Synthetics

Synthetics

Most of the products and materials we use today are of synthetic origin; from the garments we wear to the rubber used in the production of various tools। This article briefly discusses some examples of synthetics.

Synthetic Fibres

Synthetic fibres are "man-made textile fibres produced entirely from chemical substances, unlike those man-made fibres derived from such natural substances as cellulose or protein." The polymers of synthetic fibres do not occur in nature, instead, they are produced from scratch in chemical plants or laboratories, "almost always from by-products of petroleum and natural gas." Of these polymers are nylon, polyethylene terephthalate, as well as other compounds such as the acrylics, the polyurethanes and polypropylene. Synthetic fibres are "spun and woven into huge consumer and industrial products", from garments such as shirts and scarves, home furnishings such as carpets ad drapes, to industrial parts such as flame-proof linings and drive belts.

Stages in the wet spinning of polymeric fibres

Stages in the melt spinning of polymeric fibres

Examples of textured yarns

Table 1: Properties & Applications of Prominent Synthetic Fibres

Synthetic Abrasives

"Abrasives are sharp, hard materials used to wear away the surface of softer, less resistant materials." Examples of abrasives range from the soft particles used in household cleansers and jeweler's polish to the hardest known material, the diamond. The forms in which abrasives are used include grinding wheels, sandpapers, honing stones, polishes, cutoff wheels, tumbling and vibratory mass-finishing media, sandblasting, pulpstones, ball mills, and other tools and products. "Only through the use of abrasives is industry able to produce the highly precise components and ultrasmooth surfaces required for the manufacture of automobiles, airplanes and space vehicles, mechanical and electrical appliances, and machine tools." The most important characteristics that should exist in an abrasive are hardness and toughness or strength. It was proved that a certain degree of control over the characteristics of synthetic abrasives could be achieved by various methods, to develop abrasives that would "meet the operating conditions found in a variety of applications."

Table 2: Hardness of Prominent Synthetic Abrasive Materials

The Verneuil Process

The Verneuil process -also referred to as the Flame-Fusion Process, is a method by which synthetic rubies and sapphires are produced. It was originally developed in 1902 by a French chemist, Auguste Verneuil. By applying slight modifications to this method, spinel, rutile and strontium titanate can be produced. Star rubies and sapphires were first developed in 1947 in the United States. "The synthetic gems have sharper and more distinctly developed stars than the natural crystals", which is why they are superior to natural gemstones.

Synthetic Food Additives

Food additives are produced for the purpose of enhancing sensory characteristics of foods, that are subject to degradation or loss during food processing. Food additives include colouring agents, flavourings and sweeteners.

Synthetic Colorants: "Synthetic colorants are primarily petroleum-based chemical compounds", unlike natural colorants that are derived from plants, animals and mineral sources. Synthetic colorants exist in the forms of powders, pastes, granules or solutions. The fact that synthetic colorants can be modified gives them superiority to natural colorants that are associated with certain problems, including "the lack of consistent colour intensities", instability under special conditions and "reactivity with other food components".

Flavourings: The flavour of foods is influenced by their taste and smell (odour). Flavour additives form the largest group among food additives. Those of synthetic origin are mixtures of synthetic compounds, whereas natural flavourings are extracted from plants, animals, spices and herbs.

Sweeteners: Since the discovery of saccharin -the first synthetic sweetener- in the late 1800s, efforts have been carried out to develop other synthetic sweeteners that provide few or no calories or nutrients. These are thus referred to as "nonnutritive sweeteners", unlike the natural sweeteners such as sucrose, glucose, fructose....etc. that are known as "nutritive sweeteners" for the energy they provide in the form of carbohydrates. Synthetic sweeteners are used in the manufacture of low-calorie products. They also serve persons with diabetes as a carbohydrate replacement.

Synthetic Chemical Agents

Synthetic chemical agents are used to treat bacterial diseases. Examples of them include the sulfonamides; used for treating urinary tract infections, preventing infection of burns as well as certain forms of malaria, isoniazid, ethabutol, pyrazinamide and ethionamide; useful in treating tuberculosis.

Synthetic Rubber

Rubber is made of elastic polymers, which are "materials composed of long, chainlike molecules that are capable of recovering their original shape after being stretched to great extents." The molecules of rubber stretch in the direction in which they are pulled and upon release, they return to their state that existed before the application of force. Rubber is used in the manufacture of automobile tyres, mountings, gaskets, belts, hoses and consumer products such as shoes, clothing, furniture and toys. Natural rubber nowadays competes with synthetic rubber such as styrene-butadiene rubber and polybutadiene, which are extracted from the by-products of petroleum and natural gas.