ENTANGLEMENT FLUCTUATION DURING PHASE-SEPARATION IN POLYMER BLENDS

For perhaps the first time, the dynamics of liquid-liquid phase separa tion was studied by time-resolved mechanical spectrometry in order to establish the relationship between blends' properties and the phase st ructures during spinodal decomposition (SD). The selected system was c hlorinated polyethylene (CPE)/ethylene-vinyl acetate copolymer (EVA). It was found that in the early and intermediate stage of SD, the stora ge modulus (G') and the loss modulus (G'') increase with time after th e initiation of the isothermal phase separation; in the later stage, G ' and G'' decrease as phase separation proceeds. An entanglement fluct uation model was presented to manifest this phenomenon; it was found t hat the rheological behavior agrees well with the expections of the mo del in the early stage. For the later stage, the reduction of G' and G '' can be attributed to the increment of phase-domain size. (C) 1993 J ohn Wiley & Sons, Inc.