BLENDS OF POLY[ETHYLENE(VINYL ACETATE)] AND POLYCHLOROPRENE - STUDIESON CAPILLARY AND DYNAMIC FLOWS

Rheological properties of the blends of poly[ethylene(vinylacetate)] ( EVAc; vinylacetate content 28%) and polychloroprene (CR) have been mea sured through capillary and dynamic uniaxial elongational flows. Capil lary flow indicates their shear thinning behavior. The decrease in the out of phase viscosities with increasing frequency is in accordance w ith the power law equation, whereas dynamic elongational viscosities f ollow nonlinear relationship in log-log plot with an initial increase at 11 Hz, followed by a very sharp drop. With an increase in temperatu re, the viscosity for capillary flow of all blends goes down due to th eir positive activation energy of flow but for dynamic elongational fl ow of EVAc blended with CR, viscosity increases, except for 30/70 blen d and pure CR, in which case the dynamic elongational viscosity decrea ses with an increase in temperature. This abnormal behavior in dynamic elongational viscosity is due to the process of melting and recrystal lization of EVAc at low heating rate (1 degrees C/min) beyond the melt ing temperature. Capillary viscosities of all blends show positive dev iation from the log additive values of pure polymers. But in the case of dynamic elongational flow, all blends show positive deviation at fr equencies of 3.5 and 35 Hz and at higher temperatures (80-120 degrees C). (C) 1997 John Wiley & Sons, Inc.