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

Abstract

For polymer composites, interfacial crystalline structures retain an important role in the macroscopic properties and are significantly affected by the processing conditions, such as the temperature, time, and external field. In this study, the transcrystallization behavior of the carbon nanotube fiber and isotactic polypropylene composite was investigated by polarizing light microscopy. The influence of the formation of the transcrystalline layer on the interfacial adhesion was evaluated by a single-fiber fragmentation test. The results show that the growth rate of the transcrystalline layer was strongly influenced by the isothermal crystallization temperature, and the interfacial shear strength was markedly enhanced by the formation of the layer. The interfacial adhesion was further increased with the gradual perfection and growth of transcrystallinity.

Interfacial crystallization of isotactic polypropylene surrounding macroscopic carbon nanotube and graphene fibers

“…[26][27][28] When the nanotube or graphene fibers are embedded in the polymer matrix, the polymer crystals grow perpendicular to the long axis of nanocarbon fibers, resulting in the oriented lamellar microstructures at interfaces that are termed as transcrystals. [29][30][31][32] Most recently, it has been reported that many semicrystalline polymers can grow transcrystals in the present of nanotube fibers and a soft-epitaxy model has been proposed. [33] Interestingly, the crystal polymorphism often occurs in the transcrystalline layer.…”

“…[29,30,34] The single-fiber pull-out tests have demonstrated that transcrystalline microstructures markedly improve interfacial adhesion and stress transfer. [31,32] Clearly, polymer transcrystallization induced by the nanocarbon fibers is a facile approach to investigate interfacial interactions between polymers and nanocarbons.…”

Macroscopic CNT fibres inducing non-epitaxial nucleation and orientation of semicrystalline polymers

“…Some questions remain as to the origin of enhanced nucleation at the fibre surface 1 , but it is well established that the TC significantly increases fibre-matrix adhesion 2 and results in an improvement in composite mechanical properties 3 . Macroscopic fibres made up of preferentially aligned carbon nanotubes (CNT) have also been shown to induce polymer transcrystallinity when embedded in isotactic polypropylene (PP), leading to a similar effect on composite mechanical properties 4 5 and often to the preferential nucleation of the γ-phase 6 . Similarly, nanoparticles used as fillers dispersed in semicrystalline polymer matrices have been widely observed to act as nucleating agents on account of their large surface-to-volume ratio.…”

Morphological and nanomechanical characterization of anisotropic interfacial characteristic regions in CF/PA6 composites at different cooling rates

“…[8][9][10] However, inconsistencies still exist in stress transfer and interfacial shear strength (IFSS), which are affected by the interphase thickness and modulus. 18 For example, a thick transcrystalline layer increases the stress transfer, probably because of the increased radial compressive stresses. 11,12 On the contrary, when the interphase is stiffer than the matrix, an increase in the interphase modulus does not always result in an increase in the stress transfer efficiency, and an optimum modulus ratio of the interphase to the matrix is obtained.…”

“…17 Apart from the interphase thickness and modulus, transcrystallinity (TC) thickness and modulus also have a significant effect on the ultimate properties of fiber reinforced thermoplastic composites. 18 For example, a thick transcrystalline layer increases the stress transfer, probably because of the increased radial compressive stresses. 19 On the other hand, an opposite effect is observed when large thermal stresses build up during the transcrystallization process, leading to a reduction in the IFSS.…”