Semi-crystalline polymers, with typical lamellar structure built from alternatively packed crystalline layers and amorphous layers, exhibit a complex behavior during plastic deformation. In general, an isotropic polycrystalline structure gradually transforms to a highly oriented fibrillar structure with the chain axis preferentially aligned along the drawn direction during stretching. It is generally believed that the structure of polymer fibril is very stable. Only inter-fibrillar slip proceeds during further deformation. For polymers with stress induced crystal transition, some open questions still need to be answered, such as on which stage of plastic deformation does the a-� transition take place, and more importantly, what happens on the lamellar structure during crystal transition.In present talk, crystal transition was observed during tensile deformation of poly(butylene succinate) (PBS). An increase of long period was identified during stretching. The step-cycle deformation measurement showed that the long period(L) reversibly increased under stress and decreased upon removing stress. The contribution of crystalline layer thickness (lamellar thickness) and amorphous layer thickness to the long spacing was discriminated by correlation function analysis. The variation of the amorphous layer thickness was partially recoverable while the variation of lamellar thickness was nearly fully recoverable. The reversible lamellar thickening was shown to mainly stem from the reversible crystal transition: the repeating length in chain direction in the � crystal is 9% longer than that in a form due to the conformation change. Reversible lamellar thickening mechanism was also confirmed in another polymer (polyethylene succinate, PES).

Reversible lamellar thickening accompanied with stress induced reversible crystal transition in poly(butylene succinate)

248th National Meeting (2014)

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