TOUGHENING OF EPOXY-RESIN BLENDED WITH THERMOTROPIC HYDROXYETHYL CELLULOSE-ACETATE

Thermotropic hydroxyethyl cellulose acetate (HECA) was totally miscibl e with uncured epoxy resin, and the miscibility was not influenced by the degree of substitution (DS) of HECA. When the epoxy resin was cure d with diamine (DDA), HECA became immiscible with the epoxy resin matr ix, and a heterogeneous system was formed. Epoxy resin existed as a co nstant phase, and HECA-rich domains were dispersed in the matrix with dimensions of about 0.2-0.5 mu m. Epoxy resin could be toughened by HE CA, and the impact strength of the epoxy resin blends with 10 wt % HEC A was the maximum. HECA exhibited the highest toughening ability when the epoxy resin was cured at the temperature at which the HECA existed as a liquid crystalline state. The toughening ability was also influe nced by the degree of substitution for acetyl of HECA, and the impact strength of the epoxy resin blends decreased with increasing the DS fo r acetyl of HECA. (C) 1998 John Wiley & Sons, Inc.