Fibres that are made by human beings are called syntheticfibres. Most synthetic fibres are obtained from coal, petroleum, and natural gas. Rayon, nylon, polyester, acrylic, and spandex are examples of synthetic fibres.
Polyester
Polyester is of different types. The most commonly used polyester is Terylene. It is blended with natural fibres to improve its properties. Terrycot, a blend of Terylene and cotton, has better absorbing power as compared to Terylene. Terylene is blended with wool to make Terrywool, which is warm in addition to all the characteristics observed in polyesters.
Properties
It is strong, lightweight, and has good elasticity.
It resists wrinkling and springs back into shape when creased.
Polyester fabrics can be washed and dried easily and quickly.
Uses
Polyester is used for making lightweight sails
Polyester films (commonly known as Mylar) are used for making magnetic recording tapes in audio cassettes, video cassettes, and floppy disks.
Terylene is used for making, conveyor belts as it is very elastic.
Terrycot is commonly used for making shirts, skirts, and other dress materials. Terrywool is used for making formal suits.
Physical Properties of Ethanol : (i) Pure ethanol is a colourless liquid. (ii) It has a specific smell and burning taste (iii) Its boiling point is 351 K which is higher than corresponding alkanes (iv) It is soluble in water. i.e., it is miscible with water in all proportions.
Chemical properties of Ethanol : (i)Dehydration : Ethanol. when heated with Conc. H2SO4 at 443 K or Al2O3 at 623 K undergoes dehydration, i.e. loses water molecule to from alkene. (ii) Reaction with Sodium : Alcohols are very weakly acidic. Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas. (iii) Oxidation with Chromic anhydride (CrO3) : (iv) Oxidation with alkaline KMnO4 : (v) Oxidation with acidified Potassium dichromate : Ethanol is oxidized to ethanoic acid with the help of acidified K2Cr2O7 During this reaction, orange colour of K2Cr2O7 changes to green. Therefore, this reaction can be used for the identification of alcohols. (vi) Esterification : Ethanol reacts with ethanoic acid in presence of concentrated H2SO4 to form ethyl ethanoate and water. The compound formed by the reaction of an alcohol with carboxylic acid is known as ester and the reaction is called Esterification. Esters are sweet fruity smelling compounds because they occur in fruits. They are used in ice creams, cold drinks and perfumes. The reaction takes place as follows. Conc. H2SO4 acts as dehydrating agent, i.e., it removes water formed otherwise ester formed will get hydrolysed. (vii) Ethanol is highly inflammable liquid i.e., it catches fire very easily. It burns with blue flame in presence of oxygen to form carbon dioxide and water.
What is the use of ethanol?
Uses of Ethanol : (i) Ethanol is present in alcoholic beverages such as beer, wine, whisky. (ii) Ethanol is used as antiseptic for sterilising wounds. (iii) Ethanol is used incough syrups. digestive syrups and tonics. (iv) Ethanol is being mixed with petrol and is used as motor fuel. This mixture is called power alcohol. (v) A mixture of ethanol and water has lower freezing point than water. This mixture is known as antifreeze and is used in radiators of vehicles in cold countries and at hill stations. (vi) Ethanol is used for preparation of chloroform, iodoform, ethanoic acid, ethanal, ethyl ethanoate etc. (vii) Ethyl alcohol is used as hypnotic (induces sleep).
Ethanoic acid (Acetic acid) CH3COOH : Ethanoic acid is most commonly known as acetic acid. Its dilute solution in water (5-8%) is known as vinegar, which is used for preserving food-sausage, pickles etc.
Physical properties : (i) Ethanoic acid is vinegar smelling liquid. The lower carboxylic acids are liquids whereas higher ones are solids. (ii) Ethanoic acid is sour in taste. Other lower carboxylic acids are also sour in taste. (iii) Ethanoic acid has boiling point 391 K. Carboxylic acids have higher boiling points than corresponding alcohols, aldehydes and ketones. (iv) Acetic acid is soluble in water, i.e., it is miscible with water in all proportions. The lower carboxylic acids are soluble in water but solubility in water decreases with increase in molecular weight. (v) Acetic acid freezes at 290 K. Thus, in cold weather crystallization of acetic acid may take place that is why pure acetic acid is called glacial acetic acid.
Chemical Properties : (i) Ethanoic acid is weak acid but it turns blue litmus red. (ii) Reaction with Metal. Ethanoic acid reacts with metals like Na, K, Zn etc. to form metal ethanoates and hydrogen gas. (iii) Reaction with Carbonates. Ethanoic acid reacts with bicarbonates and carbonates and produces brisk effervescence due to formation of carbon dioxide. (iv) Reaction with Base. Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water. (v) Decarboxylation (Removal of CO2). When sodium salt of ethanoic acid, i.e., sodium ethanoate is heated with soda lime (3 parts of NaOH and 1 part of CaO), methane gas is formed. This reaction is known as decarboxylation because a molecule of CO2 is removed from a molecule of acid. (vi) Reaction with alcohols. Ethanoic acid reacts with ethanol in presence of concentrated sulphuric acid to form esters which are pleasant fruity smelling compounds. (vii) Reduction. Acetic acid, on reduction with lithium aluminium hydride, results in formation of ethanal, which on further reduction gives ethanol.
