The Effect of Transcrystallinity on the Interface of Green Flax/Polypropylene Composite Materials

Abstract

In recent years there has been an increasing interest in using natural fibres as potential reinforcements for polymers. The introduction of fibres such as flax in a semicrystalline thermoplastic matrix such as iPP (isotactic polypropylene) has been shown to lead to the development of transcrystallinity. The presence of an anisotropic layer such as transcrystallinity in the composite material may in turn have a profound effect on the mechanical behaviour of the interface. In this study the role of transcrystallinity has been investigated in green flax (that is flax as received direct from the crops)/iPP by means of the fragmentation test. The results are discussed in terms of previously reported results for treated flax fibres (dew retted)/iPP. Transcrystallinity leads to a stronger interface in green flax/iPP, and its thickness affects the interfacial strength, with thinner transcrystalline layers giving a stronger interface. An examination of the mode of failure at the interface after the fragmentation test also supports the conclusion that the transcrystalline interface is stronger than the spherulitic interface in green flax/iPP composites.