Polystyrene (pol-ee-STYE-reen) is a thermoplastic polymer made from styrene. A thermoplastic polymer is a material that can be repeatedly softened and hardened by alternately heating and cooling. Styrene is a hydrocarbon derived from petroleum with the formula C6H5CH=CH2. The presence of the double bond in the styrene molecule makes it possible for styrene molecules to react with each other in long chains that constitute the polymer polystyrene. Polystyrene is a hard, strong, transparent solid highly resistant to mechanical impact. It is an excellent thermal (heat) and electrical insulator, is easily shaped and molded in the liquid state, and takes dyes readily. It can be produced in a wide variety of shapes and forms, including sheets, plates, rods, beads, and foams. KEY FACTS OTHER NAMES: Styrofoam FORMULA: -[-CH2C6H5-]-n ELEMENTS: Carbon, hydrogen COMPOUND TYPE: Organic polymer STATE: Solid MOLECULAR WEIGHT: Varies g/mol MELTING POINT: Varies widely; ranges from 190°C-260°C (370°F-500°F) BOILING POINT: Not applicable SOLUBILITY: Insoluble in water and inorganic acids and bases; soluble in many organic solvents, including ethylbenzene, chloroform, carbon tetrachloride, and tetrahydrofuran The history of polystyrene dates to 1839 when a German apothecary (druggist) named Eduard Simon discovered styrene in petroleum. Later scientists attempted to incorporate styrene into some of the commercial products they made, such as rubber tires. But a polymer based on styrene was not actually produced until 1930 when researchers at the German chemical firm of I. G. Farben discovered how to make the material. Farber's parent company, BASF, shortly made the product commercially available and in 1937, Dow Chemical first made the compound available in the United States. During World War II, polystyrene was used for the manufacture of synthetic rubber products. After the war, the number of commercial and industrial uses expanded rapidly. Today, it is virtually impossible to avoid polystyrene products in one's daily life. HOW IT IS MADE Compounds like styrene with double bonds often polymerize easily. The double bond on a styrene molecule breaks open and a hydrogen atom from a second styrene molecule adds to one side of the double bond, while the rest of the second styrene molecule adds to the second side of the double bond. The product of this reaction still has a double bond. So the reaction can be repeated a second time; and a third time; and a fourth time; and so on. One goal of research on polystyrene has been to determine how the size of the polystyrene affects its properties (and, therefore, its uses) and how to stop the polymerization reaction at some desired point. All that is needed to start the polymerization of styrene is a material that will cause the first double bond to break. Such materials are known as polymerization initiators. One of the most common initiators used in the polymerization of styrene is benzoyl peroxide (C6H5COOOCOC6H5). Once the polymerization reaction begins, it tends to release enough energy for the reaction to continue on its own. An especially popular form of polystyrene is known as expanded polystyrene. It is made by blending air with molten polystyrene to make a lightweight foam sold under the trade name of Styrofoam Interesting Facts Polystyrene is sold commercially under more than a hundred trade names, the most famous of which is probably Styrofoam Only about 5 percent of a styrofoam cup is polystyrene. The rest is air. One of the innovative uses for polystyrene is as a building material for the construction of new houses. Scientists suggest that it is perfect for the purpose: lightweight, inexpensive, strong, a good insulator, and available all over the world. One of the first applications suggested for polystyrene as a building material is in the construction of houses in Afghanistan, where many families have lost their homes after two decades of wars and earthquakes. COMMON USES AND POTENTIAL HAZARDS Polystyrene is the fourth largest thermoplastic polymer made in the United States by production volume. It is used in the manufacture of hundreds of commercial, industrial, household, and personal articles. Some examples include: Plastic model kits and toys; Containers with lids; disposable cups, plates, knives, forks, and spoons; "Jewel" cases for compact discs and cases for audiocassettes; Plastic coat hangers and plastic trays; Refrigerator doors and air conditioner cases; Housing for machines; and Cabinets for clocks, radios, and television sets. Some uses of expanded polystyrene include: In all kinds of containers to keep foods either hot or cold (such as ice chests); Egg cartons; Fillers in shipping containers; Packages for carry-out foods; Insulation for buildings; In the construction of boats; and For the construction of some types of furniture. Polystyrene dust and powder formed during production can be a mild irritant to eyes.

The camel and the fox were very good friends and very good thieves. One day, the two friends decided to cross the river so that they could travel to a nearby farm to steal food. The small fox could not swim so the camel said to his friend, ‘Climb up onto my back and I will swim across the river.’ And so the fox climbed up onto the camel’s back and the strong camel swam across the river to the other side. When they had crossed the river, the camel and the fox made their way to the farm. When they finally arrived at the farm, the fox caught herself a chicken while the camel dug up some lovely fresh vegetables. The greedy fox quickly gobbled down her chicken and then said to her friend the camel, ‘When I finish eating I am accustomed to singing.’ ‘Do not sing just yet,’ said the camel as he was chewing on his dinner of vegetables. ‘I have not yet finished eating and if you sing then the farmer will hear you. Let me first finish my dinner and then you can sing as we make our way back home.’ But the fox did not pay any attention to her friend and began to sing at the top of her voice. The farmer soon heard this singing and came running out of his house waving a large stick. ‘I will teach you to steal from me!’ exclaimed the angry farmer. Because the fox was so small and nimble, she was able to run away from the farmer. But the poor camel was very slow, and still in the middle of eating his dinner, and so he did not see the farmer until it was too late. The angry famer set upon the camel with his large stick and the poor camel received many blows to his legs and back before he was finally able to escape. When the camel reached the river, his bones ached and he was very upset with his friend the fox. ‘Why did you sing when you knew that farmer would hear you and you could see that I was still eating my dinner?’ asked the camel. ‘Because it is my custom,’ replied the fox in her matter-of-fact way. ‘Now let me climb upon your back so that we may return to our home across the river.’ Then the camel walked slowly down the riverbank into the water and began to swim across to the other side with the fox upon his back. When the camel was halfway across the river, at the point where the water was at its deepest and the current at its fastest, he stopped swimming and said to the fox, ‘When I have finished eating I am accustomed to taking a bath.’ ‘Do not take a bath!’ pleaded the fox. ‘I cannot swim and if you take a bath I shall drown!’ ‘I am very sorry,’ said the camel, ‘but I always take a bath after I have eaten. It is my custom.’ And with that the camel lowered his back into the deep water until the fox lost her grip on his back and began to splash around helplessly against the fast current. ‘Help me!’ cried the desperate fox. ‘I am drowning, I am drowning!’ The camel asked the fox, ‘Are you sorry that you were so selfish and caused me to be beaten by the farmer?’ ‘Yes, yes, I am truly sorry!’ cried the fox just before her head disappeared once more beneath the surface of the water. The camel did not have the heart to watch his friend drown in the river and so he pulled the little fox out of the water and placed her upon his back. Then the camel swam the rest of the way across the river and climbed up the bank and onto the warm grass. The fox realised that she had been very selfish and said to her friend, ‘I am so sorry for what I did and I promise that you can trust me forever and that is that.’ ‘And I am sorry that I had to teach you a lesson today, but many times in life it is often a case of tit for tat.’ Then the two friends began to laugh and roll around in the warm grass while the sunshine dried their wet fur. The fox had learned a valuable lesson that day. She had learned that it was not good to betray a friend, and that if you do wrong by somebody then somebody might well do wrong by you. It was indeed a lesson of tit for tat.