Sorption Properties of PET Copolyesters and New Approach for Foaming with Filament Extrusion Additive Manufacturing

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Additive Manufacturing

Background:

• Investigates the mass transfer of binary esters of acetic acid in various polyesters, including polyethylene terephthalate (PET), polyethylene terephthalate with high glycol modification (PETG), and glycol-modified polycyclohexanedimethylene terephthalate (PCTG).
• Highlights the significant difference between sorption and desorption rates of these esters within the polyester matrix.

Purpose of the Study:

• To study the mass transfer dynamics of binary esters in PET, PETG, and PCTG.
• To explore the potential of accumulated esters as physical blowing agents in additive manufacturing.
• To produce and characterize novel, non-brittle polyester foams using additive manufacturing.

Main Methods:

• Studied the sorption and desorption kinetics of acetic acid esters in PET, PETG, and PCTG at varying temperatures.
• Utilized the accumulated ester as a physical blowing agent in the filament extrusion additive manufacturing (AM) process.
• Varied AM process parameters to control foam density and characterize the resulting material properties.

Main Results:

• Observed significantly lower desorption rates compared to sorption rates, leading to ester accumulation (e.g., 5 wt.% in PETG at 20 °C).
• Successfully produced PETG foams with densities ranging from 150 to 1000 g/cm³ via AM.
• The resulting foams exhibited improved properties, notably a lack of brittleness characteristic of conventional polyester foams.

Conclusions:

• The differential sorption-desorption kinetics of acetic acid esters enable their controlled accumulation in polyesters.
• This accumulated ester can be effectively utilized as a blowing agent for producing functional foams via additive manufacturing.
• Additive manufactured PETG foams offer a promising alternative to traditional brittle polyester foams, with tunable densities and enhanced mechanical characteristics.