The effect of transreactions on the structure and dynamic mechanical properties of 1:1 Poly(ethylene terephthalate)/Poly(ethylene 2,6-naphthalate) blends produced by cryogenic mechanical alloying

Abstract

Cryogenically alloyed poly(ethylene terephthalate) (PET)/poly(ethylene naphthalene 2,6-dicarboxylate) (PEN) blends (1:1 w/w) were subjected to melt pressing at 300degreesC for various times. The binary polymer systems so obtained were studied by means of atomic force microscopy (AFM), dynamic mechanical analysis (DMA) and proton NMR. A high level of homogenization at the nanometer scale was achieved. By changing the time of melt pressing in the range of 1-35 min, PET-PEN block copolymers with average block lengths decreasing between 10 and 2 repeat units were produced. This copolymer formation was accompanied by significant changes in the dynamic mechanical properties as revealed by the variations in the temperature dependence of the loss factor, tan delta, in the region of the glass transition. Particularly, with the increase of annealing time a transition from double to single alpha-relaxation was observed. The traditional two-phase Takayanagi model applied to these alpha-relaxation data did not provide an adequate description of the viscoelastic behavior as a function of annealing time. The results were discussed in terms of the Adam-Gibbs theory of the cooperatively rearranging regions.