Modeling diffusion mass transport in multiphase polymer systems for gas barrier applications: A review

Polymer nanocomposites offer a great interest as gas barrier materials because of their much‐enhanced properties arising from the nanoparticles shape, size, and spatial arrangement within the matrix. However, optimization and further development of such materials requires fundamental understanding of the influence of the nanocomposite structure on permeating gas diffusion. This step can be greatly facilitated through modeling/simulation strategies able to establish relationships between the material microstructure and the achieved enhancement of barrier properties. This review first presents the analytical models developed to estimate the effective diffusivity in polymer nanocomposites. The predictions of the models are analyzed with respect to experimental data reported in the literature and their ability to describe accurately the nanocomposite transport properties when the microstructure complexity increases is discussed. Then, modeling approaches based on numerical simulation techniques (e.g., the finite element method) that allow simulating the diffusion processes and assessing the effect of filler shape, orientation, dispersion, and spatial arrangement are reviewed and discussed. Finally, the importance of 3D simulation strategies for the understanding and prediction of transport properties in the most complex nanocomposite microstructures is addressed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 621–638     

Impact of coated calcium carbonate nanofillers and annealing treatments on the microstructure and gas barrier properties of poly(lactide) based nanocomposite films

Amorphous poly(lactide) (PLA) and nanocomposite films were prepared from melt‐blending with precipitated calcium carbonate nanofillers (PCC). Nanocomposites based on uncoated PCC (PCC‐UT), stearic acid coated PCC (PCC‐S), and poly(ε‐caprolactone) coated PCC (PCC‐P) were investigated for an inorganic content fixed to 8 wt %. Using coated nanofillers allowed preserving both PLA average molar mass and thermal stability while enhancing the nanofiller dispersion state. Poly(ε‐caprolactone) was identified as the best coating for optimized morphology and thermal properties. Maxwell law accurately described the increase in oxygen barrier properties observed for the nanocomposites based on PCC‐S. A modified Maxwell law was proposed to take account of the additional increase in barrier properties evidenced for the PLA/PCC‐P nanocomposites and assigned to the particularly strong compatibility between PCL and PLA. Different annealing conditions were investigated to respectively study the impact of physical ageing and PLA crystallization on gas permeability. Different extents of physical ageing did not significantly modify the oxygen transport properties. However, a high permeability decrease was observed for the semicrystalline nanocomposites with respect to the amorphous reference PLA film. Finally, the gain in barrier properties was shown to result from both contribution of the nanofillers and the crystalline phase. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 649–658     

Barrier and Mechanical Properties of Poly(caprolactone)/organoclay Nanocomposites

In this study, biodegradable poly(caprolactone) (PCL) hybrids with two types of organoclays: Cloisite 30B (30B) and Cloisite 93A (93A) have been prepared by melt mixing and their barrier performance to air permeation and mechanical properties were investigated. The hybrids of PCL/30B were found to be nanocomposites resulted from the strong interaction between organic modifier of 30B and PCL and those of PCL/93A were microcomposites. The barrier performance of PCL/30B nanocomposite film to air permeation was much more improved than pure PCL and PCL/93A microcomposites at low organoclay concentration. With the increase of organoclay content the permeability coefficient was also increased that could attributed to the extra tortuous pathway for gas permeation caused by organoclay exfoliation. The barrier behaviour of PCL/30B nanocomposites could be approximately described by a theoretical model developed for composites. The mechanical properties measurements showed that the reinforcement of organoclay 30B in nanocomposites is more significant than 93A in microcomposites. Both tensile modulus and tensile strength were increased in PCL/30B nanocomposites even at at low amount of organoclay without much loss of strain at break as compared to pure PCL. The significant improvements in both barrier and mechanical properties in PCL nanocomposites could be attributed to the fine dispersion state of organoclay 30B platelets in PCL matrix and the strong interaction between organic modifier of 30B and matrix molecules.     

