| || Polyethylene maleate copolyesters as coating materials for piezoelectric quartz crystal based chemical sensors
Author : Gupta, D. C.;Saxena, C.;Dubey, V.;Gutch, P. K.;Asrey, R.;Vyas, K. D.
Source : Defence Science Journal ; Vol:55(4) ; 2005 ; pp 505-514
Subject : 620.1 Material Science and Technology
Keywords : Sorbent coating material;Piezoelectrical crystal detector;Surface acoustic wave device;Organophosphorus compounds;Dimethylmethylphosphonate;Coating materials;DMMP;PEM;Chemical sensors;Polyethylene maleate
Abstract : Polyethylene maleate (PEM) was synthesised by direct polycondensation of maleic anhydride and ethylene glycol in toluene under reflux using p-toluene sulphonic acid as a catalyst. Structure of PEM was further modified by varying nature of diols and acid components, chain length of glycols, incorporation of aromatic and fluorine groups in the chain. Formation of PEM was monitored by gas chromatography. The parameters like degree of polymerisation, number average molecular weight (Mn) and weight average molecular weight (Mw) were calculated from the extent of reaction and stoichiometric ratio of the reactants. The number average molecular weight was also determined using Knauer vapour pressure osmometer. Cohesive energy, volume, and solubility parameters of PEM-based copolyesters were calculated by group contribution method. These PEM-based copolyesters have been evaluated as sorbent-coating materials for the detection of organo phosphorus(OP)compounds using dimethylmethylphosphonate (DMMP) as model compound and piezoelectric crystal detector. PEM-bisphenol A is found to be the most sensitive and potential coating material for the detection of OP compounds using piezoelectric crystal detector. Potential PEM-based copolyesters have been characterised by viscosity, infrared spectroscopy, NMR spectroscopy, Mn and thermal stability.
| || Waterproofing materials for Ammonium Nitrate
Author : Damse, R.S.
Source : Defence Science Journal ; Vol:54(4) ; 2004 ; pp 483-492
Subject : 623.4 Armaments and Ballistics;623 Military Science and Engineering
Keywords : Hygroscopicity;Phase transition;Waterproofing ability;Mineral jelly;Ammonium nitrate;High energy materials;Coating materials
Abstract : This study explores the possibility of overcoming the problem of hygroscopicity of ammonium nitrate by coating the particles with selected waterproofing materials. Gravimetric analysis of the samples of ammonium nitrate coated with eight different waterproofing materials, vis-a-vis, uncoated ammonium nitrate, were conducted at different relative humidity and exposure time. The results indicate that mineral jelly is the promising waterproofing material for ammonium nitrate among the materials tested, viz, calcium stearate, dioctyl phthalate, kaoline, diethyl phthalate, dinitrotoluene, shelac varnish, and beeswax. Attempts were made to confirm the waterproofing ability of mineral jelly to ammonium nitrate using differential thermal analysis and x-ray diffraction patterns as an experimental tool. Suitability of mineral jelly as an additive for the gun propellant was also assessed on the basis of theoretical calculations using THERM program.
| || Fluorinated epoxy resins based sorbent coating materials for quartz pezoelectric crystal detector
Author : Gupta, D. C.;Gutch, P. K.;Lal , G.;Vyas, K. D.;Jaiswal, D. K.
Source : Defence Science Journal ; Vol:54(2) ; 2004 ; pp 229-234
Subject : 620.1 Material Science and Technology
Keywords : Fluoroepoxy resins;Sorbent coating material;Detection;Organophosphorus compounds;Piezoelectric detector;Fluoroepoxypolymers;Coating materials;Crystal detector
Abstract : Fluorinated epoxy resins were synthesized and evaluated as sorbent coating materials for the detection of organophosphorus compounds using quartz piezoelectric crystal detector. These resins were prepared by reacting excess of epichlorohydrin with each of or in combination of fluorinated diols, ie, (alpha),(alpha),(alpha)',(alpha)', tetrakis (trifluoromethyl) 1,3 benzene dimethanol (TTFMBD), 4,4’ bis-2-hydroxy hexafluoro isopropyl) biphenyl(BHHFIBP),4,4 dihydroxyocata fluorodiphenyl(DHOFDP) and 2,2,3,3,4,4 hexafluoro 1,5 pentanediol(HFPD) in the presence of sodium hydroxide at reflux temperature. These polymers were extracted in organic solvents and dried. Each of these fluoroepoxy resins were coated over quartz piezoelectric crystal by solution-casting method and tested using dimethylmethyl phosphonate (DMMP) as model compound. Change in the frequency(Delta F) of quartz piezoelectric crystal oscillator was recorded. Sensitive and potential fluorinated epoxy resins, ie, diglycidylethers (DGE) of HFPD-TTFMBD (in the molar ratio 6:4) and DGE (HFPD-BHHFIBP in the molar ratio) were characterized by viscostity, number average molecular weight (Mn), epoxy equivalent, infrared spectroscopy, and thermal stability.