Uses of Ethanoic acid : (i) It is used for making vinegar (ii) It is used as a laboratory reagent (iii) It is used for preparation of white lead [2PbCO3.Pb(OH)2] which is used in white paints. (iv) It is used for coagulation of rubber from latex and casein (protein) from milk (v) It is used in preparation of acetone, ethyl acetate, acetic anhydride, aspirin which is used in medicines. (vi) It is used in preparation of cellulose acetate which is used for making photographic film. (vii) Its esters are used in artificial flavours in perfumes. (viii) Its 5% solution is bactericidal (destroys bacteria) (ix) Its compound basic copper acetate (verdigris) is used as green pigment. (x) Aluminium acetate and chromium acetate are used as mordants in dyeing and waterproofing of fabrics.
Most clothing materials or fabrics we use in our day-to-day lives are made from thin, thread-like fibres. Fibres can be either natural or artificial. Natural fabrics have been used for clothing since ancient times. But nowadays, synthetic fibres are largely used for clothing and other purposes.
Synthetic fibres
Fibres that are made by human beings are called synthetic fibres. Most synthetic fibres are obtained from coal, petroleum, and natural gas. A synthetic fibre consists of multiple units (each of which is a chemical substance), which are joined together to form a single unit called a polymer (poly: many; mer: unit). The structure of a polymer can be described as resembling numerous beads on a string, with the beads representing the individual units that are joined together. Rayon, nylon, polyester, acrylic, and spandex are examples of synthetic fibres.
Polyamides and polyesters are two groups of synthetic fibres with high strength, not easily stretched and used as textile.
Nylon is an example of polyamide polymers. Terylene is an example of polyester polymers.
Nylon and terylene are produced through condensation polymerisation.
Nylon (a) Nylon is a general term given to the synthetic polymer made from two types of monomer, diamine molecules and diacid molecules. (b) A diamine molecule has two -NH2 groups and a diacid has two -COOH groups. (c) Diacid molecules and diamine molecules undergo condensation reaction to form nylon and water. (d) Nylon-6,6 is manufactured from polymerisation of hexane-1,6-diamine and hexane-1,6-dioc acid. (e) Nylon-6,6 is a strong, tough and waterproof polymer and can be easily made into fibres. (f) Nylon is used to make toothbrushes, ropes, fishing lines, parachutes, carpets, textile, threads and electrical insulators.
Terylene (a) The monomers used to make polyester are diol molecules and diacid molecules. (b) A diol molecule has two -OH groups and a diacid molecule has two -COOH groups. (c) When many diacid molecules condense with diol molecules, a polyester and water are formed. (d) Terylene for example, is manufactured from ethane-1,2-diol and (benzene)benzoic- 1,4- dicarboxylic acid. (e) Terylene is suitable for making textile, stocking, parachutes and fishing nets because it is elastic, chemically inert, can be coloured and easily made into fibre.
Rayon, also called artificial silk, is prepared from cellulose (which comes from wood pulp).
Properties
It absorbs sweat. Rayon clothes are, therefore, preferred over other synthetic fibres in summer.
It is shiny and lustrous and resembles silk in appearance.
Uses
Rayon is used for making shirts, ties, home furnishing (bed sheets, curtains, tablecloths, sofa covers, etc.), and bandages.
Rayon Ties
Nylon
Nylon was the first true synthetic fibre. It was first produced in the early 1930s by the scientists at the DuPont Company from coal, water, and air.
Properties
It is elastic and does not lose strength even after repeated use.
It is lustrous and easy to wash.
Uses
Nylon is used for making saris, socks, stockings, tents, umbrellas, parachutes, and tarpaulins.
Nylon fibres are used for making toothbrush bristles.
Due to their high strength and elasticity, nylon threads are used for making fishing nets, climbing ropes, and strings of badminton and tennis racquets.
Strings of a tennis racquet are made of nylon.
Polyester
Polyester is of different types. The most commonly used polyester is Terylene. It is blended with natural fibres to improve its properties. Terrycot, a blend of Terylene and cotton, has better absorbing power as compared to Terylene. Terylene is blended with wool to make Terrywool, which is warm in addition to all the characteristics observed in polyesters.
Properties
It is strong, lightweight, and has good elasticity.
It resists wrinkling and springs back into shape when creased.
Polyester fabrics can be washed and dried easily and quickly.
Note: Elasticity Ability of a material to return to its original shape after it has been stretched or compressed
Uses
Polyester is used for making lightweight sails.
Sails made of polyester
Polyester films (commonly known as Mylar) are used for making magnetic recording tapes in audio cassettes, video cassettes, and floppy disks.
Terylene is used for making conveyor belts as it is very elastic. Terrycot is commonly used for making shirts, skirts, and other dress materials.
Terrywool is used for making formal suits.
Acrylic
Acrylic fibres, also known as Orion and Acrilan, closely resemble wool.
Properties
It is warm, soft, light, and flexible.
It is resistant to moths and chemicals.
Uses
Acrylic is used for making sweaters, socks, shawls, carpets, and blankets.
Spandex
Spandex, also known as Lycra, was invented by the DuPont chemist Joseph Shivers in 1959.
Properties
It has excellent elasticity, which makes it suitable for use in clothes that require snug fitting.
Uses
Spandex is used for making swimming costumes. It is often mixed with other fibres, like cotton, to get stretch fabrics, which are used for making caps and T-shirts.
