Thermally induced phase separation technique

Human osteoblast-like MG63 cells were cultured on the macroporous chitosan scaffolds reinforced with hydroxyapatite or calcium phosphate invert glass were fabricated using a thermally induced phase separation technique. 

Wang AJ, Cao WL, Gong K et al (2006) Controlling morphology and porosity of 3-D chitosan scaffolds produced by thermally induced phase separation technique. Asian Chitin J 2 69-78... 

Ghasem, N., Al-Marzouqi, M., Duaidar, A. 2011. Effect of quenching temperature on the performance of poly(vinylidene fluoride) microporous hollow fiber membranes fabricated via thermally induced phase separation technique on the removal of CO2 from C02-gas mixture. Int. J. Greenh. Gas Control 5 1550-1558. 

Hydrophilic MF membranes can be made by the dry-wet phase inversion technique, which can also be used to make PVDF membranes. On the other hand, other hydrophobic microflltration membranes are made by the thermally induced phase separation technique. In particular, semicrystalline PE, PP, and PTFE are stretched parallel to the direction of film extrusion so that the crystalline regions are aligned in the direction of stretch, while the noncrystalline region is ruptured, forming long and narrow pores. Hydrophobic membranes do not allow penetration of water into the pore until the transmembrane pressure drop reaches a threshold called the liquid entry pressure of water (LEPw). These membranes can therefore be used for membrane distillation. The track-etching method is applied to make microfiltration membranes from PC. 

Yoshikawa and Myoui (2005) reported interconnected porous HA fabricated via a process called form-jel, a technique which creates a scaffold with an excellent vascular network ample for blood supply, an aspect of bone regeneration. It serves as a good scaffold for the delivery of cytokines, which enhance bone tissue formation in defect sites. The use of poly(L-lactic acid)/HA composite scaffold for bone tissue engineering synthesized via a thermally induced phase separation technique records a... 

Kubota, N., Takegawa, H., and Takamura, M. (2003). An unique membrane formation technology based on thermally induced phase separation technique and appUcations of the resulting mem-hrane. In Abstracts of the 36th Autumn Meeting of Society of Chemical Engineers. Tohoku University, Sendai, Japan, p. M2P04. 

Asymmetric membranes are usually produced by phase inversion techniques. In these techniques, an initially homogeneous polymer solution becomes thermodynamically unstable due to different external effects and the phase separates into polymer-lean and polymer-rich phases. The polymer-rich phase forms the matrix of the membrane, while the polymer-lean phase, rich in solvents and nonsolvents, fills the pores. Four main techniques exist to induce phase inversion and thus to prepare asymmetric porous membranes [85] (a) thermally induced phase separation (TIPS), (b) immersion precipitation (wet casting), (c) vapor-induced phase separation (VIPS), and (d) dry (air) casting. 

A combination of thermally induced phase separation and an industrial knitting technique was used to produce a porous chitosan-gelatin complex Scaffold prepared using... 

Thermally induced phase separation Similar to the previous technique, this phase separation procedure requires the use of a solvent with a low melting point that is easy to sublime. Liquid-liquid phase separation presents the same drawbacks of emulsification/freeze-drying. 

The experimental procedures for thermally inducing phase separation of polymer blends by DSC technique are as follows. 

Another scaffold fabrication technique is thermally induced phase separation (TIPS) [34,46,84,147-149]. TIPS involves decreasing the temperature of a polymer solution to obtain a polymer-rich and polymer-poor phase. Following phase separation, the solvent is removed using one of a number of methods (freeze drying, evaporation) resulting in the formation of pores in the polymer stracture. TIPS can also be combined with the use of porogens to increase void fraction, have better control over pore size, or improve pore interconnectivity. 

Phase inversion is known to be an effective way to create porous structures in membranes, where a competitive mutual diffusion between solvent and nonsolvent occurs to yield the porous structure. Phase inversion can be described as a demixing process whereby the initially homogeneous polymer solution is transformed in a controlled manner from a liquid to a solid state [24]. Apart from immersion in a nonsolvent bath, or immersion precipitation (IP), a variety of related techniques, such as precipitation by solvent evaporation, precipitation by absorption of water Irom the vapor phase, and precipitation by air cooling, corresponding to thermally induced phase separation (TIPS), vapor-induced phase separation (VIPS), and air-casting phase separation... 

There are mainly four fabrication techniques that can produce 3-D composite scaffolds with highly interconnected pores thermally induced phase separation, solvent casting, rapid prototyping, and microsphere sintering. 

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