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Category Polymers

Why is Hermann Staudinger an important figure in polymer chemistry?

          Herman Staudinger was not the first chemist to work with polymers. But his significant contributions laid the foundations to diverse applications of polymers.

          Staudinger was a professor in organic chemistry at Zurich when he proposed some of the pioneering theories on polymer structures of fibres and plastics.

          In the 1920s, he found out that rubber has a high molecular weight. He also presented a paper showing several reactions capable of forming structures high molecular weight.

          Staudinger explained how smaller units combine to form a large structure. He called the process polymerization. Before that, polymers were thought of as aggregates of molecules and this idea was based on Thomas Graham’s work. His studies on biological macro-molecules led to a lot of later discoveries of commercial importance.

          Staudinger’s ideas were criticized heavily by other chemists of his time, but were finally accepted by the 1950s. In 1953, he was awarded the Nobel Prize in chemistry for his contributions in understanding macromolecular chemistry.

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What were some of the pioneering discoveries in polymer chemistry?

           Before chemists formulated the basic idea of polymers, Mexicans knew some ways to use polymers. They knew how to modify rubber. Several substances were added to natural rubber. These additives modified and enhanced its properties and were used to make a range of products like bouncing balls.

          Henri Braconnot’s work is the first modern work associated with polymers. In the 1830s, Braconnot along with the help of some others developed celluloid and cellulose acetate, derivatives of cellulose.

          Later in the 1840s, vulcanization of rubber entered the scene which created a huge change in the industry. It was discovered that adding sulphur to natural rubber will make it stable, flexible and prevent stickiness. This led to the production of many useful products like waterproof articles. Vulcanized rubber is undoubtedly the first commercially successful polymer.

          By the 1880s, artificial fibres entered the scene. Hilaire de Chardonnet started the first artificial fibre plant in 1884. It was based on regenerated cellulose which worked as a substitute for silk. Bakelite, the first synthetic plastic was discovered only after more than twenty years in 1907.

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What is polymer degradation?

          Have you observed PVC pipes that are attached to the water tank? You might have noticed that the pipes exposed to sunlight lose colour after a while. These pipes will also lose their strength and become brittle. PVC pipes lose hydrogen chloride gas when exposed to high temperatures.

          Polymers undergo a change their properties like colour, shape or molecular weight when they are exposed to one or more environmental factors like heat, light or chemicals. This change is known as polymer degradation. It is usually undesirable. However, it is useful in recycling polymer waste. Biodegradable plastics are degraded with the help of microorganisms.

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How are monomers combined?

            We have been talking about polymers a lot. But how are they synthesized? A polymer is made by combining monomers to form a long chain and for this; monomers react and combine in a process called polymerization.

            A monomer has the capacity to form chemical bonds with at least two other monomer molecules. Nucleic acid is a natural polymer which is formed when nucleotide monomers bond. How does a PVC pipe take shape? Vinyl chloride is the monomer that reacts in a certain fashion to form polyvinyl chloride (PVC).

            Polymers are formed either by repeated addition or condensation of monomers. Accordingly, polymerization is generally of two types which we will talk about later in detail.

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What are the characteristics of polymers?

          Polymers can be processed in various ways. The characteristics of polymers depend on the chemical bonding between the monomers and the process used to make them. However, polymers have some common attributes.

         Generally, all polymers have long chains consisting of hundreds of monomers. Most polymers show a high resistance to chemicals. Look at the cleaning materials used in your house. When it comes in contact with your skin or eyes, it can cause rashes or itching. But they are safely packed in plastic bottles and the packaging remains unaffected by its contents.

          They resist heat and that’s why, most of the handles of cook-wares are made of plastics. They are good electrical insulators as well. Remember Bakelite, which is used to insulate electric wires. All electric appliances, cords and wirings are covered with polymeric materials.

          Polymers are light in weight, but have significant strength and their inherent properties can be enhanced by using a range of additives. They do not generally melt; because of their structure, they change from crystalline to a semi-crystalline form when heated.

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How are synthetic polymers made?

          Polymers are made by bonding monomers. The process of formation of a polymer is known as polymerization and each polymer has a different combination of sub units.

         Many of the polymers are made by breaking up hydrocarbons. Hydrocarbons are heated up to break the large molecules into smaller ones. This is done in the presence of a catalyst, a material that speeds up the chemical reaction.

         To understand more about the process, let’s look at how plastic is made. To make plastic, natural gases or crude oil are broken down into monomers such as ethylene or butane. These monomers are then combined to form polymers in a chemical reaction. The properties of polymers depend on how the monomers are being bonded.

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Can we chemically modify natural polymers?

          Natural polymers can be modified by chemical treatment.

          The product obtained after the modification is known as a semi-synthetic polymer. A new polymer is synthesized out of a naturally occurring one and hence the name!

          Vulcanized rubber is a semi-synthetic polymer. Rubber in its natural form is not thermally stable. It becomes very hard when it is cold and melts down in heat. But, when treated with sulphur, rubber achieves thermal stability and becomes flexible and can be used to make a range of useful products. This chemical treatment of rubber is known as vulcanization.

           Similarly, many other natural polymers can be modified into semi-synthetic polymers with desirable properties.

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