EOCs concentration required for the single EOCs films, the CRV:TML-containing film provides effective inhibition of B. cinerea but without significant (p < 0.001) organoleptic alteration in strawberries, as described by discriminative sensory analysis.

A biodegradation study of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/organoclay nanocomposites in various environmental conditions

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/organo-modified montmorillonite (OMMT) nanocomposite films were prepared by melt compounding and cast-film extrusion at various loading rates, i.e. 1, 3 and 5 wt. %. The effect of OMMT on the biodegradability of produced PHBV nanocomposite films was investigated under controlled conditions in aqueous medium (20 °C for 28 days) by monitoring the biochemical oxygen demand (BOD), and under laboratory-scale composting conditions (58 °C for 70 days) by monitoring the weight and surface loss. The microstructural and macromolecular changes were monitored during the biodegradation process by means of scanning transmission electron microscopy (STEM), differential scanning calorimetry (DSC) and size exclusion chromatography (SEC) analysis. The initial microstructure of the nanocomposites samples exhibited an intercalated structure with a good clay/matrix affinity. BOD evolution in aqueous conditions as well as surface and weight loss in composting conditions indicated that the biodegradation rate of PHBV nanocomposites was lower than neat PHBV, which supports a barrier effect of OMMT. This was confirmed by the surface erosion observed through SEM accompanied by a significant decrease of the average molecular weight in the bulk of the films. Our results demonstrated that the biodegradation of PHBV and nanocomposite films occurred by combined hydrolytic and enzymatic processes, at the surface as well as in the bulk of the material. DSC analysis also revealed no change in the degree of crystallinity, which suggests that the amorphous and crystalline phases were degraded at same rate.

Interplay between processing and performance in chitosan-based clay nanocomposite films

Chitosan sodium montmorillonite (NaMMT) nanocomposite films, with or without addition of glycerol, are prepared by three different processing methods, i.e., solution casting, heat pressing and casting of sonicated solutions. The effect of processing is being investigated using X-ray diffraction, tensile tests, dynamic mechanical analysis, and water sorption tests. Processing plays a significant role in the hydrated crystalline structure of chitosan; however, it is less crucial for the degree of exfoliation/intercalation of NaMMT. The addition of NaMMT fillers induces substantial reinforcing effects in the chitosan/NaMMT systems with up to 160 % increase in stiffness, strength and 200 % increase in the storage modulus in comparison to the unfilled systems. Although highest stiffness and strength are achieved at different NaMMT contents for the three processing routes, the overall enhancement is similar. The addition of glycerol reduces the reinforcing efficiency of the NaMMT filler and results in plasticization by lowering the stiffness, strength, storage modulus and the glass transition temperature of chitosan (T g). In the absence of glycerol, sonication results in nanocomposite films with higher strain at break and higher T g values. Heat pressing results in a tremendous reduction (more than one order of magnitude) of the absorbed water in chitosan nanocomposite films without glycerol.

Bi-axially oriented polystyrene/montmorillonite nanocomposite films

Polystyrene (PS)/montmorillonite (MMT) nanocomposite films were prepared by bi-axially stretching compounded and extruded PS/MMT nanocomposite sheets, resulting in an improved level of exfoliation and orientation during stretching.

Characterization of clay platelet orientation in polylactide–montmorillonite nanocomposite films by X-ray pole figures

The film samples of polylactide/montmorillonite (PLA/MMT) nanocomposite were formed by compression molding, film extrusion or melt blowing. The orientation of the single-layer platelets of fully exfoliated MMT was probed in these films with X-ray diffraction utilizing analysis of 2-D WAXS patterns and the pole figure technique. The reflections of the (020) and (210) crystallographic planes of MMT, both perpendicular to the plane of the platelet, were studied.It was found that the texture of MMT created upon processing is the (100) planar texture, i.e. with MMT platelets oriented preferentially parallel to the film plane. That texture becomes significantly stronger and sharper with increasing shear deformation, according to the following order: compression molding→extrusion→blow molding. At the blow ratio of 7 the maximum of MMT orientation distribution reaches value of 8m.r.d. and the estimated Hermans orientation factor of the platelet normal with respect to the film normal, is very high, f001=0.96.The results obtained by X-ray pole figure technique were verified positively by direct TEM observations.