Functional nanocomposites prepared by self-assembly and polymerization of diacetylene surfactants and silicic acid

Conjugated polymer/silica nanocomposites with hexagonal, cubic, or lamellar mesoscopic order were synthesized by self-assembly using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. By tailoring the size of the oligo(ethylene glycol) headgroup of the diacetylene-containing surfactant, we varied the resulting self-assembled mesophases of the composite material. The nanostructured inorganic host altered the diacetylene polymerization behavior, and the resulting nanocomposites show unique thermo-, mechano-, and solvatochromic properties. Polymerization of the incorporated surfactants resulted in polydiacetylene (PDA)/silica nanocomposites that were optically transparent and mechanically robust. Molecular modeling and quantum calculations and (13)C spin-lattice relaxation times (T(1)) of the PDA/silica nanocomposites indicated that the surfactant monomers can be uniformly organized into precise spatial arrangements prior to polymerization. Nanoindentation and gas transport experiments showed that these nanocomposite films have increased hardness and reduced permeability as compared to pure PDA. Our work demonstrates polymerizable surfactant/silica self-assembly to be an efficient, general approach to the formation of nanostructured conjugated polymers. The nanostructured inorganic framework serves to protect, stabilize, and orient the polymer, mediate its performance, and provide sufficient mechanical and chemical stability to enable integration of conjugated polymers into devices and microsystems.     

Towards high‐performance biopackaging: barrier and mechanical properties of dual‐action polycaprolactone/zinc oxide nanocomposites

The properties of nanocomposites of biodegradable polycaprolactone containing zinc oxide (ZnO) nanoparticles with diverse morphologies, that is, ZnO nanospheres, nanorods, and nanodisks are investigated. It is demonstrated for the first time that the dual action of the ZnO nanoparticles reduces the gas permeability of the nanocomposites via two mechanisms: first by the creation of a tortuous path and second by gas adsorption. Depending on the morphology of the particles, the oxygen permeability can be reduced by more than 60%. Tensile tests show that the nanocomposites remain very ductile. The nominal strain for all nanocomposites is higher than 500% before fracture occurs. The Young's modulus and tensile strength of the nanocomposites increase at higher ZnO concentrations. This behavior is more pronounced in the case of ZnO nanorods. As a result, the incorporation of ZnO nanoparticles into (bio)polymers provides an opportunity to manufacture polymer‐based nanocomposite materials, resulting in the production of high‐performance (bio)packaging. Copyright © 2011 John Wiley & Sons, Ltd.     

Surface modified graphene oxide/poly(vinyl alcohol) composite for enhanced hydrogen gas barrier film

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film.     

3D Mass diffusion in ordered nanocomposite systems: Finite element simulation and phenomenological modeling

The optimization of polymer barrier properties is currently of crucial importance for a wide range of applications from packaging to building or even energy applications. To meet the requirements of these applications, polymer matrices are often combined with impermeable (nano) fillers. Different nanofiller natures, shapes, and contents have been experimentally used and a large range of barrier materials has been obtained^. In the meantime, several numerical approaches have been developed to model gas diffusion properties of nanocomposite materials. However, these approaches often considered bidimensional systems. The aim of this work is to develop 3D Finite Element Model which would be used to predict gas barrier properties of nanocomposites for disk‐shaped nanofillers. The model thus obtained is valid in a wide range of fillers volume fraction values as well as aspect ratios, which makes it possible to go from diluted regimes to semidiluted or even concentrated ones. Furthermore, an analytical equation which describes gas diffusion through nanocomposites films has been built and validated with our finite element modeling model. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 51–61     

PLA-ZnO nanocomposite films: Water vapor barrier properties and specific end-use characteristics

