MECHANISTIC STUDY OF THERMAL-BEHAVIOR AND COMBUSTION PERFORMANCE OF EPOXY-RESINS .2. TGDDM DDS SYSTEM/

The kinetics of curing of tetraglycidyl 4,4'-diaminodiphenylmethane (T GDDM) with 50% or 85% of stoichiometric 4,4'-diaminodiphenylsulfone (D DS) was studied by differential scanning calorimetry. It was found tha t the activation energy of the process increases with advancement of c uring, which is caused by concomitant homopolymerisation of TGDDM acco mpanied by cyclisation, The structure of the cured formulations was ch aracterised by infrared and C-13 NMR spectroscopy. The mechanistic stu dy of thermal decomposition of TGDDM/DDS systems was carried out by th ermogravimetry and differential scanning calorimetry in inert atmosphe re and by thermal volatilisation analysis in vacuo. It was found that above 200 degrees C elimination of water from secondary alcohol groups takes place with formation of aliphatic unsaturation. Breaking of the resulting weakened allylic C-N bonds leads to chain scission with for mation of primary amine and quinolin-type chain ends. Scission of non- allylic C-N bonds followed by evolution of acetone was observed at abo ut 300 degrees C. The volatilisation of sulfur-containing species and formation of a thermostable char occurred on further heating to 400 de grees C. The poorer fire resistance of TGDDM/DDS formulations in compa rison with homopolymerised TGDDM is discussed on the basis of a lower yield of char and a higher yield of gases.