α - International Journal of Research in Pharmaceutical and ...

International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-3701=K(T) f(α)------------------- (2) 8,9Where f(α) is the conversion function and K(T) isthe temperature function.The temperaturedependence of therate constant K for the processsis described by the Arrhenius equation (3)K=A exp [- E/RT]----------------------(3)Where A is the pre-exponential factor, T is theabsolute temperature, R is the Universal gasConstant and E is the apparent activation energyof the process. Substitution of equation (3) inequation (2) givesd E Aexp f dt RT ------(4)When the temperature increases at a constant ratei.e(constant) givesdA E exp f dT q RT ----------------(5)The conversion function f (α) for a solid statereaction depends on the reaction mechanism andf m n ln1 p1 ------------(6)Where m, n and p are empirically obtainedexponent factors, one of them always being zero 9 .The solutions of the left hand side integral dependon the explicit expression of the function f(α) andare denoted as g (α). Algebraic expressions offunctions of the most common reactionmechanisms operating in solid-state reactions aresummarized and presented in table-3 8-11 . Table-4represents the conciseTGA data and the activationenergy at different temperature range.3.2.3 Evaluation of kinetic parametersThe kinetic parameters have been calculated basingon eighteen various kinetic models. The formalexpressions of the functionsg(α) depend on theconversion mechanism. For the correct g(α), thecorresponding linear dependence should give thehighest correlation coefficient at the linearregression analysis. The plot of log g(α) versus 1/Tgives the values of R 2 (correlation co-efficient) toeach mechanism. The mechanism corresponding tohighest value of R 2 is considered to be the suitablemechanism for the degradation kinetics. From theslope value of each straight line, the values ofactivation energy ( E)is calculated.Energy From the concise TG data (table-4), it isclear that for the R-F resin the activation isminimum in the temperature range 0-150 0 C and soit undergoes thermal decomposition at a high ratethrough F 3/2 mechanism (chemical reaction) Thenano polymerA 2 (n) breaks through F 2 mechanism(chemical reaction) at a high rate in the temperaturerange 160-350 0 C .While in the other hand for thenano polymer A 1 (n) , the rate of thermaldecomposition is high in the temperature range 0-150 0 C and the reaction proceeds through P1/4mechanism (nucleation).CONCLUSIONThe thermal study reveals the nanostructuredpolymeric sample can resist temperature upto800 o C and hence they can be best used as heatproof materials. The calculated values ofactivation energy indicates that except R – F resin,the stability enhances upto temperature 350 o C dueto low dissipation of kinetic energy, after this pointit becomes unstable which may be due to breakpoint of polymeric chain. The incorporation ofUrea into the polymeric sample enhances itsthermal stability and the degree of crystallinity bothin micro scale nano scale. The sample can be usedas potential heat resisting material thus enabling itscomposite formation with different biomaterialswhich is under further investigation.ACKNOWLEDGEMENTThe authors are grateful to Laboratory of AdvancedResearch in Polymeric Materials (LARPM) CIPET,Govt of India for synthesis and characterizationof the samples .Vol. 4 (2) Apr– Jun 2013 www.ijrpbsonline.com 697

