Nanocomposites from plasticized high‐amylopectin,normal and high‐amylose maize starches

Three types of maize starch with different amounts of amylose and amylopectin were used to prepare plasticized starch/clay nanocomposite films by casting. Studies by X‐ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the intercalation/exfoliation of the plasticized starch molecules took place into the clay galleries for the three types of starch. However, the plasticized waxy starch molecules were the easiest of them all to be intercalated/exfoliated, which was reflected in the highest increment of the stress at peak of these nanocomposites. Moreover, the lowest water uptake was showed by the plasticized high‐amylose starch/clay nanocomposites. It was concluded that varying contents of amylose and amylopectin influenced the formation of intercalated/exfoliated clay structures and also affected the interactions of clay with water. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Water uptake behavior of layered silicate/starch–polycaprolactone blend nanocomposites

The water uptake behavior of biodegradable layered silicate/starch–polycaprolactone blend nanocomposites was evaluated. Three different commercial layered silicates (Cloisite Na⁺, Cloisite 30B and Cloisite 10A) were used as reinforcement nanofillers. Tests were carried out in two different environments: 60 and 90% relative humidity using glycerol solutions. The clay/starch–polycaprolactone blend nanocomposites were obtained by melt intercalation and characterized by gravimetric measurements and tensile tests. The intercalated structure (determined by wide‐angle X‐ray diffraction) showed a decrease in water absorption as a function of clay content probably due to the decrease of the mean free path of water molecules. The diffusion coefficient decreased with clay incorporation but a further increase in the clay content did not show an important effect on this parameter. Elongation at break increased with exposure showing matrix plasticization. Mechanical properties of the nanocomposites deteriorated after exposure whereas they remained almost constant in the case of the neat matrix. Copyright © 2007 Society of Chemical Industry     

Preparation and characterization of exfoliated layered double hydroxide/silicone rubber nanocomposites

Silicone rubber (SR)/Mg–Al layered double hydroxide (LDH) nanocomposites were prepared by the solution intercalation of SR crosslinked by a platinum‐catalyzed hydrosilylation reaction into the galleries of dodecyl sulfate intercalated layered double hydroxide (DS–LDH). X‐ray diffraction and transmission electron microscopy analysis showed the formation of exfoliated structures of organomodified LDH layers in the SR matrix. The tensile strength and elongation at break of SR/DS–LDH (5 wt %) were maximally improved by 53 and 38%, respectively, in comparison with those of the neat polymer. Thermogravimetric analysis indicated that the thermal degradation temperature of the exfoliated SR/DS–LDH (1 wt %) nanocomposites at 50% weight loss was 20°C higher than that of pure SR. Differential scanning calorimetry analysis data confirmed that the melting temperature of the nanocomposites increased at lower filler loadings (1, 3, and 5 wt %), whereas it decreased at a higher filler loading (8 wt %). The relative improvements in the solvent‐uptake resistance behavior of the SR/DS–LDH nanocomposites were also observed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and crystalline morphology of biodegradable starch/clay nanocomposites

An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H₂O was investigated and the gelatinized temperature (T_gel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N₂ atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.     

Synthesis and characterization of polyurethane/Mg‐Al layered double hydroxide nanocomposites

Layered double hydroxide (LDH) is a new type of nanofiller, which improves the physicochemical properties of the polymer matrix. In this study, 1, 3, 5, and 8 wt % of dodecyl sulfate‐intercalated LDH (DS‐LDH) has been used as nanofiller to prepare a series of thermoplastic polyurethane (PU) nanocomposites by solution intercalation method. PU/DS‐LDH composites so formed have been characterized by X‐ray diffraction and transmission electron microscopy analysis which show that the DS‐LDH layers are exfoliated at lower filler (1 and 3 wt %) loading followed by intercalation at higher filler (8 wt %) loading. Mechanical properties of the nanocomposite with 3 wt % of DS‐LDH content shows 67% improvement in tensile strength compared to pristine PU, which has been correlated in terms of fracture behavior of the nanocomposites using scanning electron microscope analysis. Thermogravimetric analysis shows that the thermal stability of the nanocomposite with 3 wt % DS‐LDH content is ≈ 29°C higher than neat PU. Limiting oxygen index of the nanocomposites is also improved from 19 to 23% in neat PU and PU/8 wt% DS‐LDH nanocomposites, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology and properties of stearate‐intercalated layered double hydroxide nanoplatelet‐reinforced thermoplastic polyurethane

