Relaxation behavior of poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6‐dicarboxylate) blends prepared by cryogenic blending

Abstract

A method including cryogenic grinding, melt pressing from the molten state, and quenching was used to prepare blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) in which the two phases were highly dispersed. The effect of melt‐pressing times on the thermal properties and relaxation behavior of PET/PEN films were characterized with differential scanning calorimetry and dielectric spectroscopy. For short melt‐pressing times, two glass‐transition, two crystallization, and two melting peaks were observed, indicating the presence of PET‐rich and PEN‐rich phases in these blends. Longer melt‐pressing times revealed a single glass transition and a single α‐relaxation process, showing that PET–PEN block copolymers were likely to be formed during the melt pressing. The experimental findings were examined in terms of the transesterification reactions between the blend components, as revealed by 1H NMR measurements. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2570–2578, 2002

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

“…Melt mixing of PET and PEN results in the formation of block copolymers by means of transesterification 1–19. Generally, transesterification reactions in molten blends of polyesters may advance via two various chemical pathways – inner‐inner or inner‐outer 25.…”

“…Materials and sample preparation were the same as reported in detail previously 19. Summarizing, the corresponding amounts of premixed PET and PEN pellets (1:1 w/w, 56:44 mol/mol) were cryogenically alloyed in a high‐speed grinding device equipped with a 40 μm sieve.…”

“…In doing so, we recorded the storage modulus E′ (or, the real component of the complex modulus) as a function of temperature, and also the loss factor tan δ = E″ / E′ , E″ being the loss modulus, or the imaginary component of the complex modulus. The results obtained were compared with tan δ = f ( T ) curves derived from DS data obtained with the same PET/PEN blends 19…”

“…In summary, for a successful in‐depth study on the impact of transreactions on the properties of PET/PEN blends one needs completely amorphous thin films in which the components are intimately homogenized with no chemical interaction between them. A method answering to these requirements was recently proposed 19. It involves cryogenic grinding, melt pressing at 300 °C for various times and quenching.…”

Study of nanoclay blends based on poly(ethylene terephthalate)/poly(ethylene naphthalene 2,6-dicarboxylate) prepared by reactive extrusion

“…As compared to other methods, the stacks do not go to the final exfoliation through the intercalation step, but they are directly exfoliated at the final step. This constitutes one of the most relevant points of this new method [16]. The method that allows the preparation of polymer-clay nanocomposites is described in detail in the experimental section.…”