PLA nanocomposite films with multifunctional characteristics such as mechanical, anti-UV, antibacterial, electrical, gas barrier properties are potentially of high interest as packaging biomaterials. Occasionally, desired and beneficial effects obtained by addition nanofillers come along with some drawbacks, leading to the sharp drop in the molecular weights of the polyester chains, and consequently an important loss of mechanical and thermal properties. Novel PLA-ZnO nanocomposite films were produced by melt-compounding PLA with 0.5–3% ZnO rod-like nanoparticles. The surface treatment of nanofiller by silanization (with triethoxy caprylylsilane) was necessary to obtain a better dispersion and to limit the decrease of molecular mass of PLA. The morphology, molecular, thermo-mechanical and transport properties to water vapor of PLA-ZnO films were analyzed with respect to the neat PLA. According to DSC and to XRD, the produced films were essentially amorphous. The changes in PLA permeation properties were strongly dependent on temperature and nanofiller loading. The well dispersed ZnO nanoparticles within the polyester matrix were effective in increasing the tortuosity of the diffusive path of the penetrant molecules. The activation energy remained similar for PLA and PLA-1% ZnO, but was found greater at higher loading of ZnO (3%), confirming the increased difficulty of travelling molecules to diffuse through PLA. In comparison to the neat PLA (presenting no antimicrobial efficacy), the nanocomposites were active against both Gram-positive and Gram-negative bacteria, stronger antibacterial activity being evidenced after 7 days elapsed time. By considering the multifunctional properties of PLA-ZnO nanocomposites, the films produced by extrusion can be considered a promising alternative as environmental-friendly packaging materials.     

聚乳酸纳米复合材料的研究进展

聚乳酸是一种重要的可生物降解/吸收高分子材料,广泛地用作可降解塑料、纤维和生物材料,市场前景广阔.它具有与聚烯烃相当的力学强度和加工性能,但耐热性和抗冲性较差.为满足各种应用的需要,其热性能、力学性能和气体阻隔性等尚需进一步提高.通过与无机纳米材料复合的方法,可以明显地提高聚乳酸的性能.本文介绍了近年来聚乳酸有机-无机纳米复合材料的制备、结构与性能等方面的研究进展,对三者的相互关系进行了评述,并对今后的研究方向进行了展望.     

Preparation and Characterization of PET/LDH or Clay Nanocomposites through the Microcompounding Process

Thermally stable modifier were used to modify clay or lithium aluminum layered double hydroxides (LiAl LDH) nanoparticles for preparation of poly (ethylene terephthalate)/clay or LiAl LDH nanocomposites. The effect of modify agent, studied by microcompouding process. The PET nanocomposites which were made by twin‐screw microcompounder dispersion morphology of inorganic layered materials in nanocomposites could be explained by wide‐angle X‐ray diffraction (WXRD), and transmission electron microscopy (TEM). Nanocomposite also formed the better mechanical, UV resistance, and gas barrier properties. Optical properties and crystallization behaviour of these new types of nanocomposites are investigated in this paper.     

导电高分子纳米复合材料

导电高分子纳米复合材料是纳米材料研究中一个重要部分。着重综述了导电高分子无机纳米复合材料在合成技术、材料性质和各领域中应用的最新研究进展。     

Polymer/graphite nanocomposites: Effect of reducing the functional groups of graphite oxide on water barrier properties

Water barrier properties (i.e., water resistance) of poly(styrene-co-butyl acrylate)/graphite oxide (poly(St-co-BA)/GO) nanocomposites were studied using hydrophobicity and permeability analysis. Poly(St-co-BA)/GO nanocomposite latices were obtained using the miniemulsion polymerization technique. The hydrophobicity of the synthesized nanocomposites was studied using contact angle measurements, while water permeability was obtained by measuring the moisture vapor transmission rate (MVTR). The nanocomposites were treated with hydrazine hydrate in order to reduce the functional groups on graphite oxide (GO). The focus was on determining the effect of reducing the functional groups of GO on the water barrier properties of its polymer nanocomposites. In general, the nanolayered graphene platelets in GO and RGO resulted in lower water permeation in the final films compared to pure polymer. However, results showed that nanocomposites containing the reduced-GO (RGO) had better water resistance and barrier properties compared to those made with unreduced GO (i.e., as-prepared GO). The nanocomposites containing RGO had higher hydrophobicity and lower water uptake and MVTR compared to those made with as-prepared GO, resulting in better barrier performance. This was attributed to the high hydrophobic nature of the RGO, which exhibited lower water solubility that resulted in films with lower MVTR values compared to those made with as-prepared GO.     

