Study of viscoelastic damage and micromechanism of polyurethane in freeze-thaw cycle environment

To investigate the viscoelastic properties of polyurethane under the action of freeze-thaw cycles. Polyurethane specimens excessed examined using atomic force microscopy, nanoindentation tests, and differential scanning calorimetry (DSC) after 0, 3, 5, and 7 freeze-thaw cycles. The molecular structure and property damage process was also investigated using molecular dynamics. The findings of molecular simulations revealed that the freeze-thaw cycle causes the aggregated system to disperse within the polyurethane molecule, resulting in an increase in its modulus. The testing findings revealed that the roughness of the polyurethane surface steadily decreased as the number of freeze-thaw cycles increased, as did the adhesion to various substrates. In the test results of nanoindentation, the elastic modulus showed an increasing trend, and the contact indentation depth gradually decreased. This suggests that freeze-thaw cycles impair polyurethane's elastic and flexible characteristics. The freeze-thaw cycle raised the melting temperature of polyurethane in the differential scanning calorimetry experiment findings. This confirms the experimental findings of increased elastic modulus and hardness in nanoindentation. In conclusion, further study may be undertaken to change polyurethanes by adding water-repellent compounds to them, which can be accomplished by modifying the molecular structure inside the polyurethanes to withstand environmental harm. The findings of this research lay a theoretical foundation for the resilience of polyurethane materials to environmental deterioration in a variety of industries, such as construction, where freeze-thaw cycles exist.