In the past few years, layered double hydroxides (LDHs) with monolayer structure have been much studied for the development of polymer nanocomposites. LDHs with intercalated stearate anions form a bilayer structure with increased interlayer spacing and are expected to be better nanofillers in polymers. In the work reported, thermoplastic polyurethane (PU)/stearate‐intercalated LDH nanocomposites were prepared by solution intercalation and characterized. X‐ray diffraction and transmission electron microscopy confirmed the exfoliation at lower filler loading followed by intercalation at higher filler loading in PU matrix. As regards mechanical properties, these nanocomposites showed maximum improvements in tensile strength (45%) and elongation at break (53%) at 1 and 3 wt% loadings. Maximum improvements in storage and loss moduli (20%) with a shift of glass transition temperature (15 °C) and an increase in thermal stability (32 °C) at 50% weight loss were observed at 8 wt% loading in PU. Differential scanning calorimetry showed a shift of melting temperature of the soft segment in the nanocomposites compared to neat PU, possibly due to the nucleating effect of stearate‐intercalated LDH on the crystal structure of PU. All these findings are promising for the development of mechanically improved, thermally stable novel PU nanocomposites. Copyright © 2011 Society of Chemical Industry     

Synthesis and characterization of ethylene vinyl acetate/Mg–Al layered double hydroxide nanocomposites

Mg–Al layered double hydroxide (LDH)/Ethylene vinyl acetate (EVA‐28) nanocomposites were prepared through solution intercalation method using organically modified layered double hydroxide (DS‐LDH). DS‐LDH was made by the intercalation of sodium dodecyl sulfate (SDS) ion. The structure of DS‐LDH and its nanocomposites with EVA‐28 was determined by X‐ray diffraction (XRD) and transmission electron microscope (TEM) analysis. XRD analysis shows that the original peak of DS‐LDH shifted to lower 2θ range and supports the formation of intercalated nanocomposites while, TEM micrograph shows the presence of partially exfoliated LDH nanolayers in addition to orderly stacked LDH crystallites in the polymer matrix. The presence of LDH in the nanocomposites has been confirmed by Fourier transform infrared (FTIR) analysis. The mechanical properties show significant improvement for the nanocomposite with respect to neat EVA‐28. Thermogravimetric (TGA) analysis shows that thermal stability of the nanocomposites is higher than that of EVA‐28. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1845–1851, 2007     

Effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene/layered double hydroxide nanocomposites prepared by melt intercalation

The effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene (LDPE)/layered double hydroxide (LDH) nanocomposites were studied with Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, microscale combustion calorimetry, thermogravimetric analysis, and mechanical property measurements. X‐ray diffraction and transmission electron microscopy demonstrated that after intercalation with stearate anion (SA) or dodecyl sulfate anion (DS), organo‐LDH could be nanodispersed in an LDPE matrix with exfoliated structures or intercalated structures simultaneously with partially exfoliated structures, respectively, via melt intercalation. However, the unmodified LDH composites yielded only microcomposites. Microscale combustion calorimetry, thermogravimetric analysis, and dynamic Fourier transform infrared spectra showed the following order for the flame‐retardant and thermal properties: LDPE/SA‐modified LDH > LDPE/DS‐modified LDH > LDPE/NO₃‐modified LDH > LDPE. The higher performance of the LDPE/LDH nanocomposites with respect to flame retardance and thermal stability could be attributed to the better dispersion state of the LDH layers in the LDPE matrix and the greater hindrance effect of LDH layers on the diffusion of oxygen and volatile products throughout the composite materials when they were exposed to burning or thermal degradation. The tensile strength and elongation at break of the LDPE/LDH nanocomposites decreased to some extent because of the decrease in the crystallinity of the LDPE matrix. A transmittance test showed that the transparency of the exfoliated LDPE/SA‐modified LDH nanocomposite was very close to that of neat LDPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(citrate glyceride): a hyperbranched polyester for starch plasticization

