Synthesis and characterization of a new conjugated polymer containing bithiazole group and its thermal decomposition kinetics

A new conjugated polymer containing a bithiazole group is prepared by the polycondensation of 2,2'-diamino-4,4'-bithiazole and terephthaldialdehyde in the presence of glacial acetic acid. The kinetics of thermal degradation of the new polymer are investigated by thermogravimetric analysis at different heating rates. The temperature corresponding to the maximum rate loss shifts to higher temperatures with increasing heating rate. The thermal decomposition activation energies of the conjugated polymer in a conversion range of 3–15 % are 288.4 and 281.1 kJ/mol by the Flynn–Wall–Ozawa and Kissinger methods, respectively. The Horowitz–Metzger method shows that the thermodegradation mechanism of the conjugated polymer proceeds over a three-dimensional diffusion type deceleration D3 mechanism. The optimum heating rate is 20 ºC/min.

Derivatization and Spectrophotometric Quantification of Pamidronate in Bulk and Dosage Forms

Aims: To quantify pamidronate in a sensitive and accurate way either in bulk or dosage forms. Methodology: The quantification of this group of drugs is a challenging task as they lack the presence of chromophore groups in their structure. The proposed method depends on the derivatization of the studied drug by its reaction with 4-Chloro-7-nitro-2,1,3-benzoxazole and the product is measured spectrophotometrically at 470 nm. The conditions for the reaction are optimized regarding the volume of the reagent, the optimum pH for the reaction completion, the buffer volume, the optimum temperature for the reaction and the optimum heating time. Results: The studied drug can be determined in the range of 9-30 µg/mL after optimizing the reaction conditions. Method validation is performed according to ICH guidelines and different validation parameters like, linearity, accuracy, precision and robustness are calculated and found to be excellent. Conclusion: The proposed method is accurate, sensitive and can be applied for the routine analysis of pamidronate in quality control laboratories.

Pemanfaatan Gulma Siam (Chromolaena odarata L.) Sebagai Adsorben Logam Timbal

This study aims to utilize (Chromolaena odorata L) as a metal adsorbent. The methods used to make activated charcoal are dehydration, carbonization, and activation. The activated carbon is then characterized to obtain activated charcoal that can be applied, then optimized. The results of activated carbon characterization obtained have reached the activated carbon quality requirements based on the Indonesian Industry Standard (SII No. 0258-88). Based on the adsorption test, the optimum pH of Pb2+ (Pb (NO3) 2 (in distilled water) Chromolaena odorata L charcoal activated by NaOH 0.2 M under varying pH (2,3,4,5,6) is at pH 5 with 69.00% absorption. The optimum contact time required for Pb ion adsorption is 4 hours at variation (1-5 hours) with 70.19% absorption. The optimum concentration at variation (concentration 20; 40; 60; 80; 100 ppm) on Pb ion adsorption is 100 ppm with 76.15% absorption. The optimum heating time is a variation of 1.5; 2; 2.5; and 3 hours of Pb ion adsorption is one hour 30 minutes with an absorption of 65.95%. Based on the optimization results, the activated carbon from the Chromolaena odorata L can be used as an adsorption material against the contamination of lead heavy metals (Pb).

Alternative Briquette Material Made from Palm Stem Biomass Mediated by Glycerol Crude of Biodiesel Byproducts as a Natural Adhesive

Recently, the global population has increased sharply, unfortunately, the availability of fossil fuel resources has significantly decreased. This phenomenon has become an attractive issue for many researchers in the world so that various studies in the context of finding renewable energy are developing continuously. Relating to this challenge, this research has been part of scientific work in the context of preparing an energy briquette employing palm oil stems and glycerol crude of biodiesel byproducts as inexpensive and green materials easily found in the Riau province, Indonesia. Technically, the palm oil stems are used for the production of charcoal particles and the glycerol crude as an adhesive compound in the production of energy briquettes. The heating value of palm oil stem is 17,180 kJ/kg, which can be increased to an even higher value through a carbonization process followed by a densification process so that it can be used as a potential matrix to produce energy briquettes. In detail, this study was designed to find out several parameters including the effect of sieve sizes consisting of 60, 80, and 100 mesh, respectively, which are used for the preparation of charcoal particles as the main matrix for the manufacture of the briquettes; the effect of charcoal-adhesive ratios (wt) of 60:40, 70:30, and 80:20; and the effect of varied pressures of 100, 110, and 120 kg/cm2 on the briquette quality. The quality of the obtained briquettes is analyzed through the observation of important properties which involve the heating value and the compressive strength using Response Surface Methodology (RSM). The results showed that the produced briquettes had an optimum heating value of 30,670 kJ/kg, while their loaded charcoal particles resulted from the mesh sieve of 80, in which there was a charcoal loading of 53 g and it pressed at 93.1821 bar, whereas, the compressive strength value of the briquette was 100,608 kg/cm2, which loaded charcoal particles from the mesh sieve of 100, the charcoal-adhesive ratio of 53:47 (wt) and the pressure of 93.1821 bar.

The effect of the preheating on to properties of the wear resistant welds

Wear resistant welds are used in many industries when it is necessary to protect machine components and structures against wear caused by operating conditions. Often the main parameter determining the usefulness of these welds is high hardness reaching about 60HRC. In many cases, after the surfacing process, a mesh of cracks is formed in the surface layer, which can affect the durability of the hard-wearing layers used. The paper presents the analysis of the influence of preheating before welding up to 400 ° C on the properties of welds and its effect on the number of cracks in the surface layer. The use of preheating allowed to reduce the number of cracks in the surfacing to 1. The optimum heating temperature was 200 ° C, for which the number of cracks was reduced and the lowest wear was recorded.

Thermal decomposition kinetics of a coumarin based copolymer: Poly(3-benzoyl coumarin-7-yl-methacrylate:0.54-co-methyl methacrylate:0.46)

In present study, thermal decomposition studies of a copolymer based the coumarin containing monomer 3-benzoyl coumarin-7-yl-methacrylate (BCMA) and methyl methacrylate [poly(BCMA:0.54-co-MMA:0.46)] were performed by thermogravimetric analysis (TGA). The temperature for maximum rate losses was increased from 384.81 °C to 407.45 °C with the increasing in heating rate from 5 °C/min to 20°C/min. The thermal decomposition activation energies of copolymer in the conversion range of 9% - 21% were resulted to be 212.98 kJ/mol and 210.30 kJ/mol by Kissinger’s and Flynn–Wall–Ozawa methods, respectively. The study of kinetic equations such as Coats-Redfern, Tang, Madhusudanan and Van-Krevelen methods exhibited that the thermal decomposition process of the studied copolymer was followed with a D3 mechanism, a three-dimensional diffusion type deceleration solid state mechanism, at the optimum heating rate of 20 °C/min.