Structural,thermal and physico-chemical properties of high density polyethylene/natural rubber/modified cassava starch blends

The utilization of cassava starch as one of the components in high density polyethylene (HDPE)/natural rubber (NR) blends were investigated. The true challenge in producing new materials based on natural resources is to design materials that could level the mechanical properties of existing conventional polymers. In this study, we have focused on characterizing the HDPE/NR blends incorporated with cassava starch in the form of granulates (native and silanized) as well as plasticized starch. Cassava starch acted as a biodegradation component in the HDPE/NR blends and the incorporation of cassava starch reduced thermal stability and the degree of crystallinity in general. Several series of cassava starch modifications were performed in order to improve the final properties of the blends. Cassava starch was treated with a silane coupling agent, and proved to be effective in improving tensile strength. The better dimensional stability and compatibility between the blend phases were obtained in the silane-treated cassava starch, as observed in the dynamic mechanical analysis results. Cassava starch was also converted into a plasticized form (TPS), and from the results, the degree of TPS adhesion at the inter-phase ofthe HDPE/NR-TPS blend was clearly improved, as indicated in the morphology study. Through the comparison of thermal degradation results, the HDPE/NR/TPS blends proved to be superior to the HDPE/NR/particulate starch counterparts.     

UNSTEADY ANALYSIS OF VISCOELASTIC BLOOD FLOW THROUGH ARTERIAL STENOSIS

A mathematical model of unsteady non-Newtonian blood flow in an artery under stenotic condition has been developed. The flowing blood is considered to be a viscoelastic fluid characterized by the Oldroyd-B model and the arterial wall is considered to be rigid, having cosine-shaped stenosis. The governing equations of motion accompanied by appropriate choice of the initial and boundary conditions are solved numerically by the MAC (marker and cell) method, and the results are checked, for numerical stability with desired degree of accuracy. The key factors like the wall shear stress, resistive impedance, and the other viscoelastic parameters are also examined for further qualitative insight into the flow through arterial stenosis. Comparison of the results reveals that dimensionless pressure drop for the viscoelastic model increases while it diminishes for the shear-thinning power law model over that of the Newtonian model. Moreover, the possibility of flow separation increases with increasing relaxation time (Deborah number), and in case of Newtonian fluid, delayed separation is observed. The grid independence study has also been performed successfully in order to validate the applicability of the methodology as well as the model used under consideration. Special emphasis has duly been made to compare the present theoretical results with the existing ones, and good agreement between them has been achieved both qualitatively and quantitatively.     

Effect of heat and mass transfer on non-Newtonian flow – Links to atherosclerosis

The present investigation deals with a mathematical model representing the dynamic response of heat and mass transfer to blood streaming through the arteries under stenotic condition. The blood is treated to be a generalized Newtonian fluid and the arterial wall is considered to be rigid having differently shaped stenoses in its lumen arising from various types of abnormal growth or plaque formation. The nonlinear unsteady pulsatile flow phenomenon unaffected by the concentration-field of the macromolecules is governed by the Navier–Stokes equations together with the equation of continuity while those of the heat and the mass transfers are controlled by the heat conduction and the convection–diffusion equations, respectively. The governing equations of motion accompanied by the appropriate choice of the boundary conditions are solved numerically by Marker and Cell (MAC) method in order to compute the physiologically significant quantities with desired degree of accuracy. The necessary checking for numerical stability has been incorporated in the algorithm for better precision of the results computed. The quantitative analysis carried out finally includes the respective profiles of the flow-field, the temperature and the mass concentration along with their individual distributions over the entire arterial segment as well. The key factors like the wall shear stress and the Sherwood number are also examined for further qualitative insight into the heat flow and mass transport phenomena through arterial stenosis. The present results show quite consistency with several existing results in the literature which substantiate sufficiently to validate the applicability of the model under consideration.