Physical properties of poly lactic acid/clay nanocomposite films: Effect of filler content and annealing treatment

Polylactic acid (PLA)‐based nanocomposite films, containing up to 5% by weight of two types of nanoclays: sepiolite needle‐like clay and halloysite nanotube clay, were prepared via industrially viable melt processing route. Clays modify the crystallinity of the hosting PLA affecting its gas barrier and mechanical properties. Annealing treatments of composite films were found to be critical in the optimization of these properties with an additional enhancement in crystallinity and stiffness especially in presence of clays. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39798.     

Structural,thermal, and gas transport properties of HDPE/LLDPE blend‐based nanocomposites using a mixture of HDPE‐g‐MA and LLDPE‐g‐MA as compatibilizer

Nanocomposites based on high density polyethylene (HDPE)/linear low density polyethylene (LLDPE) blend were prepared by melt compounding in a twin‐screw extruder using organoclay (montmorillonite) as nano‐filler and a 50/50 wt% mixture of maleic anhydride functionalized high density polyethylene (HDPE‐g‐MA) and linear low density polyethylene (LLDPE‐g‐MA) as the compatibilizing system. The addition of a maleated polyethylene‐based compatibilizing system was required to improve the organoclay dispersion in the HDPE/LLDPE blend‐based nanocomposite. In this work, the relationships between thermal properties, gas transport properties, and morphology were correlated. The compatibilized nanocomposite exhibited an intercalated morphology with a small number of individual platelets dispersed in the HDPE/LLDPE matrix, leading to an significant decrease in the oxygen permeation coefficient of the nanocomposites. A decrease in the carbon dioxide permeability and oxygen permeability with increase of nanoclay was observed for the compatibilized nanocomposites. The carbon dioxide permeability of the compatibilized nanocomposites was lower than the carbon dioxide permeability of the uncompatibilized nanocomposites even with the low intrinsic barrier properties of the compatibilizer. These effects were attributed to a good dispersion of the inorganic filler, good wettability of the filler by the polymer matrix, and strong interactions at the interface that increased the tortuous path for diffusion. Theoretical permeability models were used to estimate the final aspect ratio of nanoclay in the nanocomposite and showed good agreement with the aspect ratio obtained directly from TEM images. POLYM. ENG. SCI., 56:765–775, 2016. © 2016 Society of Plastics Engineers     

Preparation and characterization of polynorbornene/sepiolite hybrid nanocomposite films

Polynorbornene/sepiolite hybrid nanocomposite films were prepared using polynorbornene dicarboximide and modified sepiolite with 3‐ aminopropyltriethoxysilane (3‐APTES). Exo‐N‐(3,5‐dichlorophenylnorbornene)‐5,6‐dicarboxyimide (monomer) and their copolymers were synthesized via ring‐opening polymerization using ruthenium catalysts. Subsequently, the surface‐modified sepiolite by 3‐APTES was mixed with the polynorbornene copolymers to prepare hybrid nanocomposite films. The modified sepiolite particles were well dispersed in N,N‐dimethylacetamide and distributed randomly throughout the polynorbornene matrix in the hybrid films, which enhanced the dimensional stability and mechanical and oxygen barrier properties of the polynorbornene/sepiolite hybrid nanocomposite films. © 2014 Society of Chemical Industry     

PLA/functionalized‐gum arabic based bionanocomposite films for high gas barrier applications

The present work focuses on the microwave synthesis of lactic acid‐grafted‐gum arabic (LA‐g‐GA) by polycondensation reaction and its influence as an additive to improve the gas barrier properties of poly(lactic acid) (PLA) films, prepared by solution casting method. It is observed that during the synthesis of LA‐g‐GA, hydrophilic gum is converted into hydrophobic due to grafting of in situ grown hydrophobic oligo‐(lactic acid). Subsequently, PLA/LA‐g‐GA bionanocomposite films are fabricated and characterized for structural, thermal, mechanical and gas barrier properties. Path breaking reduction in oxygen permeability (OP) of ～10 folds is achieved in case of PLA films containing LA‐g‐GA as filler. However, water vapor transmission rate (WVTR) is reduced up to 27% after 5 wt % addition of filler. Reduction in OP of this order of magnitude enables the PLA to compete with PET in term of enhancing shelf life and maintaining the food quality. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43458.     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A model for water vapor permeability reduction in poly(lactic acid) and nanoclay nanocomposites

