Castor-Oil-Modified Epoxy Resins as Model System of Rubber- Modified Thermosets. 1. Thermodynamic Analysis of the Phase Separation.

ROXANA A. RUSECKAITE; ROBERTO J.J.WILLIAMS

POLYMER INTERNATIONAL

Wiley

Año: 1993 vol. 30 p. 11 - 16

0959-8103

Castoir oil was used to replace polydisperse commercial rubbers CTBN or ETBN in model systems developed to analyse the origin of the phase separatoion process in rubber-modified-thermosets. Mixtures of CO with an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) showed higher miscibility than typical CTBN (18%-acrylonitrile-DGEBA system. Thermodynamic factors accounting for this bahavior are discussed using the Flory – Huggins lattice model. Addition of stoichiometric amount of ethylenediamine (EDA) to a DGEBA – CO system increased the miscibility. A pseudo – binary approach was used to fit the cloud –point curve to 30%volume  fraction of CO. Percentage conversions at the cloud point during DGEBA-EDA polymerization were experimentally determined and compared with the theoretical prediction. reasonable agreement was found giving direct evidence of the fact that phase separation results from the decrease in the entropic contributions to the free energy of mixing during polymerization-