Barbara Mitchell, age 13, of Danville, I11., for her question:
HOW IS NYLON MADE?
Nylon is a name for a group of synthetic products made from coal, water, air, petroleum, agricultural byproducts and natural gas. Nylon is one of the toughest, strongest and most elastic substances in existence.
Two chemical compounds, hexamethylenediamine and adipic acid, are used to make nylon. Both of these compounds contain carbon and hydrogen.
After these two compounds are produced, they are combined to form a compound known as nylon salt. The full name of this compound is hexamethylene diammonium adipate.
Most factories make nylon by placing hexamethylene diamine, along with the adipic acid, in a machine called an autoclave. Then the mixture is heated under pressure, so that the molecules that make up each of the chemical substances combine into larger molecules. This process of making large molecules out of smaller ones is called polymerization.
When polymerization is complete, the melted nylon comes out of the machine as a.plastic ribbon. This is chilled and hardened on a metal roller. The ribbon is then cut into chips and blended for uniformity.
Nylon fibers are made by melting the chips over heated grids covered with inert gas to keep the oxygen of the air from getting into the melted nylon. When the nylon becomes liquid, it is pumped through the tiny holes of a device called a spinneret. The threads harden as soon as they strike the air and are wound on spools that handle about one half mile of thread per minute.
From one to as many as 2,520 filaments or strands from the spinneret are united into a textile nylon yarn. They are twisted a few turns per inch before they are wound on bobbins.
Nylon is cold drawn after it is made into yarn. The cold drawing process makes a great change in the structure of the yarn filaments. When the thread is stretched or drawn, the molecules fall into parallel lines. This gives the yarn strength and elasticity.
The cold drawing process is carried out by unwinding the filament from one spool and winding it onto another in such a way as to make the winding up rate four or more times as fast as the unwinding rate. The pull between the spools stretches the yarn.
The size of the yarn depends on its original size and the degree of stretching. If the yarn is drawn to four times its original length, its diameter is only half its original diameter.
The size of nylon yarn is measured in deniers. A denier is the weight in grams of 9,843 yards of yarn. As an example, 9,843 yards of nylon yarn that weigh 15 grams are called 15 denier.
Nylon fabrics are not weakened by mildew. They are not harmed by most oils, greases or such chemicals as household cleaning fluids. Nylon absorbs little water.
Nylon was first made into hosiery in 1938. Now it is also used for dresses, bathing suits, lace, tires, carpets and upholstery. In industry, nylon is used to make bearings, gears, wire coatings and machine parts. Surgeons also use nylon thread to sew up wounds.