Morphology and rheological behavior of polylactic acid/clay nanocomposites (original) (raw)
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Polymer Engineering & Science, 2012
The rheological behavior of styrene-free unsaturated polyester resin-nanoclay (Cloisite 15A and 30B) nanocomposites at various nanoclay contents prepared by melt mixing was investigated. To investigate the effect of shear and diffusion induced phenomena as well as nanoclay surface modification on the rheological behavior, samples were prepared at two different temperatures of 408C (cold mixed) and 1508C (hot mixed) and tested in a range of 40-1208C using dynamic rheometry. Viscosity-temperature curves for the cold mixed samples showed a decrease in viscosity with increasing temperature followed by the formation of a plateau with onset temperature which depends on the nanoclay type and content. The results of small angle X-ray scattering and transmission electron microscopy analysis were in agreement with the formation of a physical network in which nanoclay particles act as the nodes, whereas polymer chains serve as the links. It is believed that for the cold-mixed samples, higher shear forces break the nanoclay stacks associations efficiently, and hence more nanoparticles are available for polymer chains to form the network. In this context, the initial d-spacing was much more effective than the nanoclay modification type.
Journal of Applied Polymer Science, 2012
The structural and thermal characteristics of poly(L-lactic acid)/layered-silicate hybrid materials that were produced via two different routes, namely by solvent casting and by melt mixing, were compared in association with the degree of clay modification. Investigation of the produced materials' structure revealed that, at low modification levels, melt blending is necessary in dispersing the amine-treated clay into the polymer matrix. At intermediate degrees of modification, both techniques are capable of swelling the silicate clay with the solution casting to be a more effective method. Thermal measurements showed that the clay modification level influences significantly the thermal stability of both solution and melt processed hybrids. Moreover, the material derived from melt mixing displayed a higher onset decomposition temperature. The glass transition temperature of the polymer was not significantly affected by the preparation method followed. However, the crystallization process was found to be strongly dependent on both the preparation method and the degree of clay modification.
Mechanical and Thermal Properties of PLLA/PCL Modified Clay Nanocomposites
Journal of Polymers and the Environment, 2010
Poly(L-lactic acid) (PLLA)/poly(caprolactone) (PCL) and two types of organoclay (OMMT) including a fatty amide and ocatdecylamine montmorillonite (FA-MMT and ODA-MMT) were employed to produce polymer nanocomposites by melt blending. Materials were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Mechanical properties were also investigated for these nanocomposites. The nanocomposites showed increasing mechanical properties and thermal stability. XRD results indicated that the materials formed nanocomposites. SEM morphology showed that increasing content of OMMT reduced the domain size of phase separated particles. TEM outcomes have confirmed the intercalated type of nanocomposite. Additionally, a solution casting process has been used to prepare these nanocomposites and characterized to compare these results with the above process.
Journal of Polymer Science Part B: Polymer Physics, 2010
In this work, a comprehensive study of the rheological behavior under shear and isothermal and nonisothermal elongational flow of low density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA) based nanocomposites was reported to evaluate their ''filmability'', that is, the ability of these material to be processed for film forming applications. The influence of two different kinds of organoclay -namely Cloisite 15A and Cloisite 30B -and their concentration was evaluated. The presence of filler clearly affects the rheological behavior in oscillatory state of polyolefin-based nanocomposites but the increase of complex viscosity and the shear thinning are not dramatic. A larger strain-hardening effect in isothermal elongational flow is shown by the nanocomposites compared to that of the pure matrix, particularly for EVA based nanocomposites. The melt strength measured under nonisothermal elongational flow increases in the presence of the nanofiller, while the drawability is only slightly lower than that measured for the neat matrix. Moreover, the rheological behavior under nonisothermal elongational flow of EVA-based nanocomposites is similar for both nanoclays used. Differently, LDPE-based nanocomposites show a strong dependence on the type of organoclay. Finally, the mechanical properties of the materials were measured by tensile tests. They revealed that the presence of the filler provokes, in all the cases, an increase of the rigidity.