Effects of preparation methods on the structure and mechanical properties of wet conditioned starch/montmorillonite nanocomposite films

TPS/Na–montmorillonite nanocomposite films were prepared by solution and melt blending. Clay content changed between 0 and 25wt% based on the amount of dry starch. Structure, tensile properties, and water content of wet conditioned films were determined as a function of clay content. Intercalated structure and VH-type crystallinity of starch were found for all the nanocomposites independently of clay and plasticizer content or preparation method, but at larger than 10wt% clay content nanocomposites prepared by melt intercalation contained aggregated particles as well. In spite of the incomplete exfoliation clay reinforces TPS considerably. Preparation method has a strong influence on mechanical properties of wet conditioned films. Mechanical properties of the conditioned samples prepared by solution homogenization are much better than those of nanocomposites prepared by melt blending. Water, which was either adsorbed or bonded in the composites in conditioning or solution mixing process, respectively, has different effect on mechanical properties.

Properties of low methoxyl pectin‐carboxymethyl cellulose based on montmorillonite nanocomposite films

SummaryIn this study, the low methoxyl pectin‐carboxymethyl cellulose‐based montmorillonite (LMP‐CMC‐MMT, LCM) nanocomposite films with nine ratios of LMP:CMC (from 10:0 to 0:10) and different MMT contents (1–8 wt%) were prepared. The mechanical properties, colour, opacity and water vapour permeability (WVP) of composite films were investigated. The maximum of tensile strength (TS) of composite films was 39.85 ± 2.51 MPa at LMP:CMC ratio of 4:6 and 4 wt% MMT (LCM47), which indicated the formation of hydrogen bonds between MMT and LMP‐CMC. The reduction of WVP of the LCM47 composite film was 333% of that of the CMC film due to the tortuous path caused by MMT incorporation. LCM composite films had the higher b*‐ and ΔE*‐values and lower L*‐values in comparison with LMP‐CMC (LC) composite films. The LCM composite films showed a decrease in transparency as MMT content increased.

Water sorption and water-resistance properties of poly(vinyl alcohol)/clay nanocomposite films: Effects of chemical structure and morphology

A series of poly(vinyl alcohol)/sodium montmorillonite (PVA/NaMMT) nanocomposite films were prepared via a solution method, and their water sorption and water-resistant properties were investigated as a function of clay content. The water sorption and water resistance properties were strongly dependent on the chemical structure and film morphology originating from the NaMMT content. The water diffusion coefficient and water uptake of the PVA/NaMMT nanocomposite films were obtained by best fits to a Fickian diffusion model. The diffusion coefficient and water uptake in the PVA/NaMMT nanocomposite films varied between 8.16 × 10−10 and 3.60 × 10−10 cm2 s−1 and 35.6 and 29.9 wt%, respectively. Both the diffusion coefficient and water uptake decreased as the content of NaMMT in pure PVA was increased. Additionally, the water resistance pressure (mm) of the PVA/NaMMT nanocomposite films increased with increasing NaMMT content. Contact angle analyses showed that the chemical affinity to water and the surface energy of the nanocomposite films decreased with increasing NaMMT content. Furthermore, the well-dispersed and exfoliated structure in the nanocomposite films not only induced an increased tortuous path for water molecules to pass through, but also increased the molecular order. However, to enhance the water sorption properties and water resistance of hydrophilic PVA, further studies to increase the dispersion of clay particles and ensure desired morphological qualities such as crystallinity and molecular packing order in the PVA/clay nanocomposite films are required. POLYM. COMPOS., 36:660–667, 2015. © 2014 Society of Plastics Engineers

Effect of clay concentration on morphology and properties of hydroxypropylmethylcellulose films

Hydroxypropylmethylcellulose (HPMC)/montmorillonite (MMT) nanocomposite films are prepared by solution intercalation method. Mechanical, thermal, moisture absorption, optical clarity and water vapor permeability of HPMC/MMT nanocomposite films are measured. X-ray diffraction (XRD) and transmission electron microscopic (TEM) results establish formation of partially intercalated and partially exfoliated HPMC/MMT nanocomposite films. In presence of MMT, the tensile strength, tensile modulus and elongation at break of HPMC films are improved. The thermal stability of HPMC/MMT nanocomposites is better than pure HPMC. The moisture absorption of HPMC film measured in 75% of constant relative humidity is reduced with loading of MMT. Optical clarity of HPMC film is almost unaffected in presence of MMT. Water vapor permeability of HPMC decreases in presence of nanoclay due to increasing tortuous path for diffusion.

