Kotiba Hamad

Biodegradable polymer blends and composites: An overview

Biodegradable polymers belong to a family of polymer materials that found applications ranged from medical applications including tissue engineering, wound management, drugs delivery, and orthopedic devices, to packaging and films applications. For broadening their potential applications, biodegradable polymers are modified utilizing several methods such as blending and composites forming, which lead to new materials with unique properties including high performance, low cost, and good processability. This paper reviews the recent information about the morphology of blends consisting of both biodegradable and non-biodegradable polymers and associated mechanical, rheological, and thermal properties of these systems as well as their degradation behavior. In addition, the mechanical performance of composites based on biodegradable polymers is described.

Microstructure and texture evolution in low carbon steel deformed by differential speed rolling (DSR) method

The study examined the microstructural and textural evolution of low carbon steel samples fabricated using a differential speed rolling (DSR) process with respect to the number of operations. For this purpose, the samples were deformed by up to 4-pass of DSR at room temperature with a roll speed ratio of 1:4 for the lower and upper rolls, respectively. The DSR technique applied to low carbon steel samples resulted in a microstructure composed of ultrafine ferrite grains, approximately 0.4xa0µm in size, after 4-pass with a high-angle grain boundary fraction of ~65xa0%. The microstructural features of the ferrite phase indicated the occurrence of continuous dynamic recrystallization, beginning with the formation of a necklace-like structure of ultrafine equiaxed grains around the elongated grains, which were formed in the early stages of deformation, and ending with ultrafine recrystallized grains surrounded by boundaries with high angles of misorientations. In the pearlite phase, the microstructural changes associated with DSR deformation were presented by the occurrence of bending, kinking, and breaking of the cementite lamellar plates. In addition, the evolution of texture after DSR processing was affected by shear deformation and rolling deformation, leading to the formation of a texture composed of fractions of components with shear texture orientations such as {110} 〈001〉 (Goss) and orientations close to {112} 〈111〉, in addition to rolling texture components consisting mainly of α-fiber and γ-fiber.

Melt rheology of poly(vinylidene fluoride) (PVDF)/low density polyethylene (LDPE) blends

The aim of this work is to study the rheological properties of PVDF/LDPE blends in the molten state, in relation to shear rate, shear stress and temperature. Blends of LDPE and PVDF at different compositions, namely PVDF/LDPE = 0/100, 30/70, 50/50, 70/30, 100/0 were realized. The blends were prepared by using brabender plastograph and measurements were carried out by using capillary rheometer. For studying the viscous properties non-Newtonian index n, true viscosity η and the flow activation energy E were determined. The melt elasticity has been studied in term of die swell ratio B. The results show that PVDF/LDPE blends behave in pseudo-plastic manner (n < 1), plots of true viscosity versus blending ratio go through a minimum nearly at blending ratio (50/50), and the flow activation energy decreases with increasing shear rate at the wall γ but it increases with increasing true shear stress τ. The results of die swell ratio show that, B increases linearly with increasing true shear stress τ, while B decreases with increasing L/R. It was also found that a maximum of elastic properties is observed at certain blending ratio. This phenomenon can be attributed to the amount of elastic deformation energy stored in the melt flow and its transition due to the viscoelastic difference between the two phases.

Finite Element Analysis of Deformation Behavior in Al-2.2 wt.%Mg Alloy Subjected to Differential Speed Rolling

This paper reported the deformation characteristics of Al-2.2xa0wt.%Mg alloy processed by differential speed rolling (DSR) based on microstructure evolution and finite element (FE) analysis. The FE analysis was carried out to examine the distribution of the effective strain during DSR deformation with respect to the roll speed ratio. As the roll speed ratio increased from 1:1 to 1:4 for the lower and upper rolls, the amount of the effective strain imparted to the sample during DSR deformation increased, which was also accompanied with reasonably homogeneous distributions of microstructure and microhardness over the entire samples. At the roll speed ratio of 1:4, the effective strain of ~1.5 was calculated in the top part of the DSR-deformed sample. In addition, the rolling load was observed to decrease with the roll speed ratio increased, which was attributed mainly to the influence of friction between the rolls and sample.

Rheological properties of ABS/wood composites

AbstractIn this work, the rheological propertiesn of acrylonitrile–butadiene–styrene (ABS)/wood composites were investigated using a capillary rheometer. The present composites with different ratios of ABS and wood were prepared by means of an internal bath mixer. The viscosity of the composites that were pseudo plastics in deformation manner increased with increasing amount of wood particles. In addition, the flow activation energy of the composites increased with increasing amount of wood particles.

Slit die rheology of thermoplastic starch during extrusion process

In this work, the rheological properties of thermoplastic starch (TPS) were determined using a laboratory scale single screw extruder at different temperatures (110, 130, and 140xa0°C) and speeds (10, 15, 20, 25, 30, and 35 RPM). Glycerol was used as a plasticizer for preparing TPS. Apparent shear rate (

Effect of Deformation Temperature on Microstructure and Mechanical Properties of AZ31 Mg Alloy Processed by Differential-Speed Rolling

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Effect of deformation path on microstructure, microhardness and texture evolution of interstitial free steel fabricated by differential speed rolling

), apparent shear stress (τa), apparent shear viscosity (ηa) and flow activation energy at a constant shear rate (Eγ) were determined. The results showed that TPS melts were pseudo plastic (nu2009<u20091) and the shear viscosity decreases with increasing shear rate at different temperatures. Also it was found that that shear viscosity of TPS decreases with increasing glycerol content in TPS, according to the values of flow activation energy at a constant shear rate, TPS25 was more sensitive to processing temperature.