Mechanical and oxygen barrier properties of organoclay-polyethylene nanocomposite films

An organically modified montmorillonite was compounded with ethylene vinyl acetate copolymer (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) in a twin-screw extruder. The resulting organoclay-polyethylene nanocomposites were then blown into films. Tensile properties and oxygen permeability of these nanocomposite films were investigated to understand the effects of organoclay on different types of polyethylene. It was found that the clay enhancing effects are function of the matrix. The mechanical and oxygen barrier properties of clay/EVA systems increased with clay loading. Both the tensile modulus and oxygen barrier of EVA doubled at 5 wt% clay. Maleic anhydride grafted polyethylene (MAPE) usually is used as a compatibilizer for LDPE and HDPE-based nanocomposites. However, the MAPEs were found to weaken the oxygen barrier of the PEs, especially for HDPE. This is believed to be a result of less compactness caused by the large side groups and the increase in polarity of the MAPEs. Incorporating 5 wt% clay improves the oxygen barrier by 30% and the tensile modulus by 37% for the LDPE/MAPE system. Incorporation of clay does not enhance the properties of the HDPE-based systems, likely due to large domain structure and poor bonding. Halpin–Tsai equation and the tortuous path equation were used to model the tensile modulus and oxygen permeability of the clay/EVA nanocomposite films. POLYM. ENG. SCI., 47:1101–1107, 2007. © 2007 Society of Plastics Engineers     

All starch nanocomposite coating for barrier material

Starch nanocrystals (SNC) are nanofillers of growing interest for barrier and mechanical improvement of bio‐based polymers. However, their potential use as fillers for organic coating material of industrial packaging has never been investigated. In this study, SNC processability in coating is assessed and the final properties of coated papers are measured. Coating colors composed of plasticized starch show higher Brookfield viscosity when filled with SNC even with the addition of water but rod‐coating is still possible. These diluted water‐based coatings induce paper wetting and surface crackling issues during drying as proved by drying process analysis. However no gelatinization of the SNC is observed whichever the type of drying. SNC compensate some of the water induced loss of mechanical properties of the base paper and decrease the water vapor permeability (WVP) up to 40% compared with the base paper. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39826.     

Microstructure and thermal properties of a promising thermal barrier coating: YTaO4

High temperature gas turbine sealing can increase the thermal efficiency of a gas turbine. In this paper, monoclinic phase YTaO₄ ceramics were fabricated via solid-state reaction. Phase composition and microstructures of the high-temperature-sintered YTaO₄ ceramics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman Spectroscopy. Specific heat capacity rose gradually as temperature increased, due to volumetric expansion and phonon excitations. The thermal diffusivities and conductivities decreased significantly due to the effects of the porosity and phonon scattering. However, the thermal conductivities of the specimens were lower than that of 7–8 wt% yttria-stabilized zirconia (7-8YSZ), and YTaO₄ ceramics have better thermal stability than current (TBCs) material. The Vickers hardnesses of YTaO₄ ceramics as a function of sintering temperature were lower than that of 8YSZ, indicating YTaO₄ has better fracture toughness and thermal tolerance. The results demonstrate that YTaO₄ ceramics would be an excellent candidate for use as a thermal barrier coating material for high temperature gas turbines.     

Mechanical modeling of a three‐phase nanocomposite polymeric material

The presented model to predict the elastic modulus of a polymer/ellipsoidal filler/oblate platelet system is based on Eshelby's equivalent inclusion method and Mori‐Tanaka's back‐stress analysis. We considered wood flour and intercalated clay particles in three‐phase polymer nanocomposites as ellipsoidal and oblate platelet shapes, respectively. The intercalated clay particles along with the polymer chains in the clay galleries are treated as equivalent oblate fillers (EOFs). Via controlling wood flour and EOF aspect ratios (α and β) and the silicate layer number (n) in an EOF, the model prediction was compared with experimental data. The model predicted α and β values are within a range of 2.4–5 and 44–75, respectively, which are in good agreement with experimental observations. Quantitative agreement between model prediction and experimental data is achieved for α = 3.7 and β = 75 when n = 2. The proposed model recovers the two‐phase results for polymer/ellipsoidal filler systems or polymer/oblate platelet systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Curing and barrier properties of NBR/organo-clay nanocomposite

