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Thermoplastic Rubbers via Dynamic Vulcanization
Published in Gabriel O. Shonaike, George P. Simon, Polymer Blends and Alloys, 2019
The third possibility of network generation occurs by ionic interaction (15). Clusters are held together by ionic bonds in the so-called ionomers (the invention with ionomers is credited to Rees: U.S. Patents 3,264,272 and 3,404,134). The ionomers are usually produced by neutralization of the acidic groups (saponification by adding salts) in copolymers or functionalized polymers.
Effect of Chemical Structure on Polymer Properties
Published in Anil Kumar, Rakesh K. Gupta, Fundamentals of Polymer Engineering, 2018
Because of the special properties imparted to this new material, called an ionomer, it has been the subject of vigorous research in recent years. Ionomers are used as compatibilizing agents in blends and are also extensively employed in permselective membranes, thermoplastic elastomers, packaging films, and viscosifiers. Carboxylic acid groups are introduced through the first synthetic route by employing acrylic or methacrylic acids as the comonomer in small quantities. Sulfonate groups are normally introduced by polymer modification; they will be discussed in greater detail later in this chapter.
Self-Healing Polymers
Published in Asit Baran Samui, Smart Polymers, 2022
Ionomers, formed by incorporating up to 20 mol% ionic species to induce interactions or aggregations, belong to a class of polymers that exhibits self-healing behavior for a large number of cycles. Mechanical and physical properties are highly influenced by this behavior. The aggregates are formed by several ion pairs and are known as physical cross-linking. Thus, the ionic clusters can be dispersed in a continuous semi-crystalline polymer matrix. With increasing temperature, the polymer goes from an ordered to a disordered state and, as a result, loses its mechanical strength. Further increase in temperature causes the semi-crystalline polymer to melt. Of course, the disordered clusters contribute to increased melt strength. The ionic nature of the network is known to enable the segments to rearrange, which induces healing after mechanical damage. The impact energy is distributed over the ionomer components, which melt and penetrate into each other. This way, the intermolecular ionic attractions are maintained by the ionic regions that help in their elastic recovery and repair the damage. It is thus apparent that, for self-healing, the ionic character, along with its unique interaction, is most important. For example, simple ionomers can be synthesized by copolymerizing ethylene and sodium salt of methacrylic acid. The ionomers can heal rapidly at room temperature. However, by increasing the temperature of the film before puncture, the healing response is prevented by a more residual deformation.47 In this condition, the dispersion of impact energy over a larger area does not support the elastic recovery of the hole. The stages of the healing process in the case of projectile penetration can be depicted as: in the first stage, the localized molten polymer exhibits an elastic response by using the rigid film perimeter as a framework, while reverting back to fill the hole. In the next stage, the interdiffusion occurs in the molten surfaces to fuse them together and the strength is regained as the polymer cools. In the third stage, the strength regeneration occurs through the processes of continued interdiffusion, crystallization, and long-term relaxation of the polymer chains.
Progress on highly proton-conductive polymer thin films with organized structure and molecularly oriented structure
Published in Science and Technology of Advanced Materials, 2020
For the last 10 years, the study of ‘thin’ Nafion ionomers has attracted researchers because ionomer is necessary for fuel cell reactions [21,28,32]. Thin ionomers serve to transport protons from the proton-conductive membrane to the electrochemical catalyst in fuel cells. Protons are transported through the thick membrane but along the thin ionomer at the interface in catalyst layers. Therefore, the proton conductivity in the in-plane direction becomes important for thin ionomers. Since Siroma and co-workers reported declining in-plane proton conductivity with decreasing thickness of a Nafion thin film [33], the relation between the interfacial structure of perfluorinated sulfonic acid ionomer and proton transport properties has been discussed to an increasing degree. The author would like to introduce our progress in this area, including discussion of other related works from 2017 [21].
Performance of passive direct formate fuel cells using chitosan as an anode binder
Published in International Journal of Green Energy, 2023
Since anions transport from cathode to anode in alkaline DLFCs while generating electricity, the alkaline ionomers, such as AS4, A3, I2, and QAPS, have been commonly used as electrode binders to help conduct anions within the catalyst layer, and the resulting cell performance has also been reported (An et al. 2012; An, Zhao, and Zeng 2013; Bartrom and Haan 2012; Bartrom et al. 2013; Li, Zhao, and Liang 2009a; Su, Pan, and An 2019; Sun and Li 2019; Tran et al. 2014; Wippermann et al. 2013). Some neutral polymers, such as PTFE and PVDF-HEP (An et al. 2010; Li, He, and Yang 2013; Li, Zhao, and Liang 2009b; Luo et al. 2021), were also attempted to bind the catalyst layer of alkaline DLFCs instead of alkaline ionomer because they are easily accessible and cost-effective. Particularly, the Nafion ionomer, which was widely used to form the catalyst layer of cation-conducting fuel cells, was first tested as an anode binder for alkaline membraneless and anion-exchange membrane (AEM) DFFCs fed with KOH-added liquid fuel. Their performance was quite exceptional (Shyu et al. Shyu and Wang 2021, 2022). The measured results from both publications indicated that as the Nafion ionomer content decreased from 3.73 to 1.87 mg/cm2, the maximum power density of DFFCs significantly increased because of the decrease in mass transport losses and area-specific resistance of DFFCs. The maximum power density of DFFC peaked with 1.87 mg/cm2 Nafion ionomer content in the anode. Both articles pointed out that alkaline DLFCs can function properly regardless of the type of polymer for binding catalyst layer of the alkaline DLFCs, and the ionomer or polymer content in the catalyst layer plays an important role in the performance of alkaline DLFCs.