Journal of food …, 2010
The melt rheology and thermal properties of polylactide (PLA)-based nanocomposite films that were prepared by solvent casting method with L-PLA, polyethylene glycol (PEG), and montmorillonite clay were studied. The neat PLA showed predominantly solid-like behavior (G > G ) and the complex viscosity (η * ) decreased systematically as the temperature increased from 184 to 196 • C. The elastic modulus (G ) of PLA/clay blend showed a significant improvement in the magnitude in the melt, while clay concentration was at 6% wt or higher. At similar condition, PEG dramatically reduced dynamic modulii and complex viscosity of PLA/PEG blend as function of concentration. A nanocomposite blend of PLA/PEG/clay (74/20/6) when compared to the neat polymer and PLA/PEG blend exhibited intermediate values of elastic modulus (G ) and complex viscosity (η * ) with excellent flexibility. Thermal analysis of different clay loading blends indicated that the melting temperature (T m ) and glass transition temperature (T g ) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the T g and the T m of the blends (PLA/PEG and PLA/PEG/clay) significantly, however, crystallinity increased in the similar condition. The transmission electron microscopy (TEM) image of nanocomposite films indicated good compatibility between PLA and PEG, whereas clay was not thoroughly distributed in the PLA matrix and remained as clusters. The percent crystallinity obtained by X-ray was significantly higher than that of differential scanning calorimeter (DSC) data for PLA.
Journal of Applied Polymer Science, 2009
Polystyrene (PS) nanocomposites were prepared by the free-radical polymerization of styrene in the presence of organically modified montmorillonite (MMT) clays. MMT clay was modified with a low-molecularweight and quarternized block copolymer of styrene and 4-vinylpyridine [poly(styrene-b-4-vinylpyridine) (SVP)] with 36.4 wt % PS and 63.6 wt % poly(4-vinylpyridine) (P4VP). Special attention was paid to the modification, which was carried out in different compositions of a solvent mixture of tetrahydrofuran (THF) and water. The swelling behavior of the MMT clay was studied by an Xray diffraction technique. The diffraction peak shifted to lower 2y angles for all of the modified clays, which indicated the intercalation of the quarternized SVP copolymer into the MMT layers in different degrees. Higher interlayer distances, which showed a high degree of block copolymer insertion, were obtained for solvent compositions with THF in water. The resultant nanocomposites were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, thermogravimetric analysis, and dynamic mechanical analysis. The desired exfoliated nanocomposite structure was achieved when the MMT modification was conducted in 50 or 66 wt % THF, whereas the other modifications all resulted in intercalated structures. The resulting exfoliated nanocomposite was found to have better thermal stability and dynamic mechanical performance compared to the others, even with 2% clay loading.
Rheological and thermal properties of polylactide/organic montmorillonite nanocomposites
Journal of Applied Polymer Science, 2012
Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 • C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G ) of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (T g ) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the T g of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications.
Journal of Applied Polymer Science, 2010
Poly(butylene terephthalate)–clay nanocomposites with three different organically modified clays were prepared via melt blending in a twin‐screw extruder. Decyl triphenylphosphonium bromide, hexadecyl triphenylphosphonium bromide, and cetyl pyridinium chloride were used to modify the naturally occurring montmorillonite clay. The organically modified clays were characterized with X‐ray diffraction for the d001‐spacing and with thermogravimetric analysis to determine the thermal stability. The prepared nanocomposites were injection‐molded and examined for the dispersion quality of the clay, the mechanical properties, and the rheological behavior. The tensile strength of the nanocomposites increased with a 1% addition of clay; however, more clay decreased the tensile strength. Nanocomposites with finely dispersed clay platelets and nanocomposites with poorly dispersed clay platelets showed very different rheological behaviors. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Preparation of Polymer–Clay Nanocomposites and Their Properties
An overview of the progress in polymer nanocomposites is presented in this paper with an emphasis on the different methods used for preparing polymer-layered silicate (PLS) nanocomposites and the extent to which properties are enhanced. Other related areas that are also discussed include the types of polymers used in PLS nanocomposites preparation, the types of PLS nanocomposites morphologies that are most commonly achieved, the structure and properties of layered silicates, and the most common techniques used for characterizing these nanocomposites. C 2007 Wiley Periodicals, Inc. Adv Polym
BACKGROUND: The nature of the dispersion of clay platelets in a resin composite will play an important role in the process of enhancement of the physical properties of that material. This paper examines how different modifiers and the quantity of surface treatment for the Cloisite range of organically modified clays affect properties in in situ polymerised poly(methyl methacrylate). Another clay which is a mixture of rod-and platelet-like minerals is also investigated to understand how the shape of the clay particles can affect the polymer properties.