Critical Evaluation of the Methods for the Characterization of the Degree of Sulfonation for Electron Beam Irradiated and Non-Irradiated Sulfonated Poly(ether ether ketone) Membranes. - Pakalniete, Laura Dace; Maskova, Elizabete; Zabolockis, Rudolfs Janis; Avotina, Liga; Sprugis, Einars; Reinholds, Ingars; Rzepna, Magdalena; Vaivars, Guntars; Pajuste, Elina (Materials (1996-1944), 2023)