Organo-montmorillonite/NBR nanocomposites were prepared by a melt intercalation process. The characteristics of NBR nanocomposites were characterized by oscillating-disk rheometer, water-vapour transmission and transmission electron microscopy (TEM). Changes in cure characteristics resulting from changes in clay content and the addition of silane coupling agent were investigated. The study confirmed that organo-montmorillonite/NBR nanocomposites cure characteristics, viz minimum torque, maximum torque, scorch time and curing time, change according to the change in clay content and the addition of silane coupling agent. Of the water-vapour transport properties, the clay content and silane content are the dominating factors in determining the individual water-vapour permeability of these NBR nanocomposites. TEM analysis provided clear evidence for the homogeneous dispersion of clay in the NBR matrix without regard to increases in clay content. Copyright © 2004 Society of Chemical Industry     

A promising porous polymer-nanoclay hydrogel nanocomposite as water reservoir material: synthesis and kinetic study

A porous hydrogel nanocopmposite based on biodegradable salep and montmorillonite (MMT) was synthesized by in-situ free radical graft polymerization of salep chains with acrylic acid (AA) monomers. The chemical structure and morphological properties of the prepared hydrogels was evaluated by FTIR spectroscopy, X-ray diffraction and SEM techniques. The effect of reaction variables such as crosslinker, initiator, monomer and clay contents on equilibrium water absorption capacity and swelling kinetic of hydrogel were investigated and optimized. Swelling behavior of the hydrogels in various pH and saline solutions was also studied. Incorporation of MMT into hydrogel matrix caused the formation of porous hydrogel network. These porous structures resulted in higher water uptake capacity and swelling rate in hydrogel nanocomposite in comparison to neat hydrogel sample. Moreover, hydrogel nanocomposite sample exhibited proper salt and pH-sensitive behavior. High swelling capacity and rate, porosity, salt and pH sensitivity make hydrogel nanocomposite a profitable candidate in agricultural and horticultural applications, such as water reservoir system.     

Anticorrosive epoxy/clay nanocomposite coatings: rheological and protective properties

The preparation of epoxy/clay nanocomposites (NCs) and their insertion into coatings are of great importance since the NCs could enhance the protective performances. In this study, epoxy NCs with 1–10 wt% of nanoclay Cloisite 30B (C30B) were prepared by the sonication-assisted solution method. The rheological measurements of epoxy/C30B suspensions revealed non-Newtonian, shear-thinning behavior of the uncured NCs, with an increase in the viscosity, yield stress, and shear modules with increasing organoclay content, while the dispersion effectiveness of C30B decreased. A significant enhancement of the rheological parameters was observed at the second percolation threshold (4.1 vol%) due to the formation of a continuous network of 45-layer-thick tactoids. Although NCs with 1–3 wt% C30B exhibited slightly reduced mechanical and adhesion properties compared with the cured reference epoxy resin, the epoxy primer and topcoat based on NC with 1 wt% C30B generally displayed improved impact resistance and maintained flexibility, pendulum hardness, and good adhesion properties. Two-layer coating systems, i.e., NC-based primers and topcoats, had higher corrosion stability in a salt spray chamber compared to the unmodified system.     

聚吡咯/纳米氧化钇复合材料的结构与性能研究

用在位分散聚合法制得具有核壳结构的聚吡咯/纳米氧化钇复合材料,红外光谱和拉曼散射分析表明纳米氧化钇与聚吡咯之间存在化学作用,红外光谱有明显的蓝移现象,它们的反应发生在氮原子上。而随着Y2O3的加入,电导率呈下降的趋势。     

Nylon 11/silica nanocomposite coatings applied by the HVOF process. II. Mechanical and barrier properties

Nylon 11 coatings filled with nominal 0–15 vol % of nanosized silica or carbon black were produced using the high velocity oxy‐fuel combustion spray process. The scratch and sliding wear resistance, mechanical, and barrier properties of nanocomposite coatings were measured. The effect of powder initial size, filler content, filler chemistry, coating microstructure, and morphology were evaluated. Improvements of up to 35% in scratch and 67% in wear resistance were obtained for coatings with nominal 15 vol % contents of hydrophobic silica or carbon black, respectively, relative to unfilled coatings. This increase appeared to be primarily attributable to filler addition and increased matrix crystallinity. Particle surface chemistry, distribution, and dispersion also contributed to the differences in coating scratch and wear performance. Reinforcement of the polymer matrix resulted in increases of up to 205% in the glass storage modulus of nanocomposite coatings. This increase was shown to be a function of both the surface chemistry and amount of reinforcement. The storage modulus of nanocomposite coatings at temperatures above the glass transition temperature was higher than that of unfilled coatings by up to 195%, depending primarily on the particle size of the starting polymer powder. Results also showed that the water vapor transmission rate through nanoreinforced coatings decreased by up to 50% compared with pure polymer coatings. The aqueous permeability of coatings produced from smaller particle size polymers (D‐30) was lower than the permeability of coatings produced from larger particles because of the lower porosities and higher densities achieved in D‐30 coatings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2272–2289, 2000     

