Eur. Phys. J. E 4, 459-465
The effect of
,
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
crystalline structure
of polypropylene (PP) on its mechanical properties, it is necessary to
prepare samples with variable 
/
-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 nucleating agent in order to achieve these conditions. Then study
of the effect of the -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 -phase content. Besides, Young's modulus
and the yield stress in tensile tests decrease slowly with the -phase
content. Finally, these results are analysed taking account the
differences in structure of the and 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
