Solution for Plastics

Part -2

Extraction of raw materials (largely crude oil and natural gas, but also coal) – these are a complex mixture of thousands of compounds that then need to be processed.
Refining process transforms crude oil into different petroleum products – these are converted to yield useful chemicals including “monomers” (a molecule that is the basic building blocks of polymers). In the refining process, crude oil is heated in a furnace, which is then sent to the distillation unit, where heavy crude oil separates into lighter components called fractions. One of these, called naphtha, is the crucial compound to make a large amount of plastic. However, there are other means, such as using gas.
Polymerisation is a process in the petroleum industry where light olefin gases (gasoline) such as ethylene, propylene, butylene (i.e., monomers) are converted into higher molecular weight hydrocarbons (polymers). This happens when monomers are chemically bonded into chains.

A polymer is a large single chain-like molecule in which the repeating units derived from small molecules called monomers are bound together. The process by which monomers are transformed into a polymer is called polymerisation.

The addition polymerisation reaction is when one monomer connects to the next one (dimer) and dimer to the next one (trimer) and so on. This is achieved by introducing a catalyst, typically a peroxide. This process is known as chain growth polymers – as it adds one monomer unit at a time. Common examples of addition polymers are polyethylene, polystyrene and polyvinyl chloride.
Condensation polymerisation includes joining two or more different monomers, by the removal of small molecules such as water. It also requires a catalyst for the reaction to occur between adjacent monomers. This is known as step growth, because you may for example add an existing chain to another chain. Common examples of condensation polymers are polyester and nylon.

In compounding, various blends of materials are melt blended (mixed by melting) to make formulations for plastics. Generally, an extruder of some type is used for this purpose which is followed by pelletising the mixture. Extrusion or a different moulding process then transforms these pellets into a finished or semi-finished product. Compounding often occurs on a twin-screw extruder where the pellets are then processed into plastic objects of unique design, various size, shape, colour with accurate properties according to the predetermined conditions set in the processing machine.

Polymers are broken down into monomers in a process known as hydrolysis, which means “to split water,” a reaction in which a water molecule is used during the breakdown. During these reactions, the polymer is broken into two components. If the components are un-ionized, one part gains a hydrogen atom (H-) and the other gains a hydroxyl group (OH–) from a split water molecule. This is what happens when monosaccharides are released from complex carbohydrates via hydrolysis.

Electrolysis is the process of using an electrical current to separate water into hydrogen and oxygen gas. The electrical charge that is applied to water will break the chemical bond between the hydrogen and oxygen atoms and produce charged particles called ions.
The energy required to split water into hydrogen and oxygen by electrolysis is about 260 kJ per mole of water. Splitting one litre of water would take at least 16 MJ (4.4 kWh), which is an enormous expense on an industrial scale.
The water splitting of seawater and other salt water is used industrially to make chlorine, however, and the waste hydrogen collected comprises about five percent of the world's supply. A version of water splitting occurs in photosynthesis, but hydrogen is not produced.

Photocatalysts are defined as materials which decompose detrimental substances under the sun lights containing UV rays. Mainly, TiO2 is used as photocatalyst at present. Among polymorphs of TiO2, anatase phase shows the most effective photocatalytic effect.
Photocatalysis is the activity occurring when a light source interacts with the surface of semiconductor materials, the so called photocatalysts. During this process, there must be at least two simultaneous reactions occurring, oxidation from photogenerated holes, and reduction from photogenerated electrons.
Titanium dioxide, in thin film and nanoparticle form has potential for use in energy production: as a photocatalyst, it can break water into hydrogen and oxygen. With the hydrogen collected, it could be used as a fuel. The efficiency of this process can be greatly improved by doping the oxide with carbon.

Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.
It is convenient to divide the photosynthetic process in plants into four stages, each occurring in a defined area of the chloroplast: (1) absorption of light, (2) electron transport leading to the reduction of NADP+ to NADPH, (3) generation of ATP, and (4) conversion of CO2 into carbohydrates (carbon fixation).

Plastics are used in a wide variety of products and have displaced other materials that were previously used for the applications that plastics now dominate such as wood, metal, and glass. It can be formed into polyesters for use in fabrics and textiles, polyvinylidene chloride for food packaging, and polycarbonates for eyeglasses and compact discs, among thousands of other uses. The production of plastic requires four basic steps: the acquirement of raw material, synthesizing a basic polymer, compounding the polymer into a usable fraction, and lastly, molding or shaping the plastic. The production of plastic is quite energy intensive, requiring 62 to 108 mega joules of energy per kilogram based on U.S. efficiency averages. Producing silicon can require up to 235 mega joules per kilogram of material.

In 2018, the global production of plastics reached 359 million metric tons, with 62 million metric tons of that amount produced in Europe alone. China is one of the largest producers of plastics in the world, accounting for more than one quarter of the global production. Plastic imports into the United States are steadily increasing, with China being the top supplier. China's plastic exports have grown considerably in the past decade, with an export value of 14.4 billion U.S. dollars in 2009, increasing to 43.4 billion U.S. dollars by 2018.