Rheological behavior of isotactic polypropylene (iPP) melts in supercooling state

Decreasing the processing temperature can prevent thermal degradation of polymeric material and reduce energy consumption in the manufacturing process. In this paper, capillary rheometer was used to investigate the theological behavior of isotactic polypropylene (iPP) in supercooling states. Experimental results demonstrate that the iPP melt in supercooling state have an induction period. After the induction period, the iPP melt undergoes gelation that is manifested by rapid increasing of the shear viscosity and leads to solidification and crystallization of iPP. During the induction. period, the rheological behavior of iPP melt in supercooling states are similar to the conventional iPP melt whose temperature is above the melting temperature of iPP. The length of the induction period depends on the temperature of the melt. At 160, the length of the induction period is long enough so that it is possible to produce iPP fibers by spinning supercooling melt. In the suitable process conditions, the mechanical performance, FTIR spectra and XRD patterns of the iPP fibers produced from supercooling iPP melt are similar to those of the iPP fibers prepared from high temperature iPP melt. Thus, this work suggests that it is possible to develop an energy-saving technique to manufacturing of iPP fibers.