Ku Halim Ku Bulat

Effect of Shear Rate and Temperature on Rheological Properties of Vegetable Based Oil

Petroleum oil has been the raw material for over 90% of hydraulic fluid. Limitations of this base material in the aspect of non‐renewable, not environmental friendly and its sustainability in the future have prompted a search for more stable and environmentally friendly alternatives. This article presents rheological aspects of hydraulic fluid derived from bio‐based material when used as hydraulic fluid. Palm oil with F10 additive is found to be most shearstable. Various empirical models such as modified Power Law, Herschel‐Bulkley and Arrhenius‐type‐relationship are used to evaluate the rheological data. The influence of shear rate and temperature on the variation of viscosity is clearly observed but temperature has more significant influence. Interpretations of rheological models indicate that crop oils belong to pseudo‐plastic category. The effect of oil degradation in the aspect of physical property on viscosity is also evaluated.

Synthesis, Characterization and Preliminary Study on Acetylpyrazine N(4)Butylthiosemicarbazone as a Potential CDK2 Inhibitor Combined with DFT Calculations

In this study, a new thiosemicarbazone ligand, namely acetylpyrazine N(4)butylthiosemicarbazone (APBT), was synthesized and characterized using 1H and 13C nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. Quantum chemical calculations were performed using density functional theory at the B3LYP/6-311++G(d,p) basis set level. The optimized molecular geometry of APBT is discussed based on X-ray structural reports from the literature. The assignment of the vibrational frequencies was done based on a potential energy distribution analysis using the vibrational energy distribution analysis (VEDA) 4 software. The energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) was evaluated to study the reactivity and stability of the compound. Global chemical reactivity and local reactivity descriptors of reactants and the product (APBT) were calculated to study the reaction mechanism. The region of interaction during the reaction to form APBT was determined using molecular electrostatic potential analysis. Finally, a preliminary study of the title compound as a cyclin-dependent kinase (CDK) inhibitor was further evaluated by performing a docking calculation.

Influence of B2O3 on Phosphate Ion Released from SiO2-B2O3-P2O5-Na2CO3 Glass in Synthetic Seawater

Phosphates have been receiving important attention in various fields and one of the fundamental sources of nutrients required to be used as source of nutrients for plankton growth. The objective of this study is to determine the effect of boron oxide on phosphate ion released from the system SiO2-B2O3-P2O5-Na2CO3 glasses. The compositions of this glass system [wt%: (55-x)% SiO2- (15+x)% B2O3- 5% P2O5- 25% Na2CO3] where 15≤x≤40 % have been prepared with the different amount of B2O3 (30-55wt%) and P2O5 with Na2CO3 were fixed. The glass has been prepared by melting in the alumina crucible within 2 h of soaking time at 1300 °C in the furnace and cooled to room temperature. The obtained glass samples were crushed and sieved at mean size of 2 mm – 4 mm. The dissolution studies were determined through the immersion of the glass samples in 50 mL synthetic seawater for 30 days under static condition. The results were obtained and analyzed using Discrete Auto Analyzer. Fourier Transform Infrared (FTIR) with Attenuated Total Reflectance (ATR) method was used to determine the functional group sample of glasses and the glass phase was characterized by X-Ray diffraction (XRD) techniques. Dissolution studies showed that, the concentration of phosphate ion released decreased with increasing B2O3 content whilst, increased with immersion time. The obtained experimental data indicated that, the optimum concentration of phosphate ion (10.27 ppm) was achieved at 35 wt% of B2O3 at week three.

The Effect of Boron Oxide on Phosphate Ion Released from Borosilicate Glass in Seawater

Glasses in the system [wt%: (55-x)% SiO2-(15+x)% B2O3-15% P2O5-10% Na2CO3-5% Fe2O3] where 15 ≤ x ≤ 40 % have been prepared with the different amount (35-55 wt%) of boron oxide. The compositions were limited by fixing the P2O5 at 15 wt%, Na2CO3 at 10 wt% and fixing the Fe2O3 at 5 wt%. The objective of this study is to determine the effect of boron oxide on phosphate ion released from borosilicate glass in seawater. The glass has been prepared by melting in the alumina crucible within 2 hours of soaking time at 1300 °C in the furnace and cooled to room temperature. The obtained glass was crashed and sieved with yielding a mean size of 710 μm. The samples were immersed in seawater under dynamic condition by stirring at 310 rpm. The water sample was taken 6 times at every 15 minutes until 75 minutes and analyzed using Discrete Auto Analyzer. The functional group and morphological characterization on the glass surface have been investigated using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). Analysis of the data indicates that the amount of 50 wt% boron was the best and optimum for the phosphate ion release which is 126.53 ppm.

