Oracle IAS, the best coaching institute for UPSC/IAS/PCS preparation in Dehradun brings to you UKPCS Science Chemistry (paper 6).
POLYMER
A polymer is a large molecule, or macromolecule, composed of many repeated subunits. Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass relative to small molecule compounds produces unique physical properties, including toughness, visco-elasticity, and a tendency to form glasses and semi-crystalline structures rather than crystals.
SYNTHETIC FIBERS:
Synthetic fibers are manmade and synthetic fabrics consist of bulk fibers, yarns, woven cloth or other textile products manufactured from polymer-based materials such as polyamide (nylon), polyester, aramid, or other spun thermoplastics. The end-product is the form of the fiber/fabric when manufacturing is complete.
Nylon
Nylon is a generic designation for a family of synthetic polymers, more specifically aliphatic or semi-aromatic polyamides. They can be melt-processed into fibers, films or shapes. Nylon is made from polyamide fiber, derived from a diamine and a dicarboxylic acid that is formed into thin strands and woven into fabric. It is a synthetic fabric that utilizes the chemical by-products of coal, petroleum and agricultural products.
Nylon fabric became important as a synthetic substitute for silk in the manufacture of parachutes when silk became scarce during WWII. Nylon is still used today to make parachute canopies due to its elasticity, strength, resistance to mildew, availability and price
Rayon
Rayon is a manufactured regenerated cellulose fiber. It is made from purified cellulose, primarily from wood pulp, which is chemically converted into a soluble compound. It is then dissolved and forced through a spinneret to produce filaments which are chemically solidified, resulting in synthetic fibers of nearly pure cellulose. Because rayon is manufactured from naturally occurring polymers, it is considered a semi-synthetic fiber. Specific types of rayon include viscose, modal and lyocell, each of which differs in manufacturing process and properties of the finished product.
Properties: Rayon is a versatile fiber and is widely claimed to have the same comfort properties as natural fibers, although the drape and slipperiness of rayon textiles are often more like nylon. It can imitate the feel and texture of silk, wool, cotton and linen. The fibers are easily dyed in a wide range of colors. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not insulate body heat, making them ideal for use in hot and humid climates, although also making their “hand” (feel) cool and sometimes almost slimy to the touch.
Rising cotton prices in 2010 led clothing makers to begin replacing cotton with rayon in their fabrics.
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