What is Plastic?
It is accepted that the plastics industry started with the commercial production of nitrocellulose (1868). This is roughly 130 years ago. Following nitrocellulose, phenol-formaldehyde-based polymers, which are the second synthetic plastic in history, have been developed. Their production took place approximately 40 years after this date. Polymers, which are the basic building blocks and raw materials of this and other plastic materials that follow, emerged at the end of some trial studies in the second half of the 19th century, and many of them were discovered by chance.

Basically, we know that there are 3 different materials in nature and they are used frequently. These; polymeric materials, metallic materials and ceramic materials.

Those who easily hand over form the metals. Nonmetals form polymers, on the other hand. The mixture of metallic and non-metallic elements leads to ceramics. There are the following differences between these three basic materials. Metals conduct heat and electricity. They are bright, generally hard, and react by donating electrons. Their density is higher than 1. Polymers do not conduct electricity and heat well, they usually have a solid or dull appearance. Their density is small, around 1, they are light. Especially because of these differences, metals or polymers are preferred for different programs. Polymers are preferred over metals. Thus, plastic with different properties was produced from polymer materials.
Annual consumption of polymer materials is more than 150 million tons / year for all countries of the world. Consumption in our country is approximately one percent of this amount. Cellulose, starch, natural rubber and so on. Natural polymers have left their places to semi-synthetic and then synthetic polymers due to the difficulty of processing and the inadequacy of some physical, chemical and mechanical properties. The first polymer material was celluloid discovered by S. Hyatt in 1863. Celluloid, a semi-synthetic polymer, is obtained from cotton cellulose. However, the modern plastic industry begins in 1989, with the production of bakelite industry-wide by L. Baekeland. Bakelite, a phenol formaldehyde resin, has been used to make plastic products such as telephone handsets. Until 1924, polymer structures were thought to consist of small molecules in the "colloid aggregate" state. As a result of his large-scale investigations, H. Staudinger shows that plastics consist of macromolecules in the form of chains and that these molecules consist of small units covalently linked to each other. Based on the idea mentioned above, the polymer industry developed rapidly and cellulose acetate and polyvinyl chloride were obtained in 1927, polymethylmethacrylate in 1928 and urea-formaldehyde resins in 1929. These were later polyethylene in 1932, nylon, polyacrylonitrile, styrene-acrylonitrile and polyvinyl acetate in 1934, polyurethane in 1937, poly (tetrafluoroethylene), known as teflon in 1939, polyethylene terephthalate in 1941, and polyacrylonitrile fiber, known under the trade name ortholon. followed.

An important step in the development of plastics is to obtain reinforced plastics by mixing these materials with glass, graphite and carbon fibers. The mechanical properties of these materials reach the level of metals and plastics compete with metals in most application areas.

Plasticizers
What is plastic? Plastic is made from petroleum. It falls into the class of compounds defined in plastic polymer form. It is known as large molecules formed by covalent bonding of small molecules called polymer monomers.

The glass transition temperature of some of the most frequently used plastics today is above the Tg room temperature. As it is known, polymers below Tg are glassy and fragile. Above this temperature, they generally show rubbery behavior. And their impact resistance is high. Cellulosics, vinyls, acrylics, etc. In other words, plasticizers are used to soften these polymers. Typical examples of this are PVC. PVC's Tg is 80o C. This can be reduced to 0 ° C with the addition of a reasonable amount of plasticizer.

Plasticizers are organic liquids with high boiling points or solids with low melting points. Plasticizers can be divided into two main groups as "inner plasticizers" and "outer plasticizers".

a) Internal Plasticizers
These are used during the synthesis of polymers. They are attached as comonomer to the monomer forming the main polymeric structure and are located on the polymer chain. For this purpose, the monomer of the polymer whose Tg is desired to be reduced is copolymerized with a low Tg monomer. The Tg of the resulting copolymer is somewhere between the Tg of the pure polymer of these two monomers. The desired Tg level can be achieved by adjusting the ratio of monomers.

b) External Plasticizers
More often

It is the type that is declared. These are added to the structure during the processing (shaping) of the polymer. Quite simply, they play the role of diluent in the polymeric structure. By entering between polymer chains, they reduce the effect of secondary forces, thus softening the structure.

The compatibility of plasticizers with the polymer is the most important feature to be considered in practice. In addition, a good plasticizer is expected to be non-toxic, non-flammable, non-flammable, long-lasting and tasteless.

Properties and Uses of Plastics
There are various types of plastic. Some are as soft as wool, some are as strong as steel. There are flame-resistant ones that melt in hot water. A thin layer of Lexan plastic stops the bullet of a 38-caliber pistol firing at short range. The only common feature of all plastics is that they are inventions of chemists. None of them are found in nature like wool and silk. They are very easy to build.

Although there are thousands of plastic types, it may be possible to group them in two main groups as hot-hardening and hot-molded plastics. Hot molded plastics melt and take the desired shape. Each time they harden as it cools down. After the heat-curing plastic is heated and reformed, it does not change shape when it is reheated.

Hot hardened plastics are reused. If a way to reuse scrap plastics is found, a significant gain will be made. Unfortunately, it is very difficult to recycle scrap plastics today. Because the compositions of various types of plastic are very different from each other. There is no recycling due to this difference. Most plastics are made up of molecules containing carbon and hydrogen. Chemists combine molecules to form chains. Each chain is a large molecule. Sometimes some of these molecules have thousands of connections. These will not melt without being strongly heated. These long-structured molecular chain substances are called polymers.

Poly (many) suffix is ​​often encountered at the beginning of the names of plastics. For example, plastics called propylene are composed of long molecular chains of propylene gas. Molecule chains are sometimes branched through procedures. Sorting in the form of branches is not very strong. Branch plastics can simply melt.
These are soft and flexible. They are used for making dolls and detergent boxes. There is a third kind of polymer; It is known as crosslinked polymer. In this polymer, the chains of molecules are linked by the chains of other molecules.

Temperature hardening plastics obtained in this way are very durable and resistant to very high temperatures. Chemists make more than one variety of substances, starting with oil as the primary ingredient. The most useful of all raw materials is ethylene gas. The most well-known and easiest of ethylene plastics is polyethylene. Light buckets and additives, additionally detergent bottles are made of this material. Propylene and butylene gases are also used in the production of more than one plastic. Benzene is another raw material used in the production of plastics. It is a starting material used in the production of artificial fibers such as benzene, nylon and terilen. Plastics are divided into two as natural and artificial.

Natural Plastics
The first plastics obtained are natural plastics. The first plastics were pure plastics made from cellulose nitrate. These are made by using cellulose in plants. When cellulose nitrate is combined with two herbal substances such as camphor and beaver oil, a plastic is obtained.

An expanded form of it was obtained in 1868 using cellulose nitrate, camphor, and alcohol. It was called celluloid and was often used to make items such as photography and motion pictures. But since celluloid can simply be ignited, it has been replaced by cellulose plastics such as cellulose acetate and ethyl cellulose.

Artificial plastics
XV. At the turn of the century, artificial plastics were made. These plastics were completely obtained from chemicals in the laboratory.