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Jai Ganesh

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Registered: 2005-06-28

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Re: Miscellany

2326) Plastics/Plastic Tecnology

Gist

Plastics are polymers, which means they are made by linking chains of the molecules (called monomers) together to create a large molecule (a polymer). An example of this is polystyrene. These links make polymers strong and durable. That's why poly- appears in common names for plastic, like polyethylene.

Plastic technology encompasses the science, engineering, and practices involved in creating, processing, and utilizing plastic materials. It involves understanding the properties of polymers, developing new materials, and designing and manufacturing plastic products for various applications.

Plastic is defined as a material that contains an essential ingredient an organic substance of large molecular weight. It is also defined as polymers of long carbon chains. Carbon atoms are linked in chains and are produced in long-chain molecules

Summary

Plastics are a wide range of synthetic or semisynthetic materials composed primarily of polymers. Their defining characteristic, plasticity, allows them to be molded, extruded, or pressed into a diverse range of solid forms. This adaptability, combined with a wide range of other properties such as low weight, durability, flexibility, chemical resistance, low toxicity, and low-cost production, has led to their widespread use around the world. While most plastics are produced from natural gas and petroleum, a growing minority are produced from renewable resources like polylactic acid.

Between 1950 and 2017, 9.2 billion metric tons of plastic are estimated to have been made, with more than half of this amount being produced since 2004. In 2023 alone, preliminary figures indicate that over 400 million metric tons of plastic were produced worldwide. If global trends in plastic demand continue, it is projected that annual global plastic production will exceed 1.3 billion tons by 2060. The primary uses for plastic include packaging, which makes up about 40% of its usage, and building and construction, which makes up about 20% of its usage.

The success and dominance of plastics since the early 20th century has had major benefits for mankind, ranging from medical devices to light-weight construction materials. The sewage systems in many countries relies on the resiliency and adaptability of polyvinyl chloride. It is also true that plastics are the basis of widespread environmental concerns, due to their slow decomposition rate in natural ecosystems. Most plastic produced has not been reused. Some is unsuitable for reuse. Much is captured in landfills or as plastic pollution. Particular concern focuses on microplastics. Marine plastic pollution, for example, creates garbage patches. Of all the plastic discarded so far, some 14% has been incinerated and less than 10% has been recycled.

In developed economies, about a third of plastic is used in packaging and roughly the same in buildings in applications such as piping, plumbing or vinyl siding. Other uses include automobiles (up to 20% plastics), furniture, and toys. In the developing world, the applications of plastic may differ; 42% of India's consumption is used in packaging. Worldwide, about 50 kg of plastic is produced annually per person, with production doubling every ten years.

The world's first fully synthetic plastic was Bakelite, invented in New York in 1907, by Leo Baekeland, who coined the term "plastics". Dozens of different types of plastics are produced today, such as polyethylene, which is widely used in product packaging, and polyvinyl chloride (PVC), used in construction and pipes because of its strength and durability. Many chemists have contributed to the materials science of plastics, including Nobel laureate Hermann Staudinger, who has been called "the father of polymer chemistry", and Herman Mark, known as "the father of polymer physics".

Structure

Most plastics contain organic polymers. The vast majority of these polymers are formed from chains of carbon atoms, with or without the attachment of oxygen, nitrogen or sulfur atoms. These chains comprise many repeating units formed from monomers. Each polymer chain consists of several thousand repeating units. The backbone is the part of the chain that is on the main path, linking together a large number of repeat units. To customize the properties of a plastic, different molecular groups called side chains hang from this backbone; they are usually attached to the monomers before the monomers themselves are linked together to form the polymer chain. The structure of these side chains influences the properties of the polymer.

Details

A plastic is a polymeric material that has the capability of being molded or shaped, usually by the application of heat and pressure. This property of plasticity, often found in combination with other special properties such as low density, low electrical conductivity, transparency, and toughness, allows plastics to be made into a great variety of products. These include tough and lightweight beverage bottles made of polyethylene terephthalate (PET), flexible garden hoses made of polyvinyl chloride (PVC), insulating food containers made of foamed polystyrene, and shatterproof windows made of polymethyl methacrylate.

