Polyester based nanocomposites as matrix for lightweight reinforced composites

Polyesters like PET and PEN are very interesting as matrix for fiber reinforced composites due to their lower cost with respect to other engineering or high performance thermoplastic matrices and could extend composite applications to lower end markets. They are characterized by high glass transition temperatures (75°C for PET and 125°C for PEN, which are only few degrees lower than those of PPS and PEEK, respectively) and exhibit lower processing temperatures with respect to high performance semicrystalline polymers. To further extend the application range of such polyesters and to solve some of their weaknesses, two nanofillers (a modified MMT clay and expanded graphite) were used to prepare nanocomposites by means of the melt blending technique. The good dispersion achieved was responsible for the improved mechanical and thermal properties of the nanoreinforced matrices and a strong improvement of the thermal stability was also reached, as confirmed by thermogravimetric analysis. The foaming properties of the developed materials were investigated in order to define the compositions and the processing conditions to produce the microcellular structure needed to maximize the mechanical and thermal properties in foams. PEN/graphite nanocomposite system was selected to prepare both glass fiber reinforced composites and foamed composites, demonstrating the feasibility of the proposed approach to produce low cost/high performance lightweight composites with strong specific impact properties.