Dynamic and modulated mechanical evaluation of polymer structures

Mechanical testing is foremost a means to measure material performance, however it provides a probe into the complex elastic, viscoelastic and viscoplastic behavior of polymer morphologies. The techniques in this work utilize variables of time/frequency, temperature, stress and strain with emphasis on dynamic and modulated implementation. Several instruments were used since a particular instrument does not provide all of the capabilities. The material response is complex and it has been resolved into typically instantaneous and time-dependent components. Some of the techniques are widely used and these have been extended, while other techniques introduce control over alternate variables. Polycarbonate was chosen as the main example with support from similar polymer, though the techniques are applied to many polymer types

Assessment of Melt Rheological Behavior of PTT/PE and PTT/PA 12 Blends by Emulsion and Micromechanical Models

To describe the rheological behavior of polymer blends using emulsionbased (Palierne theory) as well as micromechanical models (Coranapproach), two immiscible polymeric blend systems of poly(trimethylene terephthalate) (PTT)/polyamide-12 (PA12) and PTT/polyethylene (PE) having different levels of molecular interactions were investigated as model systems. The role of interfacial interactions, viscosity ratio, composition, and shear rate were also explored with respect to the aforementioned theories. For both systems no reasonable agreement was noticed between the experimental data and Palierne model predictions, which was related to high viscosity ratio and high dispersed phase content. Nevertheless, the PTT/PE blend, having almost a zero interfacial thickness due to the absence of intermolecular interaction, exhibited a seemingly better correlation with experimental data compared to PTT/PA12 system. Moreover a better agreement between experimental and theoretical data was obtained in the blend where the viscosity of dispersed phase was higher than that of matrix. Also, in both model systems, the values predicted from Palierne were closer to empirical data at higher frequencies most likely due to breakdown in physical network structure. Coran analysis due to its micromechanical origin could give outputs in good agreement with the experimental results in both model systems

Crystallization and melting behavior of nanoclay-containing polypropylene/poly(trimethylene terephthalate) blends

This contribution concerns preparation and characterization of polypropylene (PP)/poly(trimethylene terephthalate) (PTT) melt-mixed blends in the presence of organically-modified montmorillonite nanoclays and functional compatibilizers. Immiscibility and nanocomposite formation were confirmed via transmission electron microscopy. An intercalated structure was observed by wide angle X-ray diffraction technique. Crystallization, and melting characteristics were studied by differential scanning calorimetry in both isothermal and non-isothermal modes, supplemented by temperature modulated DSC (TMDSC). A concurrent crystallization was found for both polymeric components in the blends. Whereas blending favored PP crystallizability, it interrupted that of PTT. The addition compatibilizers interfered with rate, temperature, and degree of crystallization of PP and PTT. On the contrary, nanoclays incorporation increased crystallizability of each individual component. However, as for blend nanocomposite samples, the way the crystallization behavior changed was established to depend on the type of nanoclay. Based on kinetic analysis, isothermal crystallization nucleation followed athermal mechanism, while that of non-isothermal obeyed thermal mode. Addition of nanoclays shifted nucleation mechanism from athermal to thermal mode

Janus hybrid silica/polymer nanoparticles as effective compatibilizing agents for polystyrene/polyamide-6 melted blends

International audienceSilica/polystyrene Janus hybrid nanoparticles (JHNPs) were synthesized at the gram scale via miniemulsion polymerization technique and then incorporated into polystyrene/polyamide-6 melted blends. Due to their intrinsic amphiphilic properties, the JHNPs migrate to the interface of the PS/PA6 blend during the mixing process and play the role of a compatibilizing agent. First, a significant decrease of the size of the dispersed nodules was observed even at low content of JHNPs, whereas an optimum content of JHNPs corresponding to the saturation of the polystyrene/polyamide-6 (PS/PA6) interface was found in the 3–5 phr range. Secondly, the rheological properties of the blends were also significantly modified. The complex viscosity increased as a function of JHNPs content over the entire frequency range studied. Up to 5 phr of JHNPs, a high increase of the viscosity at low frequencies was observed. This is attributed to the formation of a solid network through the matrix/nodules interface of the nanocomposite. Finally, the Palierne model extended to the field of immiscible polymer blends was used; an important decrease of the effective interfacial tension of the system was observed when JHNPs were added. The asymmetry of these nanoparticles allows the combination of a “Pickering effect” of a solid particle with a “copolymer effect” of an amphiphilic structure. The synthesis procedure of JHNPs developed in this work renders these silica/polymer JHNPs interesting as a route for the compatibilization of polymer blends