Impact of the Topography of Fiber Surface on the Interfacial Crystallization Behavior of Poly(lactide)

In order to determine the effect of the fiber surface topography on the polymer interfacial crystallization behavior, the nucleation processes of poly(lactide) (PLA) on a series of fibers with different surface topographies were observed in situ by polarized optical microscopy (POM). The fibers were obtained by introducing silica (SiO₂) particles of different sizes onto glass fibers. It is found that the interfacial crystalline morphology of PLA induced by the fibers is a hybrid shish-calabash (HSC) superstructure after the isothermal crystallization process. And the fiber-induced nucleation rate increases with the introduction of SiO₂ particles. Based on the heterogeneous nucleation theory, two parameters, the interfacial free energy barrier, Δσ, and the pre-exponential factor, I₀, were obtained to quantitatively assess the nucleation ability of different fibers. The results show that Δσ decreases with increasing fiber roughness, along with the reduction of SiO₂ particle size. And the linear relationship is influenced by the relative concentration of SiO₂ particles on the fiber surfaces. Combining the results of POM and Δσ suggests that a relatively small value of Δσ is only a needed condition to determine the high apparent nucleation ability of a fiber. In addition, by minimizing the chemical structure factors in the nucleation system, a positive linear relationship between Δσ and ln I₀ can be established.