Modeling the Enhanced Swelling Behaviors of Poly(ethylene terephthalate) Glycolysis with Mixed EG/CHDM Using Experiments and Molecular Dynamics Simulation

The swelling behaviors are critical for the effective alcoholysis of poly(ethylene terephthalate) (PET). However, understanding the swelling behaviors of PET in alcohol solvents is still limited. Hence, the interfacial and swelling behaviors for PET mixed alcoholysis with ethylene glycol/1,4-cyclohexanedimethanol (EG/CHDM) were studied by combining experiments and molecular dynamics (MD) simulations. The results of MD simulation indicate that introducing CHDM (EG/CHDM = 4:1) can promote PET swelling, increase interfacial thickness, and enhance diffusion behaviors of end groups and main chains of PET, in which EG/CHDM molecules obviously move into the bulk regions of the PET phase. These results of experimental characterization and kinetics also indicate that the introduction of CHDM (EG/CHDM = 4:1) can improve the surface roughness of PET particles and increase the effective contact area, thus accelerating the glycolysis rate of PET particles with lower activation energies compared with the pure PET glycolysis. This information provides a better understanding of the swelling behaviors of PET in the alcoholysis process.