Molecular characterization and rheological properties of modified poly(ethylene terephthalate) obtained by reactive extrusion

Abstract

The use of a tetrafunctional epoxy‐based additive to modify the molecular structure of poly(ethylene terephthalate) (PET) was investigated with the aim of producing PET foams by an extrusion process. The molecular structure analysis and shear and elongation rheological characterization showed that branched PET is obtained for 0.2, 0.3 and 0.4 wt% of a tetrafunctional epoxy additive. Gel permeation chromatography (GPC) analysis led to the conclusion that a randomly branched structure is obtained, the structure being independent of the modifier concentration. The evolution of shear and extensional behavior as a function of molecular weight (Mw), degree of branching, and molecular weight distribution (MWD) were studied, and it is shown that an increase in the degree of branching and Mw and the broadening of the MWD induce an increase in Newtonian viscosity, relaxation time, flow activation energy and transient extensional viscosity, while the shear thinning onset and the Hencky strain at the fiber break decrease markedly.

Sheets of branched poly(lactic acid) obtained by one step reactive extrusion calendering process: Melt rheology analysis

“…carboxyl and hydroxyl groups) can react with epoxy functional groups via ring-opening reactions, creating covalent bonds with hydroxyl groups [20]. However, a higher reactivity of epoxy towards the carboxyl groups compared to hydroxyl groups was reported in the literature [21]. This is due to the Table 2.…”

High‐melt‐elasticity poly(ethylene terephthalate) produced by reactive extrusion with a multi‐functional epoxide for foaming

“…The viscosities of these two unmodified PET remain almost consistent in the measured frequency range, which is typical of low‐molar‐mass Newtonian fluid. All the modified samples show a pronounced shear thinning behavior and a high viscosity in comparison to the unmodified PET as a result of the chain extension/branching reactions . As the content of modifier increases, shear thinning becomes more pronounced and the complex viscosity becomes higher.…”

Influence of the chain extension on the crystallization behavior of polylactide

“…Reactive Extrusion. Based on a well-documented reaction between polyester chain ends (hydroxyl and carboxylic group) and epoxy group [17][18][19][20][21], chain extension was performed through reactive extrusion on PLA 3051D with various amounts of CE (1, 2, and 3 wt%). Resulting materials were, respectively, coded as PLA_1, PLA_2, and PLA_3.…”