Key Engineering Materials Vol. 989

Abstract: A pressure-induced autoclave foaming assisted by supercritical CO₂ of degradable polylactide (PLA) has been developed. A central composite design (CCD) of response surface methodology (RSM) is used to optimize three distinct process conditions: foaming temperature, pressure, and time. The mathematical model built for examining the effect of process conditions on the foam density and volume expansion ratio was verified and determined to be acceptable with an R-square value derived from the regression model of 0.930 and 0.934, respectively. The experimental and statistical results showed that of the three factors examined, the foaming pressure had the greatest impact on the density and volume expansion ratio of the PLA foams. The foaming temperature and time also had significant interaction impacts on both responses. It was observed that the following conditions are optimal for foaming of PLA, with a maximum VER of 10.107 and a minimum foam density of 0.123 g/cc: foaming temperature of 165.86 °C and foaming pressure of 152.4 bar for 2.38 h of foaming time.

Abstract: Moringa oleifera is a plant that is predicted to be a potential source of vegetable oil. Moringa seeds contain 35-40% oil which is used in the pharmaceutical, cosmetic, automotive and fuel industries. Moringa oil contains oleic, palmitic, and behenic acid which is good for health. Obtaining oil from Moringa seeds in this study used the mechanical pressing method and continued with extraction using a solvent. Mechanical extraction was carried out by pressing Moringa seeds with a moisture content of 8 and 16% w/w. The best result was obtained with a moisture content of 8% with the yield of oil produced from 20 to 31% w/w. The pressing temperature also varied at 80, 100, and 120°C and the best result was given by the temperature of 100°C with the yield of oil produced 27.3-28.8% w/w at 8% moisture content of seeds and 20.9-23.6% w/w at 16% moisture content of seeds. The pressed cake from the mechanical pressing was extracted by maceration method using n-hexane as the solvent. The ratio of the amount of solvent to the amount of pressed cake (mL/gram) was 6/1, 8/1, and 10/1. The best ratio given by 8/1 with the yield oil produced from 8.44-22.82% w/w. Moringa oil was characterized using the standard method. The oil density obtained 0.912-0.919 g/cm³, saponification value 195-202 mgKOH/g oil, acid value 1.62-2.77 mgKOH/g oil, and peroxide value 1.85-3.70 meqO₂/kg.

Abstract: Silver nanoparticles (AgNPs) have attracted attention due to their unique properties and potential application. This research aimed to do green synthesis of AgNPs with Syzygium aromaticum leaves extract (SALE) and evaluate their antibacterial and antioxidant activities. Syzygium aromaticum leaves were extracted using distilled water at 70 °C for 30 min and the results were characterized with FTIR. AgNPs were synthesized by mixing AgNO₃ precursor with SALE. The effects of parameters such as volume ratio of AgNO₃ precursor to SALE, AgNO₃ concentrations, and synthesis times were investigated. The synthesized AgNPs were characterized using UV-Vis spectrophotometer, FTIR, and TEM. Antibacterial activity of SALE and AgNPs was investigated against Escherichia coli (E.coli) and Bacillus subtilis (B. subtilis) with disc diffusion method and antioxidant activity was tested with DPPH method. The FTIR characterization revealed that SALE and resulting AgNPs contain O-H, C-H, C=O, C=C, C-O, and C≡C functional groups. The UV-Vis characterization demonstrated that AgNPs exhibited an absorption peak at λ = 420 nm indicating surface plasmon resonance. The optimal volume ratio of AgNO₃ to SALE, AgNO₃ concentrations, and synthesis time for AgNPs synthesis was achieved at 10:3, 5 mM, and 60 min respectively. TEM characterization indicated that AgNPs have spherical form and sizes ranging from 14 to 32 nm. The antibacterial testing revealed that AgNPs have antibacterial activities against E. coli and B. subtilis with inhibition zone values are 8,38 ± 0,48 and 6,88 ± 1,47 respectively. Additionally, antioxidant testing presented that the IC₅₀ values were 85.05 µg/mL for SALE and 34.71 µg/mL for AgNPs. The results indicate that green synthesis of AgNPs from AgNO₃ precursor with SALE was done successfully and this nanoparticle has good antibacterial and antioxidant activities.

Abstract: East Kalimantan’s Coal has total humidity level at 18.21%, inherent humidity of 12.39%, fly ash content of 5.18%, volatile compounds of 38.22% and heat content of 6084 kcal/kg. However, chemical composition, functional group and crystallinity of raw and water rinsed Loa Janan bituminous coal have not been reported elsewhere. This research aims to investigate whether water rinsed treatment affects the structure of the coal or not. Coal size at 100 mesh-200 mesh is divided into 2, labeled as bituminous (a) stands for raw bituminous and bituminous (b) is for water rinsed-one. The bituminous (a) was analyzed using scanning electron miscroscopy (SEM)-energy dispersive xray (EDX), x-ray fluorescence (XRF), fourier transform infrared (FTIR) and powder x-ray diffraction (p-XRD) spectrophotometer. Meanwhile, bituminous (b) was heated at 40°C for 10 hours, cooled, rinsed using aquademin (1:5), stirred for 3 hours at 1500 rpm, and filtered. The bituminous (b) was heated at 40°C for another 10 hours and was characterized using the same technique as conducted to bituminous (a). Images revealed by SEM-EDX confirms the morphology ang topology of bituminous coal and the carbon content of them are 70.24% ± 0.87 (coal a) and 70.73% ± 0.08 (coal b). X-ray fluorescence analysis revealed that the bituminous (a) consisted of: Fe (46%), Si (21.5%), Al (5.4%) and bituminous (b): Fe (45%), Si (18.4%), Al (4.5%). There is a significant difference of their infrared spectra, both showed the peak at 1620 cm^-1 (C=C) for carbon aromatic vibration. The wide area of peak at 3423 cm^-1 is responsible for OH stretching vibration. Peaks intensity at 1620 cm^-1 and 3420 cm^-1 of bituminous (b) increased about 43.11% and 43.34%, respectively. The crystallinity degree of bituminous (b) (47.56%) is lower than that of bituminous (a) (69.72%). A sharp peak of XRD spectrum located at 2θ of 26.6^o (hkl = 002) was responsible for both quartz and graphite.