Showing papers by "Pierre J. Carreau published in 2013"

Morphological and rheological properties of PET/clay nanocomposites

Abstract: This work investigates the effects of clay chemistry and concentration on the morphology and rheology of polyethylene terephthalate (PET)/clay nanocomposites. The complex viscosity of the PET nanocomposites exhibited a more solid-like behavior, in contrast to the matrix that had a frequency-independent viscosity. In addition, at high frequencies where the behavior of the matrix should be dominant, a lower complex viscosity of the nanocomposites was observed due to PET degradation in the presence of the organoclays. The high-frequency data were used to estimate the matrix degradation using the Maron–Pierce equation. The apparent molecular weight of the PET matrix was found to decrease from 65 kg/mol for the neat PET to 30 kg/mol for a PET nanocomposite containing 8 wt% Cloisite®; 30B. The apparent yield stress in the nanocomposites was determined using the Herschel–Bulkley model. Yield stress increased with the level of exfoliation and clay concentration, from ∼0 to 166 Pa when the clay concentration increased from 2 to 8 wt%.

Crystallization behavior and morphology of polylactide and PLA/clay nanocomposites in the presence of chain extenders

Abstract: The effect of clay and chain extender on the nonisothermal, isothermal crystallization kinetics, and morphology of polylactide (PLA) was investigated in this study. PLA and PLA-based nanocomposites containing 2 wt% organoclay were prepared via melt compounding. Three commercially available chain extenders were used: polycarbodiimide (PCDI), tris(nonylphenyl) phosphite (TNPP), and Joncryl ADR4368F. The nanoclay particles were found to act as nucleating agents. Chain extender incorporation, however, had diverse effects on both crystallization rate and degree of crystallinity. Nonisothermal DSC results revealed that the addition of PCDI increased the cold-crystallization temperature (Tc) from 106 to 1148C, reduced the degree of crystallinity from 6.3 to 5.3%, and resulted in the formation of bimodal melting peaks in PLA. On the other hand, the reduction of chain ends in the presence of TNPP resulted in a significant increase of the crystallization rate and degree of crystallinity from 6.3 to 15.2%. In the case of Joncryl, its incorporation led to the formation of a long-chain branching structure, which disrupted the chain packing. Therefore, the degree of crystallinity (from 6.3 to 1.6%) and the rate of crystallization decreased, while Tc was increased from 106 to 1228C in the presence of Joncryl. POLYM. ENG. SCI., 53:1053‐1064, 2013. a 2012 Society of Plastics Engineers

Foaming behavior of microcellular thermoplastic olefin blends

Abstract: The influence of reactive compatibilization on the foaming behavior of thermoplastic olefin blends of polypropylene and a metallocene-catalyzed ethylene octene copolymer was investigated. A batch setup was used to foam the samples using carbon dioxide as blowing agent. Solubility measurements were performed to determine the relative amount of gas concentration in the pressurized polymers before foaming. A microscopic method based on the back-scattered electron imaging technique was used to determine the respective locations of the bubbles and the dispersed elastomeric domains in the polypropylene matrix. It was shown that the bubbles are preferentially formed in the dispersed elastomeric domains. A clear relationship was established between the microstructure of the blends prepared with different levels of compatibilizer and the final cellular morphology of the microcellular thermoplastic olefin foams. The initial morphology of the blends was also altered by quiescent coarsening as well as shear-induced p...

Morphology and properties of polymer/organoclay nanocomposites based on poly(ethylene terephthalate) and sulfopolyester blends

Abstract: Poly(ethylene terephthalate) (PET) nanocomposite films containing two different organoclays, Cloisite 30B® (C30B) and Nanomer I.28E® (N28E), were prepared by melt blending. In order to increase the gallery spacing of the clay particles, a sulfopolyester (PET ionomer or PETi) was added to the nanocomposites via a master-batch approach. The morphological, thermal and gas barrier characteristics of the nanocomposite films were studied using several characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, rheometry and oxygen permeability. PET and PETi were found to form immiscible polymer blends and the nanoparticles were preferentially located in the PETi dispersed phase. A better dispersion of clay was obtained for nanocomposites containing N28E with PETi. On the contrary, for nanocomposites containing C30B and PETi, the number of tactoids increased and the clay distribution and dispersion became worse than for C30B alone. Overall, the best properties were obtained for the PET/C30B nanocomposite without PETi. Higher crystallinity was found for all nanocomposite films in comparison to that of neat PET. © 2012 Society of Chemical Industry

In Situ Polymerization of PET in the Presence of Pristine and Organo-modified Clays

Abstract: In this work two types of montmorillonite, a pristine and an organo-modified clay (Cloisite 30B), were employed to produce (polyethylene terephthalate)-based nanocomposites via in situ polymerization. Using water as an intermediate medium, a stable dispersion of pristine clay in ethylene glycol was achieved. However, after polymerization, no significant gain was obtained in terms of delamination of silicate platelets. The polycondensation reaction when using Cloisite 30B was carried out at a temperature as low as 250°C in order to retain a considerable portion of the organo-modifier. The results showed that Cloisite 30B was successfully intercalated by the polymer chains, resulting in a d-spacing increase from 1.9 nm to about 3.6 nm. Although some mono and double silicate layers were observed in microscopy images, the major part of the organoclay remained in a tactoid intercalated form. Sampling during the polycondensation reaction revealed that, in this process, clay was first swelled efficiently by the ...