Antagonistic effects on mechanical properties of microfibrillar composites with dual reinforcement: Explanation by FEA model of soft interface

Abstract

Nanofillers (NF) in microfibrillar composites support melt‐drawing and may lead to improved performance. However, antagonistic effects have also been found. The deterioration of mechanical properties by drawing in the presence of NF, as found by other authors in analogous undrawn systems, has not yet been explained. Experiments indicating the importance of NF migration between the HDPE matrix and the PA6 fibrils in the course of drawing have led to a tentative conclusion of changed crystallinity in the interfacial area resulting in a layer with reduced modulus. This was confirmed by the finite element analysis considering the formation of a “soft” interface as a result of reduced content of HDPE spherulites at the fiber surfaces. The results show a marked impact of this phenomenon on modulus. This original concept presents a basis for explaining some antagonistic effects in multicomponent polymer systems and a tool for the more rational design of composite materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44712.

Effect of graphite nanoplatelets on fracture behavior of HDPE/PA66 microfibrillar composites

“…While the addition of nanofiller decreases the J‐integral, the TIS is increased by the presence of nanofiller. At the same time, the fact that in these systems migration of GNP across the interface occurs (see 3.1) further confirms important effect of this phenomenon on MFC performance . The importance of the discussed differences in sample dimension/mold filling conditions is supported by the fact, that Charpy impact testing, done on the same samples as for J‐intergral, practically correspond to J‐integral, as shown in our previous works concerning MFC modified by nanoclay .…”

“…In all MFC with at least a part of GNP applied as the HDPE masterbatch and thus with some extent of GNP migration between the components, worse properties were found. This is ascribed to affecting of parameters of the interface by GNP localized in and/or migrating through this area, and by variation in the matrix crystallinity, as recently explained by the concept of reduced amount of spherulites near the fibre surface (soft interface) . Of importance is the fact that tensile impact strength is increased by fibrils formation but also by GNP; the contribution of GNP was also important in the undrawn system.…”

“…Moreover, differences in mechanical properties were found in spite of similar final localization of GNP in the PA66 phase [14]. This was ascribed to the effect of GNP migration on parameters of the interface [12,15].…”

Nano‐modified HDPE/PA6 microfibrillar composites: Effect of aminated graphite platelets coupling

“…This could be caused by reduction of the matrix crystallinity in the vicinity of fibers. The second effect can lead to marked antagonistic effects on final mechanical behavior . We have recently showed that NF and their migration could also negatively affect the course of drawing and solidification and thus the matrix crystallinity near the interface .…”

“…The second effect can lead to marked antagonistic effects on final mechanical behavior . We have recently showed that NF and their migration could also negatively affect the course of drawing and solidification and thus the matrix crystallinity near the interface . Therefore, NF effects must be harmonized to achieve synergic instead of antagonistic effects on mechanical behavior.…”