Mechanical properties of porous carbon material: Woodceramics

The mechanical properties of Woodceramics which were made from medium-density fiberboard have been investigated with special reference to the effect of burning temperature on their bending Young's modulus and bending strength. Woodceramics made from beech wood have also been tested to clarify the compressive strength anisotropy, and the role of phenol resin impregnation in strengthening the beech based charcoal.The bending Young's modulus hardly varies for burning temperatures between 300 and 500°C, but it improves remarkably for burning temperatures between 500 and 800°C. The bending strength degrades with temperature for burning temperatures between 300 and 500°C, but it improves remarkably with increasing temperature of burning between 500 and 800°C. The bending Young's modulus and bending strength gradually degrade with temperature for burning temperatures at and above 2000°C.The compressive strength of beech wood burned at 800°C in the longitudinal direction is greater than that in the radial direction, which in turn is greater than that in the tangential direction; this reflects the anisotropy of wood. Woodceramics made from beech wood have a compressive strength superior to beech charcoal in any of the following three directions: 4.5 times in the longitudinal direction, 3.4 times in the radial direction, and 2.0 times in the tangential direction. Both for beech charcoal and beech Woodceramics, brittle fracture is brought about by the buckling of cell wall in compression along the longitudinal direction but by the bending of cell wall in the compression along radial and tangential direction.     

Physical and mechanical properties of nanocomposite barrier film containing encapsulated nanoclay

Waterborne poly(styrene‐co‐butyl acrylate) was prepared via miniemulsion polymerization in which nanoclay (Cloisite® 30B, modified natural MMT) in different concentrations was encapsulated. Scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy confirmed the encapsulation and intercalated‐exfoliated structure of Cloisite® 30B within poly(styrene‐co‐butyl acrylate). The effect of nanoclay content on water vapor permeability, water uptake, oxygen permeability, thermal, and mechanical properties of thin films containing 1.5, 2.56, 3.5, and 5.3 wt % encapsulated Cloisite® 30B in poly(styrene‐co‐butyl acrylate) was investigated. The presence of encapsulated Cloisite® 30B within the polymer matrix improved tensile strength, Young's modulus, and toughness of the nanocomposites depending on the nanoclay content. Water vapor transmission rate, oxygen barrier properties, and thermal stability were also improved. The results indicated that the incorporation of Cloisite® 30B in the form of encapsulated platelets improved physicomechanical properties of the nanoclay‐polymer composite barrier films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ceramic TiC/a:C protective nanocomposite coatings: Structure and composition versus mechanical properties and tribology

The relationship between the structure, elemental composition, mechanical and tribological properties of TiC/amorphous carbon (TiC/a:C) nanocomposite thin films was investigated. TiC/a:C thin film of different compositions were sputtered by DC magnetron sputtering at room temperature. In order to prepare the thin films with various morphology only the sputtering power of Ti source was modified besides constant power of C source. The elemental composition of the deposited films and structural investigations confirmed the inverse changes of the a:C and titanium carbide (TiC) phases. The thickness of the amorphous carbon matrix decreased from 10 nm to 1–2 nm simultaneously with the increasing Ti content from 6 at% to 47 at%. The highest hardness (H) of ~26 GPa and modulus of elasticity (E) of ~220 GPa with friction coefficient of 0.268 was observed in case of the film prepared at ~38 at% Ti content which consisted of 4–10 nm width TiC columns separated by 2–3 nm thin a:C layers. The H3/E2 ratio was ~0.4 GPa that predicts high resistance to plastic deformation of the TiC based nanocomposites beside excellent wear-resistant properties (H/E=0.12).     

