Water Clustering in Polyvinyl Butyral (PVB): Evidenced by Diffusion and Sorption Experiments

Area of Science:

• Materials Science
• Polymer Science
• Physical Chemistry

Background:

• Polyvinyl butyral (PVB) is a transparent amorphous polymer used for surface protection.
• Water transport and retention in PVB significantly influence its adhesion properties.
• Understanding water-PVB interactions is crucial for applications like glass and photovoltaic panel protection.

Purpose of the Study:

• To experimentally investigate water diffusion and sorption in PVB across various temperatures and humidity levels.
• To determine the relationship between the diffusion coefficient, temperature, and vapor concentration.
• To quantify the activation energy and heat of solution for water in PVB.

Main Methods:

• Spectroscopic measurements to analyze water diffusion.
• Gravimetric measurements to assess water sorption.
• Dynamic vapor sorption experiments to study sorption dependence on humidity and temperature.

Main Results:

• The diffusion coefficient of water in PVB shows a clear dependence on temperature and vapor concentration.
• Activation energy for water diffusion was determined.
• Sorption is strongly dependent on hydroxyl (-OH) group concentration.
• Water solubility in PVB decreases as temperature increases.
• The heat of solution for water in PVB was calculated.

Conclusions:

• Water diffusion and sorption in PVB are complex processes influenced by temperature, humidity, and polymer structure.
• Water molecules organize into clusters within PVB, mediated by hydrogen bonding.
• Thermodynamic data align with models describing water-induced clustering in polymers.