Hyperbranched polyesters (HBPETs), terminated with either hydroxyl or carboxyl groups, were prepared from citric acid and glycerol in simple one‐step syntheses. The HBPET structure and degree of branching were investigated using Fourier transform infrared and ¹H NMR spectroscopies and gel permeation chromatography. The HBPET plasticizers were combined with a maize starch via cooking and film formation. The mechanical, thermal, paste and structural properties of the plasticized starch composites were studied in detail using differential scanning calorimetry, thermogravimetric analysis, rapid viscosity analysis and X‐ray diffraction. The HBPETs reduced the pasting viscosity but slightly increased the pasting temperature of the starch. The smaller breakdown and setback values of the plasticized starch pastes relative to those of native starch suggested weaker retrogradation. Compared with glycerol/starch plasticized films, HBPET/starch composite films had lower crystallinity, lower glass transition temperature and better mechanical and thermal properties. The properties of the plasticized starch samples strongly depended on the terminal groups and the molecular weight of the HBPET plasticizers. © 2017 Society of Chemical Industry     

Structure and analgesic properties of layered double hydroxides intercalated with low amounts of ibuprofen

Ibuprofen‐intercalated layered double hydroxides (LDH‐IBU) have been successfully synthesized via a coprecipitation method with a nominal [Al³⁺]/[Mg²⁺] ratio of 0.5 and a variable molar IBU/([Al³⁺]+[Mg²⁺]) ratio of 0, 0.15, 0.18, 0.24, 0.36, and 0.72. After an accurate determination of the composition, the nature of the intercalated species and the effective intercalation yield from to IBU, it is shown that the synthesis route used allows a good control of the quantity of intercalated IBU within the LDH framework. This results in different samples with full or partial IBU intercalation in the interlayer space in exchange of nitrate anions. The analysis of the X‐ray diffraction basal reflections reveals that the intercalation of IBU in the framework only increases the basal distances with no alteration of the brucite‐type layers. Also, a computational study used to model the positions and shapes of the basal reflections showed that the structure of the nonfully intercalated compounds follows a random interstratification scheme. Finally, three samples ranging from slightly to fully IBU‐intercalated galleries were selected for preliminary in vivo assays. These tests showed a strong tendency that after 24 hours the low yield of IBU‐intercalated compounds are almost as efficient as the fully intercalated sample.     

Ethylene vinyl acetate/Mg‐Al LDH nanocomposites by solution blending

Partially exfoliated ethylene vinyl acetate (EVA‐40, 40% vinyl acetate content)/layered double hydroxide (LDH) nanocomposites using organically modified layered double hydroxide (DS‐LDH) have been synthesized by solution intercalation method. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) studies of nanocomposites shows the formation of exfoliated LDH nanolayers in EVA‐40 matrix at lower DS‐LDH contents and partially intercalated/exfoliated EVA‐40/MgAl LDH nanocomposites at higher DS‐LDH contents. These EVA‐40/MgAl LDH nanocomposites demonstrate a significant improvement in tensile strength and elongation at break for 3 wt% of DS‐LDH filler loading compare to neat EVA‐40 matrix. Thermogravimetric analysis also shows that the thermal stability of the nanocomposites increases with DS‐LDH content in EVA‐40. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Dynamic mechanical and thermal properties of the composites of thermoplastic starch and lanthanum hydroxide nanoparticles

Nanostructured lanthanum (III)‐oxide (La₂O₃) particles were prepared by a polymer complex solution method and further used for the preparation of lanthanum hydroxide (La(OH)₃) nanoparticles. The La(OH)₃ nanopowder was mixed with glycerol‐plasticized maize starch and the effect of the filler on the thermal, mechanical, and viscoelastic properties of the matrix was investigated. It was expected that this nanofiller, which shows an affinity toward OH groups, would strongly affect the physical properties of thermoplastic starch (TPS). The pure TPS and the TPS‐La(OH)₃ nanocomposite films (with 1, 2, and 3 wt % filler) were conditioned at various relative humidities (RHs) (35, 57, 75, and 99% RH). After conditioning at 99% RH, the pure TPS films exhibited higher affinity toward water than the nanocomposites. Differential scanning calorimetric measurements showed that, due to retrogradation effects, the melting enthalpies of the films increased with increasing RH. Dynamic mechanical analysis revealed that the mechanical properties in the linear range strongly depend on both the humidity conditions and the concentration of the filler. The results also show that La(OH)₃ nanoparticles are good reinforcement for TPS films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nonisothermal crystallization kinetics of polypropylene‐layered double hydroxide composites: Correlation with morphology

