Dominating factor of strain-induced crystallization in natural rubber

Alice Gros (1) , Masatoshi Tosaka (2) , Bertrand Huneau (1) , Erwan Verron (1) , Sirilux Poompradub (3) , Kazunobu Senoo (4)

1 Matériaux, Procédés et Technologie des Composites
2 Kyoto University
3 Chulalongkorn University [Bangkok]
4 Kobe University

The contribution of entropy change due to stretching of polymer chains in promoting crystal nucleation is theoretically derived for strain-induced crystallization of natural rubber. The results of theoretical calculation are compared with experimental results obtained by fast time-resolved wide-angle X-ray diffraction. Usual values of surface free energies corresponding to chain-folded nuclei lead to theoretical results far from experimental measurements. Because the discrepancy comes from the large activation energy of nucleation even after the stretching of polymer chains, additional contribution of reduced surface free energies due to the formation of bundle-like nuclei was taken into account. This treatment allows to faithfully reproduce experimental results and then to conclude that nuclei formed in natural rubber during stretching are of bundle-like type. Moreover, it reveals that surface energies have a greater effect on the decrease of critical free energy than the change in entropy due to deformation.

Mots clés: Nucleation; Crystallization rate; Shish-kebab structure

Domaines: Matériaux et structures en mécanique [physics.class-ph]

Alice Gros, Masatoshi Tosaka, Bertrand Huneau, Erwan Verron, Sirilux Poompradub, et al.. Dominating factor of strain-induced crystallization in natural rubber. Polymer, 2015, 76, pp.230-236. ⟨10.1016/j.polymer.2015.08.058⟩. ⟨hal-01276181⟩