Effect of chemical structure on combustion and thermal behaviour of polyurethane elastomer layered silicate nanocomposites

The effect of polyol molecular weight and functionality on nanodispersion of clay in PU/clay nanocomposites and the investigation of their thermal and combustion properties are reported and discussed. Lamellar elastomer polyurethane nanocomposites were synthesized using polyols with different molecular weight and functionality and according to these parameters they show several degrees of dispersion which affect their thermal and combustion behaviour. A barrier effect of clay layer is shown in TGA experiments by a delay of thermal degradation products release in nanocomposite materials compared to the virgin polymer; this barrier effect also leads to formation of char during combustion which lowers the peak of rate of heat release in cone calorimeter tests and eliminates fire-induced dripping of the nanocomposite sample during UL 94 test. However, in order to achieve non-burning behaviour nanocomposite technology must be combined with conventional flame retardant technology.     

有机-无机纳米复合材料光谱与电子性质研究进展

有机-无机纳米复合材料的研究在当前纳米科学技术的发展中占有重要地位，开创了材料与催化科学研究的新纪元。自从10年前首次合成纳米孔无机材料MCM-41至今，该领域研究不断深入，已展现出广阔的应用前景。当客体有机分子分散于纳米孔道内部时，其分子性质将产生明显变化。本文结合作者近期研究成果，力图从实验与理论两方面阐明在纳米复合体系中客体分子性质变化的原因。     

Gas barrier behavior of polyimide films filled with synthetic chrysotile nanotubes

Chrysotile nanotubes (ChNTs) were synthesized under hydrothermal conditions. These synthetic nanotubes crystallographically and morphologically mimic the nanofibrils of natural white asbestos but they are considerably shorter. ChNTs containing polyimide nanocomposites were prepared by a solution mixing/casting method. Oxygen and water vapor barrier of the nanocomposite films were tested and related to the amount, dispersion, and orientation of the nanotubes. The dispersion and orientation of the nanotubes were examined by transmission electron microscopy (TEM). The nanotubes were nanodispersed and oriented in the plane of the film in the nanocomposites with up to 4.5% (vol/vol) of ChNTs leading to a gradual increase of the gas barrier. The lowest gas permeability was 60% smaller than that for the pristine polyimide film. However, with the onset of nanotube micro aggregation at larger ChNTs loadings the nanotube dispersion and orientation were compromised and oxygen barrier was reduced. The efficacy of nanotubes to enhance polymer gas barrier was discussed and compared with that by nanoplatelets. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1184–1193     

Effect of multiscale structure on the gas barrier properties of poly(lactic acid)/Ag nanocomposite films

Poly(lactic acid) (PLA) is the most suitable for biodegradable packaging film because of its excellent integrated property, but the poor gas barrier property is its weakness. In this study, a nanocomposite film based on PLA incorporated with 0‐, 1‐, 3‐, 5‐, 10‐, or 15‐wt% nano‐Ag was developed. Effect of multiscale structure on the barrier properties of PLA/nano‐Ag films was studied. The PLA nanocomposite film with 5‐wt% nano‐Ag had the lowest water vapor permeability (WVP) value. Oxygen transmission rate (OTR) value for PLA nanocomposites with 3‐wt% nano‐Ag was found to be the lowest among all the samples. Multiscale structure was demonstrated by the scanning electron microscopy, Fourier transform‐infrared spectroscopy, X‐ray diffraction measurement, and differential scanning calorimetry results. The crystallinity of the PLA phase increased with the content of nano‐Ag in the PLA composites. The evolution of the PLA phase crystallinity could improve the barrier properties of PLA/nano‐Ag composite films for food packaging applications. From the view of multiscale structure, it is better to achieve a balance among short‐range conformation in the amorphous region, long‐range‐ordered structure, and ordered aggregated structure to improve the barrier properties of PLA/nano‐Ag composite films.     

Elastomer Nanocomposite; Properties

Polymer nanocomposites represent a class of materials that have assumed great importance in recent years and are the focus of extensive research. Unlike plastomer nanocomposites, the elastomer nanocomposites are in the stage of infancy in respect to their applications.

