Unprecedented dependence of stiffness parameters and crystallinity on comonomer content in rapidly cooled propylene-co-1-pentene copolymers

A thorough evaluation of the mechanical behavior exhibited by fast crystallized propylene-1-pentene copolymers synthesized in a broad range of 1-pentene compositions is here described. Different mechanical magnitudes derived from loading, creep and unloading processes in depth sensing indentation measurements are correlated to structural features. Several ordered forms are able to be developed at the composition interval analyzed in these propylene-1-pentene copolymers applying a fast cooling processing. Moreover, either a single polymorph or distinct ratios of two crystalline lattices can be obtained, depending on comonomer content. Crystallinity as well as the type of existing crystallites play a critical role in the value of those mechanical magnitudes. An atypical and unprecedented dependence of either stiffness or crystallinity on 1-pentene content is observed in these copolymers, associated with their capability of crystallizing in the trigonal form.The financial support from projects MAT2013-47972-C2-1-P and MAT2013-47972-C2-2-P (MINECO) and from project MAT2016-79869-C2-1-P (AEI/FEDER, UE) is greatly acknowledged. The synchrotron experiments were performed at beamline BL11-NCD at ALBA Synchrotron Light Facility with the collaboration of ALBA staff.Peer reviewe