Advanced Materials Research Vol. 812

Abstract: Poly (glycerol adipate) is enzymatically prepared by reacting glycerol with divinyl adipate in the presence of a lipase as catalyst from Candida Antarctica type B (CAL-B). The reaction yields linear polyesters with free pendent hydroxyl groups. Poly (glycerol adipate) is hydrophobically modified by incomplete acylation of some of the pendent hydroxyl groups using stearoyl chloride. The resulting polymer is further functionalized with α-bromoisobutyryl groups. The final polymer is purified and well characterized to calculate the ratio of substitution in both cases. Furthermore, nanoparticles in water are prepared from the functionalized polymer using the interfacial precipitation method. Dynamic light scattering measurements depict nanoparticles with relatively narrow size distributions and with an average hydrodynamic radius of 70 nm. Additionally, transmission electron microscopy images reveal well dispersed spherical nanoparticles with nanophase separation. Finally, the interactions between the graft copolymers and lipid monolayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are investigated on a Langmuir trough equipped with a fluorescence microscope.

Abstract: Galactomannan nanoparticles possess attractive properties such as biodegradable and biocompatible; significant in biomedical applications. Galactomannan (GA) isolated from the mature seed of a local plant, petai belalang known scientifically as Leucaena leucocephala were modified to acrylated galactomannan (AcGA) which acted as a precursor molecule for the preparation of crosslinked galactomannan nanoparticles (CL-GA). AcGA was synthesized using acryloyl chloride (AC) as a chemical modifier through esterification process. Trimethylolpropane triacrylate (TMPTA) was used as the crosslinker for the preparation of CL-GA. Successful conjugation of GA with acrylates was verified by ¹H NMR and FTIR spectroscopies. Thermal properties of pure galactomannan, AcGA and CL-GA were measured using DSC to complement spectroscopic results. TEM images revealed the particle size of AcGA to be in the range of 30-100 nm; and increased to 200-850 nm range after the crosslinking process. Efficiency of CL-GA to trap crystal violet dye as a model drug was followed by UV Vis Spectroscopy. Results showed that CL-GA is capable of trapping crystal violet dye and has the potential to be used as a drug carrier.

Abstract: Superabsorbent polymer from waste polystyrene-graft-polyacrylamide was synthesized through emulsion polymerization technique using acrylamide as a monomer and potassium persulphate as an initiator in the presence of N,N-methylenebisacrylamide (NMBA) as a crosslinking agent. The effects of acrylamide loading was investigated to obtain the optimum condition that shows the best swelling capacity in three different aqueous medium; distilled water, saline solution and urea solution. Superabsorbent hydrogel were characterized by Fourier Transform Infrared (FTIR), thermogravimetric analysis (TGA) and electron scanning microscopy (SEM). Swelling test showed optimum absorbencies for distilled water, saline and urea solution were 1230 wt%, 1160 wt% and 440 wt% from their dry weight, respectively, recorded at ratio 1:10 of waste polystyrene to acrylamide. Meanwhile, the IR Spectroscopy proves that the grafting process between acrylamide and waste polystyrene was occurred in the hydrogel. Thermal degradation of the hydrogel started at 350 °C and the existence of porous unit can be observed in SEM micrographs.

Abstract: Epoxidation reaction is an important reaction in organic synthesis because the formed epoxides are intermediates that can be converted to a variety of products. Catalytic palm oil epoxidation using titanium-grafted silica, hydrogen peroxide, and peroxoformic acid was carried out at 60 °C in a fixed batch reactor. Titanium-grafted silica with different percentages of silica content was prepared through sol-gel hydrolysis and was utilized in epoxidation of palm oil. Titanium-grafted silica particles and Epoxidized palm oil were characterized by techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM) and Nuclear Magnetic Resonance (NMR). The TiOSi bonds were detected at 960 cm^-1 in Ti-Si 0.5 and exhibited highest yield of epoxidized palm oil (EPO) in the epoxidation process which is 84% conversion of unsaturation in palm oil to epoxy groups. New peaks observed in the range of δ 2.4 ppm to 3.6 ppm in the NMR spectrum of EPO belong to protons of the epoxy cyclic ring group, CH-O-CH confirming successful epoxidation of palm oil using the prepared catalyst.

