Spectroscopic and Rheological Cross-Analysis of Polyester Polyol Cure Behavior: Role of Polyester Secondary Hydroxyl...

Area of Science:

• Polymer Chemistry
• Materials Science
• Rheology

Background:

• Understanding polymer cure behavior is crucial for material performance.
• Polyester polyols and isocyanate cross-linkers are widely used in coatings and adhesives.
• Molecular architecture significantly influences polymer network formation.

Purpose of the Study:

• To investigate the effect of secondary hydroxyl content in polyester polyols on the sol-gel transition.
• To correlate chemical conversion and microstructural evolution during the curing process.
• To examine deviations from classical gelation theory.

Main Methods:

• Dynamic rheology was employed to monitor the sol-gel transition.
• Time-resolved variable-temperature Fourier-transform infrared spectroscopy (FTIR) tracked chemical conversion.
• Arrhenius analysis was used to determine activation energies for gelation and reaction kinetics.

Main Results:

• A percolated microstructure was observed in all studied resin systems.
• Activation energies for gelation and reaction kinetics were dependent on secondary hydroxyl content.
• Significant deviations from Flory-Stockmayer gelation theory were observed, termed gel point suppression.

Conclusions:

• Secondary hydroxyl content in polyester polyols is a key factor influencing cure kinetics and network formation.
• The observed gel point suppression suggests limitations of classical gelation models for these systems.
• A qualitative model was proposed to explain the observed deviations, aligning with existing literature.