Linear stability theory model for finger formation in asymmetric membranes

Processing and characterization of polyethersulfone wet-spun nanocomposite fibres containing multiwalled carbon nanotubes

“…In addition, the observed difference between neat and nanocomposite PES fibre morphologies is probably due to an increase in the spinning solution viscosity in the presence of MWCNT. This rise of viscosity causes changes in macrovoid formation, in the demixing mechanism and consequently in fibre morphology during coagulation [31,32]. To suppress these macrovoids, solutions exist and have been considered, such as increasing polymer concentration in the spinning solution, adding solvent or non-solvent respectively to the coagulation bath or to the polymer solution, or even choosing a non-solvent/solvent pair with low mutual affinity.…”

Formation of micro-channels in ceramic membranes – Spatial structure, simulation, and potential use in water treatment

“…The first feature has long been noticed in polymer phase-inversion membranes, and some researchers have related it to the periodical surface disturbing waves, which can explain the regular distribution reasonably well while other proposed mechanisms fail [41]. These theories analyse the stability of the waves, assuming the wavelength of the surface disturbance ranges linearly from zero to infinity.…”

“…However, in reality, the formation of fingers is very fast and hence Ray denied the Marangoni instability as the main mechanism, and proposed that another source of surface instability, the excess intermolecular potential, should be responsible for the fingers. Based on the theory, Ray derived that the distance between the longest fingers (the most probable wavelength) is 4.2 times of the membrane thickness [41]. Although in their experimental results they did get a distribution of the ratio from 2.5-5.1, it should be noted that Ray used the thickness of the final membrane as the reference, instead of the thickness of the cast solution that appears in the derivation.…”

Structure and properties of polyimide (BTDA-TDI/MDI co-polyimide) fibers obtained by wet-spinning

“…21,28,39,40 Concentration gradient-induced instability is one of the important mechanisms have been proposed and used to describe the formation of macrovoids such as shrinkage of polymer matrix. 41 Contrasting the four micrographs, it was found that the concentration of the coagulation bath had remarkable influences on the morphology of the as-spun fibers.…”