Summary
The conventional pyrotechnic compositions (PCs) for firefighting application mostly consist of potassium nitrate, chlorate or perchlorate as oxidants and organic resin‐like phenol‐formaldehyde, melamine‐formaldehyde, epoxy resin and polyurethanes are used as reducers. Unfortunately, there are also some potential disadvantages to the use of conventional compositions. These are related to high combustion temperature with the generation of heat and flame which may cause secondary fire chances and hazards associated with the use of organic resins. Exposure to phenol, melamine, epoxy resins and polyurethanes are considered as a life‐threatening occupational hazard. Under the present study, new pyrotechnic compositions were prepared with the combination of natural antioxidants like ascorbic acid and gallic acid as reductant and mixture of potassium nitrate with potassium chlorate as oxidant. Fire extinguishing efficacies, calorific value, burn rate, the flame temperature of newly developed compositions was evaluated against potassium nitrate and phenol‐formaldehyde resin‐based conventional composition. Although both the new and conventional composition has shown good fire extinguishing efficacies, extinguishing 4.57 KW of small scale n‐heptane pool fire in 3 to 4 seconds, these newly developed compositions showed 67% to 76% reduction in flame temperature. It was also found that these new compositions exhibit a faster burn rate and lower calorific value than the conventional composition. To understand the fire extinguishing mechanism by the discharged aerosol particulate, its physical and chemical characteristics were assessed by a series of techniques viz; HRXRD, SEM, FTIR, EDX.
Tannic acid is a natural binder that was comparatively investigated against four different types of conventional synthetic binders phenol‐formaldehyde resin, carboxymethyl cellulose sodium salt, ethylcellulose, and hydroxyethylcellulose which are being used in aerosol forming pyrotechnic formulations for firefighting application. It has been found that the nature of the binder in an amount of 3 % significantly influences the fire suppression performance, thermal and mechanical characteristics of gallic acid‐based aerosol‐forming pyrotechnic mixture. The safety and performance characteristics of these formulations were evaluated by conducting analysis specific to pyrotechnic formulations, i. e., calorimetric analysis, linear solid strand burn rate measurement, TGA/DSC thermal analysis, compression test, moisture content, and fire suppression test. These formulations were designed to discharge fire extinguishing aerosol and it can be inferred from the values obtained from these analyses that tannic acid is a preferred binder to the other four binder systems for the Gallic acid‐KNO3‐KClO3 pyrotechnic mixture.
The magnetic chitosan beads (MCSB) prepared from the solution by using the external magnet and the adsorption of Ni (II) ions from wastewater and its cross-linked derivative with glutaraldehyde (GLU-MCSB) was investigated in a adsorption system. The GLU-MCSB sorbents that are insoluble in aqueous acidic solution and improve adsorption capacity. Adsorption process was carried out by considering into various parameters viz. adsorbent dose, contact time, pH and temperature. TGA of beads show that degradation takes place in two stages. FTIR spectra of magnetic beads exhibit absorption band at 606 cm−1 for Fe-O. The elemental analysis (EDAX) and scanning electron microscopy (SEM) were used to analyze the structure and characteristics of MCSB and GLU-MCSB. The Ni(II) removal efficiency attains a highest value of 95.12% with cross-linked GLU-MCSB in comparison 79.5% with MCSB. Adsorption processes follow the pseudo second-order rate kinetics model, which suggested that the rate-limiting step may be the chemical adsorption rather than the mass transport. The experimental data of adsorption fitted well with the Langmuir and Freundlich isotherms with a high correlation coefficient (R2 > 0.9), showing that monolayer adsorption took place on the surface of GLU-MCBS absorbents. The negative values of ΔS, −175.64 and −163.30 J/mol K and ΔH, −54.75 and −49.58 kJ/mol for MCSB and GLU-MCSB suggest that process is spontaneous and exothermic in nature.
The crab shell chitosan (CSC) and the medium molecular weight chitosan (MMWC) beads are cross-linked with ethylene glycol diglycidyl ether (EGDE) solution to get EGDE-CSC and EGDE-MMWC beads. The adsorption of CSC and MMWC beads at pH 2-4 show the adsorption of crystal violet (CV) was not significantly affected. Langmuir' isotherm study provides an equilibrium parameter R L, from the linear plots of C e /X versus C e for the adsorption of CV dye on MMWC beads and CSC beads. The adsorption is favourable if R L lies within the range, i.e. 0
The traditional aerosol-forming composites are a mixture of potassium nitrate/ chlorate and synthetic resins like phenol-formaldehyde, melamine-formaldehyde, polyurethane, and epoxy resin. Though these synthetic organic resins have excellent
Pyrotechnic‐based firefighting systems have been found to be effective in a wide variety of firefighting applications. Binders in pyrotechnic mixtures play a significant role as they consolidate the ingredients, provide excellent mechanical strength and increase the storage life. The rise in health and environmental safety concerns in recent years has directed our research towards natural binder systems of biological origins. Therefore, in this work, galactomannan, also called guar gum, was comparatively investigated against four different types of conventional binders, phenol–formaldehyde resin, ethyl cellulose, hydroxyethyl cellulose and carboxymethyl cellulose sodium salt, which are being used in aerosol‐forming pyrotechnic mixtures for firefighting application. It was found that the nature of the binder in an amount of 3% by weight significantly influences the combustion behaviour, fire suppression performance, mechanical and thermal characteristics of gallic acid–KNO3–KClO3 tertiary aerosol‐forming pyrotechnic mixture for fire fighting application. The safety and performance characteristics of these formulations were evaluated by conducting analyses specific to pyrotechnic formulations, that is, burn rate measurement, heat of combustion, TGA/DSC thermal analysis, hygroscopic study, compression test and n‐heptane pool fire suppression test. It can be inferred from the values obtained from these analyses that guar gum is a preferred binder to the other four‐binder systems for the gallic acid–KNO3–KClO3 pyrotechnic mixture.
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