Rheological and Thermal Behavior of Recycled PET Modified by PMDA

Abstract

In this work pyromellitic dianhydride (PMDA) was used as the chain extender to increase the molecular weight of the recycled poly(ethylene terephthalate) (R-PET) and improve the rheological properties of the R-PET. The reaction was performed in a Brabender torque rheometer. The rheological and thermal characterization were performed by means of a fusion index instrument and a differential scanning calorimeter (DSC ) to compare the effectiveness of the chain extending reaction of different percentages of PMDA. The experimental results showed that compared with the unmodified R-PET, the addition of PMDA decreased the melt flow index and increased the viscosity of the R-PET. In addition, increased crystallization temperatures ( ) were observed with the modified R-PET. It was also found that the modified R-PET with the concentration of 1.0wt% PMDA exhibited the lowest MFI.

Evaluation of PET recyclability and characterization of modified reprocessed‐PET for industrial application

“…45 Wang et al confirmed that the PMDA content increases above 1.0 wt%, intensifying degradation leads to a decrease in molecular weight and an increase in MFI. 4 Therefore, the PMDA content was set between 0.25 and 1.0 wt%. In Figure 6, the torque value of the modified rP-PET improved as compared with that of rP, and this could be attributed to the formation of chain entanglement increasing the weight average molecular weight (M w ) and molecular weight distribution (MWD).…”

“…28 In several studies, it has been reported that the melt viscosity and rheological properties of PET modified by ADR have been improved. 4,8,22,47 Two-step reaction for chain extension between PET and PMDA was required, and in the first step, a ring-opening reaction between the hydroxyl group of PET and the anhydride functional groups of PMDA formed two carboxyl groups. 47 At the second step, the hydroxyl group of PET additionally reacted with PMDA.…”

“…11,22,26 The chain extension reaction could introduce the rigid benzene ring group in the structure expanding the molecular chain, and an increased degree of branching could reduce the chain segment mobility affecting the thermal properties. 3,4,30 The T m and T c are also affected by the crystal size and chain branching. 19,22,26,30 With PET modification, it was found that T c and T m decreased as the content of CE increased while no significant difference in X c was observed.…”

“…Polyethylene terephthalate (PET) is a cost-effective plastic that has excellent physical properties, such as thermal stability, transparency, strength, chemical resistance, processability, and barrier properties. [1][2][3][4][5][6][7] For these reasons, PET is used in a variety of packaging applications, such as bottles, films, fibers, and so forth. [8][9][10][11][12][13][14] However, the environmental issues generated by the increase in plastic usage and packaging waste have become major global problems.…”

Extrusion and characterization of recycled polyethylene terephthalate (rPET) filaments compounded with chain extender and impact modifiers for material-extrusion additive manufacturing

“…More studies on the rheological behavior showed that adding PMDA increased the rPET molecular chain length and branching through the chemical reactions with the end groups of rPET. The melt flow index and melt strength of the rPET mixed with PMDA were investigated by Wang et al 23 and a decrease in the melt flow index and an increase in the melt strength were noted as the weight percent of PMDA increased from 0.25 to 1.25 wt%. Hirach et al 22 also noted an increase in the viscosity and molecular weight when different weight fractions of PMDA ranging from 0.1 to 0.3 wt% were added to PET.…”