Effect of Nanographite Type on Structure and Mechanical Properties of Hybrid Composites of Poly(ethylene terephthalate) Filled with Short Glass Fibers and Nanographite

Abstract

Abstract—The paper presents the results of comparative studies of the structure and rheological and strength properties of poly(ethylene terephthalate) (PET) filled with hybrid micro- and nanofillers—short glass fibers (GF) and nanographite (nG) of two types—expanded graphite (EG), prepared by hydrolysis of sodium-intercalated graphite, and thermally expanded graphite (TEG), prepared by thermal shock treatment of sulfuric acid intercalated graphite in air. The GF concentration varied within 15–60 wt %, and that of nG, from 0.4 to 3 wt %. The composites were produced by reactive compounding using a corotating twin-screw extruder (screw diameter 35 mm, L/D = 40). It is established that the nG preparation method strongly influences the structure and properties of the composites. EG, unlike TEG, displays improved dispersibility in the polymer, helps to increase the proportion of GF with an average length exceeding the critical length, and reduces PET degradation, which increases the strength characteristics of PET/GF/EG hybrid composites in comparison to PET/GF/TEG at a high GF content of 45–60 wt %. The hybrid composites also demonstrate accelerated PET crystallization and a synergetic increase in the elasticity modulus.