Soft materials are a promising alternative to design and fabricate passive de-icing systems, considering the low ice adhesion strength values reported in the literature. Nevertheless, the interwoven effects of surface and mechanical properties have been not elucidated in terms of their individual contribution to the ice adhesion performance. In this work, the wetting and mechanical properties of soft PDMS with different lubricant content were analyzed by using different strategies: sessile drop, indentation and rheology experiments. The collected information is used to understand its relation with the shear ice adhesion results. First of all, the visualization of fracture events and its synchronization with the adhesion force measurement by ice push tests allowed to identify three different de-icing mechanisms depending on the size of the ice block: (i) Single detachment, (ii) stick-slip and (iii) interfacial slippage. The outcome depends both on the surface and on the size of the ice block. An increasing amount of lubricant decreases the force necessary for the initial ice detachment, which is an advantage in single detachment regime, where the small ice blocks are completely separated at the end of the experiments. When bigger ice blocks are considered, the silanol dangling ends molecules that migrated to the interface due to the contact with water, promotes the reattachment of the ice block, inducing a change from the stick-slip to the interfacial slippage mechanism, where the ice is more likely to remain attached after the de-icing experiment. More in details, on one hand advancing and receding contact angle measurements indicated the importance of considering the migration of low surface energy uncrosslinked chains to the interface during contact with water, leading to lubrication of the ice-substrate interface. This implies that two materials with different lubricant amounts may present similar contact angles after exposure to water (time scale 10 s). However, the lubricant amount plays a role in determining both the adhesion regime and the adhesion force, nevertheless, contact angles alone are not enough to predict ice adhesion. On the other hand, ice adhesion decreases for surfaces with decreased complex shear modulus G*. Moreover, one important finding is that the ice adhesion strength, calculated as F/A, is not a material property, since it is affected by the experimental parameters, like the ice block diameter in our tests: as such, F/A should only be used for comparing ice adhesion performance of different surfaces tested in the same experimental conditions.
Anny, O., Antonini, C., Tagliaro, I., Ibanez Ibanez, P., Tosatti, S. (2024). Understanding the icephobic performance of soft materials [Esposizione].
Understanding the icephobic performance of soft materials
Ospina Anny;Antonini Carlo;Tagliaro Irene;
2024
Abstract
Soft materials are a promising alternative to design and fabricate passive de-icing systems, considering the low ice adhesion strength values reported in the literature. Nevertheless, the interwoven effects of surface and mechanical properties have been not elucidated in terms of their individual contribution to the ice adhesion performance. In this work, the wetting and mechanical properties of soft PDMS with different lubricant content were analyzed by using different strategies: sessile drop, indentation and rheology experiments. The collected information is used to understand its relation with the shear ice adhesion results. First of all, the visualization of fracture events and its synchronization with the adhesion force measurement by ice push tests allowed to identify three different de-icing mechanisms depending on the size of the ice block: (i) Single detachment, (ii) stick-slip and (iii) interfacial slippage. The outcome depends both on the surface and on the size of the ice block. An increasing amount of lubricant decreases the force necessary for the initial ice detachment, which is an advantage in single detachment regime, where the small ice blocks are completely separated at the end of the experiments. When bigger ice blocks are considered, the silanol dangling ends molecules that migrated to the interface due to the contact with water, promotes the reattachment of the ice block, inducing a change from the stick-slip to the interfacial slippage mechanism, where the ice is more likely to remain attached after the de-icing experiment. More in details, on one hand advancing and receding contact angle measurements indicated the importance of considering the migration of low surface energy uncrosslinked chains to the interface during contact with water, leading to lubrication of the ice-substrate interface. This implies that two materials with different lubricant amounts may present similar contact angles after exposure to water (time scale 10 s). However, the lubricant amount plays a role in determining both the adhesion regime and the adhesion force, nevertheless, contact angles alone are not enough to predict ice adhesion. On the other hand, ice adhesion decreases for surfaces with decreased complex shear modulus G*. Moreover, one important finding is that the ice adhesion strength, calculated as F/A, is not a material property, since it is affected by the experimental parameters, like the ice block diameter in our tests: as such, F/A should only be used for comparing ice adhesion performance of different surfaces tested in the same experimental conditions.
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