Single crystals of γ phase isotactic polypropylene: combined diffraction and morphological support for a structure with non-parallel chains

Lotz, Bernard; Graff, Sabine; Straupé, C.; Wittmann, J. C.

doi:10.1016/0032-3861(91)90185-l

Cited by 167 publications

(166 citation statements)

References 20 publications

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“…This confirms the suggested edge-on crystallization of -form lamellae. The observation that the -form nucleated on preformed -form crystals is consistent with results reported by Lotz et al 79 and Thomann et al [80][81][82] At a later stage of crystallization (Figure 5e) secondary lamellae are formed at all primary lamellae. Many of them reveals branching angles of 40 AE 3 , but also some lamellae grow with a branching angle of 80 AE 5 referring to the additional formation of -phase lamellae.…”

Section: Scanning Force Microscopysupporting

confidence: 81%

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

et al. 2009

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The time dependent crystallization of a low isotactic polypropylene with statistically incorporated stereoerrors was investigated by the combination of differential scanning calorimetry (DSC), wideangle X-ray scattering (WAXS) and scanning force microscopy (SFM). Owing to Scanning force microscopy (SFM) and WAXS experiments the crystallization of the sample in mixed =-form aggregates can be proposed. The nucleation and growth processes of crystallization in thin polypropylene films in real time were visualized with nanometer resolution by using SFM at variable temperature. During the isothermal crystallization from the melt initially crystals of the -form were developed. These lamellae act as nuclei for the further crystallization of -and mixed =-lamellae, which can be observed at longer crystallization times. Time dependent SFM and WAXS experiments showed that due to the low amount of crystallizable, regular sequences and its statistical distribution only slow crystallization rates can be observed. These results form the basis for a better understanding of the crystallization of low crystallinity polypropylenes. The investigations clearly show that the distribution of the regular isotactic segments influences the crystallization properties of propene based TEP's. This opens the possibility to tailor not only the mechanical but also the thermal properties of elastomeric polypropylenes by changing the polymer microstructure.

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Section: Scanning Force Microscopysupporting

confidence: 81%

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

et al. 2009

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“…Fortunately, even in such samples, the well-resolved peak at 2 ϭ 18.6°corresponds to the ␣-iPP (130) reflection, while the reflection at 2 ϭ 20.1°i s unique to ␥-iPP. [5][6][7][15][16][17][18][19] The orthorhombic ␥-iPP cell of Brü ckner and Meille 6 indexes this asterisked reflection as (117). Turner Jones used the heights of these two peaks to quantify the relative amount of ␥-iPP within a sample containing a mixture of the ␥-and ␣-phases by obtaining the ratio of WAXS peak heights.…”

Section: Resultsmentioning

confidence: 99%

Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

Dean¹,

1998

J. Polym. Sci. B Polym. Phys.

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“…The g-crystal phase has an orthorhombic unit cell (a = 8.54 Å, b = 9.93 Å, c = 42.4 Å) containing layers of non-parallel organized chain segments. Lamellae of the g-crystal phase generally nucleate on the a-lamellae by an epitaxial mechanism that is comparable with the cross-hatched structure within the a-crystal phase, but under an angle of 40 [1,5]. The mesomorphic phase is formed when i-PP is quenched to 0-40 C from the melt at ambient or high pressures [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…A peculiar feature of the a-crystal phase is lamellar branching, also known as cross-hatching: one type of lamellae (parent lamellae) forms a nucleation site for daughter lamellae that grow under a specific angle. For i-PP, this angle between parent and daughter lamellae is 80 [4,5]. Despite the presence of contaminations, i-PP from waste materials normally crystallizes in the a-crystal phase, which was investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) [6].…”

Section: Introductionmentioning

confidence: 99%

Fast cooling of (non)-nucleated virgin and recycled poly(propylenes): Effect of processing conditions on structural and mechanical properties

et al. 2015

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. Fast cooling of (non)-nucleated virgin and recycled poly(propylenes) : effect of processing conditions on structural and mechanical properties. Thermochimica Acta, 603, 94-102. DOI: 10.1016/j.tca.2014 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. A B S T R A C TIn this study, the effect of processing parameters, i.e., the cooling rate and pressure, on the structureproperty relationships for nucleated and non-nucleated i-PP from virgin and recycled sources was investigated. Special attention was given to the brittle-to-ductile transition of nucleated i-PP from plastic packaging waste. Differential fast scanning calorimetry and dilatometry were used to mimic industrial process conditions. From the calorimetric experiments, it was observed that under ambient pressure the mesomorphic phase was formed upon fast cooling, which was confirmed by WAXD analysis. The dilatometry results showed that by applying pressure also g-phase crystals are formed. Nucleated samples showed an increased tendency for the g-phase formation and a decreased tendency for mesomorphic phase formation. Up to now, recycled i-PP showed a brittle behavior, but this study showed that by applying a sufficiently high cooling rate, the yield stress can be reduced and a stabilization of the deformation can be obtained leading to a ductile behavior for recycled i-PP.

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Single crystals of γ phase isotactic polypropylene: combined diffraction and morphological support for a structure with non-parallel chains

Cited by 167 publications

References 20 publications

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

Nucleation and Crystallization of Low Isotatic Polypropylenes with Statistically Distributed Stereoerrors

Oriented ?-isotactic polypropylene crystallized at atmospheric pressure

Fast cooling of (non)-nucleated virgin and recycled poly(propylenes): Effect of processing conditions on structural and mechanical properties

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