Polyethylene, What’s that?

POLYETHYLENE

Polyethylene, What’s that?

Definition

Plastic is a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc., that can be molded into shape while soft, and then set into a rigid or slightly elastic form. The relatively low density of most plastic materials means the final products are lightweight. They also have excellent thermal and electrical insulation properties. However, some can even be made as conductors of electricity when required. They are corrosion resistant to many substances which attack other materials, and some are transparent, making optical devices possible. They are also easy to mold into complex shapes and forms, allowing integration of different materials and functions.

Moreover, plastics are so durable and do not corrode, thus they create considerable disposal problems. They are not good for the landfill as many will persist for hundreds of years and when incinerated, dangerous gases can be produced.

Production of Plastics

The production of plastic begins with a distillation process in an oil refinery. The distillation process involves the separation of heavy crude oil into lighter groups called fractions. Each fraction is a mixture of hydrocarbon chains (chemical compounds made up of carbon and hydrogen), which differ in terms of the size and structure of their molecules. One of these fractions, naphtha, is the crucial element for the production of plastics.

The two major processes used to produce plastics are called polymerization and polycondensation, and they both require specific catalysts. In a polymerization reactor, monomers like ethylene and propylene are linked together to form long polymers chains. Each polymer has its own properties, structure, and size depending on the various types of basic monomers used.

There are many different types of plastics, and they can be grouped into two main polymer families:

Thermoplastics (which soften on heating and then harden again on cooling).

Thermosets (which never soften when they have been molded)

Plastic Waste Challenge in UAE

Plastics are an inseparable part of modern society. However, their safe disposal is a big and highly challenging issue. A typical UAE resident uses 450 plastic water bottles on an average in a single year. With the equivalent of 43 gallons on an average per person in 2011, the United Arab Emirates had the fourth-highest level of bottled water consumption in the world. Moreover, a whopping 11 billion plastic bags are used annually, according to statistics from UAE’s Ministry of Environment and Water. This goes on to add up to an annual overall waste of 912.5 kilograms per capita. These statistics reflect on the extent of use of plastic bags and bottles in UAE and the consequent generation of plastic waste.

Plastics are used globally in industries like packaging, construction and medical equipment among others. This is because plastics are durable, waterproof, lightweight and versatile. However, some countries use them more than others due to certain socio-economic factors. UAE has witnessed rapid growth in the last decade. This has been in terms of population as well as GDP per capita, both of which have more than doubled in this period. The above two factors result in higher consumer spending.

All this consequently leads to increased waste generation. From the supply side also, plastic manufacture is a booming industry in UAE and rest of Gulf, one factor for it being an abundance of petrochemicals, the raw material for plastics, in this region.

The Waste Hierarchy

    • Prevention: If products are designed to use less plastic, then there could be less waste. This can be done by reducing the amount of plastic, particularly in packaging, or by substituting plastic with other materials.
    • Reuse: Products could be designed for re-use by facilitating the dismantling of products and replacement of parts.
    • Recycle: There are many types of plastics, some of which are easier to recycle than others.
    • Recovery: Energy can be recovered from plastics in waste-to-energy plants. By designing products to consider the possibility of energy recovery, plastic may have a greater end-of-life use.
    • Disposal: Biodegradable plastics are less persistent in the environment than traditional plastics, but need specific and suitable end of life treatment. Bioplastics could also help mitigate climate change by reducing our use of petroleum for the manufacture of traditional plastics. It is claimed that CO2 emissions released at the end of life of bio-based plastics are offset by absorption of CO2 during the growth of plants for their production.

Recycle of Plastics

There are many ways of recycling plastic:

  • Mechanical recycling

Which consist of melting down the old plastic and using it to make new products.

  • Chemical recycling

Where plastics are dissolved back into their original chemical components and then cleaned up and reused to make new plastics.

  • Plastic pyrolysis

This is the process of converting waste plastic into industrial fuels like Pyrolysis Oil, Carbon Black, and Hydrocarbon Gas. It involves subjecting plastic to the high temperature of 400 to 450 degree Celsius, in absence of oxygen. In case of oxygen is present plastic will start burning. During pyrolysis, plastic breaks down into smaller molecules of pyrolysis oil, pyrolysis gas, and carbon black. Pyrolysis is great a way of recycling waste plastics. This plant can also be used for waste tire recycling.

  • Photodegradation

The sun’s rays have capabilities in its ultraviolet light (UV light) and infrared radiation which bring about the incorporation of oxygen molecules into the plastic, a process known as oxidation. As more and more oxygen intermingles with the polymer in the plastic, it becomes brittle and easier to break into ever diminishing pieces. Eventually, the pieces of plastic will become small enough to be consumed by microorganisms, which are able to metabolize it and convert it to carbon dioxide (CO2) or absorb it into their own biomolecules.

Conclusion

Plastics are important materials that can be used in many applications. However, they are durable and do not corrode so they can’t be disposed of in landfills like many other materials. The waste Hierarchy of plastic includes five stages which are prevention, reuse, recycle, recovery, and disposal. Plastics can be recycled in many ways such as melting it to make new products, dissolve it back to its original materials, converting it into industrial fuels using pyrolysis, or using the photodegradation process. Green Mountains can help you in plastic recycling in the UAE

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