Effect of the vinyl modification of multi-walled carbon nanotubes on the performances of waste poly(ethylene terephthalate)-based nanocomposites

Production of high-performance nanocomposite materials obtained from unsaturated polyester resin, based on products of the waste poly(ethylene terephthalate) recycling, and modified multi-walled carbon nanotubes is presented. Di-hydroxy functional glycolysates, synthesized by catalytic depolymerization of poly(ethylene terephthalate) with propylene glycol, were used for the unsaturated polyester resin synthesis. The structure of the obtained glycolysis product and unsaturated polyester resin were characterized by using FTIR and NMR spectroscopy, and by acid, iodine, and hydroxyl value. Nanofillers were prepared by direct and two-step amidation of oxidized multi-walled carbon nanotubes. Direct amidation with diallylamine produced multi-walled carbon nanotube-diallylamine reactive nanofiller. Two-step modification with diamines: hexamethylenediamine and p-phenylenediamine gave multi-walled carbon nanotubehexamethylenediamine and multi-walled carbon nanotube-p-phenylenediamine nanofiller, respectively, whose amidation with methyl ester of linseed oil fatty acids gave multi-walled carbon nanotube-hexamethylenediamine/methyl ester of linseed oil fatty acid and multi-walled carbon nanotube-p-phenylenediamine/methyl ester of linseed oil fatty acid nanofiller, respectively. Influences of vinyl functionalities on mechanical properties of nanocomposite were analyzed from tensile strength (sigma(b)), elongation (epsilon(b)) and Young's modulus (E) determination. An increase of 97.4, 119 and 139% of sigma(b) was obtained for nanocomposites with addition of 0.25 wt.% of diallylamine, p-phenylenediamine/methyl ester of linseed oil fatty acid and hexamethylenediamine/methyl ester of linseed oil fatty acid multi-walled carbon nanotubes, respectively. Short techno-economic analysis, performed on the basis of fixed and variable unsaturated polyester resin production costs, showed satisfactory potential profit, which could be realized by the implementation of the presented technology.