Effect of Single-walled Carbon Nanotubes on Non-isothermal Crystallization Kinetics of Polypropylene: Comparison of Ozawa and Cazé-Chuah Methods

Non-isothermal crystallization kinetics of polypropylene (PP) and PP containing 0.5 wt% singlewalled carbon nanotubes (PP/SWNT) were studied at various cooling rates using differential scanning calorimetry technique. The non-isothermal melt crystallization data were analyzed according to Ozawa and Cazé-Chuah models. Although Ozawa model was successful in describing the nonisothermal crystallization of PP, it failed to do so for PP/SWNT nanocomposite. The results obtained from Cazé-Chuah model show that the model was successful in describing non-isothermal crystallization kinetics of the nanocomposite and the pristine polymer. Using a method developed by Dobreva and Gutzow, it was found that the nucleation activity of SWNT on PP crystallization was around 0.65. This is consistent with the fact that SWNT acted as nucleating agents for PP

Non-Isothermal modeling of a non-Newtonian fluid flow in a twin screw extruder using the fictitious domain method

In this study, using a developed mathematical model, the non-isothermal behavior of a non-Newtonian fluid flow in the conveying elements of an intermeshing co-rotating twin screw extruder (TSE) is simulated based on the combination of mixed finite elements and fictitious domain methods. The flow equations are solved employing the standard Galerkin method and a streamline-upwind/Petrov-Galerkin technique is used in the solution scheme of the energy equation to reduce numerical oscillation. This model is combined with the Carreau rheological model to solve governing equations of continuity, momentum, and energy in a 3D Cartesian coordinate system. Using a developed mathematical model, the velocity and pressure fields are simulated for a non-isothermal flow in a co-rotating TSE. The shear rate distribution as a criterion for viscous dissipation and also the temperature distribution is calculated based on the simulated flow fields. The applicability of this model is verified by the comparison of experimentally measured pressures and mass flow rates with the simulation results for a high-density polyethylene melt. This comparison shows a good correlation between experimental data and model predictions

Modification of porous calcium phosphate surfaces with different geometries of bioactive glass nanoparticles

In this study, the effects of bioactive glass nanoparticles' (nBGs) size and shape incorporated into hydroxyapatite/β-tricalcium phosphate (BCP) scaffolds were investigated. We prepared a highly porous (> 85%) BCP scaffold and coated its surface with a nanocomposite layer consisted of polycaprolactone (PCL) and rod (∼153 nm in height and ∼29 nm in width) or spherical (∼33 nm and 64 nm in diameter) nBGs. Osteogenic gene expression by primary human osteoblast-like cells (HOB) was investigated using quantitative real time polymerase chain reaction (q-RT-PCR). We demonstrated for the first time that in vitro osteogenesis is dramatically affected by the shape of the nBGs, whereby rod shaped nBGs showed the most significant osteogenic induction, compared to spherical particles (regardless of their size). Importantly, the good biological effect observed for the rod shaped nBGs was coupled by a marked increase in the modulus (∼48 MPa), compressive strength (∼1 MPa) and failure strain (∼6%), compared to those for the BCP scaffolds (∼4 MPa, ∼1 MPa and ∼0.5% respectively). The findings of this study demonstrated that the shape of the nBGs is of significant importance when considering bone regeneration.10 page(s