Formation of polyurethane membranes by immersion precipitation. II. Morphology formation

Abstract

Polyurethane membranes were prepared by an immersion precipitation process. The effects of dope concentration, coagulation bath composition, and the chemical structure of the polyurethane on the morphology of the membranes were studied. The degree of contraction was measured by quenching freshly formed polyurethane membranes in liquid nitrogen. A mechanism for the formation of membrane morphology during immersion precipitation is proposed.

Actuation behaviour of polyaniline films and tubes prepared by phase inversion technique

“…The thickness of the dense top layer is larger for the pure water bath, than for the water/NMP bath. Similar observation was reported by Kim et al [20]. Similarly, the porosity of the top layer is larger for the water/NMP bath relative to the water bath due to a slower quenching, indeed some evidence of the deep macrovoid structure is already present ( Figure 5).…”

“…Comparing with other conducting polymers such as polypyrrole in propylene carbonate electrolyte of which E is around 80 MPa, the low values of E reflect the porous nature of the samples. The higher value of E at the contraction state than that at the expansion state predicts the actuation strain will increase with the applied load [2,20]. As shown in Fig.…”

“…7). The value for PAn/HCl films and tubes is slightly better at 0.4 MPa but it is still very low compared with PPy actuator (1 -1.5 MPa) [20] and PPy/PAn composite actuator (11.8MPa) [13]. Table 2 listed the Young's modulus, E, of the PAn/MSA films.…”

Dissipative particle dynamics simulation on the polymer membrane formation by immersion precipitation

“…The thermodynamic basis of the immersion precipitation method, which is the phase diagram of the polymer/solvent/nonsolvent system, had been well developed [8,9]. Some experimental and simulation works about the kinetics of immersion precipitation process had also been done [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Koenhen et al [10] found that the growth rate of the precipitation front decreased with increasing polymer concentration. But no details of the phase separation processes could be detected.…”

“…In 1979, Cohen et al [11] developed the first mass transfer model of immersion precipitation. Since then, many improvements had been made by, for example, Smolders and coworkers [12,13], McHugh and coworkers [14][15][16], Gryte and coworkers [17][18][19], Kumar and coworkers [20], Mayes and coworkers [21], Kim and coworkers [22], and Munari and coworkers [23], in the past decades. Because there are many properties difficult to control experimentally, modelling and simulations have been applied on immersion precipitation process to provide a crucial insight and design guidance in recent years [24][25][26][27][28][29].…”