Gas barrier properties of butyl rubber/vermiculite nanocomposite coatings

Gas barrier properties of butyl rubber/vermiculite nanocomposites coatings are described here. The coating formulations consisting of a butyl rubber latex (the rubber particles are about 1 μm in diameter) to which exfoliated vermiculite was added were applied to a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) coated Anapore ceramic disc; composites containing 0, 20 and 30 wt% of vermiculite were evaluated. The permeability of the nanocomposite coatings to various gases was measured and compared to permeation models for composites with flake-like fillers proposed by Cussler, Nielsen, Fredrickson and Bicerano, and Gusev and Lusti. The gas permeability of the nanocomposite materials was decreased remarkably by the presence of the high loadings of vermiculite. Diffusion coefficients computed from time lag data also decreased remarkably with the vermiculite content. TEM and SEM were used to observe the internal structure of the nanocomposite membranes in an effort to gain further understanding of the permeability properties. Aspect ratios ranging from 100 to 480 were predicted from the gas permeation results and the above models. TEM experiments could not provide a precise estimate of the aspect ratio but the range predicted from the models are of this order. Apparent solubility coefficients, computed by dividing the experimental permeability by the diffusivity obtained from the time lag observation, increased significantly with vermiculite content in contradiction to the theoretical prediction. Independent gas sorption isotherm experiments for CO₂ were measured and found to be larger than that in butyl rubber possibly due to adsorption on the vermiculite. While this turned out to be a very complicated system, it seems clear from these results that the transient tortuosity factor defined by the time lag is significantly larger than the steady-state tortuosity factor defined by permeability.     

Mechanical and dielectric properties of polyimide/silica nanocomposite films

Polyimide/silica (PI/silica) nanocomposite films were successfully prepared via in situ dispersive polymerisation and thermal imidisation. In order to obtain homogeneous nanoscale dispersibility and good compatibility with the PI matrix, hydrophobic aerosil was selected as the nanosilica precursor. 4,4-Bis(3-aminophenoxy)biphenyl (4,3-BAPOBP) was used as diamine to improve the processability of PI. The PI/silica nanocomposite films were characterised using Fourier transform infrared spectroscopy, scanning electron microscopy and differential scanning calorimetry. The mechanical and dielectric properties of the films were also measured. The results demonstrate that the tensile strength and breakdown strength of films can be markedly improved by the addition of appropriate amounts of silica to the PI matrix. At a silica content of 4.0?wt-%, the tensile strength and the breakdown strength of the films increased by 21 and 13%, respectively, compared with the neat PI. Thus, it is feasible to use nanosilica to improve the properties of PI.     

Bio-based engineered nanocomposite foam with enhanced mechanical and thermal barrier properties

Bio-based polyurethane (PU) foams were developed from bio-polyol (castor oil-based) in the presence of selective catalyst, surfactant, and blowing agent. Bentonite nanoclay (NC) was incorporated into the bio-polyol mixture as nano-reinforcement, while, triethyl phosphate was used as flame-retardant agent. After fabrication, these bioengineered foam nano-composites were studied for microstructural, mechanical and thermal characterizations. Fourier transform infrared spectroscopy analysis indicated the presence of characteristic functionalities within biopolyol segments, which was influenced by reactant activity within the polyurethane (PU) foams. Scanning electron microscopy revealed the cellular morphology of the foam. Thermogravimetric analysis enabled the study of foam decomposition behavior for different sample compositions. Incorporation of NC into pristine foam was found to delay the onset degradation temperature. Flammability studies depicted significant enhancement of flame retardancy with incorporation of NC up to a certain loading level. Compression tests demonstrated that significant improvement of compressive strength properties of foams could be achieved by incorporating bentonite nanoclay, owing to nucleation effect of nanoclay and corresponding enhanced structural integrity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47063.     

Mechanical and antimicrobial properties of multilayer films with a polyethylene/silver nanocomposite layer

A layer of a polyethylene–silver nanoparticles composite was deposited on a five layer barrier film structure. Different methods were used for the nanocomposite layer deposition: laminating, casting, and spraying over the multilayer structure. For the casting and spraying methods, the silver nanoparticles were previously dispersed in the polymer solution, with the assistance of ultrasound energy. The effect of silver nanoparticles and deposition method on the barrier, mechanical, and optical properties of the multilayer films was evaluated. The efficiency of silver ion release from the PE‐Silver nanocomposite deposited on the multilayer films and their antimicrobial characteristics were investigated and discussed. The silver ion release and biocide effect of the multilayer films was found to be dependant on the silver nanoparticle content and on the deposition method used. The observed results could be helpful in the design of industrial films for packaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Andalusite: A promising material for manufacturing high-quality refractories

The process of mullitization of andalusite is reviewed to show that this phase transformation is based on the mechanisms of a pseudomorphism that fixes the grain shape and the chemistry of solid-phase processes. Mullite is oriented in correspondence with the generating crystal of andalusite along the C axis. A single crystal of andalusite transforms into a compound consisting of a mullite single crystal with capillary pores filled with a glass phase saturated with amorphous silica. The capillaries form a network of well-connected tubular pores with a micron cross section, and they are positioned along the C axis common for the newly formed mullite and the original andalusite. About 80% of the glass phase remains in pores of capillaries of the formed mullite. The results of the study were tested in reactions between andalusites of various grain compositions and powder alumina and are now used for fabricating unshaped refractory mixtures with an ultralow content of cement and cement-free mixtures with finely milled andalusite and alumina.     

