Preparation and properties of cationic membranes obtained by radiation grafting of methacrylic acid onto PTFE films

Abstract

SynopsisCationic membranes were prepared by direct radiation grafting of methacrylic acid (MAA) onto poly(tetrafluoroethy1ene) (PTFE) f i l m s followed by alkaline treatment to confer ionic character in the graft copolymer. The complete inhibition of homopolymerization of MAA by using ammonium feqeous sulfate (Mohr's salt) failed. However, the addition of 0.5 w t ' % FeC1, to the monomer solution effectively inhibited the homopolymerization process and higher grafting yield was obtained. I t was found that the graft polymerization proceeded successfully in presence of methanol/water mixture (30/70 w t %), and much higher degrees of grafting were obtained as compared with those in the presence of other diluents used here. The influence of irradiation atmosphere (air, N, gas, and vacuum) on the grafting process was investigated. The dependence of the grafting rate on MAA concentration was found to be of orders 2.9 and 0.72 in the presence of 0.5 wt % Mohr's salt or 0.5 wt 5 % FeCl,, respectively. This grafting system proceeds by the front mechanism. Investigation of mechanical properties, electrical conductivity, and swelling behavior of the grafted films revealed that such a copolymer could be acceptable in practical use as a cation-exchange membrane.

Ion exchange membranes: State of their development and perspective

“…In such route, two functional acidic groups were mainly identified as fixed ionic groups that confer the membrane its cation character, namely carboxylic (weakly acidic) and sulfonic acid (strongly acidic) groups. The former can be prepared either by direct grafting of acrylic monomers like acrylic [40][41][42][43][44], methacrylic acids [45][46][47][48][49] and their mixtures with acrylonitrile [50,51] and vinylacetate [52] or by grafting of epoxy acrylate monomers, such as glycidyl acrylate or glycidyl methacrylate onto polymer films followed by the conversion of the epoxy group into carboxylic group, such as iminodiacetate groups which were obtained by post-grafting ring opening reaction [53]. Strongly acidic membranes are commonly prepared by grafting of styrene onto polymer films and the resulted graft copolymer films are subsequently sulfonated [54][55][56][57][58][59][60][61].…”

Preparation and properties of ion‐exchange membranes prepared by the radiation‐induced grafting of a styrene/acrylic acid comonomer onto low‐density polyethylene

“…Therefore, styrene (Sty) is often grafted onto polymer films to produce graft copolymers that can be easily sulfonated with chlorosulfonic acid. 26 The ion-exchange properties are improved by sulfonation, which changes the overall structure of the membranes; these structural changes may be in the form of a crystalline-amorphous ratio. 20 Also, membranes containing sulfonic acid groups exhibit some demerits, such as excessive water swelling, good thermal properties, and weak mechanical strength.…”

?-Irradiated poly(tetrafluoroethylene) particle-filled low-density polyethylene. I. Effect of silane coupling agents on mechanical, thermal, and morphological properties

“…9 Ionizing or high-energy radiation were particularly studied for radiation grafting of vinyl monomers into PTFE films. Acrylic acid, 10 -12 methacrylic acid, 13 N-vinylpyrrolidone, 10,11 4-vinylpyridine, 10,11,14 and vinylfluoride 15,16 are some examples of these monomers.…”