Poly(lactic acid) (PLA) is used in packaging applications, but its moisture barrier properties are inferior to poly(ethylene terephthalate) and polystyrene. One objective of the study was to improve these by dispersing nanoclay in PLA. It was found that Cloisite 30B nanoclay showed the best dispersion based on both permeability and transmission electron microscopy results. Compression molded nanocomposite films were amorphous, and moisture permeability measurements revealed that, at the highest loading level of 5.3 vol % organoclay, permeability was reduced by 69% compared to neat PLA. Additionally, independent experiments demonstrated that moisture solubility in the polymer remains unchanged even as solubility in the nanocomposite increases with increasing clay content. A second objective was to explain the measured permeability reduction. A new model is proposed where both the mass flux and area for mass transfer are reduced due to a tortuous path around the impermeable barriers. It is shown that the permeability decreases by a factor of where h/t is the aspect ratio of the nanoplatelets, and ? is their volume fraction. Model predictions agree quantitatively with the measured permeability values when data are obtained as a function of filler volume fraction, temperature of measurement, and the concentration driving force. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46506.     

Barrier and Mechanical Properties of Clay-Reinforced Polymeric Nanocomposites

In this work, clay-based nanocomposites films were prepared by addition of clay-Na⁺ natural montmorillonite in pectin and hydroxypropyl methylcellulose (HPMC) matrices. Mechanical (tensile strength, elastic modulus, and elongation) and barrier (Water Vapor Permeability (WVP), and Oxygen permeability (O₂P)) properties were investigated. From results, it was observed that the WVP and O₂P decreased when nanoclay was included into the HPMC and pectin matrix films. Additionally, the incorporation of nanoclay in the films significantly improved the mechanical properties because the reinforcing effect of clay from its high aspect ratio and its enormous surface area. These results are very important in packaging area.     

Optimal designing of polyurethane‐based nanocomposite system for aerostat envelope

This article reports an optimal designing of thermoplastic polyurethane (TPU) nanocomposite formulation, particularly targeting aerostat envelope for enhanced weathering and gas barrier properties. The synergistic effect of conventional UV protective additive with advanced nano materials (i.e. nanoclay and graphene) on TPU‐based formulations was explored. A series of formulations were prepared in accordance with a mixture design for three components additives (UV stabilizer, nanoclay, and graphene) and coated on to a woven polyester (PET) fabric. The coated systems were evaluated for resistance to UV radiation, resistance to helium gas permeability, and loss in both the properties against accelerated artificial weathering. The composition of the additive mixture was simultaneously optimized by desirability function approach with a view to maximize UV radiation protection and minimize helium gas permeability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43529.     

Characterization and electrical conductivity of poly(ethylene glycol)/polyacrylonitrile/multiwalled carbon nanotube composites

Poly(Lactic acid) (PLA)‐layered silicate nanocomposite films were prepared by solvent casting method. The films were irradiated with Co⁶⁰ radiation facility at dose of 30 kGy. The effect of γ irradiation on mechanical properties of the neat PLA and nanocomposites was evaluated by data obtained from tensile testing measurements. The tensile strength of the irradiated PLA films increased with addition of 1 wt % triallyl cyanurate indicating crosslink formation. Significant ductile behavior was observed in the PLA nanocomposites containing 4 pph of nanoclay. Incorporation of nanoclay particles in the PLA matrix stimulated crystal growth as it was studied by differential scanning calorimetry. The morphology of the nanocomposites characterized by transmission electron microscopy and X‐ray diffraction revealed an exfoliated morphology in the PLA nanocomposite films containing 4 pph of nanoclay. Only very small changes were observed in the chemical structure of the irradiated samples as it was investigated by Fourier transform infrared spectroscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Laser transmission welding of poly(lactic acid) and polyamide66/sepiolite nanocomposites