Performance of corrosion protective epoxy blend-based nanocomposite coatings: a review

ABSTRACT

Epoxy is a thermosetting polymer with exceptional mechanical robustness, thermal stability, and chemical resistance. This article is devoted to updating development, processing, and physicochemical characterizations of epoxy-based anti-corrosion coatings. Incorporation of different polymers in epoxy matrix has motivated extensive research progress in the field of corrosion protection. Epoxy has been blended with polyaniline, polypyrrole, polythiophene, polyamide, polyester, polyurethane, poly(vinyl alcohol), and polydimethylsiloxane to form corrosion protective coatings. The addition of conducting polymer and nanofiller to epoxy matrix modified the nanocomposite morphology and facilitated the development of passive layer at metal/polymer interface. Consequently, nanocomposite coatings act as physical barrier to hinder the penetration of corrosive ions. Likewise, fine dispersion of nanocarbon and inorganic nanoparticles in compatible blends of epoxy/polyamide, epoxy/polyester, epoxy/polyurethane, and epoxy/poly(vinyl alcohol) has resulted in improved adhesion, wear, barrier and anticorrosion properties of the nanocomposite coatings. Design of epoxy blend-based nano-architectures may facilitate appropriate tailoring of overall performance of the resulting anti-corrosion coatings for advance technical applications including aerospace, automotive, construction, electronic devices, and biomedical relevances. New processing techniques may overcome challenges toward high performance future epoxy-based coatings.     

Thermal and barrier properties of EVOH/EFG nanocomposite films for packaging applications: Effect of the mixing method

Ethylene‐vinyl alcohol copolymer (EVOH)/exfoliated graphite (EFG) nanocomposite films were prepared by precoating EFG on the EVOH surface and conducting a successive melt‐extrusion process. Their physical properties were strongly dependent on the EFG content and the mixing method, which strongly affected the morphology and surface properties of the nanocomposite films. The hydrophobicity and water resistance property of EVOH increased by incorporating hydrophobic EFG and their effects were more pronounced in the precoating method, which is related to good dispersion of EFG in EVOH and an enhanced crystalline structure. The incorporation of EFG into EVOH by the precoating method more effectively diminished the dependence of the relative humidity on the oxygen transmission rate of pure EVOH and increased the oxygen barrier properties of EVOH at a high relative humidity. The incorporation of EFG into EVOH by the precoating method also induced relatively more enhanced thermal stability. These results suggest the feasibility of the application of moisture‐sensitive EVOH resin for food packaging films. POLYM. COMPOS., 37:1744–1753, 2016. © 2014 Society of Plastics Engineers     

EVOH nanocomposite films with enhanced barrier properties under high humidity conditions

To improve the oxygen and water vapor barrier properties of ethylene vinyl alcohol, EVOH/EFG nanocomposite films under high humidity conditions, we successfully prepared highly exfoliated graphite (EFG) containing a monolayer or a few layers of graphene via rapid heating treatment and ultrasonication as confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), elemental analysis (EA), and nitrogen adsorption–desorption analysis. Six different EVOH/EFG nanocomposite films containing as‐prepared EFG were prepared via a solvent blend method and their physical and barrier properties at different relative humidities were investigated as a function of EFG content. Depending on the EFG content, oxygen transmission rate (OTR) decreased from 3.7 to 0.1 cc/m²/day at dry condition, and the difference in OTR between dry condition and humid condition decreased from 6.5 to 2.3 cc/m²/day. Barrier properties of the EVOH/EFG nanocomposite films were strongly dependent on their chemical structure and morphology. Crystallinity, tortuous path length, and hydrophobicity of EVOH/EFG nanocomposite films were enhanced by the addition of EFG. However, the thermal stability and glass transition temperature of the nanocomposite films were not improved by incorporation of EFG due to the weak interaction between EVOH and EFG. To maximize the performance of EVOH/EFG nanocomposite films, the compatibility of the polymer matrix and fillers needs to be improved. POLYM. COMPOS., 35:644–654, 2014. © 2013 Society of Plastics Engineers