Synthetic Fibres and Plastics

Plastics

Plastics are a wide range of semi-synthetic or synthetic substances that contains polymers as their main ingredient. The plasticity during production enables the plastic to be moulded, extruded or pressed into solid objects of different shapes. It makes the material to be able to adapt accordingly and is useful in various ranges of applications.

This adaptability, plus a wide variety of beneficial properties, such as being lightweight, durable and flexible, alongside cheap manufacturing methods, has contributed to widespread acceptance in contemporary society. Most modern plastics come from fossil fuel-based petrochemicals such as natural gas or petroleum. However, the most recent plastic manufacturing processes use alternatives manufactured from renewable materials such as corn or cotton derivatives.

Plastics

                                                                                                    Plastics

Definition of Plastic

Plastic is a synthetic material made from various organic polymers, like polyvinyl chloride (PVC), polyethylene, nylon, etc., which can be moulded into different shapes and forms when still in melted form and then transform into a solid or slightly elastic form. It is also known as polymers of long carbon chains.

The word plastic comes from the Greek word “plastikos” meaning “capable of being shaped or moulded” and, in turn, from “plastos” meaning “moulded”.

The plasticity or the state of the malleability of material during the manufacturing process enables it to be cast, pressed or extruded into various shapes, such as films, fibre, plate, tube, bottles, boxes, among many other such examples. The usual noun plastic form should not be confused with the technical adjective plastic form. The adjective shall refer to any material which undergoes a plastic deformation or a permanent change of shape when strained beyond a particular limit. For example, the stamped or forged aluminium exhibits plasticity in this context, but is not plastic in common sense. On the other hand, certain plastics, in their finished form, can break before deformation and are thus technically not plastic.

Structure of Plastic

Most plastics contain organic polymers. A large proportion of these polymers comprises chains of carbon atoms, pure or with oxygen, nitrogen or sulphur. The chains have several repeated units, composed of monomers. Each polymer chain has several thousand repeated units. The backbone is the main section of the chain that binds a large number of repeat units together.

Different molecular groups “hang” from this backbone to customize the properties of plastic. These pendants are usually “hung” on the monomers until the monomers link themselves together to form the polymer chain. It is the arrangement of these side chains that influences the properties of the polymer. The molecular structure of the repeating units can precisely tune to affect the specific properties of the polymer.

Properties and Classifications

Plastics generally categorize as the chemical structure of the polymer base and side chains. The major categories of these classifications include acrylics, polyesters, silicones, polyurethanes and halogenated plastics. Plastics also categorize by the chemical process used in their syntheses, such as cross-linking, condensation, and polyaddition.

Plastics can also categorize by their various physical properties, such as tensile strength, hardness, resistance to heat, density, and glass transition temperature, and their chemical properties, such as organic polymer chemistry and its resistance and its reactions to various other chemical materials and processes, such as ionizing radiation, oxidation and organic solvents.

Other classifications depend on characteristics that are relevant to the manufacturing process or designing of the product. Examples of such qualities and classes are conductive polymers, thermoplastics and thermosets, engineering plastics and biodegradable plastics and other similar plastics with unique structures, such as elastomers.

Thermoplastics

Thermoplastics are plastics that do not undergo a chemical change in their composition when heated, and hence, they can mould several times. Examples are polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC) and polystyrene (PS).

Thermosets

Thermosets polymers are plastics that can melt and mould into any shape only once. They’ll undergo an irreversible chemical reaction when heated, hence, if heated again they decompose instead of melting.

Conductive Polymers

Intrinsically Conducting Polymers (ICP) are electrically conductive organic polymers. Example: Polyacetylene.

Biodegradable Plastics

Biodegradable plastics are plastics that degrade or break down when exposed to sunlight or ultraviolet radiation, bacteria, certain enzymes, dampness or water, or wind abrasion. In certain circumstances, rodents, pests or insect attacks can also act ad biodegradation modes or environmental degradation. Example: Starch-based plastics, Cellulose-based plastics, Soy-based plastics.

Bioplastics

While most plastics are products of petrochemicals, bioplastics are plastics produced substantially from renewable plant materials such as cellulose and starch. Due to the finite limits of petrochemical resources and the risk of global warming, bioplastics is still a growing field.

Recycling of Plastic

The recycling process of plastic is an essential procedure. If not recycled at the correct time, the plastic mix with other chemicals or materials, making it tougher to recycle and become a source of pollution.

They are non-biodegradable and so, do not decompose by microbial activity. It is essential to use biopolymers or biodegradable polymers to prevent this.

Uses of Plastic

  • Plastics are highly durable, lightweight and, most significantly, can be moulded into any form or shape. These properties are a few reasons for the use of plastics. Plastics are extremely versatile materials that can be useful for a wide range of applications. Below given are some applications;
  • The potential to be moulded makes plastic ideal packaging material. Plastics in packaging help keep food healthy and fresh.
  • As durable and lightweight, plastics have helped in the field of electronics. From computers and cell phones to TV and refrigerator, nearly all of the appliances around us use plastic.
  • Plastics help in making safety gears such as helmets, goggles, etc.
  • Plastics are also useful in the construction sector because of their low maintenance and high durability.
  • Because of plastic’s strength and it’s lightweight properties, it is useful in making toys, electrical switches and other household goods.
  • As it is non-reactive to air and water, they help store water in plastic bottles and chemicals in chemical laboratories.
  • Plastic is a weak conductor of electricity and heat, so its insulation properties help in the coating of electrical wire and various household products like utensils handles, etc.

FAQs about Plastics

Q1. What are the advantages and disadvantages of plastic?

Answer. The advantages and disadvantages of plastic are;

Advantages:

  • Plastics are highly flexible and cheaper in comparison to metals.
  • The manufacturing process of plastic parts is budget-friendly.
  • Plastics are highly durable and can last for a longer time.
  • The specific gravity of plastic is much lower, which makes it a lightweight material.
  • The manufacturing process of plastic is a lot faster than metals.

Disadvantages:

  • The natural decomposition of plastics will last from 400 to 1000 years and, few types of plastics are non-degradable.
  • Plastic materials affect water bodies like oceans, seas, lakes etc., killing marine animals.
  • Many animals are consuming plastic products and dying on a daily basis. About 90% of all seabirds have plastic in their stomachs.
  • Plastic is widely popular in food packaging, but research studies show that eating food out of plastic containers may cause cancer.
  • Both the production and recycling of plastics produce harmful gases and residues that pollute the air, water and soil.

Q2. Who discovered plastic?

Answer. A Belgian chemist Leo Baekeland discovered Bakelite; the first fully synthetic thermoset plastic using the chemicals phenol and formaldehyde.

Q3. What are biodegradable plastics? Give some examples.

Answer. Biodegradable plastics are plastics that degrade or break down when exposed to sunlight or ultraviolet radiation, bacteria, certain enzymes, dampness or water, or wind abrasion. Examples include Starch-based plastics, Cellulose-based plastics, Soy-based plastics.

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