Melt spinning
Melt spinning is to melt the fiber-forming polymer in a temperature range above its melting temperature and below its decomposition temperature. A thin stream of melt protrudes from the tiny holes. At the same time, it is stretched and thinned under the action of external force, and cooled and solidified in cold air to form fine fibers.
Melt spinning is suitable for the molding process of polymers with high heat resistance. The polymer should have the ability to melt and decompose. The melt spinning process is simple. The spun fibers only need to be heat-set by a stretching machine. The finished fiber is then obtained. Therefore, melt spinning is usually used for polymers that have the property of melting without decomposing.
Solution spinning
Solution spinning is to dissolve fiber-forming polymers in a certain solvent to prepare a spinning solution with a suitable concentration, and then spit the spinning solution out of tiny holes into a coagulation bath or hot gas. It is precipitated into solid filaments, and after stretching, shaping, washing and drying, the finished fiber can be obtained.
Obviously, the solution spinning production process is more complicated than melt spinning. However, for some polymers that have decomposed before melting, this spinning forming technology can only be chosen. Solution spinning also has wet French spinning, dry spinning, dry and wet spinning.
Wet spinning
Wet spinning is a type of solution spinning. The above-mentioned spinning solution is spit out from tiny holes into a coagulation bath. The coagulation bath is composed of non-solvents for polymers. Once the spinning solution encounters The coagulant solidifies and precipitates into solid filaments, and the finished fiber can be obtained through post-processing processes such as stretching, shaping, washing, and drying.
Wet spinning still requires the recycling process of coagulation bath and post-treatment solution, treatment and re-application. The production process is complicated and the production cost is high.
Dry spinning
Dry spinning is a type of solution spinning. If the fiber-forming polymer can be spun into a solvent with a lower boiling point and good solubility.�, at this time, the spinning solution can be spit out from the tiny holes and enter the heated gas. The solvent in the spinning solution will evaporate, and the polymer filaments will gradually solidify. After stretching, shaping, washing, drying and other post-processing processes, the spinning solution can be The finished fiber is obtained.
The mechanical properties of the obtained fiber are better than similar wet-spinning fibers. Dry spinning requires the recovery and reprocessing of solvents, which is simpler than the wet-spinning process.
Dry and wet spinning
Dry-wet spinning is a type of solution spinning, also known as dry-jet wet spinning. It combines the characteristics of wet spinning and dry spinning, and is particularly suitable for the molding and processing of liquid crystal polymers. Therefore, Also often called liquid crystal spinning.
That is, the fiber-forming polymer is dissolved in a certain solvent to prepare a spinning solution with a suitable concentration, and then the spinning solution is spit out from a tiny hole. It first passes through a short air sandwich, where the spinning solution is The resistance is small, and the polymer in the liquid crystal state is conducive to high orientation under high-stretch conditions. Then the filament enters the low-temperature coagulation bath to complete the solidification and molding, and the liquid crystal macromolecules are in a highly ordered frozen liquid crystal state. The finished fiber has high strength and high modulus mechanical properties.
Gel spinning
Gel spinning refers to extruding a high-concentration polymer solution or plasticized jelly from a spinneret into a high-temperature gas atmosphere. The filaments are cooled and sometimes accompanied by the evaporation of the solvent, thereby solidifying the polymer. Fiber formation is between dry spinning and melt spinning, also known as semi-melt spinning. The spinning liquid used is a solution, which is similar to dry spinning, but its concentration is extremely high and the solidification process is mainly cooling, which is similar to melt spinning.
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