Singling Out the Role of Molecular Weight in the Crystallization Kinetics of Polyester/Clay Bionanocomposites Obtained by In Situ Step Growth Polycondensation

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). Theb isothermal crystallization rates of the ionanocomposites 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

Preparation of fluorinated methacrylate/clay nanocomposite via in-situ polymerization: Characterization, structure, and properties

Novel fluorinated coating containing well-dispersed silicate nanolayers is successfully produced via in-situ free radical polymerization of 2,2,2-trifluoroethyl methacrylate in the presence of vinylbenzyl-functionalized montmorillonite with different loading. The organic modification of sodium montmorillonite is achieved through an ion exchange reaction with triphenylvinylbenzylphosphonium chloride as surfactant prepared before use by reaction with vinylbenyl chloride and phosphine. The following in-situ polymerization in the presence of organomodified clay leads to fluorinated nanocomposites with of partially exfoliated and intercalated morphologies, as determined via XRD and TEM analysis. The nanoscale dispersion of clay layers is also evidenced by thermal analysis; a moderate decrease of the glass transition temperature about 2–8 °C compared to their virgin PMATRIF and an improvement of their thermal stability as evidenced by TGA. The wettability of the nanocomposite films is also studied by contact angle measurements with water. The incorporation of organomodified clays not only increases the hydrophobicity of the fluorinated polymers but also improves the surface properties of obtained nanocomposites. Compared the virgin homopolymer, the mechanical properties of the nanocomposites are reduced by addition of organomodifed clay at temperature from 30 to 60 °C, whereas this trend is gradually decreased at higher temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 411–418. © 2016 Wiley Periodicals, Inc

Thermal Degradation Behavior of a Nearly Alternating Copolymer of Vinylidene Cyanide with 2,2,2-Trifluoroethyl Methacrylate

The thermal decomposition under non-oxidative conditions of a copolymer of vinylidene cyanide (VCN) and 2,2,2-trifluoroethyl methacrylate (MATRIF) was investigated by thermogravimetry (TG) and Pyrolysis-GC-MS. The type and composition of the pyrolytic products and the shape of the TG curve indicate that both the main thermal degradation process, with onset at 368 degrees C, and a minor weight loss at around 222 degrees C are mainly associated with random main-chain scission. The kinetic parameters were determined by means of dynamic and, in the case of the main degradation stage, also isothermal methods. The results obtained from the dynamic methods (Friedman, Flynn-Wall-Ozawa, and Kissinger, respectively) are in good agreement with those obtained from isothermal TG data. The activation energy was in the 177-213 kJ/mol range for the first stage, and 224-295 kJ/mol for the second stage, the highest respective values being determined from the kinetic analysis according to the Kissinger method. (C) 2010 Elsevier Ltd. All rights reserved

Synthesizing PLA and its composites for a new approach of reactive processing: relationship between structural, thermal and rheological properties

Keynote paper, semi-plenary lectureInternational audienc

Effect of Palm Tree Fiber Orientation on Electrical Properties of Palm Tree Fiber-reinforced Polyester Composites

The dynamic dielectrical analysis of short palm tree lignocellulosic fiber-reinforced polyester composites was carried out with special reference to the effect of fiber orientation, frequency, and temperature. Measurements were performed in the temperature range 40—200°C and in the frequency range 1—100 kHz. Three relaxations processes were identified, namely the orientation polarization imputed to the presence of polar water molecules in palm fiber, the relaxation process associated with conductivity occurring as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies, and the interfacial or Maxwell—Wagner—Sillars relaxation that is attributable to the accumulation of charges at the palm fibers/polyester interfaces. The orientation of the fiber can strongly influence the dielectrical properties and interfacial polarization processes in composites. </jats:p

Tuberculosis of the Oral Cavity Revealing Pulmonary Tuberculosis: About an Observation

Tuberculosis of the oral cavity is a rare entity, often secondary to pulmonary localization. This article reports a case of palatine tonsil tuberculosis, indicative of miliary pulmonary tuberculosis, in a 40-year-old patient who has as history of an actif smoking, alcoholism, without any notion of previous tuberculosis infection. The clinical manifestations of oral tuberculosis are not very specific. It most often results in a chronic oral ulceration that evokes many other etiologies among which a malignant tumor, a bacterial, viral or mycotic infection, a systemic disease, a foot-and-mouth ulcer or traumatic. Any chronic oral ulceration whose etiology does not appear obvious, one must think of tuberculosis of the oral cavity. To confirm this diagnosis, histopathological examination, direct bacteriological examination and culture from fresh tissue as well as search for pulmonary tuberculosis are necessary