Authors:Mariana Cristea, C. Gaina, Daniela Ionita, and Viorica Gaina
Polyaminobismaleimides (PAMBI) with diphenyl methane, diphenyl ether and hexamethylene segments were synthesized according
to Michael type addition reaction. The modification of PAMBIs with 2-glycidyl-phenyl-ether (GPE) was performed in order to
ameliorate the toughness of the products. Dynamic mechanical analysis allowed the study of the processes that concur in the
material through curing by tracking the storage modulus (E′) and loss factor (tanδ) changes. The small drop of E′ with increasing temperature in the glass transition region argues for crosslinked structures. The viscoelastic behavior
revealed complex processes, i.e., overlapping of glass transition temperature range with intra-and inter-crosslinking.
Authors:Mariana Cristea, Daniela Ionita, Maria Bruma, and B. Simionescu
Two aromatic polyimides and the corresponding poly(amic acid)s, with oxadiazole and para/meta phenoxyphenylene rings in the backbone, were synthesized and the structure — thermal properties correlation was followed
by dynamic mechanical analysis. Concerning the poly(amic acid)s, the glass transition domain was emphasized only for the compound
with meta-oriented rings because the process of imidization takes place with increasing temperature. A multiplex experiment was performed
to calculate the activation energy of the transition localized under 200°C. Consecutive heating-cooling-heating cycles were
accomplished. All phenomena are discussed by cross-examination of the storage modulus (E′), loss modulus (E″) and loss factor tanδ variation with temperature.