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


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

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.

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