Synthetic fibres are created through a chemical process that transforms raw materials, primarily petrochemicals derived from petroleum, into long, chain-like molecules called polymers, which are then spun into fibres.
Here's a breakdown of the preparation process:
Raw Materials: Petrochemicals
The foundation of most synthetic fibres lies in petrochemicals, which are compounds obtained from petroleum refining and natural gas processing. These serve as the building blocks for creating polymers. Common examples include:
- Ethylene: Used to make polyethylene (in some applications)
- Propylene: Used to make polypropylene.
- Benzene and Xylene: Used to make nylon and polyester.
Polymerization: Creating the Building Blocks
Polymerization is the chemical reaction where small molecules, called monomers, join together to form a large molecule called a polymer. There are two main types of polymerization used in synthetic fibre production:
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Addition Polymerization: Monomers directly link together without the loss of any atoms. An example is the formation of polyethylene from ethylene monomers.
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Condensation Polymerization: Monomers link together with the elimination of a small molecule, such as water. An example is the formation of polyester from a dicarboxylic acid and a dialcohol.
Spinning: Forming the Fibres
Once the polymer is created, it needs to be formed into fibres. This is done through a process called spinning, which involves forcing the polymer solution or melt through small holes in a device called a spinneret. There are three main spinning methods:
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Melt Spinning: The polymer is melted and then forced through the spinneret. The molten polymer solidifies upon cooling. This method is used for polymers like polyester and nylon.
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Dry Spinning: The polymer is dissolved in a solvent, and the solution is forced through the spinneret. The solvent evaporates, leaving the solid fibre. This method is used for polymers like acrylic.
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Wet Spinning: The polymer is dissolved in a solvent, and the solution is forced through the spinneret into a chemical bath that causes the polymer to precipitate and solidify. This method is used for polymers like rayon.
Drawing: Strengthening and Aligning
After spinning, the fibres are often drawn or stretched. This process aligns the polymer molecules, increasing the fibre's strength, elasticity, and overall performance.
Additional Treatments: Enhancing Properties
Finally, the fibres may undergo additional treatments to improve their properties, such as:
- Dyeing: Adding color to the fibres.
- Finishing: Improving wrinkle resistance, water repellency, or other desirable characteristics.
In summary, the preparation of synthetic fibres is a multi-step process involving petrochemicals as raw materials, polymerization to create polymers, spinning to form fibres, and drawing and treatments to enhance their properties.