Influence of sepiolite nanoclay on the properties of the resulting join between poly(lactic acid) (PLA) and different Polyamide66 (PA66)/nanoclay nanocomposites was studied in this work. Six different polymer nanocomposites based on PA66 were manufactured through a melt compounding process by adding a fixed 1.64 wt % of a commercial IR absorber additive and the respective weight percentages of sepiolite to the polymer matrix. Several nanocomposite/PLA joints were finally performed by means of the transmission laser welding technology and the resulting weldings were characterized in terms of mechanical properties by performing peeling and shearing tests. Furthermore, both welded and mechanically tested samples were also analyzed by scanning electron microscopy in order to study the morphology of the weld seam. The results of the performed tests show that the addition of sepiolite to the PA66 improves the welding performance only in those cases in which the percentage of sepiolite of the nanocomposites is higher than 5 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46638.     

Barrier properties of poly(lactic acid)/cloisite 30B composites and their relation between oxygen permeability and relative humidity

Poly(lactic acid) based nanocomposite films were prepared by melt compounding and subsequent flat film extrusion. After characterizing the nanocomposites with the help of transmission electron microscopy and wide angle X‐ray diffraction to estimate the nanoclay distribution in the matrix material, the oxygen and water vapor permeability of untreated and annealed nanocomposite films were analyzed. A reduction to 34% of both permeability values could be realized by the addition of 6 wt % Cloisite 30B and subsequent annealing to realize maximum crystallinity. Experimental permeability as a function of nanoclay concentration was successfully described by the Tortuous Path Model. In addition, the correlation between oxygen permeability and relative humidity was analyzed for pure PLA and PLA based nanocomposite films. For both untreated films oxygen permeability decreased almost linearly between 0% and 96% RH to approximately 70% of the respective value for the dry sample. Annealed PLA films, on the other hand, showed a similar behavior up to 70% RH but an increase in oxygen permeation for higher moisture content. This is explained by the observed reduction in crystallinity generating more free volume, bringing the system closer to the amorphous case where permeability is generally higher. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44424.     

Temperature dependency of gas barrier properties of biodegradable PP/PLA/nanoclay films: Experimental analyses with a molecular dynamics simulation approach

Polypropylene (PP)/poly(lactic acid) (PLA)/clay nanocomposite films with various compositions (PP‐rich and PLA‐rich) were prepared. Their structural and barrier properties against CO₂, O₂, and N₂ were investigated. The microstructure of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy, and wide angle X‐ray scattering. The PP‐rich with 75/25 composition revealed the best barrier properties against all the gases which could be justified according to its microstructure. Selectivity of O₂/N₂ and CO₂/N₂ was also measured. It was found that the addition of nanoclay as a gas barrier component reduced the permeability in both systems. The permselectivity was also reduced in the PP‐rich films while it was increased in the PLA‐rich system. Moreover, the temperature dependency of permeability, selectivity, and permselectivity for PP, PLA, and PP/PLA (75/25) samples was examined. The results showed that the temperature dependence of permeability obeyed an Arrhenius equation and order of activation energy of permeability for O₂, CO₂, and N₂ gases was found to be E_P < E_P/PLA < E_PLA. According to solubility measurements, the order of solubility coefficient for gases was as follows: CO₂ > O₂ > N₂. Finally, the molecular dynamics (MD) simulation was performed to estimate the diffusivity coefficients of the gases and showed that solubility increases with increasing temperature, which was in accordance with the experiments. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46665.     

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     

Influence of Nanoclay Localization on Structure–Property Relationships of Polylactide‐Based Biodegradable Blend Nanocomposites

This article highlights the recent research achievements regarding the development of nanoclay‐containing biodegradable composites of polylactide (PLA)‐based immiscible blends. The structure–property relationships of particular blends, namely, PLA/poly(ε‐caprolactone), PLA/poly(butylene succinate), and PLA/poly[(butylene succinate)‐adipate], are studied with respect to the nanoclay incorporations. For different nanoclay types and concentrations, the morphologies of these nanocomposites are probed and correlated to their viscoelastic, mechanical, and thermal properties, along with their crystallization behavior and kinetics and gas permeability. The nanoclay dispersion and distribution characteristics are found to be key parameters influencing the final properties. In particular, nanocomposites with a higher degree of nanoclay dispersion exhibit significant enhancement in their mechanical, thermal, and barrier properties, and some agglomerations are effective as regards favorable crystallization behavior. In terms of the clay localization, the positioning of nanoclays at the interface reduces the minor phase size remarkably, because of the droplet encapsulation that counteracts coalescence. However, for improved understanding of the influence of nanoclay localization on the structure–property relationships of these blends, further systematic study is required. That is, nanocomposites with different localizations but the same nanoclay loads should be compared. This can be achieved by tuning the processing protocols and the nanoclay inclusion orders in the blends.     

