Water vapor absorption of Polyvinyl Butyral (PVB) interlayer for laminated glass

Abstract

The absorption of water vapor from external environments into the Polyvinyl Butyral (PVB) interlayer is a significant cause of humidity aging, property degradation, reliability problems, and safety concerns in laminated glass. Existing literature reports inconsistent estimates regarding the material’s sorption and diffusivity properties, as well as the effects of humidity and temperature. Therefore, this work aims to explore the rules and mechanisms of how external factors affect water vapor absorption properties. Dynamic vapor sorption tests were conducted at various temperatures ranging from 25 to 65 °C and humidity levels from 0 % to 95 % relative humidity (RH). The results indicate that the water vapor absorption in the PVB interlayer is closely related to the polymer network via the hydrolysis of the hydroxyl groups and the formation of water clusters in the region rich in vinyl alcohol, which would, in turn, negatively impact the interlayer network. A notable finding is the estimated mean size of water clusters, ranging from 1 to approximately 2.1, across humidity levels from 5 % RH to 95 % RH. This leads to a dependence of diffusivity on water content. To account for this, an additional term was added to the Arrhenius equation to include the effect of water content. Predictive models for sorption and diffusivity have been developed and validated using existing literature on commercial PVB interlayers. The findings are expected to enhance understanding and prediction of the degradation of interlayers and laminated glazing exposed to long-term humidity aging.