Enhancement of drawdown force in polypropylene containing nucleating agent

Abstract

The effect of the nucleation efficiency of three commercial nucleating agents, such as 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS), sodium 2,2′‐methylene‐bis‐(4,6‐di‐tert‐butylphenyl)phosphate (SMBP), and magnesium silicate (talc), on the melt‐stretching performance of isotactic polypropylene (PP) is studied. It is found that the addition of 0.5 wt % of a nucleating agent enhances the crystallization temperature and that effect is pronounced for DMDBS and SMBP. Furthermore, DMDBS is more efficient than the other tested nucleating agents in enhancing the drawdown force, defined as a force required for stretching a molten strand. Nanofibers of DMDBS, which show significant alignment in the flow direction, are responsible for the rapid crystallization of PP in the flow field leading to an increase of drawdown force. The stretched strand shows a highly oriented structure in which the α‐form crystals orient to the flow direction. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47295.

Modulus enhancement of polypropylene by sorbitol nucleating agent in flow field

“…Homogeneous mixing of an ultrahigh molecular weight fraction and/or crosslinked fraction is, in general, difficult, especially by melt blending. However, fibrous materials having nucleating activity for crystallization are also found to act as shish; that is, as a precursor for flow‐induced crystallization 17–22 . One example is the addition of carbon nanotubes (CNT) to polyethylene (PE) 17,21 .…”

“…Sorbitol derivatives such as 1,3:2,4‐bis‐ o ‐benzylidene‐D‐sorbitol (DBS), 1,3:2,4‐bis‐ o ‐(4‐methylbenzylidene)‐D‐sorbitol (MDBS), and 1,3;2,4‐bis‐ o ‐(3,4‐dimethylbenzylidene)‐D‐sorbitol (DMDBS) are known as clarifiers to improve the transparency of isotactic polypropylene (PP). Their fibrils also have the capability to act as shish for PP, 19,20,25,26 because they exhibit excellent nucleating activity. The mechanism of the nucleating activity, miscibility and phase‐separation with molten PP, self‐organization behavior, and effects of the species and contents on the PP crystallization have been reported greatly since the mid‐1990s 27–38 .…”

“…These fibers then act as nucleating agents for PP. Under a flow field, PP chains that are oriented by the flow can easily attach to the surface of the fibrils owing to matching of the orientation directions 20,25,26 . As a result, the orientation of PP chains is greatly enhanced, leading to a high modulus in the flow direction.…”

Effect of carbon nanotube addition on structure and properties for extrudates of high‐density polyethylene

“…This can be achieved by adding a high‐molecular‐weight fraction with a Rouse relaxation time that is longer than the inverse of the strain rate . As well as high‐molecular‐weight components, fibrous nucleating agents also behave like “shish,” greatly affecting the processability, structure, and properties of the polymer in the solid state …”

“…[11][12][13][14][15][16][17] As well as high-molecular-weight components, fibrous nucleating agents also behave like "shish," greatly affecting the processability, structure, and properties of the polymer in the solid state. [18][19][20][21] In the present study, we focused on the strong nucleating ability of multi-walled carbon nanotubes (MWCNTs) in high-density polyethylene (HDPE). We investigated the effect of MWCNTs on shish-kebab formation using a capillary rheometer.…”