Development of dense void-free electrospun SPEEK-Cloisite15A membrane for direct methanol fuel cell application: optimization using response surface methodology by Awang, N., Jaafar, J., Ismail, A. F., Othman, M. H. D., Rahman, M .A., Yusof, N., Aziz, F., Salleh, W. N. W., Suradi, S. S., Ilbeygi, H., Wan Mohd. Noral Azman, W. N. E., Arthanareeswaran, G.