Suharno Rusdi

In this work silver nano/micro-particles have been synthesized using sambiloto (Andrographis paniculata) plant extract as a bio-reducing agent. The effects of different plant extract concentrations, AgNO3 precursor concentrations, and reaction time on the synthesized silver nano/micro-particles were investigated. The silver nano/micro-particles samples were then analyzed using UV-Vis spectrophotometer (UV-Vis), X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FESEM), Particle Size Analyzer (PSA), and Fourier Transform Infra-Red (FTIR) spectroscopy. The UV-Vis absorbance spectrum of the colloid silver nano/micro-particles exhibited that all samples had absorbance peaks at a wavelength around 450 nm, confirming the formation of silver nano/micro-particles. It was also found that the UV-Vis absorbance peak of the silver nano/micro-particles inversely increased with decreasing AgNO3 solution concentration. Whereas, the higher the sambiloto extract concentration the higher the UV-Vis absorbance peaks. The UV-Vis absorbance peak increased with increasing synthesis time, suggesting that silver nano/micro-particles became more prominent. The UV-Vis absorbance peaks of the silver nano/micro-particles were about 0.0462, 0.0637, 0.0729, and 0.0936 at reaction time of 5, 10, 20, and 40 min, respectively. The XRD analysis result confirmed that the synthesized silver nano/micro-particles were in the form of nanocrystals with a face-centered cubic centered without any impurities. Additionally, the FESEM images showed that the silver nano/micro-particles had the primary particle size of 150-300 nm. There was the formation of some secondary particles with the size of about 0.7-1.5?m due to the agglomeration of primary particles. The particle size distribution analysis further confirmed the presence of primary and secondary particles. Meanwhile, the FTIR analysis confirmed the presence of four main peaks, linked to functional groups in the sambiloto extract and involved in the creation of silver nano/micro-particles.

In this study, bioplastics made of Konjac glucomannan have been successfully prepared via film casting method. The effects of addition of beeswax content (i.e. of 0%, 0.5%, and 1%,), as well as glycerol content (i.e. 0.5%, 1%, and 1.5%) on the properties of the bioplastics have been investigated. The bioplastics produced have been characterized for their tensile strength, percent elongation, swelling degree, and biodegradability. The results of this study, showed that most of the bioplastic samples have weight loss of about 95% after the drying process as well as the finished film. The addition of beeswax and glycerol concentrations also increased tensile strength and percent elongation of the bioplastics. The highest value of tensile strength occurred at bioplastic film with a concentration of 1.5% beeswax and 1% glycerol (i.e. Sample C3) with a value of approximately 3.5 MPa. Whereas, the highest percent elongation value occurred at bioplastic film with a concentration of 1.5% beeswax and 1% glycerol (i.e. Sample C3) with a value of approximately 23.29%. These tensile and percent elongation values were higher or comparable to other bioplastic samples made from starch of different raw materials reported by literatures. In the other hand, the addition of beeswax and glycerol decreased the degree of swelling. The degree of swelling for all the bioplastic film samples were in the range of 316.77 – 481%.

Acid protonation constant (K_a) is one of the parameters required for thermodynamic modelling. In addition, a rigorous thermodynamic model requires solvent non-ideality properties in order to have a better model representation. This study aims to evaluate species activity coefficients from potentiometric titration data of the MEA-H2O system at temperatures ranging from 303 to 333K. The results show that the activities of the free MEA and the protonated MEA depend on pH. In addition, the activity coefficients of the protonated MEA determined by the extended Debye-Hückel model were less than unity at different temperatures. This means that the system observed was the non-ideal one.

One of the safety factors in riding a motorcycle is the braking system in which the brake lining plays an important role in the braking performance, therefore, application of an appropriate brake lining material which gives a low brake lining wear value is a must. The objective of this study is to evaluate the effect of brake lining material compositions on the value of brake lining wear. The brake lining was made from a mixture of corn cob powder, Al₂O₃, BaSO₄, and polyester resin with a certain composition. The brake lining wear value was then determined by the Ogoshi wear testing by varying the material compositions. The brake lining wear values were then compared to those obtained from the brake linings existing in the market, e.g. Texiar. The results show that the higher the concentration of the corn cob, the better the value of the brake lining wear. This is due to the nature of the corn cob that gives less wear value compared to Al₂O₃. It was found that the brake lining wear value of 2.8 × 10⁻9 mm²/kg, corresponding to the brake lining wear value of Texiar, was achieved at which the compositions of the corn cob powder, Al₂O₃, BaSO₄, and the polyester resin are 30, 30, 20, and 20 wt%, respectively. The result indicates that variations in the composition of constituent material have an influence on the brake lining wear value.

Natural dyes are dyes that are environmentally friendly, harmless to actors and users, and the colors are more diverse. Natural dyes can be obtained by extraction treatment that is removing pigments from plant parts. The results of Kesumba Keling seed extract (Bixa orellana) and Secang wood (Caesalpinia sappan Linn) were obtained from boiling. The purpose of this study are to extract natural dyes from Kesumba Keling seed and secang wood and to determine the direction of the color produced from dyeing the fabric using extracted solution of Kesumba Keling and Secang wood. The dyeing fabric has the shortest wavelength of 624 nm and the longest is 776.5 nm. The direction of the color produced was red. The use of different fixators gives different colors. Lime fixator (Ca (OH)₂) gives a color younger than the original color, while the tunjung fixator (FeSO₄) gives an effect of color older than the original color. The lime fixator produces red to orange, while the tunjung fixator produces red in the direction of brown. While, the different dipping temperatures did not significantly affect the color of the cloth. Additionally, the different cloth dipping schemes considerably affected the color of cloth produced, especially the intensity of the color.

Everyday human life cannot be separated from plastic. Almost all objects that are around us are made of plastic. In general, plastics are non-biodegradable, causing environmental problems caused by the increased volume of plastic waste. One way to overcome this is by recycling existing plastic waste. But the use of recycled plastics is very limited and considered inefficient because the process is more difficult and processing is more expensive than buying new plastic raw materials. Another alternative is to use bioplastics or biodegradable plastic. This plastic is more environmentally friendly because it is biodegradable or easily decomposed by microorganisms. Basically, bioplastics can be made from vegetable starches. In this study we will use starch extracted from banana peel waste as a base material for making bioplastics. In this research, glycerin which is used as a bioplastic adhesive or plasticizer will be used. Whether or not bioplastics depend on the resistance to water, the attractiveness of the bioplastics, the ability of the plastic to be decomposed by microorganisms. From this research, it is expected to produce bioplastics with high water resistance and high tensile strength and easy to decompose microorganisms.