2020 Impact factor 1.890
Soft Matter and Biological Physics


Eur. Phys. J. E 4, 459-465

The effect of $\mathsf{\alpha}$, $\mathsf{\beta}$ crystalline structure on the mechanical properties of polypropylene

Ph. Tordjeman1, C. Robert2, G. Marin3 and P. Gerard2

1  Laboratoire des Verres, Université de Montpellier 2, CC 69, 34095 Montpellier Cedex 5, France
2  Groupement de Recherches de Lacq, AtoFina BP 34, 64 170 Lacq, France
3  Laboratoire de Physique des Matériaux Industriels, UPPA, avenue de l'université, 64 000 Pau, France

tordjeman@ldv.univ-montp2.fr

(Received 18 September 2000 and Received in final form 19 December 2000)

Abstract
In order to study the effect of the $\alpha, \beta$ crystalline structure of polypropylene (PP) on its mechanical properties, it is necessary to prepare samples with variable $\alpha $/$\beta $-phase content but with constant crystallinity and constant spherulite size. With this objective, heat treatment was first defined to be applied to an isotactic PP containing a $\beta $ nucleating agent in order to achieve these conditions. Then study of the effect of the $\beta $-phase content on the tensile properties and fracture behaviour has been done at room temperature. The mechanical properties at fracture were assessed by three-point bending tests and were analysed on the basis of the "Essential Work of Fracture"(EWF). The results show that the elongation at fracture under tensile stress and the "near" Plane-Strain Essential Work of Fracture, wIe, increase substantially with the $\beta $-phase content. Besides, Young's modulus and the yield stress in tensile tests decrease slowly with the $\beta $-phase content. Finally, these results are analysed taking account the differences in structure of the $\alpha $ and $\beta $ spherulites.

PACS
81.05.Lg - Polymers and plastics; rubber; synthetic and natural fibres; organometallic and organic materials.
62.20.Mk - Fatigue, brittleness, fracture and cracks.
81.70.Bt - Mechanical testing, impact tests, static and dynamic loads.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001