They have a lot of repetitions of small monomer units make them a very high molecular weight. Non-biodegradable plastics, usually known as synthetic plastics, are derived from petrochemicals. The chemical properties of plastics can be used as criteria for differentiating them into degradable and non-degradable polymers. Different parameters can be used, such as electrical conductivity, durability, tensile strength, degradability and thermal stability. Plastics are also classified based upon their relevance to the manufacturing process and design. Examples include phenol–formaldehyde, polyurethanes, etc… 2.2. The chemical change here is irreversible, and hence these plastics are not recyclable because they have a highly cross-linked structure, whereas thermoplastic are linear. Thermosetting polymers remain solid and cannot be melt and modified. Thermosetting polymers are different types of plastics. They are also known as common plastics, range from 20,000 to 500,000 AMU in molecular weight and have different numbers of repeating units derived from a simple monomer unit. These polymers are different types such as Polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polytetrafluoroethylene (PTFE). Thermoplastics are polymers cannot change in their chemical composition when heated, and can therefore undergo moulding multiple times. Thermal Propertiesīased on the plastic’s thermal properties, plastics can be dividing in two groups: thermoplastics and thermosetting polymers. There are various types of plastics, classified according to their properties and chemical structure. Categories and Classification of Plastics This study focuses on the role of microorganisms in the biodegradation of synthetic and natural plastics polymers, and describes the biodegradation pathways. Some strains of Microorganisms can produce Polyhydroxy Alkonates (PHA), a bio plastic that is safe, has no toxic effects and can be easily biodegraded. īiodegradable plastics are materials designed to degrade under environmental conditions or in municipal and industrial biological waste treatment facilities, and thus open the way for new waste management strategies. Generally, the biodegradation of plastic by microorganisms is a very slow process, and some microorganisms can’t degrade certain plastics. Microorganisms can also play a vital role in this process, as over 90 genera of bacteria, fungi and actinomycetes have the ability to degrade plastic. Plastic can degrade by a variety of mechanisms such as chemical, thermal, photoxidation and biodegradation, all of which take an extremely long time depending on the molecular weight of polymer, it could take up to 1000 years for some types of plastics to degrade. In addition, the burning of Polyvinyl chloride (PVC) plastics produces persistent organic pollutants known as furans and dioxins, and the burning of polyethylene, polyurethane, polyvinyl chloride and polystyrene produces toxic irritant products that lead to immune disorders and lung diseases, and are classified as possible human carcinogens. Various health problems can be present as a result of open burning of these wastes which release pollutants into the air. Instead, plastics are disposed of through open, uncontrolled burning and land-filling. Figure 1 illustrates the percentages of the different types of solid wastes produced by this municipality in 2014.ĭue to the presence of plastics in municipal wastes, many countries do not allow the incineration of these wastes. According to the 2014 statistics of the Holy Mecca Municipality, about 82,933 tons of municipal solid wastes were produced, 26% of which were plastics. In Saudi Arabia, approximately 12 million tons of municipal solid wastes are produced annually, consisting of 40% organic wastes, 20% paper wastes, and 12–15% of plastic products.
Due to the absence of efficient methods for safe disposal of these synthetic polymers, they often end up accumulated in the environment, posing an ever-increasing ecological threat to flora and fauna. They are different types such as polyethylene (PE), Poly Ethylene Terephthalate (PET), nylons, Poly-Propylene (PP), Polystyrene (PS), Polyvinyl Chloride (PVC), and Polyurethane (PUR).
Plastics are extensively used because of their stability and durability. It is derived from different sources such as oil, coal and natural gas. It consists of carbon, hydrogen, silicon, oxygen, chloride and nitrogen.