Nano and hybrid composites based on poly( ethylene terephthalate): blending and characterization

Abstract

This study addresses the characterization of nano and hybrid poly(ethylene terephthalate) (PET)-based composites obtained by injection molding process. The aim is to demonstrate the effect of adding various nanoclay amounts on the morphology and mechanical behavior of unreinforced and glass fiber (GF) reinforced PET matrices. Also, it addresses the possibility of preserving the mechanical response of the composites while decreasing the amount of GF. Nanocomposites were prepared by adding 0.5, 1.0, 3.0, and 5.0 wt% of montmorillonite to the unreinforced PET matrix; hybrid composites were also prepared by adding the aforementioned nanoclay amounts to the 20% GF reinforced PET (PET20). A 35% GF reinforced PET was used as a reference material for the mechanical properties comparison. X-ray diffraction and transmission electron microscopy studies revealed that the characteristic (001) peak of the nanocomposite obtained by extrusion shifted to the lower angle region stating an intercalated structure. The subsequent injection molding process altered the morphological structure of the composites, reducing the basal distance for small loadings of nanoclays. Differential scanning calorimetry showed that the addition of nanoclay increases the degree of crystallinity and decreases the cold crystallization temperature of both PET systems. Full exfoliation of the nanoclay was not attained but the nanoparticles dispersion in combination with their intercalated morphology improved the mechanical properties of PET composites optimally for 1% of incorporation. The envisaged mechanical properties of PET20 were improved (initial modulus 22%, stress at yield 14%, and strain at break 4%) for the aforementioned optimal value of incorporation.