Crystallization-induced formation of rigid amorphous fraction

Semicrystalline polymers contain amorphous fractions of different mobility that develop upon crystallization or ordering. The restraints created by the ordered phase, together with the entanglements present in the amorphous areas, set up a disordered nanophase called rigid amorphous fraction (RAF). The RAF is located at the crystal/amorphous boundary and mobilizes at temperatures higher than the glass transition of the mobile amorphous fraction. An updated three-phase description of semicrystalline polymers is here depicted, with special attention given to the link between RAF vitrification and crystallization kinetics. The methods commonly used to quantify the RAF, and the influence of thermal history and crystal structure/morphology on the RAF, as well as the influence of RAF on materials properties, are presented and discussed in this review.