Abdul Hamid Yahaya

Dielectric behaviour of PVC-based polymer electrolytes

Abstract Thin films of poly(vinyl chloride) (PVC)–poly(methyl methacrylate) (PMMA) blend with lithium triflate (LiCF 3 SO 3 ) salt and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The conductivity and dielectric measurements were carried out on these films as a function of frequency at various temperatures. The addition of DBP significantly improved the ionic conductivity. The conductivity–temperature plots were found to follow an Arrhenius nature. The dielectric behaviour was analysed using dielectric permittivity ( e ′), dissipation factor (tan δ ) and electric modulus ( M ′) of the samples.

Miscibility studies of PVC blends (PVC/PMMA and PVC/PEO) based polymer electrolytes

Abstract The miscibility of PVC blends (PVC/PMMA and PVC/PEO) was investigated. Experiments using viscosimetry and differential scanning calorimetry (DSC) were performed. The presence of attractive forces among polymers was evaluated according to the Sun theory by the determination of the α parameter from the viscosimetric data. The melting depression in a binary blend is an indication of miscibility. Viscosimetric and thermal analysis showed that the PVC/PMMA and PVC/PEO blends are miscible. The miscibility of the PVC/PMMA and PVC/PEO blends is explained in terms of donor–acceptor interactions between chlorine atoms (a weak acceptor species) of PVC and oxygen atoms (a donor species) of the PMMA and PEO.

The Preparation and Characterization of Chitosan / Poly (Vinyl Alcohol) Blended Films

In this study, chitosan and PVA were blended at different proportions (considering chitosan as the main component) in solution forms. The chemical structure and the morphology of the obtained blend films were investigated using FTIR and field emission scanning electron microscope (FESEM). The thermal stability of the blend films were also studied using thermal gravimetric analysis (TGA). Our results showed that chitosan and PVA form a compatible blend and their films displayed homogenous and smooth surface properties compared to their individual pure components. The blending of PVA with chitosan at all proportions was found to highly enhance the swelling of the obtained films compared to that of pure chitosan one.

A zinc-air cell employing a porous zinc electrode fabricated from zinc-graphite-natural biodegradable polymer paste

Porous zinc anodes have been fabricated from a mixture of zinc and graphite powder using gelatinized agar solution as the binding agent. Agar is a biodegradable polysaccharide polymer extracted from marine algae. The graphite content and the agar solution concentration were varied to find the best electrode composition. Zinc–air cells were fabricated using the porous zinc anode, a commercially available air cathode sheet and KOH electrolyte in the form of elastic jelly granules. The electrode performance was evaluated from the zinc–air cell galvanostatic discharge capability. In the cell design, a thin agar layer was introduced between the electrode-gelled electrolyte interfaces, resulting in substantially improved cell discharge performance. The inclusion of particulate graphite into the electrode did not enhance the electrode performance due to the formation of a graphite-rich layer, which obscured the electrode porosity. A zinc–air cell employing the optimized porous zinc electrode demonstrated a capacity of 2066 mA h and specific energy density of 443 Wh kg−1.

Preparation and characterization of chitosan/poly(vinyl alcohol) blended films: Mechanical, thermal and surface investigations

In this study, blends of chitosan (CS) and polyvinyl alcohol (PVA) (CS/PVA) having various proportions were prepared and characterized by universal mechanical tester, the differential scanning calorimetry (DSC) and contact angle measurements. Studying the mechanical properties of the films showed that blending improved the tensile strength, which increased with increasing PVA content up to 40% while the elongation% at break of the blends was decreased compared to that of the pure components. The obtained results of DSC suggested that some interaction between chitosan and PVA mostly took place. Static water contact angle measurements showed an improvement in the wettability of the obtained films.

Preparation and Characterization of Chitosan/Agar Blended Films: Part 1. Chemical Structure and Morphology

Chitosan/agar (CS/AG) films were prepared by blending different proportions of chitosan and agar (considering chitosan as the main component) in solution forms. The chemical structure and the morphology of the obtained blended films were investigated using Fourier transform infrared (FTIR) and field emission scanning electron microscope (FESEM). It was revealed that chitosan and agar form a highly compatible blend and their films displayed homogenous and smooth surface properties compared to the individual pure components.