In this work the effect of nanofiller on nonisothermal crystallization behavior of composites based on polypropylene (PP) was investigated by differential scanning calorimetry. The materials were prepared by melt mixing. Both an alkyl sulfonate salt modified layered double hydroxide (LDH) and an unmodified LDH were used as nanofillers and both PP and PP/polypropylene grafted with maleic anhydride (PP‐g‐MA) blend were used as matrices. The morphology of composites was investigated by X‐ray diffraction and transmission electron microscopy. No exfoliation was noticed in all prepared composites, but the hybrid materials showed an intercalated structure. The thermal properties and crystallization behavior were studied by conventional differential scanning calorimetry. In particular, the kinetic crystallization parameters were obtained using the modified Avrami equation for a nonisothermal process, whereas the activation energy of the global crystallization process was estimated using the Kissinger equation. The Avrami parameters suggest a significant effect on the crystallization of PP for the composites containing both the organically modified LDH and PP‐g‐MA. The results indicate a complex crystallization process of PP and evidence that the crystallization process can not be only explained by intercalation phenomenon, but the constrain effect ofpolymer chains on the filler surface and/or betweenthe filler clusters should play a significant role. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Dynamic rheological properties of Yam starch/hectorite composite gels

The rheological properties of composite gels of starch extracted from Yam roots (Discorea sp) and hectorite (a mineral clay belonging to the smectite group) were studied in aqueous solutions as a function of hectorite concentration. The elastic (G′) and viscous (G″) moduli of the composite gels were dependent on the clay content, and for all samples G′ was greater than G″. Composite gels with clay contents of <30% presented higher G′, G″ and viscosities |η*| when compared with pure starch gel, while those with a content of 50 % showed lower values. The addition of hectorite significantly inhibited the creeping properties in relation to pure starch at 25 °C but, after heating/cooling cycles between 25 and 85 °C, this effect was not observed and the composite gel showed similar behavior to that of pure starch. Copyright © 2005 Society of Chemical Industry     

Natural rubber-based nanocomposites by latex compounding with layered silicates

Natural rubber (NR) based nanocomposites with 10 wt% natural and synthetic layered silicates were produced via the latex compounding method. As layered silicates, sodium bentonite (natural) and sodium fluorohectorite (synthetic) were selected in addition to a non-layered inert filler (English India clay or commercial clay) as reference material. The nanocomposites were prepared by compounding the dispersions of clays and other latex chemicals necessary for vulcanization. The vulcanized nanocomposites were subjected to mechanical, thermal and swelling tests. The silicate dispersion was studied by transmission electron microscopy. Layered silicates outperformed the reference material (commercial clay) in all aspects. This was attributed to the intercalation/exfoliation of the silicates and to the formation of a skeleton ‘(house of cards)’ silicate network in the NR matrix.     

Mechanical properties of layered silicate/starch polycaprolactone blend nanocomposites

The mechanical behavior of layered silicate/starch polycaprolactone blend nanocomposites was evaluated. Three different clays (Cloisite Na⁺, Cloisite 30B and Cloisite 10A) were used as reinforcement. Nanocomposites were prepared by melt intercalation followed by compression molding. These nanocomposites were characterized using X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis and tensile testing. X‐ray diffraction results showed that most of the clays were intercalated within the polymeric chains. In all cases, mechanical properties were improved with clay incorporation and the improvement was better as the clay content was increased. The best properties were achieved with Cloisite 10A due to their greatest compatibility with the matrix. A mechanical model, which takes into account the effective parameters of the clay, was used in order to estimate the dispersion of clay within the polymer. The highest dispersion was obtained for Cloisite 10A, which is in accordance with the experimental mechanical properties. Although dynamical‐mechanical properties improved with clay incorporation, the glass transition temperature was not affected. Copyright © 2006 Society of Chemical Industry     

