Studies on the thermal stability of the perfluorinated cation-exchange membrane Nafion-417

Abstract

The thermal stability of the perfluorinated cationexchange membrane Nation-417 was determined by means of simultaneous TG-DTA. The individual decomposition stages were studied via IR spectroscopy and ion-exchange capacity determinations. Nafion-417 is thermally stable up to 280 ~ Above this temperature, sulfonic groups present in the membrane are split off (Tmax ----345 ~ In the temperature range 420-590 ~ oxidative destruction of the perfluorinated matrix occurs, which is accompanied by practically total weight loss.Perfluorinated ionomer membranes represent a major advance in membrane technology. Although a variety of applications have been found for these polymers since their appearance about fifteen years ago, the main driving force for their development has been their potential application as membrane separators in commercial alkali metal chloride solution electrolysis. This major chemical technology is in the process of being revolutionized through the use of these materials.Among the polymeric synthetic ion-exchange membranes, special attention has been paid to the Nation membranes, based on sulfonated fluorocarbons. Owing to their chemical inertness, thermal and mechanical stability, and high permeability and mechanical stability, and high permeability and selectivity, they have proved to be particularly suitable for many industrial processes [1,2]. Nation membranes have found wide application in the chemical industry, e.g. as separators in chloralkali electrolysis or as solid polymer electrolytes in fuel cells [3]. Perfluorinated ion-exchange polymers can also serve as "superacid" catalysts for many organic reactions [4].The structures and physicochemical.properties of Nation membranes have been studied extensively by many authors [1,[5][6][7][8][9]. Only a few papers have been published on the thermal stabilities of Nation membranes; these have concerned the thermal behaviour of Nafion in solutions of chemicals up to 200-250 ~ .The purpose of our studies was to investigate the thermal properties of Nafion-417 in the temperature range 20-1000 ~ through the use of thermogravimetry (TG) and differential thermal analysis (DTA).

Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °C

“…It was found that the sulfonic acid group in Nafion was stable at temperatures up to 280°C in air. 223,224 This also seems to apply to most of the sulfonated hydrocarbons. Degradation temperatures of 240-330 and 250°C, respectively, were reported for SPEEK 43,182,197,226,225 and sulfonated polysulfone (SPSF), 196,215 though Trotta et al 198 reported a decomposition temperature of the SO 3 H group at about 400°C for the sulfonated PEEK-WC.…”

“…33 The desulfonation of PFSA membranes has been widely studied [222][223][224] by means of TGA, DTA, FT-IR, and TGA-MS measurements. It was found that the sulfonic acid group in Nafion was stable at temperatures up to 280°C in air.…”

Recast Nafion‐117 thin film from water solution

“…The line may be divided into two regions: in one, between 298 and 423 K, the sample loses 14.3 wt.-%, which can be assigned to water loss; in the other, between 423 and 573 K, it loses 1.5 wt.-%, and this loss can be assigned to the water release and a small amount of sulfur dioxide and carbon dioxide, in agree- ment with ref. [14][15][16] , i. e. to the beginning of the polymer decomposition. Fig.…”

“…Yeager and others have investigated, using infrared spectroscopy, [2] the modifications in air of Nafion-1100 coated onto a platinum film, heating it at temperatures from 295 -573 K. After 15 min at 573 K the polymer loses its sulfonic acid group. Thermogravimetric analysis (TGA), differential thermal analysis (DSC) and infrared spectroscopy [14] led Surowiec and others to the conclusion that Nafion loses only water below 553 K, while above 553 K it also loses the sulfonic acid groups. Nafion-H has been studied by thermogravimetric analysis and Fourier transform infrared spectroscopy (FTIR) [15] to identify the evolved gases: between 308 and 553 K Nafion lost about 5 wt.-% and produced water as well as small amounts of sulfur dioxide and carbon dioxide.…”

Propriedades físico-químicas relacionadas ao desenvolvimento de membranas de Nafion® para aplicações em células a combustível do tipo PEMFC

“…No entanto, Samms et al [42] realizaram estudos sobre decomposição térmica do Nafion ® , na faixa de 0 a 600 °C, utilizando técnicas de Termogravimetria (TGA) e Espectrometria de massas (MS) acopladas. Com base nos valores de razão m/z, concluíram que na região entre 75 e 225 °C havia apenas perda de água (m/z =18), conforme também relatado por outros pesquisadores [43][44][45] . Na região de 275 a 400 °C, obteve-se sinais de m/z = 48 e 64, que os autores atribuíram a liberação de SO 2 .…”