Rubber -Modified EpoxiesIII. Influence of the Rubber Molecular Weight on the Phase Separation Process.

DONG CHEN; JEAN PIERRE PASCAULT; HENRY SAUTEREAU; ROXANA A. RUSECKAITE; ROBERTO J.J.WILLIAMS

POLYMER INTERNATIONAL

Wiley

Año: 1994 vol. 33 p. 253 - 260

0959-8103

separation taking place in rubber-modified epoxies is reported. Three butadiene-acrylonitrile copolymers with number-average molecular weights of 2030, 3600 and 6050 g mol-1 were used. The thermosetting polymer was an epoxy based on diglycidylether of bisphenol-A cured with a cycloaliphatic diamine. Increasing the rubber molecular weight showed the following effects: (i) a decrease in the conversion at the cloud point; (ii) a corresponding decrease in the viscosity at the cloud point; (iii) a primary morphology of a low concentration of particles with a large size; (iv) a more complete segregation of the rubber from the matrix leading to a smaller decrease of the glass transition temperature of the system; (v) a decrease in the toughening. The Flory-Huggins lattice model may be used as a simple approximation to describe the phase separation process when varying the rubber molecular weight.