In general, in polymer composites, the matrix and the filler are bonded to each other by weak intermolecular forces and covalent bonding are rarely involved. If the filler could be dispersed in the polymer matrix at the nanometre level and is able to interact with the matrix by chemical bonding, nanocomposites with significant properties improvement are obtained. These improvements can include mechanical properties (module, strength, etc.), thermal resistance, decrease in gas permeability (barrier), flammability, etc.

This paper is a review of the property improvements of different elastomers using nanofillers like silicates, carbon black, metallic powders, cellulose crystals, mixture of nanofillers, etc, with the intention of obtaining elastomer nanocomposites.     

Functional inorganic nanofillers for transparent polymers

The integration of inorganic nanoparticles into polymers has been used for the functionalization of polymer materials with great success. Whereas in traditional polymer composites, micron sized particles or agglomerates typically cause significant light scattering hampering optical applications, in nanocomposites the particle dimensions are small enough for the production of highly transparent composites. A challenge for the generation of such materials is to develop an integrated synthesis strategy adapting particle generation, surface modification and integration inside the polymer. Surface grafting using polymerizable surfactants or capping agents allows for linking the particles to the polymer. Novel techniques such as in situ polymerization and in situ particle processing are beneficial to avoid aggregation of inorganic particles inside the polymer matrix. The functions associated with inorganic fillers are widespread. Layered silicates and related materials are nowadays commercially available for improving mechanical and barrier properties in packaging. With the availability of highly transparent materials, the focus has shifted towards optical functions such as luminescence and UV-protection in transparent polymers. IR-active fillers are used in laser-holography for transparent poly(methyl methacrylate) (PMMA) nanocomposites. Refractive index modulation and ultrahigh refractive index films were developed based on inorganic materials such as PbS. The integration of magnetic nanoparticles has a great potential for applications such as electromagnetic interference shielding and magneto-optical storage.This tutorial review will summarize functions associated with the integration of inorganic nanofillers in polymers with a focus on optical properties.     

In situ synthesis of polyethylene terephthalate nanocomposites using bis (2‐hydroxyethyl) phthalate monomer

In this article, we address in situ synthesis of polyethylene terephthalate (PET) nanocomposites using the bis (2‐hydroxyethyl) phthalate monomer and inorganic layered materials (sulfanilic acid salt‐modified magnesium aluminum‐layered double hydroxides [MgAl LDH‐SAS] and Dimethyloctadecyl [3‐(trimethoxysilyl) propyl] ammonium chloride [DTSACl] and tetraethyl orthosilicate [TEOS]‐ modified clay [CL120‐DT]). The dispersion morphology of the synthesized nanocomposites was evaluated using XRD and TEM, from these results, it was confirmed that 0.5 wt% loaded PET/MgAl LDH‐SAS and PET/CL120‐DT nanocomposites have flocculated and intercalated morphologies, respectively. Thermomechanical analyses were performed by thermogravimetric analysis, dynamic mechanical analysis, and differential scanning calorimetry, respectively. Moreover, the water vapor transmission rate (WVTR) values of a pure PET, PET/CL120‐DT 0.5 wt%, and PET/MgAl LDH‐SAS 0.5 wt% nanocomposites were found to be 49, 45, and 46 g·m^?2·day^?1, respectively. Furthermore, the gas barrier properties of PET composite films containing various amounts of inorganic nanoparticles were investigated using Gas permeability analysis (GPA).     

Bionanocomposites of Cassava Starch and Synthetic Clay

Starch-based biofilms containing synthetic Laponite clay and glycerol were prepared using a solvent casting technique. Electron microscopy images showed predominance of the exfoliated type of nanocomposite. Dynamic mechanical analysis revealed a larger influence of glycerol content on the polymer β relaxation and T _g than the clay content. Gas barrier properties were influenced by clay particles and plasticizer content. An increase of clay content led to lower gas permeability values. Although both glycerol and Laponite are hydrophilic, no significant changes were observed on the water sorption by starch films at different relative humidity values. Mechanical properties are kept similar after the inorganic filler incorporation.