Influence of the morphology on the impact fracture behaviour of iPP/EPR blends

Grein, C.; Béguelin, Ph.; Plummer, C. J. G.; Kausch, H. H.; Tézé, L.; Germain, Yves

doi:10.1016/s1566-1369(00)80028-x

Cited by 7 publications

(3 citation statements)

References 10 publications

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“…The broken samples displayed in Figure 13 show the SEM measured radius, r p , of plastic zone as a function of β‐phase content. A slight enlargement of the plastic zone size can be observed as the β‐phase content increases for both filled and unfilled samples, in agreement with previous findings from dart23 or CT impact testing 24. However, quite novel data have been found regarding the specific energy dissipated in the plastic zone that significantly increase in parallel to the β‐phase content for unfilled samples, as shown in Figure 14.…”

Section: Resultssupporting

confidence: 90%

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Influence of the β‐crystalline phase on the mechanical properties of unfilled and calcium carbonate‐filled polypropylene: Ductile cracking and impact behavior

Labour

Vigier

Séguéla

et al. 2001

J Polym Sci B Polym Phys

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The ␤-crystalline form of isotactic poly(propylene) (PP) has been long recognized to have a greater mechanical absorption capacity than the ␣-crystalline form. This is of major importance for improving impact properties and crack resistance of injection-molding parts. Unfilled PP samples together with calcium carbonate-filled PP samples having various ␤/␣-phase ratios, with nearly constant morphological parameters, have been investigated from the standpoint of ductile crack propagation and impact behavior. The presence of the ␤-crystalline phase turned out to improve both properties. The ␤ spherulites are notably more prone to craze initiation than ␣ spherulites that display a propensity for cracking. Subsequent crack propagation appears to be faster in the latter ones. The plastic zone ahead from the crack tip broadens, and the specific plastic energy increases with increasing ␤-phase content. The lower elastic limit of the ␤ phase is likely to promote the early crazing. However, the suspected higher density of tie molecules in ␤ spherulites provides more numerous and stiffer microfibrils. The impact strength of PP is also improved by the presence of ␤ crystals as a result of greater energy-absorption capabilities. However, filled samples turned out insensitive to the ␤ phase. A discussion is made about the origins of the ␤-phaseinduced improvement of the mechanical properties. The possible role of the ␤ 3 ␣ transition is also explained.

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Section: Resultssupporting

confidence: 90%

“…Irrespective of the actual role of the β → α phase change in PP toughening, there is plenty of evidence that β PP is much more craze prone than α PP 22–24, 28, 40. Cavitation generally originates from negative hydrostatic stresses.…”

Section: Discussionmentioning

confidence: 99%

Influence of the β‐crystalline phase on the mechanical properties of unfilled and calcium carbonate‐filled polypropylene: Ductile cracking and impact behavior

Labour

Vigier

Séguéla

et al. 2001

J Polym Sci B Polym Phys

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“…Its potential as a macroscopic toughness indicator has already been mentioned in several studies. Quantitative or at least qualitative relationships between the strengths of the principal or secondary relaxations and the fracture resistances have been found, [1][2][3][4][5][6][7][8][9][10][11][12] although the small strain, linear viscoelastic measurements in DMA differ fundamentally to the large strain, nonlinear behavior observed under impact conditions.…”

Section: Introductionmentioning

confidence: 99%

Potential and limits of dynamic mechanical analysis as a tool for fracture resistance evaluation of isotactic polypropylenes and their polyolefin blends

Grein

Bernreitner

Gahleitner

2004

J of Applied Polymer Sci

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Potential and limits of dynamic mechanical analysis (DMA) as a tool for fracture resistance evaluation of isotactic polypropylenes and their polyolefin blends are presented. A minimum of information about the materials under investigation is a prerequisite to interpret the DMA traces in a right way. Although DMA is, in general, a powerful method to rank materials in term of toughness, care should be taken with (1) nucleated materials (where both intensity and strength of molecular relaxations need to be taken into account in material evaluation) and with (2) visbroken (i.e., peroxyde treated) grades. Except for these cases, the strengths of the principal or secondary molecular relaxation evaluated by DMA and the Charpy impact toughness correlate quantitatively when all the grades of a series exhibit unstable crack propagation. When changes in the macroscopic mode of fracture or in blend morphology occur, only qualitative correlations remain possible.

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Impact modified isotatic polypropylene with controlled rubber intrinsic viscosities: Some new aspects about morphology and fracture

Grein

Bernreitner

Hauer

et al. 2002

J of Applied Polymer Sci

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ABSTRACT:The influence of the molecular weight of the dispersed phase of ethylene-propylene rubber modified isotactic polypropylene (iPP/EPR) reactor blends was studied in a systematic way by varying their intrinsic viscosity (IV) from 1.7 to 6 dg/L while keeping the matrix melt flow rate (MFR) constant. Standard Charpy measurements were completed by a continuous analysis of the impact properties over a wide range of temperatures at fixed test speed. As expected, the higher the IV, the tougher the iPP/EPR blends. However, ductile-brittle transitions as key mechanical descriptors did not correlate linearly with M w , suggesting the macroscopic behavior of the blend to be controlled primarily by the morphology of the EPR particles. Moreover, strong correlations were found between impact mechanical properties, amount of stress-whitening, and strength of the molecular relaxations estimated from dynamical mechanical analysis.

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Influence of the morphology on the impact fracture behaviour of iPP/EPR blends

Cited by 7 publications

References 10 publications

Influence of the β‐crystalline phase on the mechanical properties of unfilled and calcium carbonate‐filled polypropylene: Ductile cracking and impact behavior

Influence of the β‐crystalline phase on the mechanical properties of unfilled and calcium carbonate‐filled polypropylene: Ductile cracking and impact behavior

Potential and limits of dynamic mechanical analysis as a tool for fracture resistance evaluation of isotactic polypropylenes and their polyolefin blends

Impact modified isotatic polypropylene with controlled rubber intrinsic viscosities: Some new aspects about morphology and fracture

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