Network structure dependence on unconstrained isothermal-recovery processes for shape-memory thiol-epoxy "click" systems
The shape-memory response (SMR) of “click” thiol-epoxy polymers produced using latent catalysts, with different network structure and thermo-mechanical properties, was tested on unconstrained shape-recovery processes under isothermal conditions. Experiments at several programming temperatures ( Tpro...
| Autores: | , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2017 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/113435 |
| Acceso en línea: | https://hdl.handle.net/2117/113435 https://dx.doi.org/10.1007/s11043-016-9322-z |
| Access Level: | acceso abierto |
| Palabra clave: | Thiol-epoxy Shape-memory polymer Isothermal-recovery Click chemistry Àrees temàtiques de la UPC::Enginyeria dels materials::Materials plàstics i polímers |
| Sumario: | The shape-memory response (SMR) of “click” thiol-epoxy polymers produced using latent catalysts, with different network structure and thermo-mechanical properties, was tested on unconstrained shape-recovery processes under isothermal conditions. Experiments at several programming temperatures ( TprogTprog ) and isothermal-recovery temperatures ( TisoTiso ) were carried out, and the shape-memory stability was analyzed through various consecutive shape-memory cycles. The temperature profile during the isothermal-recovery experiments was monitored, and it showed that the shape-recovery process takes place while the sample is becoming thermally stable and before stable isothermal temperature conditions are eventually reached. The shape-recovery process takes place in two different stages regardless of TisoTiso : a slow initial stage until the process is triggered at a temperature strongly related with the beginning of network relaxation, followed by the typical exponential decay of the relaxation processes until completion at a temperature below or very close to TgTg . The shape-recovery process is slower in materials with more densely crosslinked and hindered network structures. The shape-recovery time ( tsrtsr ) is significantly reduced when the isothermal-recovery temperature TisoTiso increases from below to above TgTg because the network relaxation dynamics accelerates. However, the temperature range from the beginning to the end of the recovery process is hardly affected by TisoTiso ; at higher TisoTiso it is only slightly shifted to higher temperatures. These results suggest that the shape-recovery process can be controlled by changing the network structure and working at Tiso<TgTiso<Tg to maximize the effect of the structure and/or by increasing TisoTiso to minimize the effect but increasing the shape-recovery rate. |
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