M. Abu Bakar

Effect of anion of lithium salt on the property of lithium salt-epoxidized natural rubber polymer electrolytes

Lithium salt, LiX (where X = BF4−, I−, CF3SO3−, COOCF3− or ClO4−), was incorporated into epoxidized natural rubber (ENR). Thin films of LiX-ENR polymer electrolytes (PEs) were obtained via solvent casting method. These electrolytes were characterized using SEM/X-mapping, FTIR, differential scanning calorimeter, thermogravimetry analysis, and impedance spectroscopy. The trend in thermal stability and ionic conductivity of LiX-ENR PEs follow LiBF4 > > LiCF3SO3 ~ LiCOOCF3 > LiI > > LiClO4. The LiClO4 hardly dissociates and formed LiClO4 aggregates within the polymer matrix that resulted in a PE with low thermal stability and low ionic conductivity. The LiCF3SO3, LiCOOCF3, and LiI, however, exert moderate interactions with the ENR, and their respective PEs exhibit moderate ionic conductivity and thermal property. The occurrence of epoxide ring opening and complexation or cross-linking reactions in and between the ENR chains that involve BF4− ions have produced a LiBF4-ENR PE with superior thermal property and ionic conductivity as compared to other PEs studied in this work.

Filler treatment effects on the weathering of talc-, CaCO3- and kaolin-filled polypropylene hybrid composites

Talc, calcium carbonate (CaCO3), and kaolin hold considerable promise in the development of polymer composites for good mechanical properties and stability. Comparative studies on the usage of these minerals as single fillers in polypropylene (PP) have shown varying degrees of reinforcement due to their differences in terms of particle geometry, surface energy and affinity towards the matrix polymer. In this study, comparisons were made in terms of mechanical, thermal and weatherability properties between hybrid-filler PP composites (i.e. PP filled with either talc–CaCO3 or talc–kaolin hybrid filler combinations), with particular attention directed towards the effect of surface modification of the fillers. The talc/CaCO3 hybrid composites have shown exceptional performance in terms of flexural and impact properties. The contribution of talc in the talc–kaolin hybrid composite system has been significant in terms of enhancing the overall tensile and flexural properties. The ability of silane and titanate coupling agents in boosting the resistance of the composites to severe damage and degradation due to natural weathering has been shown.

Electrical and thermal behavior of copper-epoxy nanocomposites prepared via aqueous to organic phase transfer technique

The preparation, electrical, and thermal behaviors of copper-epoxy nanocomposites are described. Cetyltrimethylammonium bromide - (CTAB-) stabilized copper (Cu) particles were synthesized via phase transfer technique. Isopropanol (IPA), sodium borohydride (NaBH4), and toluene solution of diglycidyl ether of bisphenol A (DGEBA) were used as transferring, reducing agent, and the organic phase, respectively. The UV-Vis absorbance spectra of all the sols prepared indicate that the presence of Cu particles with the particles transfer efficiency is ≥97%. The amount, size, and size distribution of particles in the organosol were dependent on the content of organic solute in the organosol. The composites were obtained upon drying the organosols and these were then subjected to further studies on the curing, thermal, and electrical characteristic. The presence of Cu fillers does not significantly affect the completeness of the composite curing process and only slightly reduce the thermal stability of the composites that is >300°C. The highest conductivity value of the composites obtained is 3.06 × 10-2 S cm-1.

Metal Chloride Induced Formation of Porous Polyhydroxybutyrate (PHB) Films: Morphology, Thermal Properties and Crystallinity

Polyhydroxybutyrate (PHB) films with highly porous structures were synthesized using a one phase system comprising of metal chloride/methanol/PHB/chloroform (MCl2/CH3OH/PHB/CHCl3). SEM analyses confirmed that the MCl2 (where M = Cu2+ or Ni2+) induced porous structures with pore sizes ranging from 0.3 - 2.0 μm. The average pore size increased with the increasing MCl2 content. There existed weak physical interactions between the PHB chains and MCl2 as revealed by FTIR and NMR spectroscopies. The residue of MCl2 in the porous PHB film does not exert significant influence on the thermal stability of PHB. Nevertheless, the crystallinity of the prepared film is enhanced, as MCl2 acts as the nucleation sites to promote the growth of spherullites.

Hydrogenation of Liquid Styrene by Alumina Supported Nickel Catalysts: Comparison between Classical and Non-Classical Methods

Almina supported Ni catalysts (Ni/Al2O3) with different Ni weight percentages (wt%) were prepared via classical and non-classical methods. All samples were prepared via impregnation technique. The samples prepared via non-classical methods were reduced using KBH4 as the reducing agent. The catalysts were tested for the hydrogenation of styrene in liquid phase. Optimum activation conditions for the hydrogenation reaction were found to be 633 K for 2 hours. Comparison of the catalytic reactivity for all catalysts at these activation conditions showed that catalysts prepared via classical methods exhibited better activity. Furthermore the 7.6wt% Ni-Al2O3/C showed enhanced activity when compared to the 5.9wt% and 13.8wt% Ni-Al2O3/C catalyst. This phenomenon is mainly attributed to the type of Ni active sites available on the catalyst. The surface properties of the catalysts investigated via H2- temperature programmed reduction (H2-TPR), H2-chemisorption and H2-temperature programmed desorption (H2-TPD) confirm this.

