The effect of KOH stabilizer on mechanical and chemical properties of liquid rubber compound has been examined. Liquid rubber made by mixing stearic acid and zinc oxide as activator, 3,5-di-tert-butyl-4-hydroxy toluene and liquid smoke as antioxidant, CaCO3 as filler, dibenzothiazole disulfide and tetramethyl thiuram disulfide as accelerator, KOH as stabilizer and sulphur as vulcanizing agent with concentrated latex at room temperature, then maturated for 72 h. In this research the use of KOH stabilizer was varied as 3, 4, 5, 6 and 7 phr. Before being examined, rubber film made from liquid rubber compound by dyeing process then vulcanization done at 100 °C with water vapor. The rubber film which produced from liquid rubber compound then was characterized their mechanical and chemical properties such as resistance to heating, resistance to acid and alkaline resistance. The result showed that KOH content changed the mechanical and chemical properties of liquid rubber compound.
This research provides a new route to obtain gold nanoparticles (AuNPs) using an aqueous extract of air-dried Pseuderanthemum acuminatissimum Radlk leaves. The extract was used as a reducing agent in the formation of metallic gold from gold ions, and acted as a stabilizer of the obtained AuNPs in the reaction mixture. The formation of AuNPs in aqueous extract of P. acuminatissimum Radlk leaves was validated by change in color and the appearance of surface plasmone resonance (SPR) peak at 552 nm. The average size of the gold nanoparticles was 63 nm, and irregular shapes were observed in the reaction mixture. Fourier transform infrared spectroscopy (FT-IR) reveals the presence of organic compound containing hydroxyl functional groups in the air-dried P. acuminatissimum Radlk leaves, which predicted to be the most responsible for the reduction of gold ions to form metallic gold. The antibacterial properties of the gold nanoparticles were studied using Escherichia coli (ATCC 8739 TM*) strain; the AuNPs significantly inhibited the growth of E. coli indicated by a slight increase in the size of the inhibition zone as the volume of added nanocolloid was increased. Therefore, the present study indicated the promising of green synthesis of AuNPs using biological agents and as a potential material to inhibit the bacterial growth.
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