Abstract: Quartz Crystal Microbalance (QCM) has been typically used as a mass sensor in the study of monolayer and multilayer depositions and dissolution, mass transport in polymer films on electrodes, corrosion processes at electrodes and mass changes caused by protein adsorption at electrodes. Thin films of an aromatic poly (amide ester) hydrogel with hydrolyzable cross links were prepared in-situ on a gold-coated quartz crystal which is the transducing element of a Quartz Crystal Microbalance (QCM). Here we report the synthesis and degradation behavior of an aromatic poly (amide ester) hydrogel with hydrolyzable cross links using QCM. Degradation of the hydrogel films was found to proceed with Δf increment, indicating mass decrease and is in line with the theory proposed by Sauerbrey. Films with a higher cross-link density underwent partial degradation with swelling; and are depicted as a decrease in the Δf values with time. Deviation from the general base catalysis of ester hydrolysis was observed at higher base concentration due to the biphasic environment of the hydrolysis reaction.

Abstract: In this study, waterborne maleinized epoxidized soybean oil (WMESO) films were prepared and characterized in order to investigate their thermal properties, mechanical properties and surface morphology. A series of coating films were cured onto glass substrate. Differential Scanning Calorimetry (DSC) analysis showed that the coating films have glass transition temperature (T_g) ranging between 36-38 °C. Thermogravimetric analysis (TGA) revealed that waterborne films couls stand very high temperature up to 600 °C. W-2.0 was the best sample in terms of hardness. Film adhesion test showed that the adhesion between film and substrate was good. Higher initial water content gave films with better physical properties but poorer adhesion to substrate. Scanning Electron Microscopy (SEM) was used to visualize the surface morphology of film as well as the formation of resin. It was observed that, the particles were well dispersed and were crosslinked to each other.

Abstract: For decades, carbon black is the most preferred reinforcing filler in rubber industry especially in tyre manufacturing. Carbon black which originated from crude oil is a non renewable source that may diminish over time. Therefore, an alternative from natural source is needed to replace carbon black as the reinforcing agent in rubber industries without so much affecting the physical and mechanical properties of the final products. Since bamboo is an abundant natural source in Malaysia and proved to be one of the strongest natural fibres comparable to other building materials like steel, concrete, and timber that have been subjected to lot of studies, bamboo seems to be the best alternative to replace carbon black in reinforcing rubber. Bamboo chips were first treated using alkalinisation method and dried before ground to 180-250μm to improve the interfacial adhesion with the rubber matrix. The bamboo fibres were then incorporated into rubber through compounding process at different loading. The cure characteristics of the composites were determined at 150oC using rheometer. The curing times were then used to vulcanise the rubber compounds using a hot press. The mechanical behaviour of the bamboo fibre filled natural rubber composite like tensile strength, elongation at break, and hardness are then evaluated by taking the optimum loading of carbon black as the comparison. The strength of the composite were decreased and become harder as the fibre loading were increased. The weak adhesion of fibres to rubber matrix and uneven particle size distribution of fibres contribute to the fracture of the composites. These can be observed through the surface morphological analysis of the composite by using scanning electron microscopy (SEM).

Abstract: The annealing temperature for 250 nm PVDF-TrFE (70:30 mol %) spin coated thin films were varied at solvent evaporation (T_s = 79 °C), Curies transition (T_c= 113 °C₎, till melting temperature (T_m = 154 °C). XRD measurement showed that, there was an improvement in the crystallinity of the annealed films, consistent with the increased in the annealing temperatures. Morphological studies of the annealed PVDF-TrFE thin films as observed with Field Emission Scanning Electron Microscope (FESEM) (100k magnification), showed enhanced development of elongated crystallite structures known as ferroelectric crystal. However, thin film annealed at 160 °C (AN160) showed fibrous-like structure with appearance of nanoscale separations, which suggested high possibility of defects. Ferroelectric characterization indicated an improvement in the remnant polarization of annealed PVDF-TrFE thin films with the exception to AN160 in which leakage of current was inevitable due to the presence of cracks on the film surface.

Abstract: In recent years, natural fibres appear to be as an outstanding material to substitute the conventional reinforcement materials in polymer composites. Kenaf fibre reinforced natural rubber (KFNR) composite was prepared by incorporating of different loadings of kenaf fibre using two roll mill machines. The compound was vulcanised at 150°C according to their respective cure time. The intention of this study is to investigate the influence of kenaf fibre on cure characteristics and mechanical bahaviour of (KFNR) composites.The result showed that the higher fibre content in composites led to shorter optimum cure time, t₉₀. It was also observed that the tensile strength and elongation at break gradually decreased with an increment in fibre loadings. However, the trend was not similar for the hardness where the hardness value was increased by the increment of fibre loadings. The study has exhibited that the optimum fibre loading for the best performance of the composite achieved was 10 phr. The Scanning Electron Microscopy micrograph clarified that fibre dispersion and adhesion were weak thus resulting low in tensile strength and elongation at break.