My Science School

           Take a look around and you would find at least ten things made of low density polyethylene (LDPE) toys, utensils, films, bottles, pipes, insulating wires, plastic wraps, juice cartons and so on.

           Low density polyethylene is class of flexible thermoplastic depending on how they are being made. As the name suggests, it has a lower density and the force of attraction between the molecules is weak. LDPE is cheap and can be easily processed. It is generally not reactive at room temperatures. It is flexible and quite tough. These qualities make it a desirable polymer for making a lot of things.

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           Most of us have plastic food containers at home. These food containers are airtight and do not absorb moisture easily. A material called polypropylene is used to make such food containers. It is a thermoplastic polymer made of propylene monomers and is also known as PP. Polypropylene doesn’t absorb water and dries quickly. It is an effective insulator and does not transfer heat. PP is also resistant to acids and alkalies.

           A range of other products like bottles, various parts of automobiles, plastic hinges, carpets and clothing use polypropylene.

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           None of us will compromise when it comes to buying a backpack. It should be strong, durable and should not tear off easily. But, have you ever thought of the materials that are used for making a quality backpack?

           Long ago, backpacks were mostly made of cotton canvas with wax coating. The coating waterproofed them. But, these bags were prone to damage. Today, most of the backpacks are made of synthetic fibres like nylon and polyester. Though nylon has better waterproof traits than many other fibres, it can be easily damaged. But nylon can be strengthened using different techniques.

           Ripstop nylon is thicker and can be sewn close to get a tightly stitched fabric. It is used to make hiking backpacks. Your school-bags are often made of polyester. It is cheap and can be dyed into any attractive colour.

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           Mountaineering is not an impulsive activity. It requires proper planning and preparation which would not be complete without certain polymers.

           You need breathable clothes in which you can easily move around. Most of these clothes are made of nylon. You need strong ropes made of synthetic fibres and shoes with a firm grip. Hiking and mountaineering shoes are often made of materials like rubber with laces made of fibres like kevlar.

           You need a good backpack and that is made of a set of polymers. The bottles that you carry water in are yet another thing made of polymers.

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           Nomex suits have saved the lives of many race car drivers. Here is what Jeff Gordon, veteran racer, says about Nomex.

           “I’ve been racing for a lot of years and I’ve been wearing a Nomex suit for many of those, starting out in the go-cart days. Nomex is an amazing material. I have, unfortunately, had the opportunity to test this product in my racing.”

           “I was in a midget several years ago and (the car) did catch fire, which is pretty scary because you can’t see the flames. You don’t know you’re on fire until it’s almost too late. I was actually running through a practice and a fuel line came loose and I noticed my steering wheel was on fire and that’s why I knew I was on fire. I felt some heat, but nothing ever touched me, no flames ever got to me, no burns ever got to me.”

           “Of course in the midget cars we’re wearing three layers plus a Nomex underwear lining underneath it and that’s the reason why I certainly wouldn’t get in a race car and do my job without having Nomex on.”

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            Du Pont developed Nomex in the 1960s. This polymer is used to make the masks of firefighters, racing vehicles and to build aircraft for military use. Race car drivers and wildfire fighters wear suits made of nomex. It is used to reinforce the insides of helicopters and tail fins of aeroplanes. Needless to say, Nomex is a fireproof material.

            Nomex resists heat, chemicals and several radiations. The monomers of Nomex have a ring-like structure held together in a strong bond. It is sold as fibres and sheets.

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           You would be thinking that it is ridiculous to ask something like this. But, solar cooking stoves and nail polish have something in common- a polymer called Mylar.

           Mylar is a special type of stretched polyester generally known as BoPET. It is also known as Melinax and Hostaphan. Don’t be confused with too many names. It is made of polyethylene terphtalate (PET) monomers. It is transparent and chemically stable. It also provides good electrical insulation.

           Mylar is used for making packaging and lids for food products. It is also used as a covering over paper or clothing. This coating gives a shiny surface and a protective coating. It is used in a range of other products like the diaphragms of headphones.

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           When you pour the dosa batter on a non-stick pan, the flour is sticky. But you can easily take out the dosa from the pan with a wooden spatula once it’s cooked. You don’t have to smear the pan with oil like the traditional ones. Wonder why? This would not be possible if not for the Teflon coating in the pans.

          Teflon does not melt easily. It has a high melting point and is also stable at very low temperatures. Teflon is extremely resistant to corrosion. It cannot be dissolved by most of the materials. In addition to this, it is very slippery and has high resistance corrosive chemicals. Therefore, Teflon provides a perfect coating material for cooking utensils that resists heat, friction and wear and tear. Teflon is also used widely in carpets, wall coverings, paints and as weatherproofing on outdoor signs.

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           Teflon is familiar to all of us from the advertisements of non-stick cookware and paints. But, Teflon is just the brand name. Polytetrafluoroethylene is the chemical name of Teflon. Quite a mouthful, right?

           Teflon is a compound made of tetrafluoroethylene monomers. The discovery of Teflon was not deliberate. A young scientist named Roy Plunkett who worked at Du Pont accidentally made Teflon while he was working on a refrigerant compound. He combined hydrochloric acid with tetrafluoroethylene to obtain a new compound.

           The gas formed in the reaction cooled down and transformed to a white powder overnight forming the new material - Teflon.

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