This chapter discusses the supermolecular structure and interphase phenomenon in composite-reinforced natural fibers. We analyzed the formation of the polymorphic forms in polypropylene (PP) matrix. It was found that in the composites with natural fibers, the hexagonal form arises when the fibers are in motion in relation to the polymeric matrix. of Moving temperature of the natural fibers was found to have a strong influence on the content of the hexagonal modification. If the temperature of the moving fibers is low, then the amount of β-PP significantly increases. The content of β-PP also depends on the rate of the moving of fibers; however, the chemical modification of the natural fiber’s surface reduces the content of this form. Also, the processing conditions play an important role for structural changes in PP matrix.
Further, this chapter provides a survey about the formation of a transcrystalline layer in the composite system. The occurrence of transcrystallization was found to strongly depend on the type of chemical treatment of the fiber surface. Predominant nucleation ability was found for unmodified fibers. However, chemical modification of fiber surface slightly depressed the nucleation of polypropylene matrixes.
The influence of physical and chemical treatment methods of natural fibers on mechanical properties was analyzed also. Additionally, the mechanical and other physical properties of the composite are generally dependent on the length, content, and dispersion of fibrous filler and processing parameters.