Thermal and Mechanical Properties of Anhydride – Cured Epoxy Resins with Different Contents of Bio-Based Epoxidized Soybean Oil

F.I. ALTUNA; L. ESPÓSITO; R. A. RUSECKAITE; P. M. STEFANI

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Año: 2011 vol. 120 p. 789 - 798

0021-8995

Abstract: Thermosetting resins were synthesized by partially replacing the synthetic  epoxy pre-polymer based on diglycidyl ether of bisphenol A (DGEBA) by increasing amounts of epoxidized soybean oil (ESO), using methyltetrahydrophthalic anhydride  (MTHPA) as cross-linking agent and 1-methyl imidazole (1-MI) as initiator.  Calorimetric studies showed a drop in the reaction heat with ESO content associated to the lower reactivity of oxirane rings in ESO due to steric constrains. The effect of  replacing increasing amounts of synthetic DGEBA by ESO on the network properties such as storage modulus in the glassy and rubbery region, glass transition temperature as well as impact and compressive properties was examined. All formulations were transparent despite phase-separated morphologies were evidenced by SEM observations. The intensity of the transmitted light passed to a minimum at a short reaction time associated to the cloud point and then increased continuously until the refractive index of the dispersed phase approximated that of the continuous phase at complete conversion. The combination of DGEBA with 40 wt.% ESO resulted in a resin with the optimum set of properties; the storage modulus in the glassy state was  93% of that of neat DGEBA resin, the glass transition temperature decreased only about 11ºC while the impact strength increased about 38% without loosing transparency.