Rheological properties of liquid-solid transition in isothermal crystallization for high-density polyethylene

The rheological properties of liquid-solid transition during the crystallization for high-density polyethylene(HDPE) was investigated through the static and dynamic rheological measurements. It is found that with the crystallization proceeding, a tensile force upon the parallel-plates is induced by volume contraction of the sample. In the case of static test with the motionless parallel plates, this tensile force relaxes quickly in liquid states, while starts to accumulate after certain time. Accordingly, a new method to determine the liquid-solid transition depending on the static tensile force is proposed. A comparison between it and the classic dynamic one for detecting liquid-solid transition evidences that the dynamic method is preferred to slow crystallization, and static method is more appropriate for the crystallization at moderate rates. Furthermore, the latter has the advantage of no disturbing the crystallization behavior of HDPE before the transition.