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

Structure and Physical Properties of Starch/Poly Vinyl Alcohol/Sodium Montmorillonite Nanocomposite Films

Nanocomposites of starch, poly vinyl alcohol (PVOH), and sodium montmorillonite (Na(+)MMT) were produced by solution mixing and cast into films. Tensile strength (TS) and elongation at the break (E%) of the films ranged from 11.60 to 22.35 MPa and 28.93-211.40%, respectively, while water vapor permeability (WVP) ranged from 0.718 to 1.430 g·mm/kPa·h·m(2). In general, an increase in Na(+)MMT content (0-20%) enhanced TS and decreased E% and WVP. Use of higher molecular weight PVOH increased both TS and E% and also decreased WVP. Mechanical properties were negatively affected, but water vapor barrier properties improved with increasing starch content (0-80%). X-ray diffraction and transmission electron microscopy were used to analyze the nanostructure, and molecular conformations and interactions in the multicomponent nanocomposites were inferred from glass transition behavior. Interactions between starch and PVOH were strongest, followed by polymer/clay interactions. On the basis of this insight, a conceptual model was presented to explain the phenomena of intercalation and exfoliation in the starch/PVOH/Na(+)MMT nanocomposites.

Carboxymethylcellulose–montmorillonite nanocomposite films activated with murta (Ugni molinae Turcz) leaves extract

► The addition of MMT to CMC films, improve their physicochemical properties. ► Extract of murta as a solvent produce active films with antioxidant properties. ► Murta active compounds plasticized the films modifying the ratio permeability to gases. The functionality of nanocomposite films based on carboxymethylcellulose (CMC) and montmorillonite (MMT) activated with murta ( Ugni molinae Turcz) leaves extract was studied. Films were prepared by casting from film-forming dispersions containing CMC, glycerol (used as plasticizer) and different concentrations of MMT, using water or murta extract as solvent. The addition of MMT increased the tensile strength and the elasticity modulus of the films, and decreased their permeabilities to water vapor, oxygen and carbon dioxide. Besides the antioxidants properties provided to the films, the addition of murta leaves extract changed the gas permeability in different forms according to the MMT content, and plasticized the nanocomposite matrix.

Preparation of active antimicrobial methyl cellulose/carvacrol/montmorillonite nanocomposite films and investigation of carvacrol release

Methyl cellulose (MC)/carvacrol (CRV)/montmorillonite (MMT) nanocomposite films were prepared to obtain active antimicrobial packaging materials. The characterization of film samples by X-ray diffraction and transmission electron microscopy showed that composite films were of nano structures. CRV addition to the MC film and MC/MMT nanocomposite films led to a decrease in the thickness and opacity values of them, whereas MMT addition to the film matrix caused an increase in these values. Thermal stability of films slightly increased with increasing MMT concentration in film matrix. CRV release from films was investigated at different temperatures for 30 days. An increase in the MMT concentration matrix caused a decrease in CRV release at 25.0 ± 0.5 °C and in 60 ± 4% relative humidity (RH). CRV release increased with temperature at a constant RH. The antimicrobial activities of films were tested against Escherichia coli ( E. coli) and Staphylococcus aureus ( S. aureus) by the microatmosphere method and these organisms were completely inhibited on the nutrient broth/bacteriological agar medium when film samples containing 11.1 ± 0.2 mg CRV were present. MC/CRV film and MC/CRV/MMT-60% nanocomposite films on sausage reduced E. coli and S. aureus counts by 0.9 and 0.7 log cfu/mL, respectively, compared to the control film. The amount of CRV release from developed antimicrobial films can be controlled by MMT concentration within the film matrix and by the storage temperature of film.