Synthesis and properties of nanosized silver catalyst supported on chitosan-silica nanocomposites

This work described the immobilization of noble metal nanoparticles on silica microspheres mediated by chitosan. The dual support system is comprised of organicinorganic materials prepared via core-shell method. Chitosan/silica nanocomposites were successfully synthesized with different chitosan concentrations in order to get the optimized shell thickness. When high concentration of chitosan was employed, it was found that the shell completely coats the silica. The silver nanoparticles were then immobilized on the shell of the support through a sol-gel method. Various quantities of silver were studied in order to get the maximum loading thereby it is related to coating thickness. The catalyst was then tested by employing hydrogenation of cyclohexene in methanol as a model reaction.

Effects of sodium doping on phase composition and morphology of barium titanate particles

Tetragonal barium titanate (BaTiO3) was synthesized via sol-gel method and calcined at 900 °C. The crystal phase of barium titanate still remained after doping with sodium showing that the phase had not been distorted by dopants. However, an additional phase of sodium barium titanium oxide (Na1.7Ba0.45Ti5.85O13) was detected and is believed to be formed on the surface of particles. Surface microstructures of undoped BaTiO3 show no distinct shape and high agglomeration. These preparations described the effects of different calcination duration on the composition and shape and size of BaTiO3 particles. Upon doping with sodium, the morphology of the particles becomes distinct. However, with the effect of increasing calcination duration from 2 to 6 hours, the morphology of particles progressively transformed from cube to sphere. Particles agglomeration was still unavoidable. The average size of the particles varied slightly between 0.24 - 0.36 μm with narrow size distribution after calcination.

Kinetics of p-nitrophenol reduction by copper - porous silicon catalyst in the presence of KBH4

Copper supported on porous silicon (Cu-PS) was prepared via deposition of Cu° on the surface of chemically etched PS powder. The particle size of Cu° varied with the Cu content in Cu-PS. The distribution of Cu° in or around the pores of PS resulted in a lower BET surface area and pore size of the Cu-PS as compared to pristine PS. Catalytic efficiency of Cu-PS was evaluated for the reduction of p-nitrophenol (p-NP). Optimum conditions were achieved when 0.77 wt% Cu-PS and 25.00 mg KBH4 was used. Cu-PS also exhibit sustainable catalytic activity.

Solvent effect on the morphology of copper (I) oxide: A fundamental study towards copper (I) oxide-epoxy composites

The study on the influence of solvent environments on the Cu2O particles preparation via aqueous to organic phase transfer technique is described. In aqueous, the morphologies of the as-formed particles are of whisker-like or ellipsoidal shape dependent on the amount of CTAB used. At lower concentration of CTAB (r=2.7), Cu2O particles tend to form bundle of fine needle-like structures with an average diameter of 14.1±4.3 nm. Upon phase transfer process, transformation of Cu2O morphology occurred. Two organic solvents namely chloroform and toluene is studied. Chloroform with higher dielectric constant and dipole moment exert better particle-solvent interaction thus give better particle dispersion as compared to toluene. Addition of 10% v/v epoxy in the organic solvent further affects the particles morphology. Spherical particles as small as 8.1 ± 2.1 nm are obtained for Cu2O particles transferred into the 10%v/v epoxy/chloroform. Better solvation of epoxy resin in chloroform makes it a better stabilizer thus protecting the particles from agglomeration and secondary growth.

Nano silica dispersion in epoxy : the investigation of heat, milling speed and duration effect

Nano composites are a promising development but the challenge of homogenous and discrete dispersion of the nano fillers are barriers that must be overcome before they can be effectively implemented. Although the common dispersion methods such as particle surface modification, comprehensive milling metrologies and the usage of solvents bear results, these are time consuming and not cost effective. In this paper, we explore the efficiency of coupling the usage of ball-media and heat on the dispersion of nano silica in epoxy. No solvents are involved. The effects of milling speed and duration are also studied albeit under a fixed ball media : silica-epoxy volume ratio of 3:5. The experiment set-up involves a simple 3-blade mixer, round bottom flask and 60 ? m zirconia ball. At nano silica loading of 10 wt % the nano silica clusters are systematically reduced from 1.5 - 2 ? m to 100 - 200 nm with the usage of ball media and application of heat. At the optimum milling speed and duration of 500 rpm for 5 hours, the aggregate sizes were further reduced to 30 - 70 nm, which is almost a discrete dispersion.