Crystallization studies on a clay nanocomposite prepared from a degradable poly(ester amide) constituted by glycolic acid and 6-aminohexanoic acid (original) (raw)
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Thermochimica Acta, 2011
An intercalated nanocomposite of the organically modified montmorillonite Cloisite C25A and a degradable poly(ester amide) based on glycolic acid and 6-aminohexanoic acid units (poly(glc-alt-amh)) was prepared using a twin-screw co-rotating extruder. The non-isothermal degradation kinetics was investigated by thermogravimetric analysis (TG and DTG) in the temperature range of 50-600 • C at five heating rates (2, 5, 10, 20 and 40 • C/min) and compared with the neat polymer. Significant differences were found since the nanocomposite showed three degradation steps instead of the two decomposition processes detected in the pristine sample. The onset mass loss temperature decreased in the nanocomposite due to the presence of the organo-modifier compound, but the presence of the silicate layers significantly decreased the degradation rate at the last stages of decomposition. Kinetic analysis was performed using the Kissinger method and the isoconversional (Kissinger-Akahira-Sunose and Friedman) methods. The true kinetic triplets (E, A, f(˛)) were determined for the first two steps of degradation through the Coats-Redfern and the Invariant Kinetic Parameters methods. The results clearly indicated that the presence of the organo-modified clay modified the mechanisms of degradation.
European Polymer Journal, 2009
Several organo-modified montmorillonites were studied to prepare nanocomposites of polyoctamethylene suberate, a biodegradable polyester. Mixtures were analyzed by conventional powder X-ray diffraction and transmission electron microscopy techniques. C30B clay was effective in rendering an intercalated structure with rather variable silicate layer spacing. The hydroxyl groups of the organo-modifier may allow the establishment of good interactions with the polar carbonyl groups of the studied polyester. A slight decrease in thermal stability was detected when the modified clay was incorporated into the polymer matrix. Isothermal and nonisothermal crystallization kinetics were studied by DSC and results compared with those for the neat polyester. The overall crystallization rate determined by calorimetric methods depends on the nucleation density and the crystal growth rate, which were independently evaluated by means of optical microscopy. Crystallization and morphological features were also analyzed by simultaneous SAXS/WAXD measurements made at a selected crystallization temperature and cooling rate under both isothermal and nonisothermal conditions, respectively.
ACS Applied Polymer Materials
The isothermal crystallization kinetics of a set of bio-nanocomposites produced by in situ catalytic step growth polycondensation of adipic acid and 1,4-butanediol in the presence of Moroccan clay beidellite (BDT) organo-modified with hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTA) was investigated and compared with that of the parent poly(butylene adipate) (PBA) matrices from which the clay had been extracted. In situ bio-nanocomposites had different contents (0−5 wt %) of CTA/BDT nanofillers characterized by different extents of organo-modification (CTA/BDT equivalent ratios from 0 to 5). The isothermal crystallization rates of the bionanocomposites and of the parent PBA matrices were investigated by differential scanning calorimetry (DSC) at 45, 40, and 37°C and analyzed according to the Avrami model. The bionanocomposites with an intermediate (2 wt %) concentration of organoclays with a higher CTA/BDT ratio (3 and 5) showed the highest exfoliation degree, along with an increase in the crystallization rates, compared to those of the parent PBA matrices, which was larger than that in the other nanocomposites. The lack of a simple correlation between the nanoclay content/composition and crystallization kinetics was ascribed to the molecular mass, an additional variable for in situ bio-nanocomposites as compared to nanocomposites prepared by simple physical blending of nanoclays with a single polymer matrix. The specific contribution of the molecular mass to the crystallization kinetics was untangled from those of the organoclay content and CTA/BDT ratio by comparing each bio-nanocomposite with its parent polymer matrix. The crystallization rate of the nanocomposites was always found to reach a maximum within an intermediate range of molecular weights of the polymer matrix, a behavior previously reported only for pure polymers. Such differences in the crystallization rate of in situ bio-nanocomposites may affect the crystalline phase morphology and, in polymorphs such as in PBA, phase composition, with consequent effects on properties that may be of interest for specific applications.
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.
