Thermodynamically “strong” and kinetically “fragile” polymeric glass exemplified by melamine formaldehyde resins

摘要: Abstract The variations of the heat capacity ΔC p =[ C l − g ] T = at glass transition, and value fragility index m were determined for two melamine formaldehyde resins by calorimetric investigations. These values characterise respectively thermodynamic aspect kinetic Angell “Strong–Fragile” concept. For cured with a neutral pH, 3D network formed is made massive molecular units connected together small length chains, are =0.13 J K −1  g =143. acid pH curing conditions, only we obtain =0.12 =35. By comparing our results literature concerning three-dimensional networks inorganic polymers, able to conclude that relaxation occurs in these systems mainly movements involving triazine rings.