Preparation and characterization of chitosan/agar blended films: Part 2. Thermal, Mechanical, and surface properties

Chitosan/agar (CS/AG) films were prepared by blending different proportions of chitosan and agar (considering chitosan as the major component) in solution forms. The thermal stability of the blended films was studied using thermal gravimetric analysis (TGA). It was revealed that chitosan and agar form a compatible blend. Studying the mechanical properties of the films showed a decrease in the tensile strength and elongation at break with increasing agar content. Blending of agar with chitosan at all proportions was found to form hydrogel films with enhanced swelling compared to the pure chitosan one. Static water contact angle measurements confirmed the increasing affinity of the blended films towards water suggesting that blending of agar with chitosan improves the wettability of the obtained films.

PREPARATION AND CHARACTERIZATION OF CHITOSAN/AGAR BLENDS: RHEOLOGICAL AND THERMAL STUDIES

In this work, a number of mixture aqueous solutions of chitosan/agar (CS/AG) at different ratios (considering chitosan as the main component) were prepared. The rheological properties i.e. shearing viscosity and shear stress of the blend solutions as a function of shear rate as well as the thermal properties of the blend films were investigated. Among the parameters studied were temperature, shearing time and storage time. Results showed that almost Newtonian behavior was observed at temperatures from 40°C to 55°C for the ratios 100/0, 90/10, 80/20 and 70/30. However, the proportions 60/40 and 50/50 showed a clear shear thinning behavior (pseudoplastic non-Newtonian behavior). It was also found that all the blend solutions obeyed the Arrhenius equation. In addition, the effect of shearing time on the shearing viscosity of all blends did not show any significant differences at all shearing times applied in this study except the proportion 50/50 wherein decreasing in shearing viscosity and shear stress was observed as the shearing time increased. Furthermore, different behaviors were observed for the blend solutions when the period of storage was extended to three weeks. The FTIR results and the differential scanning calorimetery (DSC) curves showed that the interaction between chitosan and agar can occur.

Parametric investigations on proton conducting membrane by radiation induced grafting of 4-vinylpyridine onto poly(vinylidene fluoride) and phosphoric acid doping

Abstract Proton conducting membrane composed of grafted basic moiety doped with phosphoric acid (PA) was studied. The membrane denoted as PVDF-g-4-VP/PA was prepared by radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(vinylidene fluoride) (PVDF) films followed by doping with PA. The effect of grafting conditions on the degree of grafting (G%) was investigated. The acid doping conditions (G%, time and PA concentration) were also investigated with respect to doping level. The grafted precursors and the acid doped membranes were characterized by means of Fourier transform infrared (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM). The membranes showed a thermal stability up to a temperature of ∼ 160 ℃, above which they undergo a multi-step degradation pattern due to decomposition of the protonated functions, poly(4VP) grafts and PVDF matrix, respectively. The proton conductivities of the membranes were found to increase with the increase in G% ( doping level) and the temperature with a maximum proton conductivity of 62 mS cm−1 achieved at 100 ℃ without any humidification. The results of the present study show that the prepared membrane has a potential to be proposed for operating polymer electrolyte membrane fuel cell above 80 ℃.

Preparation and Characterization of Chitosan/Polyvinyl Alcohol Blends-A Rheological Study

Blends of chitosan (CS) and polyvinyl alcohol (PVA) of different proportions (considering chitosan as the main component) were prepared. The rheological properties of the obtained blend solutions such as the shearing viscosity and the shear stress were investigated as a function of shear rate under various temperatures, shearing times and solution storage times using a digital viscometer. The CS/PVA solutions showed a Newtonian behavior at temperatures in the range of 40-55 °C regardless of the blend composition. This was accompanied by a general decrease in the viscosity with increasing PVA content in the blend. The heat-dependant viscosity changes of the blend solutions were found to follow Arrhenius equation. The shearing time was found to have no significant effect on the shearing viscosity of all blended solutions. However, the variation of solution storage period was found to have a mixed effect when time was extended to 3 weeks.