Distribution of Shish-Kebab Structure of Isotactic Polypropylene under Shear in the Presence of Nucleating Agent

Zhu, Peng; Edward, Graham H

doi:10.1021/ma0358374

Cited by 46 publications

(36 citation statements)

References 12 publications

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“…This indicates that the incorporation of NA extends the distribution range of oriented structures. Such enhanced orientation induced by the presence of NA was also found in the conventional injection‐molded iPP containing α‐NA [10]. As suggested by Dukovski and Muthukumar [22], the introduction of NA will lower the free energy barrier for the formation of shish which can partially account for this.…”

Section: Resultsmentioning

confidence: 64%

“…Additionally, it is well known that nucleating agents (NAs) are widely used in thermoplastic processing due to their abilities to increase the crystallization rate, reduce the cycle time, and improve the optical properties. More interestingly, for the isotactic polypropylene (iPP) molded by CIM, the presence of NA could not only change the multilayered structure but also improve the overall orientation [10]. To the best of our knowledge, however, crystalline orientation of the semicrystalline polymers molded by WAIM, especially for those containing crystallization NA, is scarcely studied.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced orientation of the water‐assisted injection‐molded ipp in the presence of nucleating agent

Zheng¹,

Jia²,

Liu³

et al. 2012

Polymer Engineering & Sci

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The nucleated isotactic polypropylene (iPP) was molded by water‐assisted injection molding. The crystalline morphology and orientation distribution were studied. The results show that shear brought by melt filling and pressurized water penetration can separately induce the formation of oriented structures in skin region (i.e., the region near mold cavity wall) and the water channel region. For virgin iPP, slightly oriented lamellae appear exclusively in the above aforementioned regions. However, shish‐kebab structure occurs not only in skin and water channel region of the iPP containing moderate content of nucleator (0.2 wt%) but also in the whole region of the iPP containing a higher content of nucleator (1 wt%). It is well known that nucleator cannot directly induce the development of shish‐kebab in the absence of shear, thus the results indicate: shear flow actually distributes over a much broader range than expected; in shear field, nucleator is significantly helpful for the shear which is not sufficient to solely induce oriented structure to promote the formation of the oriented structure. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

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Section: Resultsmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Enhanced orientation of the water‐assisted injection‐molded ipp in the presence of nucleating agent

Zheng¹,

Jia²,

Liu³

et al. 2012

Polymer Engineering & Sci

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show abstract

“…32, hierarchical structure of injectionmolded parts is generally divided into three regions called skin region, shear region and core region due to the shear and temperature gradients created by the boundary conditions during injection molding process. However, since the skin region is extremely thin and polymer in this region is considered to be amorphous, 8,33 therefore, we mainly focus our attention on the shear region and core region in this study. 8,9,33 That is, skin region is the outmost region of the injection-molded part, while the region next to skin region is dened as shear region.…”

Section: Resultsmentioning

confidence: 99%

Suppressing the skin–core structure in injection-molded HDPE parts via the combination of pre-shear and UHMWPE

et al. 2015

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In this study, pre-shear and ultrahigh molecular weight polyethylene (UHMWPE) were introduced to suppress the skin-core structure of injection-molded high density polyethylene (HDPE) parts. The structural characteristics of the injection-molded parts were systematically elucidated through scanning electron microscopy (SEM), two-dimensional wide-angle X-ray diffraction (2D-WAXD) and twodimensional small-angle X-ray scattering (2D-SAXS). The results showed that oriented lamellae were formed in the core region upon pre-shear, and the orientation level of oriented lamellae in core region was further enhanced with increasing concentration of UHMWPE. More interestingly, a much narrowed orientation gap between the shear region and core region was obtained if the UHMWPE concentration was increased to 5 wt%. Moreover, crystallinity, long period, and lamellar thickness also increased with increasing UHMWPE concentration upon pre-shear. Naturally, the tensile strength of the blend parts was promoted due to the narrowed orientation gap between the shear region and core region along with an enhanced orientation level and increased crystallinity, long period, and lamellar thickness.

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“…A microbeam SAXS determination along the thickness of CIM iPP bar indicated that shish-kebab emerges at the sub-skin layer, which may disappear quickly with increase of thickness [85]. Nevertheless, Zhu and Edward [86,87] found that the shish structure is reversed even at deep position of molded bar with the presence of nucleating agent (NA). It was considered that NA may act as a template for facilitating oriented crystallization of polymer [88,89].…”

Section: Control Of Polyolefin Shish-kebab Via Dynamic Packing Injectmentioning

confidence: 99%

Shish–kebab of polyolefin by “melt manipulation” strategy in injection-molding: A convenience pathway from fundament to application

Wang

Chen

Zhang

et al. 2008

Polymer

104

100

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a b s t r a c tDue to both theoretical and practical importance, the formation mechanism of shear-induced shishkebab and the precise microstructure and molecular composition in shish-kebab have been extensively investigated for many years. However, a systematic review on the manipulation of shish-kebab superstructure in the injection-molded specimens, taken account of combining theoretical understanding, preparation processing, structural/morphological control and macroscopic properties, has rarely seen in the open publication by far. In this article, we will discuss mainly the topic of formation of fine polyolefin shish-kebab superstructure facilitated by ''melt manipulation'' strategy in injection-molding process. The main body of this review is governed by a logical sequence of (fundamental research)-(injection molding of melt manipulation)-(manipulation of shish-kebab)-(macroscopic mechanical properties). The fundamental understandings of the early stage of shish-kebab crystallization, transition process from random entangled chains network to stable shish-kebab cylindrulite, and the role of long polymer chains on shish-kebab formation, are very helpful for in-depth comprehension of shear-induced shishkebab in realistic processing. Various highly oriented morphologies with fine shish-kebab superstructure in injection-molded bars of polyolefin melts, including single component polyolefin melt, biphase melts of blend and heterogeneous melts of polyolefin/inorganic filler composites, could be achieved via ''melt manipulation'' strategy, as demonstrated by the work mainly from our group.

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Distribution of Shish-Kebab Structure of Isotactic Polypropylene under Shear in the Presence of Nucleating Agent

Cited by 46 publications

References 12 publications

Enhanced orientation of the water‐assisted injection‐molded ipp in the presence of nucleating agent

Enhanced orientation of the water‐assisted injection‐molded ipp in the presence of nucleating agent

Suppressing the skin–core structure in injection-molded HDPE parts via the combination of pre-shear and UHMWPE

Shish–kebab of polyolefin by “melt manipulation” strategy in injection-molding: A convenience pathway from fundament to application

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