Development of highly oriented polymer crystals from row assemblies

Nogales, Aurora; Mitchell, Geoffrey R.

doi:10.1016/j.polymer.2005.04.088

Cited by 22 publications

(25 citation statements)

References 19 publications

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“…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]. Contrasting to CIM, the oriented morphology will be maintained at the best level throughout the whole process of injection molding of ''melt manipulation'', which ensures a maximum formation of shish-kebab along the sample thickness.…”

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

105

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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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

105

100

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“…It was found that DBS greatly enhances nucleation in polyethylene and that, following phase separation at high crystallization temperatures, the rejected low molar mass polyethylene decorated the DBS network to form shish‐kebab‐like structures. Nogales and Mitchell also observed shish‐kebab structures upon shearing a propylene/ethylene copolymer containing DBS . Lipp et al used transmission electron microscopy (TEM) and small‐angle X‐ray scattering (SAXS) to determine the kinetics of nanofibril formation of 1,3:2,4‐di(3,4‐dimethylbenzylidene) sorbitol (DMDBS) in an i ‐PP matrix.…”

Section: Introductionmentioning

confidence: 99%

On clarification of haze in polypropylene

Bernland

Goossens

Smith

et al. 2016

J. Polym. Sci. Part B: Polym. Phys.

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The mechanism of reducing light scattering in isotactic polypropylene (i-PP), through the addition of so-called clarifying agents, is studied with small-angle light scattering (SALS) and scanning electron microscopy (SEM). The clarifying agents used in this study depict monotectic phase behavior with i-PP, crystallizing in a relatively narrow concentration range in a nanofibrillar network, providing an ultrahigh nucleation density in the i-PP melt. It is found that the clarifying effect, a dramatically increased transparency and reduced haze, that occurs within the aforementioned additive concentration range, coincides with a change in morphology from strongly scattering spherulites to shish-kebab-like crystalline structures, as evidenced by in situ SALS measurements and confirmed by SEM images. A simple scaling law, relating the diameter of the shish-kebab structures to the fibril diameter and volume fraction of the clarifying agent is proposed, suggesting that the performance of a (fibril-forming) clarifying agent will improve by reducing the fibril diameter and/or increasing the volume concentration of the clarifying agent.

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“…There are relatively few efforts in the literature to investigate the influence of flow on morphological development in the iPP/DMDBS system. Nogales et al [14–16] showed that isothermal structure development in iPP containing dibenzylidene sorbitol is a strong function of shear rate and strain units, in addition to the sorbitol concentration and temperature. They showed that, on shearing, an oriented network of DMDBS is formed on cooling and that, the iPP crystals template this network, with the iPP lamellae growing orthogonal to the sorbitol fibers.…”

Section: Introductionmentioning

confidence: 99%

The influence of DMDBS on the morphology and mechanical properties of polypropylene cast films

Sreenivas

Pol

Kumaraswamy

2011

Polymer Engineering & Sci

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We investigate extrusion film casting (EFC) of polypropylene (PP) and examine the effects of varying the concentration of nucleating agent, dimethyl dibenzylidene sorbitol (DMDBS); melt temperature at the die exit; and the draw ratio. Addition of DMDBS increases the PP crystallization temperature, and consequently the PP lamellar repeat spacing. For the draw ratios explored, we do not observe any substantial orientation of iPP crystals for films of neat iPP. However, addition of DMDBS results in the formation of oriented PP crystals, with greater orientation for higher draw ratios. On cooling from the melt, a network of DMDBS nanofibers forms in the PP. We believe that flow‐alignment of this DMDBS network templates the orientation of PP crystals. We observe that the tensile modulus and yield stress increase with PP crystal orientation. However, at high DMDBS concentrations (0.8%), films have poor mechanical strength due to formation of voids and defects. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

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Development of highly oriented polymer crystals from row assemblies

Cited by 22 publications

References 19 publications

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

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

On clarification of haze in polypropylene

The influence of DMDBS on the morphology and mechanical properties of polypropylene cast films

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