Crystallization Behavior and Morphology of Biodegradable Polylactide/Layered Silicate Nanocomposite
Macromolecules, 2003
An intercalated polylactide (PLA)/layered silicate nanocomposite was prepared by simple melt extrusion of PLA and organically modified montmorillonite. The detailed crystallization kinetics and morphology of neat PLA before and after nanocomposite preparation were studied by using polarized optical microscopy, light scattering, differential scanning calorimetric, and wide-angle X-ray diffraction analyses. The overall crystallization rate and spherulitic texture of pure PLA were strongly influenced in the presence of montmorillonite particles.
Development and Thermo-Physical Properties of Bio-Based Polymer/Clay Nanocomposites
speautomotive.com
Bio-based resin systems obtained as blends of functionalized vegetable oils and petroleum based resins have been found to increase toughness of petroleum based resins and improve their environmental friendliness. Nevertheless, this improvement in toughness generally compromises the stiffness of the resin system. Nano-scale layered silicate (nano-clay) polymer nanocomposites exhibit enhanced mechanical and physical properties at relatively low weight fractions of inclusions. The reported study shows that proper stiffness-toughness balance along with enhancement in many other physical properties can be obtained by incorporating nano-scale layered silicates in bio-blended polymers. Polymer nanocomposites with varying clay contents and varying bio-blend (epoxidized soya bean oil) in unsaturated polyester resins were manufactured. Tensile properties and moisture absorption properties were studied. Fracture surface morphologies and characterization of nanocomposites were performed using electron microscopy. The resulting bio-blended polymer nanocomposites exhibit promising results for use in structural applications.
Crystallization of polycaprolactone–clay nanocomposites
Journal of Applied Polymer Science, 2008
The isothermal crystallization process of polycaprolactone/clay nanocomposites was studied at several temperatures. The effects of the clay type (modified and unmodified) and clay content were analyzed. Bulk crystallization was studied with differential scanning calorimetry and modeled with Avrami's equation. The reinforcement phase lowered the time at which the first crystal nucleus appeared (i.e., the induction time) and fastened the global crystallization rate in comparison with that of neat polycaprolactone. The spherulitic growth was ana-lyzed by optical microscopy with polarized light. The presence of the clay produced more and bigger spherulites in the same time and with the same undercooling degree. All these properties were strongly dependent on the polycaprolactone/clay compatibility and hence the dispersion degree achieved in the nanocomposites.
Journal of Polymer Science Part B, 2007
The study of the nonisothermal crystallization behavior of layered silicates micro-and nano-biocomposites based on poly(butylene adipate-co-terephthalate) (PBAT), a biodegradable copolyester, has been carried out with different theoretical models. They were applied and developed with the aim to describe and better understand the influence of the layered silicates dispersion on crystallization. The nucleation efficiency of the layered silicates has been demonstrated with the use of the ''Modified Avrami model,'' thanks to the higher crystallization rate parameter, Z c , and of the lower crystallization half-time, t 1/2 , compared to the neat matrix. The crystallization activation energies, E a , calculated from ''Kissinger's model'' have shown that layered silicates have a negative effect on the crystallite growth process. Thus, these analyses have shown that layered silicates have a double effect on the crystallization process. These two opposites' phenomena depend on the dispersion quality and are more pronounced for the intercalated nano-biocomposites. V
Journal of Material Science and Technology Research, 2019
The aim of this work is the preparation and properties of poly 2-thiozyl methacrylamidevinylbenzyldimethyloctadecylammonium/montmorillonite (TMAAm-VBOA/MMT) nanocomposites. Firstly 2-thiozyl methacrylamide (TMAAm) monomer was synthesized by reacting 2-amino thiazole with methacryloyl chloride in the presence of triethylamine. Synthesis of nanocomposites were performed in three steps which are; purification and cation exchange capacity (CEC) determination of clay, preparation of organoclay and synthesis of nanocomposites. Nanocomposites with various amounts of TMAAm and VBOA/MMT were synthesized through in-situ and free radical polymerization using benzoyl peroxide as an initiator. Changes in the structure of the nanocomposites were examined through Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Additionally, thermogravimetric analysis and BET analysis were conducted to investigate the thermal properties and particle size distribution of the nanocomposites. The results of X-ray and SEM analysis suggest that the exfoliated structure of the new nanocomposite materials. In addition, the thermal decomposition temperatures of nanocomposites were found to be higher than that of pure organoclay and poly(TMAAm) and thermally degradation rate decreased.