Microstructure Changes in Polyester Polyurethane upon Thermal and Humid Aging

Area of Science:

• Polymer science
• Materials science
• Chemical engineering

Background:

• Estane 5703, a polyester urethane, is susceptible to degradation under environmental stress.
• Understanding microstructural changes is crucial for predicting material lifespan and performance.

Purpose of the Study:

• To investigate the effects of humidity and thermal aging on the microstructure of Estane 5703 films.
• To elucidate the molecular mechanisms behind observed degradation.

Main Methods:

• Small-angle neutron scattering (SANS) for nanoscale structure analysis.
• Fourier transform infrared spectroscopy (FTIR) for chemical bond analysis.
• Gel permeation chromatography (GPC) for molecular weight determination.
• Differential scanning calorimetry (DSC) for thermal property analysis.

Main Results:

• Increased humidity and aging time led to larger domain sizes and interdomain distances.
• Polyurethane chain shortening (hydrolysis) was observed, correlating with increased aging.
• Hydrolysis promoted hard segment organization into domains, increasing phase separation.
• A decrease in glass transition temperature and increased soft segment crystallization were noted.

Conclusions:

• Hydrolysis of ester links in polybutylene adipate residues is a key degradation pathway.
• This hydrolysis facilitates hard segment organization, increasing domain size and phase separation.
• The study provides molecular to nanoscale insights into Estane degradation under humidity and thermal stress.