Transparent low‐density polyethylene/starch nanocomposite films

Low‐density polyethylene (LDPE)/starch nanocomposite films were prepared by melt extrusion process. The first step includes the preparation of starch–clay nanocomposite by solution intercalation method. The resultant product was then melt mixed with the main matrix, which is LDPE. Maleic anhydride‐grafted polyethylene (MAgPE), produced by reactive extrusion, was used as a compatibilizer between starch and LDPE phases. The effects of using compatibilizer, clay, and plasticizers on physico‐mechanical properties were investigated. The results indicated that the initial intercalation reaction of clay layers with starch molecules, the conversion of starch into thermoplastic starch (TPS) by plasticizers, and using MAgPE as a compatibilizer provided uniform distribution of both starch particles and clay layers, without any need of alkyl ammonium treatment, in LDPE matrix. The nanocomposite films exhibited better tensile properties compared to clay‐free ones. In addition, the transparency of LDPE film did not significantly change in the presence of TPS and clay particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology and properties of layered silicate‐polyethylene nanocomposite blown films

Film grade ethylene vinyl acetate (EVA), low density polyethylene (LDPE), and high density polyethylene (HDPE) were melt compounded with an organically modified montmorillonite, then blown into films. The morphology studies showed that all three types of film involve intercalated clay particles. The dependence of intercalation extent on the matrix as well as on the molecular weight of compatibilizers is discussed. The tensile testing data showed that the clay enhancing effects apply mainly to the modulus, instead of to the strength. The EVA‐based nanocomposite films exhibit the most significantly improved modulus while the HDPE‐based films have the least. Lower molecular weight compatibilizers could promote the clay enhancing effects while higher molecular weight compatibilizers could increase the matrix properties. Steady shear viscosities of an intercalated and an exfoliated system were also investigated. Comparing our data with that from the literature lead us to conclude that: 1) the zero‐shear viscosity of a nanocomposite is mainly determined by clay loading instead of by clay intercalation/exfoliation structures and the matrix viscosity; and 2) the clay orientation during a shear flow is highly dependent on the matrix flow behavior and to a lesser extent on the clay structural state. POLYM. ENG. SCI., 45:469–477, 2005. © 2005 Society of Plastics Engineers     

Technological and processing properties of natural rubber layered silicate‐nanocomposites by melt intercalation process

Natural rubber nanocomposites were produced by melt‐mixing of natural rubber with organically modified silicates. For comparison, a pristine‐layered silicate and a nonlayered version [English Indian clay (EIC)] were also included in the study. The layered silicate used was sodium bentonite (BNT) and organoclays used were octadecylamine‐ modified montmorillonite (MMT‐ODA) and methyltallow bis‐2‐hydroxyethyl ammonium‐modified montmorillonite (MMT‐ TMDA). Accelerated sulfur system was used for the vulcanization of the nanocomposites. The dispersion of these silicates was studied by X‐ray diffraction and transmission electron microscopy. The organoclay‐incorporated composites exhibited faster curing and improved mechanical properties. The improvement in the mechanical properties of the composites followed the order MMT‐ODA > MMT‐TMDA > EIC > BNT. The property improvement was attributed to the intercalation/exfoliation of the organically modified silicates because of their high initial interlayer distance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2537–2543, 2006     

Intercalation of lecithins for preparation of layered nanohybrid materials and adsorption of limonene

The intercalation of biosurfactants (lysolecithin and lecithin) in layered clay mineral supports was investigated to assess the suitability of the resulting nanohybrid materials as flavor and fragrance delivery system. The protonated biosurfactant molecules (pH = 2.3) were intercalated into the Na-montmorillonite, whereas the deprotonated biosurfactants (pH ~ 12) were intercalated into Mg–Al layered double hydroxides. The amount of lysolecithin and lecithin bound to the layered adsorbents was estimated by measuring adsorption isotherms. The basal spacing obtained from X-ray diffraction measurements suggested that the molecules are arranged in parallel with the layers of montmorillonite, whereas in the case of layered double hydroxides, the adsorbed molecules are in a vertical position between the layers. The interaction of layered adsorbents and biosurfactants was further evidenced by infrared spectroscopy. The intercalated montmorillonite and LDH particles were then probed for their ability to intercalate limonene molecules. Only the lysolecithins modified samples adsorbed limonene. The theoretical sizes of molecules and their possible arrangement between the layers were modeled by HyperChem 7.0 molecular calculations to correlate the ability to bind the lecithins in the confined space of the layered materials.