Theoretical and Experimantal Studies on the Performance of TBHQ and BHA as a Chain-Breaking Radical Scavenger

The aim of this research project is to study the performance of two antioxidants, TBHQ (1) and BHA (2) as a chain-breaking radical scavenger of the selected vegetable oil which contained high oleic fatty acid constituent i.e. canola oil. Experimental studies involved heating the vegetable oil in the forced air-flow oven for 15 days at 60oC. Samples subjected for peroxide value determination were analysed at 0, 1, 3, 6, 10 and 15 days of exposure. For the theoretical investigation, Gaussian 09 software package at the theoretical level of DFT B3LYP/6-31G(d,p) were used to evaluate the physical parameters of the antioxidants (TBHQ and BHA), the homo-chain of tri-oleic TAG (3) with hydroperoxide group at carbon-11 and its radical, and the transition-state complex of the two components in questions. The selected physical parameters such as the total electronic energy (SCF energy), the stabilization energy, the hydrogen bond distance of the complex, the properties of the O-H of antioxidant (bond length, bond dissociation energy, Wiberg bond-index), and the dipole moment, were then utilized to correlate with the actual performance of the two antioxidants. Experimental results showed that TBHQ exhibit better performance than BHA in inhibiting the production of hydroperoxides in canola oil. These experimental observations were in line with the theoretical results where all the physical parameters except hydrogen bond distance support the findings.

Theoretical Studies on the Effects of Palmitic Acid Adulteration to theHydroperoxyl Methyl Linoleate-Tbhq System

The aim of this research project is to study the effects of adding palmitic acid on the performance of TBHQ(1) in inhibiting the autoxidation of vegetable oil. Quantum mechanical software package of Gaussian 09 at the theoretical level of DFT B3LYP/6-31G(d,p) were used to evaluate the physical parameters of TBHQ, hydroperoxyl methyl linoleate radical of C9OO(2), palmitic acid(3) and their complexes. Based on the stabilization energy of the complex which is comparable to the hydrogen bonding strength, palmitic acid formed more stable complex with C9OO radical than of TBHQ. Details Natural Bond Orbital analyses revealed that the addition of palmitic acid would reduced the effectiveness of TBHQ by weakening the hydrogen bonding (1.910 to 1.963 Å) with the C9OO radical and strengthening the O-H sigma bond of TBHQ (Bond order: 0.673 to 0.683).

Theoretical Studies on the Physical Properties of 2,6-ditert-Butyl PhenolDerivatives as a Chain-Breaking Radical Scavenger

The aim of this research project is to study the effect of para-substituents on the physical properties of 2,6-ditert-butyl phenol derivatives as a vegetable oil chain-breaking radical scavenger. In this theoretical studies, Gaussian 09 quantum mechanical software package at the theoretical level of DFT B3LYP/6-31G(d,p) were employed to evaluate the optimized geometry at the local minimum of total potential energy structures. The physical parameters such as the total electronic energy, the strength and the length of hydrogen bonding, the O-H antioxidants parameters(bond length, bond strength, Wiberg bond index), and the dipole moment of the molecules involved were assessed at the same theoretical level by using Natural Bond Orbital method. The para-substituents in consideration were –H, -CH3, -OH, -OCH3 and propyl ester (COOCH2CH2CH3). Results showed that hydroxyl (-OH) para derivative formed the strongest transition-state complex (24.5 kJ/mol) with C9-hydroperoxyl radical of methyl linoleate followed by -OCH3 (23.7 kJ/mol), -CH3 (21.8 kJ/mol), –H (21.4 kJ/mol), and -COOCH2CH2CH3 (20.7 kJ/mol). However, the para-derivative of propyl ester (-COOCH2CH2CH3) has the lowest Wiberg bond index of O-H bond (0.653) compared to the other derivatives of the 2,6-ditert-butyl phenol [–H (0.661), -CH3 (0.663), -OCH3 (0.664), -OH (0.665)]. This means that the derivatives with hydroxyl or propyl ester group at para-position should be more effective as an antioxidant for high-linoleic vegetable oil rather than the available commercial BHT where the substituent is methyl group.

Theoretical Evaluation on the Performance of TBHQ and BHA in Inhibiting the Autoxidation of Linoleic Acid-Rich Vegetable Oils

The aim of this paper is to disclose the major physical parameters responsible in determining the effectiveness of TBHQ (1) and BHA (2) as a hydroperoxyl C9-OO methyl linoleate radical (3) scavenger. In this study, Gaussian 09 software package at the theoretical level of DFT B3LYP/6-31G (d,p) were used to evaluate the physical parameters of antioxidants and the complexes formed with hydroperoxyl methyl linoleate radical of C9-OO such as SCF energy, hydrogen bonding strength, and the O-H bond order of antioxidants. Results of the geometry optimization combined with Natural Bond Orbital analyses of antioxidants and their complexes revealed that even though the hydrogen bonding with BHA is stronger than with TBHQ (E BHA = 31.9043 kJ/mol; E TBHQ = 31.6793 kJ/mol), but the O-H sigma bond order of TBHQ is about the same as of BHA (TBHQ= 0.6731; BHA= 0.6736). These findings are in agreement with previously reported experimental results where TBHQ performs better than or equally as good as BHA.