Weathering action on thermo-viscoelastic properties of polymer interlayers for laminated glass

• The effects of weathering have been produced on small laminated glass elements.
• Humidity action, solar radiation and thermal variation were simulated in laboratory.
• The use of small specimens enabled reproducibility of the mechanical tests.
• The effects of weathering on the constitutive response of interlayer were evaluated.
• Hypotheses on the structural changes of the material at molecular scale were made.

Mechanical properties of interlayer polymers are recognized to be essential for a correct design of laminated glass structures. Although several researches have been carried out on the consequences of weathering actions on a laminated glass, few quantitative data on the properties of polymers are available. The response of structures to a long duration load is therefore evaluated taking into account the effects of viscosity of the interlayer, but in the hypothesis that the interlayer material does not degrade over time. In this paper the results are reported of an experimental analysis of the thermo-viscoelastic properties of polyvinyl butyral used as interlayer of laminated glass, subjected to weathering actions (humidity, thermal cycles and UV radiation). The results were interpreted in the light of the connection between microstructure and rheology of polymers, and highlight two different damage mechanisms, promoted in different extents by the different weathering actions.