Gel spinning technologies

Gel spinning, also known as semi-melt spinning, is a method that prepares high-strength and high-elastic module fibre in the gel state. After the extrusion of the polymer solution or plasticised gel from the spinnerets, it is cooled in solvent or water before being stretched into gel fibre by ultra-high 

The general gel spinning process can be divided into the following four steps  

Dissolution the dissolution of polymer in solvent. The molecular chains of the solid polymers may be entangled, and the entanglements will affect the molecular chain stretching. The dissolution of polymers in solvent can disentangle these entanglements to aid the gel fibre stretching. 

Remove solvent the most commonly used methods to remove solvent in gel spinning include the natural drying method and the use of extractant, which mainly aims to remove the solvent residuals in gel fibre. The extractant can displace the gel fibre solvent based on diffusion and penetration principles. In gel spinning, the selection of solvent and extractant directly affect the stretching stability, and is key to the gel spinning method. 

Raw materials of high molecular weight the raw materials are mainly polymers of high molecular weight. Polymers of high molecular weight 

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R. Kirschbaum, J. L. J. van Dingenen, Advances in gel spinning technology and Dyneema fibre applications . Integration of polymer science and technology, 3 Rolduc Conf. Elsevier Amsterdam (1988). 

Kirschbaum R., van Dingenen J., (1989), Advances in gel-spinning Technology and Dyneema fiber applications. Integration of Polymer Science and Technology 3. Elsevier Appl. Sci. Publ. 

Advances in gel-spinning technology and Dyneema fiber applications... 

With a few exceptions (e.g., gel-spinning technology), the above-mentioned methods of spuming from polymer solutions have historical importance only. Melt spinning, however, is still used [16]. 

The technology of gel spinning has not been successful with polypropylene. Unlike polyethylene with a simple linear chain conformation, the hehcal chain conformation of polypropylene can conceivably forfeit a tight crystal packing required for a high-strength,... 

H. Yasuda, K. Ban, and Y. Ohta, Gel spinning processes, in Advanced Fiber Spinning Technology, T. Nakajima, Ed., Woodhead Publishing Limited, Cambridge, pp. 171-185 (1994). 

Jacobs, M.J.N. and Mencke, JJ. (1995) New technologies in gel spinning the world s strongest fibre. Internationales Techtextil Symp., Frankfurt, Paper 2.13. 

Considering fibres based on poly(hydroxybutyrate) or higher PHAs, no successful process was reported for preparation of PHB fibres by conventional fibre processing technology, i.e. melt or gel spinning with subsequent hot drawing. Therefore, more sophisticated procedures have to be developed to achieve reasonable draw ratios, resulting in production of anisotropic material with important improvement of properties. 

A modern wet spinning technology, known as solution gel spinning, is now used for ultrahigh molecular weight PE (UHMWPE) (500,000-5000,000), to obtain extended-chain PE fibers. 

Angelopoulos et al. [42] reported that A -methylpyrroli-dione (NMP) could dissolve PANI in the base form. Subsequent work demonstrated that PANI solutions formed in NMP at solids concentrations above 6% formed gels after a short period of time [43-45]. The formation of these gels at concentrations necessary for the formation of fibers and films by solution spinning technologies (>10%) prohibited the use of this solvent without modification to a binary solvent system. 

Solution Deposition of Thin Films. Chemical methods of preparation may also be used for the fabrication of ceramic thin films (qv). MetaHo-organic precursors, notably metal alkoxides (see Alkoxides, metal) and metal carboxylates, are most frequently used for film preparation by sol-gel or metallo-organic decomposition (MOD) solution deposition processes (see Sol-GEL technology). These methods involve dissolution of the precursors in a mutual solvent control of solution characteristics such as viscosity and concentration, film deposition by spin-casting or dip-coating, and heat treatment to remove volatile organic species and induce crystaHhation of the as-deposited amorphous film into the desired stmcture. 

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