Intumescent fire-retardant systems have been studied in detail from all points of view. However, all works passed around questions of mechanical stability of foamed chars produced during burning. In the present work, mechanical properties of intumescent chars has been discussed. Technique and method of such investigations have been supposed. It was supposed that mechanical stability of foamed chars correlates with high molecular fraction in char residue.
The kinetics associated with the reaction of aromatic and aliphatic diamines with phthalic anhydride in glacial acetic acid was studied. This model system was intended to simulate the synthesis of polyimides from diamines and dianhydrides in molten benzoic acid. The reaction proceeds in two discrete steps, the first acylation occurs by the reaction of the diamine with phthalic anhydride followed by cy-clodehydration of the corresponding bis-(o-carboxyamides). The focus of the work was on the influence of chemical composition and basicity of the diamines on the kinetics. Kinetic and thermodynamic characteristics of model reactions were determined. It was established that acylation of aromatic and aliphatic diamines in acid medium proceeds as a reversible second-order reaction catalyzed by acid medium. On the basis of kinetic data obtained, an explanation is given for the observed phenomenon of reactivity leveling of diamines regardless of the basicity.
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