Small- and wide-angle X-ray scattering investigations of injection-moulded polypropylene

Zipper, Peter; Jánosi, A.; Wrentschur, E.; Abuja, Peter M.

doi:10.1107/s0021889891001917

Cited by 28 publications

(23 citation statements)

References 6 publications

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“…1,2 Generally, the injection molded samples of various semicrystalline polymers exhibit a clear multiphase structure of skin layers and core, and furthermore, the relative weights of the two contributions change with the polymer melt properties and molding conditions. [3][4][5][6][7][8][9][10] To a large extent, the mechanical properties of semicrystalline polymers are related to the microstructure and morphology. [11][12][13][14] It is therefore anticipated that the macroscopic deformation behavior and physical properties will be affected by the heterogeneous nature of molded samples.…”

Section: Introductionmentioning

confidence: 99%

Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)

Jiang

Wang

et al. 2013

Macromolecules

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The structural evolution of micro-molded poly(ε-caprolactone) (PCL) and its miscible blends with noncrystallizable poly(vinyl methyl ether) (PVME) at the nanoscale was investigated as a function of deformation ratio and blend composition using in situ synchrotron small-angle X-ray scattering (SAXS) and scanning SAXS techniques. It was found that the deformation mechanism of the oriented samples shows a general scheme for the process of tensile deformation: crystal block slips within the lamellae occur at small deformations followed by a stress-induced fragmentation and recrystallization process along the drawing direction at a critical strain where the average thickness of the crystalline lamellae remains essentially constant during stretching. The value of the critical strain depends on the amount of the amorphous component incorporated in the blends, which could be traced back to the lower modulus of the entangled amorphous phase and, therefore, the reduced network stress acting on the crystallites upon addition of PVME. When stretching beyond the critical strain the slippage of the fibrils (stacks of newly formed lamellae) past each other takes place resulting in a relaxation of stretched interlamellar amorphous chains. Because of deformation-induced introduction of the amorphous PVME into the interfibrillar regions in the highly oriented blends, the interactions between fibrils becomes stronger upon further deformation and thus impeding sliding of the fibrils to some extent leading finally to less contraction of the interlamellar amorphous layers compared to the pure PCL.3

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Section: Introductionmentioning

confidence: 99%

Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)

Jiang

Wang

et al. 2013

Macromolecules

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“…nucleating agents) and the sample dimensions. Similar morphology distributions across injection-molded poly(propylene) parts were obtained by Zipper et al [6] Dragaun et al [7] analysed the morphology of iPP-H pipes using polarised-light microscopy. They found a layer structure with a lightmicroscopically structureless outer layer and larger spherolites in the core of the pipe wall.…”

Section: Introductionmentioning

confidence: 57%

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

Brüll¹,

Geertz²,

Kothe³

et al. 2008

Macro Materials & Eng

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The supramolecular structure in pipe walls of isotactic PP‐R is a function of compound composition and processing parameters, which both influence the mechanical properties of the pipes. µFTIR shows a gradient of the crystallinity across the pipe wall, with a lower‐crystalline outer layer, and a higher‐crystalline core layer. The rate of extrusion has an influence on the thickness of the outer layer. The nucleating effect on the morphological profile throughout the pipe wall can be visualised. µFTIR shows a homogeneous distribution of the primary antioxidant in the pipe wall. Both the spectral crystallinity and the antioxidant concentration distribution are calculated.magnified image

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“…[14][15][16][17][18][19][20][21][22][23][24] Clearly, the size, shape or form, orientation, and perfection of the crystals, as well as the fraction (i.e., crystallinity) of the polymer bulk they constitute will affect the polymer solid-state properties. For example, it is well-established that the inhomogeneous and anisotropic structures of skin and core of injection-molded samples [25][26][27][28][29][30][31][32] can significantly influence the physical properties such as dimension stability, 33 Young's modulus, and tensile strength. [34][35][36] Generally, the fraction with a low degree of crystal orientation, which is often present in thick molded samples, does not have a significant effect on the mechanical behavior.…”

Section: Introductionmentioning

confidence: 99%

Thermal stability of shear‐induced precursor structures in isotactic polypropylene by rheo‐X‐ray techniques with couette flow geometry

Somani

Šics

Hsiao

2006

J Polym Sci B Polym Phys

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Combined in situ rheo-SAXS (small-angle X-ray scattering) and -WAXD (wide-angle X-ray diffraction) studies using couette flow geometry were carried out to probe thermal stabilty of shear-induced oriented precursor structure in isotactic polypropylene (iPP) at around its normal melting point (162 8C). Although SAXS results corroborated the emerging consensus about the formation of ''long-living'' metastable mesomorphic precursor structures in sheared iPP melts, these are the first quantitative measures of the limiting temperature at which no oriented structures survive. At the applied shear, rate ¼ 60 s À1 and duration t s ¼ 5 s, the oriented iPP structures survived a temperature of 185 8C for 1 h after shear, while no stable structures were detected at and above 195 8C. Following Keller's concepts of chain orientation in flow, it is proposed that the chains with highly oriented high molecular weight fraction are primarily responsible for their stability at high temperatures. Furthermore, the effects of flow condition, specifically the shear temperature, on the distributions of oriented and unoriented crystals were determined from rheo-WAXD results. As expected, at a constant flow intensity (i.e., rate ¼ 30 s À1 and duration, t s ¼ 5 s), the oriented crystal fraction decreased with the increase in temperature above 155 8C, below which the oriented fraction decreased with the decrease in temperature. As a result, a crystallinty ''phase'' diagram, i.e., temperature versus crystal fraction ratio, exhibited a peculiar ''hourglass'' shape, similar to that found in many two-phase polymer-polymer blends. This can be explained by the competition between the oriented and unoriented crystals in the available crystallizable species. Below the shear temperature (155 8C), the unoriented crystals crystallized so rapidly that they overwhelmed the crystallization of the oriented crystals, thus depleting a major portion of the crystallizable species and increasing their contribution in the final total crystalline phase.

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Small- and wide-angle X-ray scattering investigations of injection-moulded polypropylene

Cited by 28 publications

References 6 publications

Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)

Tensile Deformation of Oriented Poly(ε-caprolactone) and Its Miscible Blends with Poly(vinyl methyl ether)

Analysis of the Influence of Processing Conditions on the Supramolecular Structure and Antioxidant Distribution in PP‐Pipes Using Infrared Microscopy

Thermal stability of shear‐induced precursor structures in isotactic polypropylene by rheo‐X‐ray techniques with couette flow geometry

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