A new perspective on the glass transition, tack and rheology of oligomeric epoxy resins

Bis-phenol A based oligomeric epoxy resins with known molecular characteristics were selected as model liquids for the study of glass transition processes, rheological properties and tack. The effect of cooling and heating rates on the glass transition dynamics of epoxy resins has been studied. Rheology and differential scanning calorimetry methods were used to determine the fragility indices of oligomeric epoxy resins. The tack of oligomers was determined as a function of the reduced temperature T/Tg, and it is shown that the tack parameters for all studied oligomers correlate well with their fragility indices.Rheological measurements of epoxy oligomers were performed in the oscillation mode in a wide frequency range. Applying the principle of time-temperature superposition, generalized dependencies of the storage and loss modulus on the weight average molecular weight and molecular-mass distribution was determined. The parameters of generalized frequency dependences of the complex modulus components and the molecular weight characteristics of oligomers were correlated.