Transcrystallization in nanofiber bundle/isotactic polypropylene composites: effect of matrix molecular weight

Abstract

Polyamide 66 (PA 66) nanofiber bundles were first electrospun and then introduced into isotactic polypropylene (iPP) melts to prepare nanofiber bundle/iPP composites. To reveal the influences of matrix molecular weight (M n ) on the transcrystalline layer, three kinds of iPP with different M n were adopted. Polarized optical microscope was employed to investigate the transcrystallinity. In the presence of PA 66 nanofiber bundle, the heterogeneous nucleation distinctly happened in iPP melts. Moreover, the higher the iPP M n , the denser the nuclei. Both a decrease in matrix M n and an increase in isothermal crystallization temperature led to an increase in the induction time. The maximum temperature at which the transcrystalline layer can be optically observed increased with the increase of M n . The growth rate of transcrystallinity decreased with the increasing M n and crystallization temperature. Moreover, selective melting of the transcrystalline layers confirmed that it was merely composed of α form crystal for all composites.

Shear-induced interfacial sheath structure in isotactic polypropylene/glass fiber composites

“…6b. This is owing to the fact that the growth rate of a specific crystal modification in a given iPP based composite is mainly dependent on the crystallization temperature, while the imposed mechanical history prior to the crystallization has no significant influence on it [41]. Furthermore, one can obtain the crystallization induction periods from the intercept of the straight lines in Fig.…”

Transcrystallinity and relevant interfacial strength induced by carbon nanotube fibers in a polypropylene matrix

“…Generally, the mechanical properties of fiber‐reinforced polymer composites not only depend on the properties of the fibers and polymer matrix, but they also depend on the interfacial adhesion between the fibers and the matrix. In semicrystalline polymer composites, the fibers can act as orientation templates for polymer crystallization . When the fiber nucleates the crystallization of the polymer with its massive nuclei, the restricted development of the spherulites occurs, and the crystal grows unidirectionally normal to the fiber axis.…”

Surface interaction induced transcrystallization in biodegradable poly(butylene succinate)-fibre composites

“…In polymer/fibre systems, fibres generally act as a nucleating agent and induce highly dense nuclei along the fibre axis. The active nuclei has so high density that it has the advantages of hindering the lateral extension of spherulites and forcing them to grow in the direction perpendicular to the fibre, which results in a transcrystalline layer finally [2][3][4][5][6][7]. The formation mechanisms of TC may be summarized as follows: epitaxy, chemisorption, and stress (or strain).…”