Polyethylene‐based nanocomposite films: Structure/properties relationship

Polyethylene (PE) is the most used thermoplastic commodity as a consequence of its convenient cost‐processing‐performance relationship and it can be used in the form of films for food, goods and farming packaging. On the other hand, sepiolite is a high surface area and porosity hydrated magnesium silicate with both remarkable adsorptive and absorptive properties. Thus, PE and sepiolite can combine their properties synergetically to obtain new materials with enhanced properties. In this work, a systematic study of final properties of PE‐sepiolite nanocomposite films was performed to investigate the influence of the sepiolite content and modification on the PE properties. Nanocomposites films with 1, 3, 5 and 10 wt % of sepiolite, with and without surface modification, were prepared by cast film extrusion and tested. The filler dispersion and distribution were evaluated by Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR), whereas the film crystalline morphology was analyzed using Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC) and X‐ray Diffraction (XRD). Final properties as mechanical ones, oxygen permeability and transparency were also studied and related with the film structure. Mechanical properties, crystallization and oxygen permeability were increased maintaining good film translucency. POLYM. ENG. SCI., 54:1931–1940, 2014. © 2013 Society of Plastics Engineers     

Thermal,mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

For the application of single‐layer food packaging films with improved barrier properties, an attempt was made to prepare ethylene‐vinyl alcohol (EVOH) copolymer‐based nanocomposite films by incorporation of organically modified montmorillonite nanoclays via a two‐step mixing process and solvent cast method. The highly intercalated tactoids coexisted with exfoliated clay nanosheets, and the extent of intercalation and exfoliation depended significantly on the level of clay loadings, which were confirmed from both XRD measurements and TEM observations. It was revealed that the inclusion of nanoclay up to an appropriate level of content resulted in a remarkable enhancement in the thermal, mechanical (tensile strength/modulus), optical, and barrier properties of the prepared EVOH/clay nanocomposite films. However, excess clay loadings gave rise to a reduction in the tensile properties (strength/modulus/elongation) and optical transparency due to the formation of clay tactoids with a larger domain size. With the addition of only 3 wt % clay, the oxygen and water vapor barrier performances of the nanocomposite films were substantially improved by 59 and 90%, respectively, compared to the performances of the neat EVOH film. In addition, the presence of clay nanosheets in the EVOH matrix was found to significantly suppress the moisture‐derived deterioration in the oxygen barrier performance, implying the feasibility of applying the nanocomposite films to single‐layer food packaging films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40289.     

Rheological,crystal structure,barrier, and mechanical properties of PA6 and MXD6 nanocomposite films

In this study, rheological, crystal structure, barrier, and mechanical properties of polyamide 6 (PA6), poly(m‐xylene adipamide) (MXD6) and their in situ polymerized nanocomposites with 4 wt % clay were studied. The extent of intercalation and exfoliation as well as type of crystals, crystallinity, and thermal transitions were investigated using X‐ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. Dynamic rheological measurements revealed that incorporation of nanoclay significantly increases complex viscosity of MXD6 nanocomposites at low frequencies, which was related to the formation of a nanoclay network and exchange reaction between MXD6 chains. The comparative study of dynamic characteristics (G′ (ω) and G″ (ω)) for aliphatic and aromatic polyamide nanocomposites with their neat resins as well as the relaxation spectra for both polymer systems confirmed the possibility of the aforementioned phenomena. Although, the crystallinity of MXD6 films was lower as compared to PA6 films, the permeability to oxygen was more than 5 times better for the former. Incorporating 4 wt% clay enhanced the barrier property, tensile modulus, and yield stress of PA6 and MXD6 nanocomposite films in both machine and transverse directions without sacrificing much puncture and tear resistances. The PA6‐based films showed higher tear and puncture strength as compared to MXD6 films. POLYM. ENG. SCI., 54:2617–2631, 2014. © 2013 Society of Plastics Engineers     

