INTER- AND INTRACHAIN ASSOCIATIONS OF AN ETHYLENE-VINYL ACETATE RANDOM COPOLYMER IN DILUTE 1,2-DICHLOROETHANE SOLUTIONS

摘要

Laser light scattering (LLS) has been used to study an ethylene-vinyl acetate (EVA) random copolymer in 1,2-dichloroethane. The EVA solution was treated using two different thermal processes: (1) quickly quenching from 70 degrees C to 0 degrees C; and (2) slowly cooling from 70 degrees C to room temperature and annealing at room temperature for 24 h before further quenching to 0 degrees C. The LLS results reveal the formation of larger EVA aggregates in both of the thermal processes. After the EVA. solution was reheated from 0 degrees C to a higher temperature, we found that the size of the EVA aggregates formed in the fast cooling process is nearly independent of temperature in the range of 15-30 degrees C, but the size of the EVA aggregates formed in the slow cooling process increases and reaches a maximum in the same temperature range. In both of the cases, the EVA aggregates dissociate at higher temperatures. The formation kinetics of the EVA aggregates at 40 degrees C and the effect of the annealing time at room temperature were also investigated. All results lead us to realize that in the fast cooling process the EVA aggregates were formed mostly through the aggregation (packing) of individual EVA collapsed chains (intrachain aggregation), while in the slow cooling process, the EVA aggregates are microgel-like particles formed through the winding of the EVA chains (interchain association). We also found that there is a good correlation between the size of the EVA aggregates and the pour point of a wax solution doped with EVA. [References: 16]