International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-3701Table 1: Structural study of Nano Resin Polymer A 1 (n) and A 2 (n) from XRD DataName of theCompoundA 2(n)A 1(n)2 d (A o FWHMAverage % of)D (nm)(Radian)of D(nm) Crystallinity17.8188 4.97377 0.0048441 28.9720.64119.2637 4.60384 0.0049938 28.161 0.58423.1224 3.84353 0.008004 17.681 0.50925.4210 3.50097 0.0074855 13.032 25.165 0.17428.2695 3.15434 0.0060813 23.511 0.32329.4347 3.03709 0.0050147 28.586 0.57633.8944 2.64263 0.004002 36.218 1.12517.932 4.94268 0.0034226 41.01131.81619.13 4.63468 0.0023733 32.9821 3.09419.44 4.56297 0.004263 32.9970 0.94123.16 3.83594 0.0032172 43.991 1.66425.35 3.51035 0.0021228 66.9448 7.64547.83525.60 3.47581 0.0026082 54.5139 4.57428.33 3.14726 0.0033129 43.163 2.00328.44 3.13478 0.0030624 46.706 2.51529.55 3.02075 0.0030154 47.5518 2.6546.25 1.96133 0.0022011 68.4922 6.826Average %of crystalinity0.5093.373MicroScaleNanoScaleTable 2: Weight loss pattern of the resin polymers at different temperature range in micro scaleand nano scaleS. No.Name of the% of wt. loss at different temperaturecompound 100 o C 200 o C 300 o C 400 o C 500 o C 600 o C 700 o C 800 o C1 R – F 5.3 12.3 20.3 29.7 41.5 50.0 55.1 64.02 R – PNA – F (A 2) 6.6 7.7 12.6 20.4 33.0 50.0 62.6 72.03 R – U – PNA – F (A 1) 8.3 10.3 24.3 35.6 45.0 53.4 60.6 67.34 A 2 (n) 2.6 34.4 64.0 65.9 68.7 72.7 75.9 77.45 A 1 (n) 2.2 23.8 38.0 42.4 47.3 53.5 58.2 60.5Table3: Algebraic expressions of function, g( ) and its corresponding MechanismSl. MechaName of the function g( ) Rate. determining MechanismNo. -nisma. (based on the diffusion mechanism)1 D 1 Parabola law 2One-dimensional diffusionln l 2 D 2 Valensi (Barrer) Equation 3 D 3 Jander Equation1 1 1/ 3 21-2 /3- 1 1/ 3equation 1 1 21 1/ 314 D 4 Ginstling-Brounstein Equation5 D 5 Zhuravlev, LesokinTempelman6 D 6 Anti-Jander Equationb. (random nucleation and subsequent growth)7 A 1 Avrami –Erofeev Equation8 A 3/2 Avrami –Erofeev Equation9 A 2 Avrami –Erofeev Equation10 A 3 Avrami –Erofeev Equation11 A 4 Avrami –Erofeev Equationc. (Phase boundary equation)12 R 2 Power Law1Two-dimensional diffusion 2-ln 1 ln1 2 / 3ln1 1/ 2ln1 1/ 3 ln11- 1/ 21Three- dimensional diffusion Sphericalsymmetry2 / 3 Three- dimensional diffusion CylindricalsymmetryThree- dimensional diffusionThree- dimensional diffusionAssumed random nucleation and itssubsequent growth n=1Assumed random nucleation and itssubsequent growth n=1.5Assumed random nucleation and itssubsequent growth n=2Assumed random nucleation and itssubsequent growth n=31 / 4 Assumed random nucleation and itssubsequent growth n=4Contracting cylinderCylindrical symmetryVol. 4 (2) Apr– Jun 2013 www.ijrpbsonline.com 698

International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-370113R 3 dPower Law1- 1/ 31d. (Acceleratory rate equation)14 P 1/2 Mampel Power Law 1/ 215 P 1/3 Mampel Power Law 1/ 316 P 1/4 Mampel Power Law 1/ 4e. (Chemical Process or Mechanism non-invoking equation)17 F 2 Second order18 F 3/2 One and a half order1 1 1 21 1/1Contracting SphereSpherical symmetryNucleationNucleationNucleationChemical reactionChemical reactionTable 4: Concise TG data showing the activation energy for the highest regression correlationcoefficient and the corresponding degradation mechanism for thermal analysis of the resins atdifferent temperature rangesSl. NoName of theCompound1 R – F Resin23R-PNA-FNano resin polymerA 2(n)R-U-PNA-FNano resin polymerA 1(n)Temperature ( o Function / Activation Energy (E) in CorrelationC)mechanismK Joule / Mole coefficient (R 2 )0-150 o C F 3/2 0.2739 0.9495160-350 o C D 6 3.9963 0.9021360-500 o C D 6 22.0091 0.9882Above 500 o C D 4 38.9241 0.99610-150 o C F 2 11.22 0.852160-350 o C F 2 8.482 0.755360-500 o C D 2 95.295 0.979510-650 o C D 1 54.99 0.999660-800 o C F 2 42.6 0.9850-150 o C P 1/4 4.71 0.979160-350 o C F 2 20.68 0.859360-500 o C D 4 75.26 0.991510-650 o C D1 13.95 0.999660-800 o C F 3/2 47.24 0.988Vol. 4 (2) Apr– Jun 2013 www.ijrpbsonline.com 699

International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-3701Fig. 2(a): TGA curves of resin polymer R-PNA-F (), R-F ( ),R-PNA-U-F ( ) shows thermal stability of the resin polymersVol. 4 (2) Apr– Jun 2013 www.ijrpbsonline.com 700

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