The composition, structure, and properties of plastics

Many of the chemical names of the polymers employed as plastics have become familiar to consumers, although some are better known by their abbreviations or trade names. Thus, polyethylene terephthalate and polyvinyl chloride are commonly referred to as PET and PVC, while foamed polystyrene and polymethyl methacrylate are known by their trademarked names, Styrofoam and Plexiglas (or Perspex).

Industrial fabricators of plastic products tend to think of plastics as either “commodity” resins or “specialty” resins. (The term resin dates from the early years of the plastics industry; it originally referred to naturally occurring amorphous solids such as shellac and rosin.) Commodity resins are plastics that are produced at high volume and low cost for the most common disposable items and durable goods. They are represented chiefly by polyethylene, polypropylene, polyvinyl chloride, and polystyrene. Specialty resins are plastics whose properties are tailored to specific applications and that are produced at low volume and higher cost. Among this group are the so-called engineering plastics, or engineering resins, which are plastics that can compete with die-cast metals in plumbing, hardware, and automotive applications. Important engineering plastics, less familiar to consumers than the commodity plastics listed above, are polyacetal, polyamide (particularly those known by the trade name nylon), polytetrafluoroethylene (trademark Teflon), polycarbonate, polyphenylene sulfide, epoxy, and polyetheretherketone. Another member of the specialty resins is thermoplastic elastomers, polymers that have the elastic properties of rubber yet can be molded repeatedly upon heating. Thermoplastic elastomers are described in the article elastomer.

Plastics also can be divided into two distinct categories on the basis of their chemical composition. One category is plastics that are made up of polymers having only aliphatic (linear) carbon atoms in their backbone chains. All the commodity plastics listed above fall into this category. The structure of polypropylene can serve as an example; here attached to every other carbon atom is a pendant methyl group (CH3):

The other category of plastics is made up of heterochain polymers. These compounds contain atoms such as oxygen, nitrogen, or sulfur in their backbone chains, in addition to carbon. Most of the engineering plastics listed above are composed of heterochain polymers. An example would be polycarbonate, whose molecules contain two aromatic (benzene) rings.

Additional Information:

Introduction

A plastic is a kind of material that is made by people and can be formed into almost any shape. Most plastics are strong, long-lasting, and lightweight. They resist damage by water, heat, chemicals, and electricity. In addition, plastics can be made in many colors.

There are about 50 main types of plastic. They have countless uses. Manufacturers often use plastics in place of more expensive materials. In nylon stockings, for example, plastic takes the place of silk. In vinyl house siding, plastic takes the place of wood. In many automobile body parts, plastic takes the place of metal.

Making Plastics

Most plastics are made from chemicals that come from petroleum (oil), natural gas, or coal. Heating these chemicals causes them to break down into molecules. (Molecules are groups of two or more atoms, which are the tiny building blocks of everything.) Scientists then join these molecules into chains. These chains make up plastics. Different combinations of molecules form different kinds of plastic.

Plastics can be made into almost any shape by heating them at a high temperature. The heat softens the plastic, which can then be poured into a mold. As the softened plastic cools, it hardens. When reheated, some types of plastic will soften again. The plastic can then be made into new shapes. Other types of plastic will stay hard even when reheated.

History

In 1869 John Wesley Hyatt, a U.S. inventor, made the first plastic. He called it celluloid because he made it from a plant material called cellulose. In 1909 a U.S. chemist named Leo H. Baekeland developed the first plastic made completely from synthetic (human-made) materials. Baekeland named the new material Bakelite. Scientists developed many more plastics from the 1920s through the 1940s. Later scientists invented stronger plastics and blended plastics with other materials.

Plastics and the Environment

Plastics are very useful, but they can also cause many problems for the environment. Items made out of plastic do not break down. When they are thrown out they take up room in landfills. A great deal of plastic waste winds up in the oceans, where it can hurt animals. Because they do not break down, things like plastic bags, bottles, and fishing lines collect in large areas of the ocean. Sea turtles and other animals may eat the plastic. The animals can also be hurt when plastic fishing lines get wrapped around their bodies. People who are concerned about the environment try to encourage people to recycle plastics instead of throwing them away. Recycled plastic can be turned into clothing, outdoor furniture, playground equipment, and more bottles.

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