PLASTIC  MATERIAL 

 Plastic  are a wide range of synthetic or semi-synthetic materials that use polymer sas a main ingredient. Their plasticity makes it possible for plastics to

be moulded, extruded or pressed into solid objects of various shapes. This adaptability, plus a wide range of other properties, such as being lightweight, durable, flexible, and inexpensive to produce, has led to its widespread use. Plastics typically are made through human industrial systems. Most modern plastics are derived from fossil fuel-based chemical like natural gas or petroleum however, recent industrial methods use variants made from renewable materials, such as corn or cotton derivatives.

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% plastic ), furniture, and toys. In the developing world, the applications of plastic may differ; 42% of India's consumption is used in packaging. In the medical field, polymer implants and other medical devices are derived at least partially from plastic. Worldwide, about 50 kg of plastic is produced annually per person, with production doubling every ten years.

             Properties and classifications 

Plastics are usually classified by the chemical structure of the polymer's backbone and side chains. Important groups classified in this way include the acrylics, polyester, Silicones,polyurethenee, and halogeneted plastics. Plastics can be classified by the chemical process used in their synthesis, such as condensation, polyaddition, and cross-linking.They can also be classified by their physical properties, including hardnes, density, tensile strength, thermal resistance, and glass transition temperature. Plastics can additionally be classified by their resistance and reactions to various substances and processes, such as exposure to organic solvents, oxidation, and ionizing radiation classifications of plastics are based on qualities relevant to manufacturing or product design for a particular purpose. Examples include thermoplastics , thermosets, conductive polymers, biodegradable plastic, engineering plastics and elastomers

Thermoplastics  and thermosetting polymers 

The plastic handle of a kitchen utensil has been
deformed by heat and partially melted.

One important classification of plastics is the degree to which the chemical processes used to make them are reversible or not.

Thermoplastics do not undergo chemical change in their composition when heated and thus can be molded repeatedly. Examples include polyethylene (PE), polypropylene (PP)polystyrene (PS), and polyvinyl chloride (PVC).

Thermosets, or thermosetting polymers, can melt and take shape only once: after they have solidified, they stay solid. If reheated, thermosets decompose rather than melt. In the thermosetting process, an irreversible chemical reaction occurs. The vulcanization  of rubber is an example of this process. Before heating in the presence of sulfur, natural rubber (polyisoprene) is a sticky, slightly runny material; after vulcanization, the product is dry and rigid.

Amorphous plastic and crystalline plastics 

Many plastics are completely amorphous  (without a highly ordered molecular structure), including thermosets, polystyrene, and methyl methacrylate  (PMMA). Crystalline  plastics exhibit a pattern of more regularly spaced atoms, such as high-density polyethylene (HDPE), polybutylene terephthalate (PBT), and polyether ether ketone (PEEK).

These so-called semi-crystalline  plastics include polyethylene, polypropylene, polyvinyl chloride, polyamides (nylons), polyesters and some polyurethanes.

Conductive polymers 

Intrinsically conducting polymers (ICP) are organic polymers that conduct electricity. While a conductivity of up to 80 kS/cm in stretch-oriented polyacetylene, has been achieved, it does not approach that of most metals. For example, copper has a conductivity of several hundred kS/cm.

Chemical structure of conductive 
Polymers 

Biodegradable plastics and bioplastics

Biodegradable plastic 

Biodegradable  plastics are plastics that degrade (break down) upon exposure to sunlight or ultra-violet radiation ; water or dampness; bacteria; enzymes; or wind abrasion. Attack by insects, such as waxworms and mealworms, can also be considered as forms of biodegradation. Aerobic  degradation requires that the plastic be exposed at the surface, whereas anaerobic  degradation would be effective in landfill or composting systems. Some companies produce biodegradable additives  to enhance biodegradation. Although starch powder can be added as a filler to allow some plastics to degrade more easily, such treatment does not lead to complete breakdown. 

Bioplastics 

While most plastics are produced from petrochemicals, bioplastics  are made substantially from renewable plant materials like cellulose and starch. Due both to the finite limits of fossil fuel reserves and to rising rising level of greenhouse gases     caused primarily by the burning of those fuels, the development of bioplastics is a growing field. Global production capacity for bio-based plastics is estimated at 327,000 tonnes per year.

Bioplastics 

                    Plastic Industry 

The plastic industry includes the global production, compounding , conversion and sale of plastic products. Although the middle East and Russia produce most of the required petrochemical raw materials; the production of plastic is concentrated in the global East and West. The plastic industry comprises a huge number of companies and can be divided into several sectors:

Production 

Since the birth of the plastic industry in the 1950s global production has increases enormously, reaching some 381 million metric tonnes in 2015 (excluding additives). The total amount of plastic generated in that time is estimated to be 8.3 billion tonnes.

Plastics are produced in chemical plants by the polymerization  of their starting materials (monomers); which are almost always petrochemical in nature. Such facilities are normally large and are visually similar to oil refineries , with sprawling pipework running throughout. The large size of these plants allows them to exploit economies of scale. Despite this, plastic production is not particularly monopolized, with about 100 companies accounting for 90% of global production.This includes a mixture of private and state-owned enterprises.

             ENVIRONMENTAL  EFFECTS 

 

A communication campaign infographic showing that there will be more plastic in the oceans than fish by 2050

Because the chemical structure of most plastics renders them durable, they are resistant to many natural degradation processes. Much of this material may persist for centuries or longer, given the demonstrated persistence of structurally similar natural materials such as amber.

There are differing estimates of how much plastic waste has been produced in the last century. By one estimate, one billion tons of plastic waste have been discarded since the 1950s.Others estimate a cumulative human production of 8.3 billion tons of plastic, of which 6.3 billion tons is waste, with only 9% getting recycled.

                           Microplastics 

Microplastics  are fragments of any type of plastic less than 5 mm (0.20 in) in length, according to the U.S. National Oceanic and Atmospheric Administration  (NOAA) and the European chemicals Agency .They cause pollution  by entering natural ecosystems  from a variety of sources, including cosmetics, clothing , and industrial processes.

Two classifications of microplastics are currently recognized. Primary microplastics include any plastic fragments or particles that are already 5.0 mm in size or less before entering the environment. These include microfibers from clothing, microbeads , and plastic pellets (also known as nurdles).