Preparation,dynamic rheological behavior,crystallization, and mechanical properties of inorganic whiskers reinforced polylactic acid/hydroxyapatite nanocomposites

The novel inorganic SiO₂–MgO–CaO whiskers (SMCWs) were incorporated into nano hydroxyapatite (HA) contained polylactic acid (PLA) system to prepare the reinforced PLA/HA/SMCWs nanocomposite. Maleic anhydride grafted PLA (PLA‐g‐MAH) was then used to modify the interface between filler and matrix. The morphology, rheological behavior, crystallization, and mechanical property of the prepared nanocomposites were systematically investigated using scanning electronic microscope, dynamic rheometer, differential scanning calorimeter, polarized light microscope, and mechanical test, respectively. The results showed that the introduced PLA‐g‐MAH obviously improves the filler dispersion and the filler–matrix interfacial compatibility. Interestingly, the incorporated whiskers obviously decrease the complex viscosity and hence could significantly improve the processability of system. However, the introduction of PLA‐g‐MAH increases the complex viscosity to a greater extent. In addition, the added whiskers were found to have complicated influences on the PLA crystallization. On one hand, the incorporated whiskers can enhance the melt crystallization capability of PLA macromolecular chains; on the other hand, the introduced whiskers also show the inhibitive effect on the nucleation of PLA polymer chains and the inhibition degree is related to the loading of whiskers. The combination of whiskers and PLA‐g‐MAH could remarkably improve the mechanical performance of PLA/HA nanocomposite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43381.     

Mechanical and barrier properties of poly(lactic acid) films coated by nanoclay–ink composition

In this study, poly(lactic acid) (PLA) films were coated by an ink formulation containing nanoclay dispersed with ultrasonic homogenization for 20 min. Mechanical and barrier properties of the coated films were evaluated according to clay type and concentration. PLA films coated by ink formulations containing Cloisite 30B displayed the best mechanical and barrier properties in six types of nanoclays. PLA films coated by Cloisite 30B‐containing ink varying in clay concentration were investigated. Tensile strength and elongation at break of these coated films were improved in 1% Cloisite 30B. Oxygen permeability decreased significantly upon the addition of clay levels up to 1% and slightly decreased with further increases in the amount of the clay. The value of water vapor permeability also decreased depending on the increases of clay (0%–20%). When the clay content in the sample was 2.0%, the surface of coated PLA films displayed aggregation visible using film emission scanning electron microscopy. X‐ray diffractometry and transmission electron microscopy indicated that a mixture of exfoliated and intercalated structure was formed with addition of 1% (w/w) Cloisite 30B to the ink after ultrasonication. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sugar palm fiber/polyester nanocomposites: Influence of adding nanoclay fillers on thermal,dynamic mechanical,and physical properties

In this research, nanoclay used as filler in sugar palm‐reinforced composites was investigated by the physical, thermal, and dynamic mechanical properties. Various concentrations of nanoclay were used to fabricate composites by using hand lay‐up technique, followed by hot compression molding with naturally woven sugar palm fiber‐reinforced in polyester matrix. Among various weight concentrations such as 1–5% of nanoclay, it was found that 2% nanoclay‐filled composite (NC) demonstrated the best balance of thermomechanical properties and significantly enhanced the composite. DMA demonstrated that 2% nanoclay content resulted in improved viscoelastic behavior and higher glass transition temperature (T_g) of the composites. TGA also showed improvement in properties, whereas 3% nanoclay‐filled composite showed superior onset temperature, and 5% nanoclay‐filled composite exhibited highest remaining residue. The nanoclay filler was very effective to fill the porous structure and maintain the thickness stability. The thickness swelling was reduced with increasing amount of nanoclay in composites. Overall, the addition of nano clay improved thermal and physical properties of sugar palm‐reinforced polyester composite. J. VINYL ADDIT. TECHNOL., 26:236–243, 2020. © 2019 Society of Plastics Engineers