Structure and mechanical property relationship of PCL, its nanocomposites, and its graft copolymer

Abstract

Polycaprolactone (PCL) is a biodegradable polyester that is very tough and has a melting point of around 60°C. PCL becomes soft in warm water and can be shaped; therefore, it is proper for use as a boil and bite mouth guard. This work aims to study the relationship of the properties of pure PCL and PCL with added rigid and soft parts for use as mouth guard materials. The different molecular weights affected the mechanical properties and crystallization behavior of the PCL. The impact strength of the PCL increased as the molecular weight increased. The lowest molecular weight PCL (M[subscript w]∼17,000) Showed the highest crystallinity and T[subscript c] onset. Its nanocomposites and graft copolymers represent the addition of the rigid part (Organoclay) and the soft part (Ethylene Vinyl Acetate: EVA), respectively. The moduli of the PCL nanocomposites were higher than that of the pure one, and thermal stability was also enhanced. On the other hand, its graft copolymers have lower modulus, and the thermal stability decreased clearly from 370°C to around 300°C. These graft copolymers also showed an interesting property: a decreasing of the melting point from pure PCL and EVA, which brings about more viscoelasticity, allowing better shaping of the mouth guard materials at lower temperature.