EFFECT OF ANNEALING ON THE STRUCTURE OF INJECTION-MOLDED PEN

The influence of annealing at temperatures where thermally activated c rystallization rates become significant on the structural variations i n the injection-molded polyethylene naphthalate (PEN) was investigated . In these studies, two distinct shear crystallized layers are observe d. The shear crystallized layer near the skin forms during the filling stage, and the second shear crystallized layer forms during the packi ng stage but remains optically unobservable until the annealing takes place. Upon annealing, additional layers with larger crystallite sizes form around these preformed highly oriented layers. The alpha and bet a phases were observed in both of the shear crystallized layers. The b eta phase is generally grown either under high deformation fields or u nder quiescent conditions at high temperatures. (C) 1996 John Wiley & Sons, Inc.